Advances in Radioactive Isotope Science

4 juin 2023, 10:00 → 9 juin 2023, 23:59 Europe/Paris

Conclave (Palais des Papes - Avignon - France)

David Lunney (CNRS/IN2P3), Wolfram KORTEN (CEA Paris-Saclay)

The 4th International Conference on Advances in Radioactive Isotope Science (ARIS) will be held in France's beautiful city of Avignon from 4-9 June 2023. 

 

ARIS is the flagship meeting on rare isotope science, born from a merger of the international conferences ‘Exotic Nuclei and Atomic Masses (ENAM)’ and ‘Radioactive Nuclear Beams (RNB)’.  Following the tradition of the ARIS meetings in 2011 (Leuven), 2014 (Tokyo), and 2017 (Keystone), ARIS 2023 (rescheduled from 2020) will facilitate vibrant exchange through a program highlighting the most recent experimental and theoretical work including: 

• Nuclear structure and reactions
• New approaches in nuclear theory
• Nuclear astrophysics including nucleosynthesis and compact objects
• Ground-state properties and fundamental interactions in nuclei
• Drip-line nuclei, heavy elements and fission
• Radioactive ion beam production and experimental developments
• Applications of radioisotopes in medicine and other fields

You can now cite your abstracts via:   https://doi.org/10.5281/zenodo.10655037

Photographs of the conference here      Conference-dinner performance of highway to hell 

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Sponsors

                       

           

                          

       

ARIS2023 will abide by the
IUPAP Conference Policies      

ARIS2023_abstract-book.pdf

ARIS2023_final-Circular.pdf

ARIS2023_program-book.pdf

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map to reach Jardin Benoit XII.pdf

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program-at-a-glance.pdf

dimanche 4 juin

19:00 Welcome Reception

lundi 5 juin

opening

plenary 01

Président de session: Ani Aprahamian (University of Notre Dame)

1 Prevailing triaxial shapes in exotic and heavy nuclei

Shapes of heavy deformed nuclei are discussed from the viewpoint of the Monte Carlo Shell Model with realistic effective NN interactions. The prevailing triaxial shapes then emerge due to the nuclear tensor force, in contrast to the conventional picture of the prolate-shape dominance since 1950's. The triaxiality with $\gamma\sim9^\circ $ arises commonly for rare-earth nuclei around $^{166}$Er. The mechanism for the low-lying second 2$^+$ state is presented, and the relation to the Davydov model is mentioned. Possible new M1 mode due to the triaxiality is pointed out. Triaxial shapes of exotic Ne, Na and Mg isotopes are also discussed with the ab initio EEdf1 interaction for the sd-pf combined shell.

Orateur: Takaharu Otsuka (University of Tokyo / RIKEN)

Otsuka_ARIS.pdf

Otsuka_ARIS.pptx

2 FRIB and the Neutron-Rich Mg Isotopes

The study of nuclei far from stability is one of the most active and challenging areas of nuclear structure physics. The neutron-proton imbalance in nuclei approaching the dripline(s) affects the detailed impacts of the residual interaction, modifying single-particle energies and potentially leading to altered ground and excited-state properties. In addition, at the very edge of stability, the proximity of the continuum to the bound states may modify wavefunctions further. I will discuss a range of recent experimental measurements exploring different aspects of the structure in the most neutron-rich isotopes. I will present recent work in the region of neutron number N=28, below the Ca isotopes. There is a breakdown of the N=28 harmonic oscillator magic number as protons are removed from the sd shell, and the isotones below Ar are understood to be dominated by multi-particle-multi-hole excitations and deformation in their low-lying structure. I will discuss results from the first experiment at FRIB on half-lives in this region. I will also explore the specific case of Mg-40, which sits along the N=28 isotones and very near (or possibly at) the neutron dripline, where first spectroscopy resulted in an unexpected excitation spectrum.

Orateur: Heather Crawford (Lawrence Berkeley National Laboratory)

ARIS2023-Crawford.pdf

3 Nuclear astrophysics at storage rings (presentation sponsored by EPJ)

Most of the time, stars gain their energy from fusion of the very light left-overs of the Big Bang into heavier elements over long periods of time. The observation of radioactive isotopes in different regions of the Universe is an indicator of this ongoing nucleosynthesis. In addition, short-lived nuclei are often intermediate steps during the nucleosynthesis in stars. A quantitative analysis of these relations requires a precise knowledge of reaction cross sections involving unstable nuclei. The corresponding measurements are very demanding and the applied techniques therefore manifold.

Ion storage rings offer unprecedented possibilities to investigate radioactive isotopes of astrophysical importance in inverse kinematics. During the last years, a series of pioneering experiments proofed the feasibility of this concept at the Experimental Storage Ring (ESR) at GSI. I will present recent experiments and ideas for future setups for the investigation of capture reactions with astrophysical motivation.

Orateur: Rene Reifarth (Goethe University Frankfurt)

reifarth_2023_ARIS.pdf

10:25 coffee break

plenary 02

Président de session: Isao Tanihata (Osaka University)

4 Highlights of GANIL-SPIRAL2 facilities

The SPIRAL2 Phase 1 LINAC moved from project status to full operation on December 31st 2021, after the important milestone of acceleration of 45 A deuton beam at 40 MeV. Beams of protons and alpha particles were also accelerated. These beams were sent to the Neutron For Science (NFS) experimental cave. Two NFS campaigns have been performed with neutron beams in Fall 2021 and 2022. The S3 spectrometer installation is progressing well and the commissioning should start at the end of 2024. The first heavy ion beams were already accelerated by the LINAC with the dedicated ion source, to prepare for the S3 physics program. The presentation will give an overview on these different achievements together with an update of the DESIR project status. The new project NEWGAIN will also be presented. It will increase the capabilities of SPIRAL2 LINAC with the construction of a second injector able to produce and accelerate ion beams with mass to charge-state ratios ranging from A/q=3 up to A/q=7. This second injector will be designed to be fully compatible with the existing facility and to further enhance its ‘multi-user’ capabilities.

In parallel to SPIRAL2 developments, a refurbishing program of the GANIL cyclotrons is being planned. New beams are under development with SPIRAL1 target-ion sources. Selected results will be presented, together with the vision for the medium and long term plans.

Orateur: Dr Patricia Roussel-Chomaz (CEA)

GANIL SPIRAL2_ARIS2023_v2.pptx

5 Observation of a correlated free four-neutron system

An isolated system of four neutrons is studied in the SAMURAI experiment at the Radioactive-Ion Beam Factory at RIKEN [1]. The key reaction 8He(p,pα)4n in inverse kinematics populates the final state of four neutrons through a prompt quasi-free-scattering process close to 180 degrees in the p-α centre-of-mass frame. The resulting energy spectrum of the free 4n system reveals a distinct peak-like structure with positive energy centered at 2.4 MeV in addition to a more broad distribution associated with the continuum. The details of the experimental method and the analysis results will be presented along with the further perspectives of studying multi-neutron systems.

Orateur: Dr Valerii Panin (GSI, Darmstadt)

Tetraneutron_Panin_light.pdf

6 Alpha-clustering in atomic nuclei from first principles

Owing to recent computational and methodological advances, ab-initio approaches in low-energy nuclear theory have been developed rapidly in recent years. As one of such approaches, the no-core Monte Carlo shell model (MCSM) is briefly introduced in this presentation. After verifying the capability of the no-core MCSM on actual computations, the alpha-cluster structure of light nuclei is discussed from an ab-initio point of view, especially focusing on the appearance of molecular-orbital structure of valence neutrons in Be isotopes and the intrinsic shapes of the C-12 nucleus.

Orateur: Takashi Abe (CNS, the University of Tokyo)

tabe_ARIS_20230605.pdf

7 Studies of Weakly-Bound, Neutron-Rich Nuclei using HELIOS and SOLARIS

The solenoidal-spectrometer technique developed at Argonne some 15 years ago in the form of HELIOS continues to evolve, adding new capabilities. A similar device has been recently installed at the Facility for Rare Isotope Beams (FRIB), called SOLARIS, for use with reaccelerated (ReA) beams. SOLARIS operates as a dual-mode spectrometer, both in a vacuum with position-sensitive silicon arrays and in Active-Target Time Projection Chamber (AT-TPC) mode. This allows for reaction studies across a broad dynamic range in terms of beam intensities (hundreds of particles per second to nano-Ampere beams), masses, and incident beam energies. SOLARIS has been used in both modes of operation during the operation of ReA with long-lived radioisotopes. The capabilities of these two devices will be demonstrated via a series of recent highlights: for HELIOS, the role of quenching in weakly-bound systems using the ($d$,$p$) reaction [1], and for SOLARIS studies using the ($t$,$p$) reaction [2] where the inverse kinematics technique allows for almost background-free measurements and a determination of branching ratios of unbound states.

*This material is based upon work supported the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract Number DE-AC02-06CH11357. SOLARIS is funded by the U.S. Department of Energy, Office of Science, under the FRIB Cooperative Agreement DE-SC0000661.

References
[1] B. P. Kay et al., Phys. Rev. Lett. 129, 152501 (2022).
[2] A. Muñoz-Ramos, in preparation.

Orateur: Ben Kay (Argonne National Laboratory)

kay_airs.pdf

12:45 lunch break

plenary 03

Président de session: Byungsik Hong (Korea University)

8 The Decay Spectroscopy Setup at the GSI-FAIR fascility and the physics results from FAIR-0

The DEcay SPECtroscopy (DESPEC) setup assembled for the future GSI-FAIR fascility in Darmstadt, Germany, aims to study the nuclear footprint mainly through gamma ray spectroscopic measurements.
As a part of the NUSTAR project, the DESPEC collaboration aims to search for the exotic nuclear structure phenomena such as shell evolution in nuclei which take part in the astrophysical r-processes. The FAIR “Phase-0” programme has already been started. In persuit of chracterising the exotic nuclei, the gamma-spectroscopy was combined with charge particle spectroscopy using an array of DSSSD’s of the AIDA. AIDA could also sort out the implanted ion possition and time, with precission. The filtered out gamma-rays could be used to measure nuclear energy levels precisely by the high resolution HPGe detectors, while the nuclear level lifetimes could be measured using LaBr3 scintillator detectors of the FATIMA array. Some interesting development in the Phase-0 programme has already been observed by studying the basic nuclear structure phenomena in exotic nuclei south west to the “N=Z=50” line. In future, the neutron delayed gamma-ray spectroscopic studies would be possible using the MONSTER detectors. In summary, with a multidimensional system for particle and gamma spectroscopy, the DESPEC setup once placed at the final focal plane of FRS/SUPER-FRS of the GSI-FAIR accelarator complex, is a robust tool to explore the nuclear landscape,.

Orateur: Biswarup Das (GSI Helmholtzzentrum für Schwerionenforschung)

Aris_BDAS.pdf

9 Evolution of single-particle properties probed with the ISOLDE Solenoidal Spectrometer

The ISOLDE Solenoidal Spectrometer (ISS) has been built for measuring direct reactions in inverse kinematics with radioactive beams (RIBs) from HIE-ISOLDE, with a focus on obtaining excellent charged particle resolution. ISS was fully commissioned in 2021 with a new silicon array developed by the University of Liverpool. This array makes use of double-sided silicon strip detectors, with ASIC readout, to determine the position of interaction and the energy of light ejectiles from reactions of RIBs with a light-ion target, when they return to the beam axis in the solenoid field. ISS has now completed two full physics campaigns focussing on measurements of the (d,p) reaction to probe single-neutron behaviour in various systems. This talk will give an overview of ISS and a summary of the physics campaigns from the last two years with a focus on evolving single-particle structure.

The study of single-particle structure in light neutron-rich systems has led to discoveries of dramatic changes which are otherwise gradual near stability, leading to the weakening and appearance of shell closures. For example, the disappearance of $N = 20$ and emergence of $N = 16$ [1, 2] as well the emergence of $N = 32, 34$ in calcium isotopes [3]. Pronounced trends have also been observed in stable heavier nuclei, in the changes in high-j states as high-j orbitals are filling. Studies of chains of stable, closed-shell isotopes [4] and isotones [5] have pointed to robust mechanisms for these changes, such as the importance of a tensor interaction [6]. The beams available at ISOLDE allow an extension of these studies both in light neutron-rich systems but also in heavier systems such along $N=126$. Measurements looking at the properties of the single neutron outside both $N=16$ and $N=126$ will be covered here.

[1] A. Ozawa et al., Phys. Rev. Lett. 84, 5493 (2000).
[2] C. R. Hoffman et al., Phys. Lett. B 672, 17 (2009).
[3] D. Steppenbeck et al., Nature 502, 207 (2013).
[4] J. P. Schiffer et al., Phys. Rev. Lett. 92, 162501 (2004).
[5] B. P. Kay et al., Phys. Lett. B 658, 216 (2008), D. K. Sharp et al., Phys. Rev. C 87, 014312 (2013).
[6] T. Otsuka et al., Phys. Rev. Lett. 95, 232502 (2005).

Orateur: David Sharp (The University of Manchester)

ARIS-2023-DKS.pdf

10 Proton radioactivity studies with ACTAR TPC

(for the E690 and E791 collaborations)

For nuclear systems that are slightly unbound with respect to the nuclear strong interaction, the 1- and 2-proton radioactivity decay channel opens [1,2]. The experimental study of these radioactivities offers a unique access to the structure properties of the emitting states. Such data can represent real challenges in terms of theoretical interpretations.
This kind of exotic decay modes is part of the physics program that motivated the development of the ACTAR TPC (Active Taget and Time Projection Chamber) device [3], as well as several other TPC detectors worldwide. ACTAR TPC has been successfully used in recent experiments, related to proton(s) radioactivity in the A~50 mass region.
The first experiment allowed for the imaging of the proton emission from the ${}^{53m}$Co and the (short-lived) ${}^{54m}$Ni isomeric states [4,5,6]. In both cases, the observation of the high angular momenta proton branches allowed for the determination of the complete decay pattern of these states. The second experiment aimed at the direct observation of the ground state 2-proton radioactivity of ${}^{48}$Ni [7]. The scientific context and the experimental results will be presented, and compared to state of the art theoretical interpretations.

[1] B. Blank and M.J.G. Borge, Progress in Particle and Nuclear Physics 60 (2008) 403–483
[2] M. Pfützner et al., Review of Modern Physics, vol. 84 (2012)
[3] B. Mauss et al., Nuclear Inst. and Methods in Physics Research, A 940 (2019) 498–504
[4] J. Giovinazzo et al., Nature Comm. 12, (2021) 4085
[5] D. Rudolph et al., Physics Letters B 830 (2022) 137144
[6] L.G. Sarmiento et al., accepted for publication in Nature Comm.
[7] A. Ortega Moral et al., proceedings of Zakopane 2022 conf.

Orateur: Jérôme Giovinazzo (LP2IB (CENBG) CNRS / Univ. Bordeaux)

2023-06_ARIS_Giovinazzo.pdf

11 r process and supernova signatures in deep-sea archives

Half of the heavy elements are produced in r-process nucleosynthesis, which is exclusively responsible for actinide production, such as Pu-244 (t$_{1/2}$=81 Myr). The r-process requires an explosive scenario but is far from being fully understood; in particular, its sites and history.

The solar system moves through the interstellar medium (ISM) and collects interstellar dust particles that contain such signatures, including the radionuclides Fe-60 (t$_{1/2}$=2.6 Myr) and Pu-244. These nuclides are incorporated into terrestrial archives over millions of years and once recovered can be measured with Accelerator Mass Spectrometry (AMS) with high sensitivity.

Recent technical developments have seen an exceptional gain in measurement efficiency and sensitivity, in particular for actinides, including Pu-244. On the other hand, very large accelerators with >10 million volts allow for effective isobar separation using techniques derived from nuclear physics research. Such AMS systems are unique but required for the identification of small traces of interstellar Fe-60.

New data demonstrate a global Fe-60 influx and is evidence for exposure of Earth to recent (<10 Myr) supernova explosions. In addition, the recent finding in deep-sea archives of ISM-Pu-244, exclusively produced by the r-process, allows to link supernovae and r-process signatures. The low concentrations of Pu-244 measured in deep-sea archives suggest a low abundance of interstellar Pu and supports the hypothesis that the dominant actinide r-process nucleosynthesis is rare. However, the data allow some actinide production in supernovae while implying r-process contributions from additional sources.

Orateur: Anton Wallner (Helmholtz Center Dresden-Rossendorf / Australian National University)

A Wallner ARIS 05062023.pdf

16:15 coffee break

plenary 04

Président de session: alfredo poves (Departamento de Física Teórica and IFT UAM-CSIC, Universidad Autónoma de Madrid)

12 Microscopic models of nuclear structure at scale

The diversity of atomic nuclei is enormous: the number of possible species is estimated to be 7000 while we know that adding a single nucleon to one nucleus can dramatically change its properties. This diversity renders nuclear structure interesting in itself, but it is also crucial to the progress in several other fields of research: from searches for beyond-the-standard-model physics to the chemistry of (possibly long-lived) superheavy nuclei. The need for nuclear data is particularly large in astrophysics: answering fundamental questions about the Universe (What is the origin of the elements? What is the composition of the core of neutron stars?) requires data on many properties of thousands of nuclei at the extremes of isospin, temperature and angular momentum.

Since exotic nuclei are hard to produce and handle, the only realistic way to provide all required nuclear data is nuclear theory. To maximize predictive power, models should incorporate as much of the relevant physics ingredients as current computers can handle while describing the maximum number of properties simultaneously with a limited number of parameters. Models based on energy density functionals (EDFs) offer an attractive compromise: starting from an effective interaction they rely on the mean-field approximation to render the many-body problem tractable and can provide a microscopic description of all relevant quantities in terms of individual neutrons and protons and a modest amount of parameters across the scale of the nuclear chart. The success of EDF-based models is largely due to spontaneous symmetry breaking: by considering deformed configurations, these models can account for large parts of the effects of nuclear collectivity at the mean-field level.

In this contribution, I will introduce the recent EDF-based models constructed in Brussels: the BSkG-series. Fitted to over two thousands binding energies, they all achieve a root-mean-square error on the known masses of less than 800 keV which is competitive with simpler models. What sets the BSkG-series apart from other large-scale models based on EDFs is the sophistication of their representation of the nucleus: a three-dimensional coordinate representation results not only in a well-controlled numerical accuracy but also allows us to exploit the power of spontaneous symmetry breaking fully. All BSkG-models allow the nucleus to explore triaxial deformation, while the most recent ones also allow in addition for (i) non-zero angular momentum in the ground-states of odd-mass and odd-odd nuclei through time-reversal breaking and (ii) reflection asymmetry, i.e. octupole deformation.

I will discuss the performance of the BSkG-models for a diversity of (pseudo-)observables relevant to nuclear structure and astrophysical applications: from bulk properties such as masses, charge radii and deformations to the large-scale description of nuclear fission; from fine-grained aspects of ground states such as moments of inertia and magnetic moments to statistical properties such as nuclear level densities. Throughout the presentation, I will explain the impact of spontaneous symmetry breaking and underline its importance to achieve a state-of-the-art simultaneous description of all these quantities. Finally, I will discuss ongoing refinements of these models and the challenges we intend to tackle in the long run.

Orateur: Wouter Ryssens (Université Libre de Bruxelles)

ARIS23-2.pdf

13 Emission channeling investigations of impurities with interesting quantum properties in single crystals

As we enter the second quantum revolution, where non-classical properties of quantum systems are being explored for practical applications, the interest in impurity atoms embedded in crystalline materials has been extended, going far beyond previous, more conventional applications like doping to modify electrical, optical or magnetic properties of semiconductors or other materials. For instance, systems composed of a single impurity atom in a crystalline matrix, like the nitrogen vacancy (NV) center in diamond, which is already finding applications in nanoscale magnetometry, or of small ensembles of such defects, could be at the base of future quantum communication, computation and metrology devices. In that respect, one of the crucial issues is the targeted creation of specific configurations of impurity atoms in the lattice, where ion implantation plays a critical role, however, competing with other techniques.
In this talk I will discuss two examples where emission channeling experiments with radioactive ion beams at the CERN-ISOLDE facility contributed to investigating the microscopic structure of impurity configurations that may play a role in future quantum applications based on ion-implanted single crystals. The first example will address the lattice location of the “nuclear clock” isotope 229mTh in CaF2, where for the observation of the emitted 8.3 eV photons it was crucial to have the radioactive isotope occupy substitutional Ca sites [1,2]. Another set of examples addresses the structure and formation mechanism of ion implanted colour centers in diamond based on impurities like Sn [3], Ge, or Mg [4]. For these defects with desired quantum properties it is vital to incorporate the foreign atom in the center of a double vacancy, the so-called split-vacancy configuration.
[1] M. Verlinde, S. Kraemer, J. Moens, et al., “Alternative approach to populate and study the 229Th nuclear clock isomer”, Phys. Rev. C 100 (2019) 024315.
[2] S. Kraemer, J. Moens, et al., “ Observation of the radiative decay of the 229Th nuclear clock isomer”, accepted by Nature.
[3] U. Wahl, et al., “Direct structural identification and quantification of the split-vacancy configuration for implanted Sn in diamond”, Phys. Rev. Lett. 125 (2020) 045301.
[4] E. Corte, et al, “Magnesium-vacancy optical centers in diamond”, ACS Photonics 10 (2023) 101.

Orateur: Ulrich Wahl (Instituto Superior Técnico, Universidade de Lisboa)

ARIS_2023_ECSLI_Quantum.pptx

public lecture

Président de session: Ulli Köster (Institut Laue-Langevin)

14 Treatment of metastatic cancer by Radiomolecular Precision Oncology - an ongoing revolution

The radiopharmaceuticals toolbox has expanded dramatically over the last few years. Isotopes with well-established chemistries continue to be used routinely, while newer isotopes have grown more available, with a wider variety of chemistries, decay modes and in vivo behaviors, making it easier to pair radiopharmaceuticals for imaging and therapy, a pairing referred to as radiomolecular theranostics. In much the same way that the development of targeted agents and immunotherapy revolutionized medical therapies for cancer, the rapid development and availability of these new isotopes and agents has fundamentally changed the landscape for radiopharmaceutical therapy.
Radiomolecular Precision Oncology is being driven by rapid advances in novel diagnostics and therapeutic interventions. As part and integral in the current era of precision oncology, theranostics aims to identify the appropriate molecular targets in neoplasms (diagnostic tool), so that the optimal ligands and radionuclides (therapeutic tool) with favorable labeling chemistry can be selected for personalized management of a specific disease, taking into consideration the specific patient, and subsequently monitor treatment response for personalized cancer care.
Peptide receptor radionuclide therapy (PRRT) and PSMA Radioligand Therapy (PRLT)
Over the past two decades, the use of 68Ga labeled peptides for somatostatin receptor (SSTR)-targeted PET imaging followed by beta emitters like 177Lu and 90Y or alpha-emitters like 225Ac and 212Pb labeled SSTR-analogues for peptide receptor radionuclide therapy (PRRT) has demonstrated remarkable success in the management of neuroendocrine neoplasms and paved the way to other theranostics indications.
Targeted Alpha radioligand therapy (ART)
While beta-emitters have demonstrated efficacy, alpha-emitters have a 100-fold higher LET. Remarkable results have been achieved by switching non-responders from 177Lu to alpha therapies. Our experiences indicate that the combination of 225Ac and 177Lu labeled PSMA and somatostatin receptor antagonists ligands for TANDEM treatments are feasible, safe, and effective, and suggest a potential synergistic effect.
FAP-targeted peptide targeted radionuclide therapy (PTRT)
FAP is overexpressed on cancer-associated fibroblasts (CAFs) in over 90% of epithelial. We recently published the worldwide first clinical experience using 177Lu-FAP-2286. We are now performing PTRT using 3BP-3940 to explore the theranostic approach applying 68Ga-3BP-3940 for PET/CT imaging and selection of the patients for PTRT with 177Lu, 90Y, 225Ac and combinations of the radioisotopes for TANDEM-PTRT.
RadioVakzination - Combination of radioligand therapy with immunotherapy
By combining molecular targeted radioligand therapy with immune check-point inhibitors (ICPI), e.g. PD-L1 mAb like pembrolizumab, a promising paradigm of cancer immunotherapy has been developed that could reprogram TME from “cold” to “hot”, to make low immunoactivity tumors sensitive to therapy.
Conclusions
PRRT lends a significant benefit in progression-free survival in metastasized NENs as compared to other treatment modalities. Quality of life is significantly improved. The combination of 177Lu and/or 90Y, 225Ac (DUO-PRRT) may be more effective than either radionuclide alone.
177Lu-PSMA RLT is safe and effective with appropriate selection/follow-up of patients by 68Ga-PSMA PET/CT. 225Ac-PSMA or TANDEM-ART is prolonging overall survival for end-stage mCRPC.
The initial clinical results of PTRT provide evidence for the feasibility of radiomolecular precision theranostics in a number of advanced, therapy-refractory adenocarcinomas.
New targets, novel radionuclides (225Ac, 212Pb and Terbium radioisotopes), tumor microenvironment with optimized peptide and optimal isotopes (177Lu, 225Ac, 90Y, TANDEM) and administration schedules, RadioVax (combination of radioligand with immunotherapy), radioprotectors and radiosensitizers will be systematically explored in future.
Personalized, molecular radiotherapy of malignancies, tailored to the individual patient in a PRECISION ONCOLOGY setting (including genomics) is moving from innovation to implementation in real-world, and large patient populations are expected to be in the mainstream of future applications.

Orateur: Richard P Baum

mardi 6 juin

plenary 05

Président de session: Navin Alahari (GANIL)

15 Unravelling the mysteries of the atomic nucleus via high resolution laser spectroscopy at COLLAPS

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Orateur: Liss Vazquez Rodriguez (CERN, MPIK)

16 Nuclear Structure investigations of most exotic nuclei via mass measurements at TITAN

High precision mass measurement using ion trapping continue to play an important role in shaping our understanding of the nucleus. State-of-the-art spectrometers nowadays are able to reach far from the valley of beta stability, where new phenomena, as e.g. shell quenching, weakening or disappearance of classical and appearance of new magic numbers can be observed and studied via their characteristic signatures in the mass surface.
TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) [1] located at the Isotope Separator and Accelerator (ISAC) facility, TRIUMF, Vancouver, Canada is a multiple ion trap system specialized in performing fast high-precision mass measurements and in-trap decay spectroscopy of short-lived radioactive species. Since its installation in 2017, the new Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) has been in routine operation [2] and has expanded TITANs reach to even more exotic nuclei.
Mass selection is achieved using dynamic re-trapping of the ions of interest after a time-of-flight analysis in an electrostatic isochronous reflector system [3]. Re-using the injection trap of the device for the selective re-trapping, the TITAN MR-TOF-MS can operate as its own high resolution isobar separator prior to a mass measurements within the same device. This unique combination of operation modes boosts the dynamic range and background handling capabilities of the device, enabling high precision mass measurements with ion of interests to contaminant ratios of 1:10^7.
Among other, we will discuss recent results of mass measurements of neutron-deficient Yb and Tm isotopes investigating the persistence of the N=82 neutron shell closure far from stability, made possible by online mass-selective re-trapping supressing strong isobaric background. On the opposite side of the nuclear chart, we will investigate the evolution of the N=40 island of inversion in the neutron-rich Mn to Fe isotopic chains and give an outlook towards future mass measurements for nuclear structure investigations.

References:
[1] J. Dilling et al., NIM B 204, 2003, 492–496
[2] M. P. Reier et al., NIM A 1018, 2021, 165823
[3] T. Dickel et al. J. Am. Soc. Mass Spectrom. (2017) 28: 1079

Orateur: Moritz Pascal Reiter (University of Edinburgh)

ARIS 2023 - Reiter TITAN_red.pdf

17 Study of the Pygmy Dipole Resonance using neutron inelastic scattering at GANIL-SPIRAL2/NFS

The pygmy dipole resonance (PDR) is a vibrational mode described as the oscillation of a neutron skin against a core symmetric in number of protons and neutrons. The PDR has been the subject of many studies, both experimental and theoretical [1,2]. Indeed, the study of the PDR has been and still is of great interest since it allows to constrain the symmetry energy, an important ingredient of the equation of state of nuclear matter that describes the matter within neutron stars [3]. Moreover, the PDR is predicted to play a key role in the r-process via the increase of the neutron capture rate [4]. However, despite numerous experiments dedicated to the study of the PDR, a consistent description could not be extracted. In this context, we propose to study the PDR using a new probe: the neutron inelastic scattering reaction (n,n’g).

An experiment to study the pygmy resonance in 140Ce using the (n,n’g) reaction has just been carried out. This experiment has been made possible thanks to the high-intensity proton beam of the new accelerator SPIRAL2 at GANIL and the NFS (Neutron For Science) facility. The experimental setup consisting of the new generation multi-detectors PARIS [5], for the detection of gammas coming from the de-excitation of the PDR, and MONSTER [6], for the detection of scattered neutrons, was used.

[1] D. Savran, T. Aumann, A. Zilges, Prog. Part. Nucl. Phys. 70, 210-245 (2013)
[2] A. Bracco, E.G. Lanza, A. Tamii, Prog. Part. Nucl. Phys. 106, 360-433 (2019)
[3] A. Carbone et al., Phys. Rev. C 81, 041301(R) (2010)
[4] S. Goriely, E. Khan, M. Samyn, Nucl. Phys. A 739, 331-352 (2004)
[5] A. Maj et al., Acta Phys. Pol. B40, 565 (2009)
[6] A. R. Garcia et al., JINST 7, C05012 (2012)

Orateur: Marine Vandebrouck (CEA Saclay DPhN)

ARIS2023_MVandebrouck.pdf

18 Observation of the radiative decay of the low energy thorium-229 isomer: En route towards a nuclear clock

The radioisotope thorium-229 features a nuclear isomer with an exceptionally low excitation energy of ≈ 8 eV and a favourable coupling to the environment, making it a candidate for a next generation of optical clocks allowing to study fundamental physics such as the variation of the fine structure constant [1,2]. While first indirect experimental evidence for the existence of such a nuclear state dates from almost 50 years ago, the proof of existence has been delivered only recently by observing the isomer’s internal electron conversion decay [3]. This discovery triggered a series of successful measurements using the α-decay of uranium-233 of several properties, including its energy, an important input parameter for the development of laser excitation of the nucleus. In spite of recent progress, the difficulties to observe the isomer’s radiative decay remains a dark spot of this research field. The development towards a "nuclear clock" is further hindered by a too large uncertainty on the isomer energy.

In order to overcome limitations of previous experiments and to increase the population of the isomer while easing at the same time background contributions, a novel approach is used to populate the isomeric state in radioactive decay [4]. It is based on the β-decay of actinium-229 and
uses radioactive ion beams provided by the ISOLDE facility at CERN implanted into large-bandgap crystals.

In this contribution, a dedicated setup for the implantation of a francium/radium/actinium-229 beam into large-bandgap crystals and the vacuum-ultraviolet spectroscopic study of the emitted photons will be presented. From the results obtained during a first measuring campaign using MgF2 and CaF2 crystals as host material it can be concluded that the radiative decay of the thorium-229 isomer has been observed for the first time, the excitation energy of the isomer has been determined with a factor of 5 improved uncertainty.

References
[1] E. Peik et al., Europhys. Lett. 61, 2 (2003).
[2] E. Peik et al. Quantum Sci. Technol. 6 (3), 034002 (2021).
[3] L. von der Wense et al. Nature 533 (7601), 47–51 (2016).
[4] M. Verlinde et al., Physical Review C, 100, 024315 (2019).

Orateur: M. Sandro Kraemer (Instituut voor Kern- en Stralingsfysica, KU Leuven)

10:25 coffee break

parallel session

Président de session: Thomas Cocolios (KU Leuven)

19 Structure of $^{13}$Be using TexAT active target.

$^{13}$Be is the first neutron-unbound isotope of beryllium on the neutron-rich side. Its structure has been the subject of many experimental and theoretical studies with often conflicting results. Even the spin-parity of the ground state is still uncertain. We performed an experiment in which the T=5/2 states in $^{13}$B, the isobaric analogs of $^{13}$Be, were populated in $^{12}$Be+p resonance elastic scattering. The experiment was performed at TRIUMF using Texas Active Target (TexAT). New constraints on the structure of low-lying resonances in $^{13}$Be will be discussed.

Orateur: Grigory Rogachev (Texas A&M University)

ARIS_2023_Rogachev.pdf

20 Initial RI Beam Commissioning of the RAON ISOL Facility

The ultimate goal of RAON (Rare Isotope Accelerator Complex for Online Experiments) is to combine the Isotope Separator On-Line (ISOL) and In-Flight Separator (IF) systems to produce more exotic rare isotope (RI) beams and access unexplored regions of the nuclear landscape. As the first step, we completed the installation of the ISOL facility in June 2021. The RAON ISOL facility consists of a driver accelerator, a target/ion source (TIS) capable of full remote handling, a pre-mass separator, a Radio Frequency Quadrupole Cooler Buncher (RFQ-CB), an Electron Beam Ion Source Charge Breeder (EBIS-CB) and an A/q separator. The driver accelerator utilizes an H- Cyclotron with an energy of 70 MeV. The primary proton beam of up to 0.75 mA is delivered to the ISOL target/ion source (TIS) module, producing relatively pure and low-energy rare isotopes. The existing TIS module can accommodate up to 10 kW beam power, and it is expected that neutron-rich isotope ions will be produced by uranium fission reaction processes with the rates of 10$^{13}$ fission/s from the maximum beam power. The development of a high-power target and module system that can be operated reliably up to 70 kW proton beam power without compromising the yield of rare isotopes will be a future challenge.
The RI ion beams extracted from the TIS can be transported to the pre-mass separator and cooled in the RFQ-CB. Cooled ion beams can be sent to either a mass measurement system (MMS) or collinear laser spectroscopy (CLS) for the investigation of the fundamental properties of exotic nuclei in the ISOL experimental hall. Alternatively, RI beams can be transported to an A/q separator after charge breeding with the energy of 10 keV/u through RFQ-CB and EBIS-CB and later sent to the RAON injector system for post-accelerator.
The beam commissioning of the 70 MeV proton cyclotron was completed in January 2023, and the first RI beam commissioning using the SiC target for RAON ISOL has started.

Orateur: Dr Jinho Lee (Institute for Basic Science)

ARIS-2023(June 6)_ID530_JHLee.pptx

21 Shape coexistence studies of Pb-186 employing the SAGE spectrometer

Shape coexistence is a phenomenon in which the same nuclei can possess different macroscopic shapes. The  alpha-decay study for Pb-186 have shown a unique triplet of 0+ states which has been associated with spherical, prolate and oblate shapes [1]. Collective bands built upon these deformed 0+ states have been observed in in-beam gamma-ray spectroscopy experiments [2; 3]. However, gamma-ray spectroscopy can not probe E0 transitions which proceed primarily through internal conversion. These transitions are typically present in nuclei featuring shape coexistence.

Simultaneous conversion electron and gamma-ray studies for Pb-186 have been conducted exploiting the SAGE spectrometer [4] and the recoil-decay tagging technique, employing a 106Pd(83Kr,3n)186Pb fusion-evaporation reaction. The experiment was performed in 2013 at the Accelerator Laboratory of the University of Jyväskylä.

As a result of this experiment, direct feeding of the first excited 0+ state, which allowed us to reassign the shapes of the excited 0+ states in the Pb-186. Also, the 0+ -> 0+ transitions from the excited 0+ states to ground state, the E0 transitions of the 2+ -> 2+ and the 4+ -> 4+ transitions were observed. These results have been published in Communication Physics [5]. This work introduces a way to have systematic studies of E0 transitions in this region.
References
[1] A. N. Andreyev et al. Nature, 405:430 (2000).
[2] J. Heese et al. Phys. Lett. B, 302, 4:390 (1993).
[3] J. Pakarinen et al. Phys. Rev. C, 72:011304 (2005).
[4] J. Pakarinen et al. Eur. Phys. J. A, 50, 3:53 (2014).
[5] J. Ojala et al. Commun. Phys.5:1 (2022).

Orateur: Dr Joonas Ojala (University of Liverpool)

Pb-186_Aris_2023.pdf

22 Statistical and shell effect in beta-delayed neutron emission

With access to very neutron-rich isotopes, the neutron emission from excited states populated after beta decay becomes a dominant decay mode. The neutron energy measurement informs about beta-decay strength distribution, which is driven by shell effects. The neutron emission is considered to be statistical. Discrete neutron and gamma-ray spectroscopy measurements performed in nuclei ranging from 24O to 134In were performed with hybrid neutron arrays at RIBF, ISOLDE, NSCL, and FRIB. In addition to providing the first measurement of the strength distribution for many nuclei with a large beta-n energy window, we found evidence for non-statistical neutron emission process. It forced us to revisit a conventional picture of neutron emission thought to proceed via a compound nucleus phase. A model which connects nuclear structure and neutron emission was developed to explain the observed phenomena [1].

[1] J. Heideman et al. submitted to Phys. Rev. C.

Orateur: Prof. Robert Grzywacz (University of Tennessee)

ARIS_2023_01.pdf

23 Testing ab-initio calculations in light nuclei via high-precision spectroscopy

The development and improvement in terms of performances of accelerator facilities and detectors has paved the way for extending the study of nuclear structure towards more exotic nuclei and experimental quantities that have been, until now, less accessible.
In parallel, theoretical methods have advances in precision and prediction capabilities.
In recent years, ab-initio calculations in particular have proven to be powerful tools to address open questions in nuclear structure; one example is the role of three-body forces in the evolution of nuclear structure far from stability.
The importance of their contribution is evident in the case of the oxygen isotopic chain.
In fact, only by including these forces in the calculations it is possible to correctly reproduce the neutron dripline in correspondence of $^{24}$O, instead of $^{28}$O as predicted by standard calculations.
However, in order to quantify the contribution of these forces, spectroscopic information is crucial.

In this context, the $^{20}$O nucleus is a perfect playground for these measurements; in fact, the properties of the $2^+_2$ and $3^+_1$ states of this nucleus are expected to be influenced by three-body forces.
By measuring the spectroscopic properties of these nuclei, such as the excitation energy, the branching ratio and the lifetime, and comparing them to theoretical calculations, it is possible to understand the depth of their influence.

For these reasons, an experiment aimed at studying the $^{20}$O was performed in GANIL. The radioactive beam of $^{19}$O, provided by the SPIRAL1 complex, impinged on a deuterated target, populating the nucleus of interest by means of a $(d,p)$ reaction.
The target was deposited on a layer of gold in order to measure the lifetime of the states by using the Doppler-Shift Attenuation Method.
The recoils of the binary reaction were detected using the MUGAST array and the VAMOS++ magnetic spectrometer, while the $\gamma$ rays emitted were detected using AGATA.

The nucleus was first investigated via particle-$\gamma$ spectroscopy to reconstruct the level scheme and measure the branching ratios.
Then the lifetimes of the $2^+_2$ and $3^+_1$ states were measured. To do so, the experimental lineshapes were compared to realistic Monte Carlo simulations and the lifetimes were extracted by using the least-$\chi^2$ method.
Finally the reduced transition probabilities, B(E2) and B(M1) deduced from the lifetime measurements, were compared to ab-initio calculations.

In this contribution, the results of the particle-$\gamma$ spectroscopy and the lifetime measurements of the $2^+_2$ and $3^+_1$ states are reported.
An interpretation of the nature of the excited states of $^{20}$O is presented as well as the future perspectives for further investigation in this region.

Orateur: Irene Zanon (INFN-LNL)

Zanon_ARIS.pdf

24 Study of the N = 32 and N = 34 shell gap for Ca and Ar isotopes with quasi-free scattering reactions

Shell gaps represent the backbone of nuclear structure and are a direct fingerprint of the in-medium many-body interactions. The nuclear shell structure is found to change, sometimes drastically, with the number of protons and neutrons, revealing how delicate the arrangement of interacting nucleons is. The neutron-rich $\it{pf}$-shell nuclei have received much attention on both experimental and theoretical fronts with the possible appearance of new subshell closures at $\it{N}$ = 32 and 34. The N = 32 subshell closure has been reported in the region from Ar to Cr isotopes based on E(2$^{+}_{1}$), transition probability, and mass measurements. However, the laser spectroscopy of Ca and K isotopes reveals an increase of the charge radii with a slope larger than expected from $\it{N}$ = 28 to $\it{N}$ = 32 and 33, which were interpreted to challenge the magic character of $\it{N}$ = 32. For the $\it{N}$ = 34 subshell closure, experimental evidence favors a new doubly-magic nucleus $^{54}$Ca with a neutron subshell closure at $\it{N}$ = 34, although the systematics of E(2$^{+}_{1}$) and B(E2; 0$^{+}_{1}$ $\rightarrow$ 2$^{+}_{1}$) in Ti and Cr isotopes does not show any evidence for the $\it{N}$ = 34 magicity. It is natural to ask how the $\it{N}$ = 34 subshell evolves below $\it{Z}$ = 20 towards more neutron-rich systems, such as $^{52}$Ar.
In this presentation, I will present the quasi-free one-nucleon removal measurements performed at the RIBF facility using the MINOS and DALI2 set up to study the $\it{N}$ = 32 and 34 shell gaps in Ca and Ar isotopes. The $^{52}$Ca$(p,pn)$ reaction in inverse kinematics was performed at $\sim$230 MeV/nucleon. The measured partial cross sections and momentum distributions support the doubly-magicity of $^{52}$Ca. The analysis of the momentum distributions leads to a difference of the root-mean-square radii of the neutron 1f$_{7/2}$ and 2p$_{3/2}$ orbitals of 0.61(23) fm, in agreement with the modified-shell-model prediction of 0.7 fm suggesting that the large root-mean-square radius of the 2p$_{3/2}$ orbital in neutron-rich Ca isotopes is responsible for the unexpected linear increase of the charge radius with the neutron number. The low-lying structure of $^{52}$Ar was extracted using the $^{53}$K$(p, 2p)$ reaction. The 2$^{+}_{1}$ excitation energy is found at 1656(18) keV, the highest among the Ar isotopes with $\it{N}$ > 20. This result is the first experimental signature of the persistence of the $\it{N}$ = 34 subshell closure beyond $^{54}$Ca. Shell-model calculations with phenomenological and chiral-effective-field-theory interactions both reproduce the measured 2$^{+}_{1}$ systematics of neutron-rich Ar isotopes and support a $\it{N}$ = 34 subshell closure in $^{52}$Ar.

Orateur: Dr Hongna Liu (Beijing Normal University)

25 The N=126 Factory: A new multi-nucleon transfer reaction facility at Argonne National Laboratory

Multi-nucleon transfer (MNT) reactions between two heavy ions offer an effective method of producing heavy, neutron-rich nuclei that cannot currently be accessed efficiently using traditional projectile-fragmentation, target-fragmentation or fission production techniques [1]. These nuclei are important for understanding many astrophysical phenomena. For example, properties of the neutron-rich nuclei near the $N=126$ shell closure are critical to the understanding of the $r$-process pathway and the formation of the $A\sim195$ abundance peak [2]. The $N=126$ Factory currently under construction at Argonne National Laboratory's ATLAS facility will make use of these reactions to allow for the study of these nuclei [3]. Due to the wide angular distribution of MNT reaction products, a large-volume gas catcher will be used to convert these reaction products into a continuous low-energy beam. This beam will undergo preliminary separation in a magnetic dipole of resolving power $R\sim10^3$ before passing through an RFQ cooler-buncher and MR-TOF system of resolving power $R>10^5$, sufficient to suppress isobaric contaminants. These isotopically separated, bunched low energy beams will then be available for experimental systems at ATLAS such as the CPT mass spectrometer for precision mass measurements. Results of commissioning the component devices will be presented, as will the status of the final assembly and commissioning of the facility, which is expected to be operational this year.

This work is supported in part by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357; by NSERC (Canada), Application No. SAPPJ-2018-00028; by the National Science Foundation under Grant No. PHY-2011890; by the University of Notre Dame; and with resources of ANL’s ATLAS facility, an Office of Science User Facility.

[1] V. Zagrebaev and W. Greiner. PRL 101, 122701 (2008)
[2] M.R. Mumpower, R. Surman, G.C. McLaughlin, and A. Aprahamian. PPNP 86, 86–126 (2016)
[3] G. Savard, M. Brodeur, J.A. Clark, R.A. Knaack, and A.A. Valverde. NIM-B, 463, 258 – 261 (2020)

Orateur: Adrian Valverde (Argonne National Laboratory)

ValverdeARIS2023.pdf

parallel session

Président de session: Kyle Leach (Colorado School of Mines)

26 Precision half-life measurements of mirror transitions at Notre Dame

Despite its success, the Standard Model (SM) is currently being scrutinized on multiple fronts as it fails to explain many features of nature including the matter/anti-matter asymmetry, dark matter and even gravity. One probing mechanism for new physics is the unitarity test of the Cabibbo-Kobayashi-Maskawa matrix. A series of recent transition-independent radiative corrections resulted in a reduction of the Vud matrix element creating a 2.4 sigma tension with unitarity. Consequently, the determination of this matrix element, derived from the ft-value of superallowed beta decays, is under scrutiny. While superallowed pure Fermi transitions currently allow for the most precise determination of Vud, there is currently a growing interest in obtaining that matrix element from superallowed mixed transitions to test the accuracy of Vud and the calculation of isospin symmetry breaking corrections. In the past few years, a research program aimed at solidifying the determination of Vud from mirror transitions was initiated using radioactive ion beams from the Twin Solenoid (TwinSol) separator at the Nuclear Science Laboratory of the University Notre Dame. As part of this program, several half-lives have been measured, some for the first time in 40 years, to relative uncertainties in the 0.01% range. These range from 11C to 33Cl and include the measurement of 20F and, more recently, 28Al, which are also both of interest for searches of second-class currents. These recent measurements as well as future measurements will be presented.

Orateur: Maxime Brodeur (University of Notre Dame)

MBrodeur-ARIS2023-v2.pdf

27 Electromagnetic Dipole Response of Nuclei: Exploring Nuclear Structures and Constraining Nucleosynthesis Processes

The gamma-ray decay of nuclear states in the quasi-continuum provides important insights into nuclear structure effects and constraints to nucleosynthesis processes. In particular, measurements of Nuclear Level Densities (NLDs) and Photon Strength Functions (PSFs) have and will continue to play a central role as we are entering an era of incredible potential for novel measurements. This is due to many institutes across the world having established programs to provide enhanced, state-of-the-art research infrastructure. These range from significant increases in efficiencies for particle and gamma-ray detectors, to new or upgraded radioactive ion beam facilities. In parallel, several new experimental and analytical techniques were developed which allow for more reliable PSF and NLD studies, even on nuclei away from stability. All this progress will undoubtedly lead to unprecedented insight into the structure of nuclei and provide reaction rates of relevance to nucleosynthesis processes.

In this talk, I will provide an overview of the most significant advances made and how these have laid the foundation for novel and ambitious measurements of PSFs and NLDs at radioactive and stable ion beam facilities. I will further discuss recent progress in exploring the underlying nuclear structure of resonances from PSF measurements, focusing on the scissor’s mode and the low-energy enhancement, whose mechanisms are still not fully understood. Our understanding of observed isotopic abundances can be improved greatly through the measurement of PSFs and NLDs as will be demonstrated.

This work is supported by the National Research Foundation of South Africa under grant number 118840.

Orateur: Mathis Wiedeking (iThemba LABS and University of the Witwatersrand)

ARIS_2023_Wiedeking.pdf

28 Search for $^{22}$Na in novae supported by a novel method for measuring femtosecond nuclear lifetimes

Astrophysical simulations predict that $^{22}$Na is produced in novae explosions. With its half-life of 2.6 years and its characteristic $\gamma$-ray of 1.275 MeV, it could be easily identified and measured with $\gamma$-ray space telescopes, which has not been the case yet. The amount of $^{22}$Na produced in novae depends on the rate of nuclear reactions, and in particular on the $^{22}$Na($p,\gamma)^{23}$Mg reaction rate. It has been shown that the amount of $^{22}$Na ejected from novae is directly proportional to the lifetime of the excited state at Ex=7.785 MeV in $^{23}$Mg.

We have measured this lifetime in an experiment at GANIL-France, associating the VAMOS++ magnetic spectrometer, the AGATA $\gamma$-ray tracking spectrometer and a silicon detector. The analysis of angle-integrated velocity-difference profiles allowed us to obtain a femtosecond sensitivity.

The obtained result places strong limits on the amount of $^{22}$Na produced in novae, explains its non-observation to date in $\gamma$ rays (flux $<$~2.5$\times$10$^{-4}$~ph.cm$^{-2}$s$^{-1}$), and constrains its detectability with future space-borne observatories.

Ref: https://arxiv.org/abs/2212.06302

Orateur: Dr François de Oliveira Santos (GANIL)

oliveira_final.pdf

29 First measurement of a p-process reaction using a radioactive ion beam

Approximately 30 stable nuclides on the neutron-deficient side of stability cannot be produced via the same neutron-capture driven mechanisms responsible for synthesizing all other elements heavier than iron. These “p-nuclei” are instead thought to originate from photodisintegration reactions on s- and r-process seed nuclei, which can occur in the extreme high-temperature environments of core-collapse supernovae. However, significant discrepancies exist, in some cases extending to orders of magnitude, between observed p-nuclei abundances obtained via isotopic analysis of meteorite samples, and supernovae model predictions. Improving on the available nuclear reaction data is an essential part of solving the puzzle of the p-nuclei, but experimental efforts in this regard must overcome significant technical challenges. This talk will describe the first ever measurement of a p-process reaction cross-section obtained with a radioactive ion beam. The 83Rb(p,γ)84Sr reaction was investigated at the TRIUMF-ISAC facility using a radioactive 83Rb beam impinged on CH2 foil targets. The recoiling reaction products were selected by m/q using the newly commissioned Electromagnetic Mass Analyser (EMMA), with γ-rays detected in-coincidence using the TIGRESS HPGe array. The high sensitivity of the combined EMMA-TIGRESS set-up allowed detection of low-lying transitions in 84Sr populated by 83Rb(p,γ)84Sr. The measured partial cross-section was then combined with statistical model calculations to obtain a total reaction cross-section that is 4x smaller than predicted, in-turn affecting the abundance of the 84Sr p-nucleus predicted by massive-star models.

Orateur: Matthew Williams (Lawrence Livermore National Laboratory)

ARIS_2023_Presentation_Rb83pg.pptx

30 Determination of fission barrier height of 210Fr via neutron measurement

Fission of 210Fr, produced by (d,p)-transfer reaction of the 209Fr beam was investigated at HIE-ISOLDE. Four Timepix3 pixel detectors were installed on the body of Actar TPC demonstrator chamber. Polyethylene converters were used for the detection of fast neutrons. Since no significant background was observed, it was possible to measure the spatial distribution of emitted neutrons. Subsequent simulations employing the results of Talys code and available data on fission fragment distributions allowed to estimate directly the value of fission barrier height for neutron-deficient nucleus 210Fr, which confirmed the reduction of the fission barrier compared to theoretical models by 15 - 30 % for such extremely neutron-deficient unstable nuclei.

Orateur: Martin Veselský (Czech Technical University Prague)

aris2023.pdf

31 First study of proton capture reaction on stored radioactive $^{118}$Te beam

For the first time, the proton capture reaction for a stored radioactive isotope has been directly measured. This measurement became possible by combining two unique facilities at GSI (Helmholtz Centre for Heavy Ion Research),
the fragment separator (FRS) and the experimental storage ring (ESR). The combination of sharp ion energy, ultra-thin internal gas target, and the ability to adjust the energy of the beam in the ring enables precise, energy-differentiated measurements of the (p,$\gamma$)-cross-sections. This provides a sensitive method for measuring (p,$\gamma$) and (p,n) reactions relevant for nucleosynthesis processes in supernovae, which are among the most violent explosions in the universe and are not yet well understood.

The cross section of the $^{118}$Te(p,$\gamma$) reaction was measured at energies of astrophysical interest. The heavy ions were stored with energies of 6~MeV/u and 7~MeV/u and interacted with a hydrogen gas-jet target providing the protons. A Double-sided silicon strip detector was used in order to detect the produced $^{119}$I ions. The radiative electron capture process occurring in collisions of the fully stripped $^{118}$Te ions with electrons from the hydrogen target were used as a luminosity monitor.
These measurements follow a proof-of-principle experiment which was performed in 2016 to validate the method on the stable isotope $^{124}$Xe [1].
An overview of the experimental method and preliminary results from the ongoing analysis will be presented.

[1] J. Glorius et al., Phys. Rev. Lett. 122, 092701 (2019)

Orateur: Sophia Florence Dellmann (Goethe University Frankfurt)

ARIS_SDellmann.pptx

32 Simultaneous pH sensing and gamma-ray imaging via angular correlation measurement using cascade nuclides

Gamma-ray imaging techniques such as positron emission tomography and single photon emission computed tomography (SPECT) have been utilized in nuclear medicine for diagnosis. The radioactive tracer imaging can provide functional or metabolic information non-invasively at the molecule or cellular level. However, nuclear medicine imaging techniques cannot extract the local molecule or cellular environment information. While single photon emission radionuclides are conventionally used for SPECT, some of them emits two or more cascade photons with a short duration of intermediate state; for example, In-111 emits 171 keV and 245 keV gamma-rays with 84.5 ns time constant. An angular correlation between cascade photons that originates from the nuclear spin state is perturbed by the external fields. We have proposed a novel simultaneous gamma-ray imaging and local environment sensing method via the angular correlation measurement, which provides radionuclide position and its local environmental information simultaneously. In this study, we demonstrated simultaneous measurements of angular correlation and gamma-ray imaging using 8 x 8 array high-resolution Gd3(Ga,Al)5O12(Ce) scintillator detectors coupled with silicon photo multipliers (Hamamatsu, S13361-3050). We succeeded to obtain the local pH information of In-111 solution and the accumulation image simultaneously. We will report the detail in our presentation.

Orateur: Dr Mizuki Uenomachi (Kyoto University)

20230606_ARIS_uenomachi_v2.pptx

12:45 lunch break

parallel session

Président de session: Jens Lassen (TRIUMF - Canada's particle accelerator centre)

33 First results from ATLANTIS - A new collinear laser spectroscopy setup at Argonne National Laboratory

The region of refractory metals, below the magic number $Z=50$ is of particular interest for nuclear physics studies and exhibits phenomena such as deformations, shape coexistence and hints of triaxial nuclei. Laser spectroscopy has provided valuable and complementary input, providing information about the shape, size and electromagnetic moments of radioactive isotopes and isomers in this region. The CARIBU californium-252 fission source at Argonne National Laboratory can uniquely produce sufficiently intense low-energy ion beams of neutron-rich isotopes in this part of the nuclear chart. Therefore, the new collinear laser spectroscopy setup, ATLANTIS – the Argonne Tandem hall LAser beamliNe for aTom and Ion Spectroscopy– was installed at the low-energy branch of CARIBU.

The setup includes a dedicated open-gate cooler-buncher that prepares and delivers cooled ion beams with minimal energy and time spread and a laser ablation source to produce stable isotope beams. The laser spectroscopy beamline is fitted with a low-energy charge exchange cell suited for high-temperature application to also allow spectroscopy on atomic beams and a highly efficient 4$\pi$ mirror system to collect fluorescence ions.

In this talk, the results of the first measurements of short-lived isotopes of palladium and ruthenium obtained at ATLANTIS will be discussed, and an outlook of future laser spectroscopy endeavors at Argonne National Laboratory will be given.

This work was supported by DFG – Project-Id 279384907-SFB 1245, BMBF 05P19RDFN1 and NSF Grant No. PHY-21-11185, and by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357, with resources of ANL’s ATLAS facility, an Office of Science User Facility.

Orateur: Bernhard Maaß (Argonne National Laboratory)

bernhard_maass_ARIStuesday.pdf

34 Electromagnetic moments of the antimony ($Z=51$) isotopic chain $^{112-133}$Sb in comparison to shell-model ab initio calculations

Antimony (Sb) contains 51 protons, one proton above the magic $Z = 50$ proton shell closure. Therefore, its nuclear magnetic moments serve as an ideal candidate to probe the proton single particle behavior along the Sb isotopic chain, while its quadrupole moments shed light on collective effects as a function of neutron number towards the shell closure at $N = 82$.

Phenomenological shell-model calculations work well in the mass region around magic tin. Moreover, ab initio methods such as the valence-space in-medium similarity renormalization group (VS-IMSRG) have recently expanded their scope and are now capable of computing nuclear properties around $Z = 50$. Following collinear laser spectroscopy measurements of the antimony isotopic chain from $^{112-133}$Sb, the experimental magnetic and quadrupole moments are compared to their calculation in the phenomenological shell-model and VS-IMSRG. Since both nuclear models employ the same valence-space diagonalization, their full comparison as well as the artificial use of the shell model’s effective g-factors and charges in VS-IMSRG allows to investigate the operator-evolution within VS-IMSRG separated from the obtained wave functions.

This contribution will present the new experimental results from collinear laser spectroscopy and discuss the underlying physics with the help of state-of-the-art shell-model and ab initio calculations.

Orateur: Simon Lechner (CERN)

Simon_Lechner_Sb.pdf

35 Storage ring facilities for radioactive ions -New detectors and upgrade plans

I will overview storage-ring nuclear physics at GSI/FAIR and RIKEN with a focus on recent technical developments with future perspectives. The experimental storage ring ESR at GSI has pioneered mass measurements of exotic nuclei and decay studies of highly charged ions (HCI)[1]. Radioactive ions produced at the fragment separator FRS are in-flight separated and are stored into the ESR where two methods of mass spectrometry have been established. One is the time-resolved Schottky mass spectrometry where stored ions, cooled with the stochastic and/or electron cooling techniques, are frequency analyzed by non-destructive Schottky detectors, and the other is the isochronous mass spectrometry where revolutions of short-lived ions are directly measured by an in-ring dedicated time-of-flight detector under a specific optical condition. The FRS-ESR facility features relativistic energy and cooled heavy ions, highlighted by the discovery of new isotopes, new long-lived isomers, and the observation of bound-state beta decays, hyperfine effects of HCI. The facility will be upgraded to the FAIR ring branch based on the Isomeric beams, Lifetimes and Masses (ILIMA) collaboration.
The RI Beam Factory (RIBF) at RIKEN features the largest cyclotron facility complex. Taking advantage of the highest intensities of radioactive ions, a new mass spectrometer, Rare-RI Ring (R3) [2], for exotic nuclei has recently been launched. The spectrometer consists of a cyclotron-like storage ring coupled with the fragment separator BigRIPS. The isochronous mass spectrometry is employed, where only dipole magnets form a weak focusing lattice to realize the precise isochronous optical condition with a large momentum acceptance. Because of the beam characteristic, exotic nuclei of interest are individually, in-flight selected to be stored in the storage ring. Thus, single-ion mass spectrometry with the individual injection scheme has been accomplished. The first application for neutron rich Pd isotopes has recently been published [3].
Both facilities are unique and complementary. Collaborative technical studies are proceeding toward common goals; a position-sensitive transverse Schottky detector has been designed at GSI and will be tested at RIKEN. A high-resolution GAGG(Ce) crystal telescope (~50 ps time and ~1% energy resolution) was tested with heavy ions at the Heavy Ion Medial Accelerator in Chiba (HIMAC) facility in Japan and has been installed as a decay study pocket detector at the ESR. Additionally, new specific detectors: a time-of-flight detector based on delta-ray readout technique (~80 ps time resolution) and low-cost position-sensitive plastic scintillation detectors with fiber readout techniques (~1 mm spatial resolution) have been developed in Japan, which can be extended as a general purpose as well. With these instruments, the facilities will be upgraded for decay and reaction studies, beyond conventional mass measurements, of exotic nuclei available at both facilities.

References
[1] F. Bosch et al., Prog. Part. Nucl. Phys. 73, 84 (2013).
[2] A. Ozawa et al., Prog. Theor. Exp. Phys. 2012, 03C009 (2012).
[3] H. F. Li et al., Phys. Rev. Lett. 128, 152701 (2022).

Orateur: Takayuki Yamaguchi (Saitama University)

36 Indirect measurements of neutron-induced reaction cross-sections at heavy-ion storage rings

Obtaining reliable cross sections for neutron-induced reactions on unstable nuclei nuclei is crucial to our understanding of the stellar nucleosynthesis of heavy elements and for applications in nuclear technology. However, the measurement of these cross sections is very complicated due to the radioactivity of the targets involved. The NECTAR (NuclEar reaCTions At storage Rings) project aims to circumvent this problem by using the surrogate-reaction method in inverse kinematics. A heavy, radioactive nucleus in the beam is to interact with a light, stable nucleus in the target to produce the compound nucleus formed in the neutron-induced reaction of interest via an alternative or surrogate reaction such as transfer or inelastic scattering. This compound nucleus may decay by fission, neutron or gamma-ray emission, and the probabilities for these modes of decay are to be measured as a function of the excitation energy of the compound nucleus. This information is used to constrain model parameters and to obtain much more accurate predictions of neutron-induced reaction cross sections [1].
Yet, the full development of the surrogate method is hampered by numerous long-standing target issues. The objective of the NECTAR project is to solve these issues by combining surrogate reactions with the unique and largely unexplored possibilities at heavy-ion storage rings. In these storage rings, heavy radioactive ions revolve at high frequency passing repeatedly through an electron cooler, which greatly improves the beam quality and restores it after each passage of the beam through the internal gas-jet serving as ultra-thin, windowless target. This way, excitation energy and decay probabilities can be measured with unrivaled accuracy.
In this contribution, we will present the technical developments and the methodology, which we are developing within NECTAR to measure for the first time simultaneously the fission, neutron and gamma-ray emission probabilities at the heavy-ion storage rings of the GSI/FAIR facility. In particular, we will present the first results of the proof of principle experiment, which we successfully conducted in June 2022 at the ESR storage ring of GSI/FAIR.

[1] R. Pérez Sánchez, B. Jurado et al., Phys. Rev. Lett. 125 (2020) 122502

Orateur: Michele Sguazzin (CNRS/LP2iB)

Indirect measurements of neutron-induced reaction cross-sections at heavy-ion storage rings .pptx

37 Probing the $N=152$ neutron shell gap by laser spectroscopy of fermium isotopes

Determining the limits of existence of the heaviest nuclides is a forefront topic in nuclear-physics research [1]. Nuclides with proton numbers $Z\geq$100 are stabilized by shell effects that retard spontaneous fission and they feature properties distinctly different from those of lighter nuclei. However, our understanding of such shell effects in the region of the heaviest elements is limited as predictions by state-of-the-art nuclear models are challenging and experimental studies are hampered by production capabilities. Recent mass measurements confirmed the location and the size of such a shell gap leading to an increased nuclear stability at neutron number $N=152$ in a region of strong prolate deformation [2,3].
Here, laser spectroscopy can serve as a powerful tool to extract experimental information on nuclear parameters such as the change in the mean-square charge radii and nuclear moments in a nuclear-model independent manner [4,5]. Access to the heaviest elements however is limited by production yields, their short half-lives and sparse information on atomic levels. The recent findings in the heavy actinide element nobelium ($Z=102$) with the RADRIS method paved the way for such observations [6,7].
New studies of fermium (Fm, $Z = 100$) isotopes allowed the determination of the isotope shift in an atomic transition for a long chain of eight isotopes ranging from the accelerator-produced $^{245}$Fm to the reactor-bred $^{257}$Fm. On-line and off-line laser spectroscopy techniques were significantly advanced to access these isotopes via various production methods down to minute production rates. The investigated isotopic chain spans across the known deformed shell gap at $N = 152$ allowing to probe its effect on changes in the mean-square charge radii. The experimental results revealing a discontinuity in the evolution of mean-square charge radii around the neutron shell gap will be discussed. These observations will trigger new developments in theoretical models which will eventually improve their predictive power towards the heaviest elements.
[1] W. Nazarewicz et al., Nat Phys 14, 537–541 (2018).
[2] E. Minaya Ramirez et al., Science 337, 1207–1210 (2012).
[3] C. Theisen et al., Nucl Phys A 944, 333–375 (2015).
[4] X. Yang et al., Prog Part Nucl Phys 129, 104005 (2023).
[5] M. Block et al., Prog Part Nucl Phys 116, 103834 (2021).
[6] M. Laatiaoui et al., Nature 538, 495–498 (2016).
[7] S. Raeder et al., Phys Rev Lett 120, 232503 (2018).

Orateur: Mlle Jessica Warbinek (GSI Helmholtzzentrum für Schwerionenforschung GmbH; Johannes Gutenberg-Universität Mainz)

ARIS2023_JWarbinek.pptx

38 Island of inversion at the N=Z line

The development of collectivity along the $N=Z$ is one of the subjects that has recently attracted great experimental efforts. In particular, heavy $N=Z$ nuclei in the mass region $A=80$ are expected to be some of the most deformed ground states which have been found [1] in mid-mass nuclei, typically $8p-8h,12p-12h$ for e.g. the cases of $^{76}$Sr, $^{80}$Zr. This strong enhancement of collectivity with respect to lighter $N=Z$ nuclei has its origin
in cross shell excitations across the $N=40$ shell gap to $g9/2$, $d5/2$ and $s1/2$ which are intruder quadrupole partners generating deformations.
These structures can be interpreted in terms of algebraic Nilsson-SU3 self-consistent model to describe the intruder relative evolution in the vicinity of $^{80}$Zr [2]. In this presentation, we will expose some of the latest developments in microscopic nuclear structure calculations for exotic nuclei far from stabilitity at the N=Z [3].
The new theoretical calculations for the very region of $^{80}$Zr will be presented for the first time within the interacting shell model framework using an enlarged model space outside a $^{56}$Ni core comprising the pseudo-SU3 $p_\frac{3}{2}f_\frac{5}{2}p_\frac{1}{2}$ and quasi-SU3 $g_\frac{9}{2}d_\frac{5}{2}s_\frac{1}{2}$ orbitals for both protons and neutrons. We will present and compare results from both exact Shell Model diagonalization [4] and our newly developed DNO Shell Model approach employing beyond mean field techniques [5]. These theoretical calculations allow a very good description of the rapid transition ($A=60-100$) from spherical to deformed structures which can be intepreted in terms of ``simple'' many particles - many holes configurations. Emphasis will be put on the intimate relationship between shell evolution far from stability at the neutron-rich AND proton-rich edges.

[1] R. D. O. Llewellyn et al., Phys. Rev. Lett. 124, 152501 (2020).
[2] A. P. Zuker et al., Phys. Rev. C 92, 024320 (2015)
[3] D. D. Dao, F. Nowacki, A. Poves in preparation
[4] E. Caurier, G. Martínez-Pinedo, F. Nowacki, A. Poves, and A. P. Zuker, Rev. Mod. Phys. 77, 427 (2005).
[5] D. D. Dao and F. Nowacki, Phys. Rev. C 105, 054314 (2022).

Orateur: Dr Frederic NOWACKI (IPHC Strasbourg)

Nowacki-Aris.pdf

39 Towards in-gas-jet studies of isomeric 229Th+

Short half-lives, low production rates and the need to produce them by fusion-evaporation reactions all complicate laser spectroscopy studies of (trans)actinides. The In-Gas Laser Ionization and Spectroscopy (IGLIS) technique has been succesfully employed in studies on short-lived actinides (see for instance [1,2]). The addition of a convergent-divergent (de Laval) nozzle to create a cold hypersonic gas jet combines efficiency with sub-GHz spectral resolution. The new generation of nozzles with a Mach number of $8$ enables laser spectroscopy studies of actinides with spectral resolutions around $200 \,$ MHz [3].

The light actinide $^{229}$Th and its nuclear clock isomer have attracted significant attention in the last years. A remarkable feature is the suggested short half-life ($ < 10 \,$ ms) of the isomer in its, not-yet observed, singly charged state [4]. We report on the design of a fast-extraction gas cell (evacuation time of $ \sim 1 \, $ ms) and tailor-made recoil ion sources of $^{233}$U prepared by TU Vienna and JGU Mainz which are installed inside the gas cell to provide the isomeric thorium ions. A new set of de Laval nozzles was designed and characterized to operate under the required low-stagnation-pressure conditions of the recoil sources as well as for spectroscopy studies of (trans)actinides in the JetRIS experiment at GSI [5]. A level search above the second ionization potential of thorium revealed several auto-ionizing states which are used to improve laser ionization efficiency for future in-gas-jet laser spectroscopy studies of $^{229m}$Th$^+$.

[1] C. Granados et al. Phys. Rev. C, 96:054331, 2017.
[2] S. Raeder et al. Phys. Rev. Lett., 120:232503, 2018.
[3] R. Ferrer et al. Physical Review Research, 3:043041, 2021.
[4] L. von der Wense et al. Nature, 533:47–51, 2016.
[5] S. Raeder et al. Nucl. Instrum. Methods Phys. Res. B, 463:272–276, 2020.

Orateur: Arno Claessens (KU Leuven)

ARIS-2023_talk _ArnoClaessens.pptx

parallel session

Président de session: Prof. Wilton Catford (University of Surrey)

40 Isospin symmetry in the A=78 triplet - gamma-ray spectroscopy of 78Y and 78Zr

The isospin symmetry concept has its origins in the charge-symmetry and charge-independence characteristics of the strong nuclear force. This implies that the strong interaction has an equal strength between the proton-proton, neutron-neutron and proton-neutron pairs. Therefore, the isobaric analog nuclei of the same mass A = N + Z, but with the neutron and proton numbers differing as N = Z - 2, N = Z and N = Z + 2, should contain the same set of excited states at similar excitation energies. This assumption holds in the absence of the electromagnetic effects, but in practice the isobaric analog states (IAS) manifest energy differences resulting, e.g., from the Coulomb interaction. Investigations of the Coulomb, mirror and triplet energy differences have proven to be an effective probe for the nuclear structure, but have also provided information on the conservation of the isospin symmetry. During the past two decades a wealth of evidence has been collected for an isospin-breaking two-body interaction in the A = 50 - 70 mass region. This additional schematic interaction, in combination with the Coulomb force, appears to be required to reproduce the experimental data on the triplet energy differences.

Since the N = Z line approaches the proton-drip line in the A > 70 mass region, spectroscopic data for these triplets are scarce, which in turn prevents the investigations of the energy differences between IAS. This is particularly true for the mass A = 78 triplet ($^{78}$Zr, $^{78}$Y and $^{78}$Sr). The excited states in $^{78}$Zr are not currently known at all, while only two excited states have been tentatively assigned in $^{78}$Y. Recently, an experiment was performed at the Accelerator Laboratory of the University of Jyvaskyla to investigate the structures of $^{78}$Zr and $^{78}$Y. This study employed the $^{40}$Ca($^{40}$Ca, 2n/pn)$^{78}$Zr/$^{78}$Y fusion evaporation reaction, the JUROGAM 3 Ge-array coupled to the vacuum-mode recoil separator MARA and the recoil-beta tagging technique. The preliminary analysis of this data has resulted in the discovery of several new excited states in $^{78}$Y and a candidate for the 2$^+$ -> 0$^+$ transition in $^{78}$Zr observed via recoil-beta-beta correlations. This presentation discusses the new experimental results obtained for the mass A = 78 triplet in the context of the predictions obtained from nuclear theory.

Orateur: Dr Panu Ruotsalainen (University of Jyväskylä)

41 Isospin-symmetry breaking in the $B(E2)$ transitions of $T=1$ isotriplets

The study of $T=1$ triplets plays an important role in our understanding of isospin physics. A linear dependence of the proton matrix elements ($M_p$) with respect to isospin projection $T_Z$ indicates the isospin purity of states, an effect that has been studied and observed for triplets of 22 $\leq$ $A$ $\leq$ 50 [1]. As measurements of reduced electromagnetic transition probabilities become available for heavier $T_Z=-1$ nuclei, some studies suggest that beyond-Coulomb isospin symmetry-breaking (ISB) effects affect this observable in mirror nuclei [2].

In this work, we investigate all even-even $T=1$ mirrors with 42 $\leq$ $A$ $\leq$ 98 within the nuclear-density-functional-theory (nuclear-DFT) approach and analyse systematic properties of the obtained $B(E2: 0^+ \rightarrow 2^+)$ values. For this purpose, we use the numerical software HFODD [3] to identify the deformed minima and to perform angular momentum projection. In addition, we employ the Generalised Bohr Hamiltonian [4, 5] to study effects of the quadrupole collectivity. For both methods, we utilise the Skyrme energy density functional with the UNEDF1 parameterisation [6]. We compare the obtained results with the available experimental data. Our results show significant differences between the mirror pairs without considering beyond-Coulomb ISB effects.

Furthermore, for the $A=70$ and $A=78$ triplets, including the odd-odd $N=Z$ nuclei, we perfom calculations utilising a variety of nuclear-DFT parameterisations. The $A=70$ triplet is the heaviest one for which the $B(E2)$ are known for all members, whereas the $A=78$ triplet is the subject of interest for further experimental measurements. To obtain the $B(E2)$ of the odd-odd $N = Z$ nuclei, we performed the angular-momentum projection of the Hartree-Fock-Bogoliubov states with pair-blocked configurations. Our results allow for a full investigation of the linearity of $M_p$ in function of $T_z$.

References:
[1] A. Boso et al., Physics Letters B 797 (2019) 134835;
[2] K. Wimmer et al., Physical Review Letters 126 (2021) 072501;
[3] J. Dobaczewski et al., J. Phys. G: Nucl. Part. Phys. 48 (2021) 102001;
[4] L. Próchniak and S. G. Rohoziński, J. Phys. G: Nucl. Part. Phys. 36 (2009) 123101;
[5] D. Muir, PhD thesis, University of York (2021);
[6] M. Kortelainen et al., Phys. Rev. C, 85 (2012) 024304.

Orateur: Betania Camille Tumelero Backes (University of York)

ARIS-betania-backes.pdf

42 Probing the rapid onset of deformation below $^{68}$Ni through the beta decay of $^{67}$Mn

One of the best-known divergences from the independent-particle shell model description is the existence of islands of inversion [1]. The IoI of the region N=40 draws particular attention since the neutron number 40 was postulated as a non-traditional “magic” number and N = 40 represents the boundary between the negative-parity pf shell and the positive-parity g shell. In stable nuclei, the neutron g$_{9/2}$ orbital is close enough to the pf shell to reduce this shell gap resulting in a more stable subshell closure at N = 50. Measurements of B(E2) values and E(2$^{+}$) in the neutron-rich region show increased collectivity through the N = 40 shell gap, with the clear exception of $^{68}$Ni [2,3]. Deformation and shape coexistence have been identified in the area, LNPS calculations predict triple shape coexistence for $^{67}$Co (N=40), with three rotational bands [4]. And, recent experiments on $^{67}$Fe (N=41) propose a spin-parity of $5/2^+$ or $1/2^-$ for its ground state [5] which indicates a significant deformation. In addition, shape coexistence is also expected for $^{67}$Fe. Despite the high interest in the region, very limited information is available, to this end, an experiment was performed at the TRIUMF-ISAC facility utilizing the GRIFFIN spectrometer [6], where the β and βn decay of $^{67}$Mn populated the $^{67,66}$Fe, $^{67,66}$Co and $^{67,66}$Ni isotopes.
This data set contains orders of magnitude more statistics than previous studies allowing us to build for the first time a complete level scheme of $^{67}$Fe and $^{67}$Ni, and to improve upon the known $\beta$- decay level schemes of $^{67}$Co, by expanding the number of transitions and levels, as well as by improving the precision of branching ratios and ground-state half-life measurement. In addition, measurements of level lifetimes down to the picosecond range will allow us to investigate the band structure in these nuclei. For the $^{67}$Fe isotope, the good level of statistics will make it possible to measure the energy of the identified isomeric state and improve the lifetime measurement.
These results can provide further insight into the detailed structure of the states by comparison to simple models and large-scale shell model calculations in order to confirm or refute the shape coexistence picture predicted by LNPS calculations and the shrinking of the N=40 gap just one proton below $^{68}$Ni.
Preliminary results from the analysis will be presented and discussed.
References
[1] B. A. Brown. Physics, 3:104 (2010).
[2] S. Naimi et al.,Phys. Rev. C 86 (2012), p. 014325
[3] M. Hannawald et al., Phys. Rev. Lett. 82 (1999), pp. 1391–1394.
[4] F. Recchia et al.,Phys. Rev. C, 85:064305 (2012)
[5] M. Sawicka et al., The European Physical Journal A - Hadrons and Nuclei, 16(1):51–54, 2003
[6] Garnsworthy et al., Nucl. Inst. Meths. A 918, 9 (2019)

Orateur: Victoria Vedia (TRIUMF)

43 Towards N=126 shell closure using multi-nucleon transfer reaction between 136Xe and 198Pt

The neutron-rich unstable nuclei in the vicinity of neutron magic numbers are relatively well studied, far from the stability lineup to the neutron magic number N = 82. However, for the neutron-rich nuclei to the south of 208Pb, there is limited knowledge of the excited states of these nuclei. This arises from the difficulty in producing these nuclei using conventional methods. Even for nuclei that have already been produced only limited information is known. The recent multi-nucleon transfer reaction showed promising results with several orders of magnitude larger cross-sections than those for fragmentation reactions.
A new experiment was carried out at GANIL to explore these isotopes of interest using multi-nucleon transfer reactions of 7MeV/u 136Xe beam and 198Pt target. Large acceptance VAMOS++ magnetic spectrometer and AGATA Ge tracking array were used to measure excited states of nuclides of interest. And several new experimental techniques were implemented in this experiment. First, a second arm detector was newly installed, which is composed of a vacuum chamber and multi-wire proportional counter to measure the velocity vector of the target-like fragments. Second, four EXOGAM HPGe clover array was installed at the end of the second arm to measure the delayed gamma rays from the excited states of the produced nuclei. Finally, a new method to determine particle identification is under development using a machine learning algorithm, where energy and charge states are determined using supervised machine learning and atomic numbers are determined by the unsupervised learning method. The preliminary result of the experiment such as particle identification with the help of machine learning and gamma-ray spectroscopy neutron-rich nuclei will be presented.

Orateur: Yung Hee KIM (Center for Exotic Nuclear Studies, Institute for Basic Science)

44 Towards the r-process path at N=126

The 208Pb nuclide is the heaviest known doubly-magic nucleus. Information on its neutron-rich neighbourhood is rather scarce, due to the limited mechanisms by which these nuclei can be populated. However, experimental information on neutron-rich N=126 nuclei is of paramount importance not only for nuclear structure physics, but also for implications for astrophysics. Theoretical predictions for exotic nuclei in this region are essential inputs into nucleosynthesis calculations, influencing the yields in the A~195 r-process peak.
Neutron-rich nuclei around 208Pb are under intense scrutiny. However, no B(E2;2+->0+) transition strength was extracted on any of the N=126 nuclei below 208Pb. This quantity, connected to the wave functions of the involved states, often provide the first hint of the erosion of the magicity by exhibiting enhanced collectivity.
The radioactive semi-magic two proton-hole 206Hg nucleus was Coulomb excited for the first time at a safe beam energy using the HIE-ISOLDE facility at CERN [1]. Two gamma rays depopulating low-lying states in 206Hg were observed. The determined reduced transition strength B(E2;2+->0+) of the 1068 keV transition is in line, but slightly lower, than the shell-model predictions. Furthermore, a collective octupole state was identified, and the corresponding transition strength of was extracted. The obtained results were confronted with large scale shell model and time-dependent Hartree-Fock calculations, and are crucial for furthering understanding of both quadrupole and octupole collectivity in the neutron-rich vicinity of the heaviest doubly-magic nucleus 208Pb.
The most exotic N~126 nuclei studied so far were populated in fragmentation reactions at GSI (see e.g. [2,3]). Within the FAIR-0 experimental campaign a number of such studies will be performed within the DESPEC (Decay Spectroscopy) collaboration in spring 2022. An experiment aimed at the beta decay and isomeric decays of the most neutron-rich N=126 nuclei presently accessible, 202Os and 203Ir took place May 2022. The obtained statistics is an order of magnitude higher than previously [2].
The status of knowledge on neutron-rich N=126 nuclei will be presented. This will include the new results on the Coulomb excitation of 206Hg, and hopefully isomeric decays in 202Os, as well as recent works on the competition between allowed and first-forbidden beta decays [4].

[1] L. Morrison et al., Phys. Lett. B 838, 137675 (2023)
[2] S.J. Steer et al., Phys. Rev. C 84, 044313 (2011).
[3] A.I. Morales et al., Phys. Rev. Lett. 113, 022702 (2014).
[4] R.J. Carrol et al., Phys. Rev. Lett. 125, 192501 (2020)

Orateur: Zsolt Podolyak (University of Surrey)

aris_avignon_june2023_wide_web.pdf

45 Core-breaking effects around 100Sn: lifetime measurements in the most neutron-deficient Sn isotopes.

The long Sn isotopic chain is a formidable testing ground for nuclear models aiming at describing the evolution of the shell structure. Low-lying excited states roughly exhibits the typical behavior predicted by the generalized seniority scheme. However, the corresponding B(E2; 0⁺→2⁺) values, approaching the N=Z=50 shell closure, have shown a presumed deviation from the expected parabolic behavior [1]. From a theoretical point of view, various attempts have been done to explain such experimental results, in particular by including core-breaking excitations in the shell-model calculations and promoting protons and neutrons from the g9/2 orbital across the shell gap [2]. From the experimental side, limited data are available beyond 104Sn and no lifetime information are known in this extremely neutron-deficient region, leading to a difficulty in a firm evaluation of any core-breaking effects.

In this contribution, we will report recent results on lifetime measurements in 102,103Sn. The experiment was performed in May 2021 at GSI using the AIDA Si active stopper surrounded by the EUROBALL HPGe and the FATIMA LaBr3 array. The nuclei of interest were identified in the FRS separator, following the production via fragmentation reactions of a 124Xe beam on a ⁹Be target. The Sn isotopes have been stopped in the AIDA array and the decaying gamma rays collected by the FATIMA array, which allowed for a direct lifetime measurement with a precision up to few tens of ps. The analysis is ongoing and the preliminary results will be presented, together with their possible implications.

[1] G. Guastalla et al., Phys. Rev. Lett. 110, 172501 (2013); V.M. Bader et al., Phys. Rev. C 88, 051301(R) (2013); P. Doornenbal et al., Phys. Rev. C 90 (R), 061302 (2014).
[2] T. Togashi et al., Phys. Rev. Lett.121, 062501 (2018).

Orateur: Marta Polettini (University of Milano & INFN Milano)

46 Cross-shell interactions at the N=28 shell closure via 47K(d,p) and 47K(d,t) with MUGAST+AGATA+VAMOS.

Shell evolution in the region around the magic numbers $N=28$ and $Z=20$ is of great interest in nuclear structure physics. Moving away from the doubly-magic isotope $^{48}$Ca, in the neutron-rich direction there is evidence of an emergent shell gap at $N=34$ [1], and in the proton-deficient direction, the onset of shape deformation suggests a weakening of the $N=28$ magic number [2]. The $^{47}$K(d,p)$^{48}$K reaction is uniquely suited to investigating this region, as the ground state configuration of $^{47}$K has an exotic proton structure, with an odd proton in the $\pi(1s_{1/2})$ orbital, below a fully occupied $\pi(0d_{3/2})$ orbital [3]. As such, the selective neutron transfer reaction (d,p) will preferentially populate states in $^{48}$K arising from $\pi(1s_{1/2}) \otimes \nu(fp)$ cross-shell interactions. The implications of this extend both down the proton-deficient $N=28$ isotonic chain, where these interactions are expected to dominate the structure of the exotic, short-lived $^{44}$P nucleus [4], and across the neutron-rich region, where the relative energies of the $\nu(fp)$ orbitals is the driving force behind shell evolution.

The first experimental study of states arising from the interaction between $\pi(1s_{1/2})$ and the orbitals $\nu(1p_{3/2})$, $\nu(1p_{1/2})$ and $\nu(0f_{5/2})$ has been conducted, by way of the $^{47}$K(d,p) reaction in inverse kinematics. A beam of radioactive $^{47}$K ions was delivered by the GANIL-SPIRAL1+ facility, with a beam energy of 7.7 MeV/nucleon. This beam was estimated to be $>99.99$% pure, with a typical intensity of $5\times10^{5}$ pps, and was impinged upon a 0.3 mg/cm$^2$ CD$_2$ target. The MUGAST+AGATA+VAMOS detection setup [5] allowed for triple coincidence gating, providing a great amount of selectivity. An analysis based both on excitation and gamma-ray energy measurements has revealed a number of previously unobserved states in $^{48}$K, and preliminary differential cross sections for the most strongly populated of these states will be presented. Spectroscopic factors for these states will be discussed in the context of shell model calculations, with regard to the N=28, 32 and 34 shell gaps. Additionally, results for positive and negative parity states in $^{46}$K, measured simultaneously via the $^{47}$K(d,t) reaction, will also be presented.

[1] D. Steppenbeck et al., Nature 502, 207 (2013).
[2] O. Sorlin and M.-G. Porquet, Prog. Part. Nucl. Phys. 61, 602 (2008).
[3] J. Papuga et al., Phys. Rev. C, 90 034321 (2014).
[4] L. Gaudefroy, Phys. Rev. C, 81, 064329 (2010).
[5] M. Assié et al., Nucl. Instrum. Methods A 1014, 165743 (2021).

Orateur: Charlie Paxman (University of Surrey)

16:15 coffee break

parallel session

Président de session: Julia Even (University of Groningen)

47 Gamow-Teller Giant Resonance in $^{11}$Li neutron drip line nucleus

At the RIKEN Radioactive Isotope Beam Factory, the spin-isospin response of $^{11}$Li was measured in charge-exchange $(p,n)$ reaction at 182 MeV/nucleon beam energy. There is no available data for isovector spin-flip giant resonances in nuclei with large isospin asymmetry factors, where (N−Z)/A>0.25 [1]. Our work aims to investigate this unexplored region up to (N−Z)/A=0.5.
The charge-exchange $(p,n)$ reactions in inverse kinematics combined with the missing-mass technique are powerful tools to extract the B(GT) strengths of unstable isotopes up to high excitation energies, without Q-value limitation of the β decay [1]. In our previous work on $^{132}$Sn [2], we demonstrated that accurate information about giant resonances can be obtained for unstable nuclei by using this probe. The combined setup [3] of PANDORA low-energy neutron spectrometer [4] and SAMURAI large-acceptance magnetic spectrometer [5] together with a thick liquid hydrogen target allowed us to perform the experiment with high luminosity. The recoil neutrons with kinetic energy of 0.1–10 MeV were identified with PANDORA, while the SAMURAI was used for tagging the decay channels of the reaction residues.
The β decay of $^{11}$Li is complex. The $^{11}$Li β-decay involves the largest number of decay channels ever detected [6] and experimental results have been reported for cases, when the daughter breaks into fragments, and emission of one, two, and three neutrons, α particles and $^{6}$He, tritons, and deuterons has been observed in several β-decay studies [8,9]. However, the B(GT) values were not clearly deduced as these studies were effected by the Q value.
In this talk, the final results of our analysis will be presented. Deduced double differential cross section up to about 40 MeV, including the Gamow-Teller (GT) Giant Resonance region in $^{11}$Li will be reported, as well as the comparison of the obtained B(GT) values with those from β-decay studies. We will discuss the nature of several newly identified decay channels of $^{11}$Be also.
Our observation, that the GT peak occurs below the Isobaric Analog State in $^{11}$Li, will be discussed in connection with the variation of residual spin-isospin interaction in exotic nuclei.

[1] K. Nakayama, et al., Phys. Lett. B 114, 217 (1982).
[2] M. Sasano et al., Phys. Rev. Lett. 107, 202501 (2011).

[3] J. Yasuda et al., Phys. Rev. Lett. 121, 132501 (2018).
[4] L. Stuhl et al., Nucl. Instr. Meth. B 463, 189 (2020). 

[5] L. Stuhl et al., Nucl. Instr. Meth. A 866, 164 (2017).
[6] T. Kobayashi, et al., Nucl. Instr. Meth. B 317, 294 (2013).
[7] M. Madurga et al., Nucl. Phys. A 810, 1 (2008).
[8] M.J.G. Borge et al., Nucl. Phys. A 613 199 (1997).
[9] R. Raabe et al., Phys. Rev. Lett. 101, 212501 (2008).

Orateur: Dr László Stuhl (Center for Exotic Nuclear Studies, Institute for Basic Science)

48 $\beta$-decay of $^{36}$Mg and $^{36}$Al: Identification of a long-lived isomer in $^{36}$Al

A long-lived isomeric state in $^{36}$Al has been identified for the first time via $\beta$-decay of $^{36}$Mg and $^{36}$Al. Neutron-rich $^{36}$Mg and $^{36}$Al were produced at the Facility for Rare Isotope Beams(FRIB) via projectile fragmentation of a $^{48}$Ca beam of energy 172.3 $\text{MeV/u}$. The beam was impinged on a 8.89 mm thick $^{9}$Be target. The fragmented beam was delivered to the $\beta$-decay station after being resolved by the Advanced Rare Isotope Separator(ARIS). A fast timing scintillator of 2mm thickness followed by two Si PIN detectors, each 500 $\mu m$ thick, were placed in the upstream side for the particle identification (PID). The energies lost by the ions in PIN2 were plotted against the time-of-flight between the ARIS scintillator and the sintillator at the decay station in order to generate the PID. At the heart of the decay station, a 5mm thick YSO scitillator implantation detector was placed. The $\beta$-delayed $\gamma$-rays were identified with 11 clover detectors and 15 $\text{LaBr}_3$ detectors. The half-lives of the two parent nuclei were determined and were compared to the previous measurements. The $\beta$-delayed $\gamma$-ray transitions were observed in $^{36}$Al and $^{36}$Si for the first time and their level schemes were built from the correlated $\beta$-decays of $^{36}$Mg and $^{36}$Al. Excited energy states of $^{36}$Al populated by the $\beta$-decay of $^{36}$Mg are proposed, whereas only the ground state information was available prior to this work. A long-lived isomer in $^{36}$Al was identified which undergoes $\beta$-decay to an excited state of $^{36}$Si. The experimental results were interpreted by using the nuclear configuration interaction studies with the FSU shell-model Hamiltonian. The results will shed light in our understanding of the structure of more exotic neutron-rich nuclei to be produced with the new generation facilities like FRIB.

Orateur: Rebeka Sultana Lubna (FRIB, Michigan State University)

ARIS_REBEKA_June6.pdf

49 Measurement of reaction cross section for $^{17}$F with a solid hydrogen target

T. Moriguchi$^1$, R. Kagesawa$^1$, A. Ozawa$^1$, W. Horiuchi$^2$, Y. Abe$^3$, M. Amano$^1$, D. Kamioka$^1$, A. Kitagawa$^4$, M. Mukai$^3$, D. Nagae$^5$, M. Sakaue$^6$, S. Sato$^4$, B. H. Sun$^7$, S. Suzuki$^8$, T. Suzuki$^6$, T. Yamaguchi$^6$, A. Yano$^1$, K. Yokota$^6$

$^1$University of Tsukuba, $^2$Osaka Metropolitan University, $^3$RIKEN Nishina Center, $^4$National Institutes for Quantum Science and Technology, $^5$Tokyo Institute of Technology, $^6$Saitama University, $^7$Beihang University, $^8$Japan Synchrotron Radiation Research Institute

Measurement of reaction cross section ($\sigma_{\rm R}$) is an effective method for investigations of nuclear size properties such as radii and density distributions. In particular, $\sigma_{\rm R}$ on a proton target has the possibility to extract the proton and neutron density distributions separately because of the asymmetry of the nucleon–nucleon total cross sections. However, only a few experimental $\sigma_{\rm R}$ for unstable nuclei on a proton target are reported at this time. It is important to understand collisions between unstable nuclei and a proton from both experimental and theoretical sides. In this study, we measured $\sigma_{\rm R}$ for $^{17}\rm{F}$, which is the proton drip-line nucleus of fluorine isotopes, with a solid hydrogen target (SHT) in a wide energy range. So far, the existence of the proton skin in the ground state of $^{17}\rm{F}$ has been discussed because of the small one-proton separation energy ($S_{\rm p}$=0.6 MeV), but the skin thickness of $^{17}\rm{F}$ is not reported yet experimentally. Experiment has been performed in the Heavy Ion Medical Accelerator in Chiba (HIMAC). Our SHT was developed for $\sigma_{\rm R}$ measurements, and its effective area and maximum thickness are $\phi$50 mm and 100 mm, respectively. From the present experiment, we found that $\sigma_{\rm R}$’s for $^{17}\rm{F}$ on a proton target are almost the same as those of $^{17}\rm{Ne}$, which is known to be a two-proton halo nucleus. These experimental results are very interesting because, in the case of proton-rich nuclei, the decrease of $\sigma_{\rm R}$ on a proton target was reported theoretically despite the increase of the root-mean-square matter radius towards the proton dripline. In this presentation, we will explain the details of the experiment, and discuss the energy dependence of $\sigma_{\rm R}$ for $^{17}\rm{F}$ on a proton target with the Glauber model calculation.

Orateur: Tetsuaki Moriguchi (Univ. of Tsukuba)

50 First characterization of Short-Range Correlations in an exotic nucleus at R3B

Most of the knowledge we have to date about Short-Range Correlations (SRC) in nuclei comes from electron induced quasi-free scattering (QFS) experiments in large momentum transfer kinematics. Experiments performed at Jefferson Lab with a $^{12}$C nucleus showed that the high-momentum tail of the nuclear momentum distribution is dominated by SRC and that the neutron/proton pairs are about 20 times more abundant than isospin-like pairs due to the tensor part of the nucleon-nucleon (NN) interaction [1]. Moreover, indications of a possible dependence of the high momentum fraction of protons and neutrons with the N/Z ratio was proposed from measurements on stable nuclei [2].
In this talk, I will present a novel experiment performed at the GSI accelerator facility with the R$^3$B setup [3]. For the first time we made use of a short-lived nucleus scattering off a proton probe in inverse kinematics, allowing a more direct and systematic access to SRC properties as function of the N/Z ratio. The study of $^{16}$C will add a new measurement at N/Z = 1.67, above the largest available N/Z ($^{208}$Pb) and at a much smaller mass, close to the one of the reference system $^{12}$C measured in the same experiment. Furthermore, we aim to extract the ratio of np/pp pairs as function of missing momentum and thus gain information about the NN interaction in comparison to different NN interaction theories. The concept of this experiment and some preliminary results will be discussed.

[1] R. Subedi, R. Shneor, Science, 1156675, 2008.
[2] M. Duer et al. (CLAS Collaboration), Nature, 560:617, 2018.
[3]https://www.gsi.de/work/forschung/nustarenna/nustarenna_divisions/kernreaktionen/activities/r3b.

Orateur: Andrea Lagni (CEA Saclay)

ARIS23_AL.pdf

51 Gamma-ray spectroscopy of the neutron-rich $\mathrm{^{55,57,59}}$Sc isotopes

Experimental data have shown that far from the valley of stability the nuclear shell structure evolves. New magic numbers can emerge and the traditional ones can disappear. In particular, two new magic numbers at N=32 and N=34 have been suggested in the vicinity of Z=20 based on gamma-ray spectroscopy and mass measurements. In order to assess the impact of a single valence proton outside of the Z=20 shell on the shell-evolution mechanism in this region, it is necessary to study the neutron-rich Sc isotopes around, and even beyond, neutron number N=34. Investigation of exotic nuclei in this region was the goal of the third SEASTAR campaign at RIKEN-RIBF. Neutron-rich isotopes in the vicinity of $^{53}$K were produced by fragmentation of a primary $^{70}$Zn beam on a $^{9}$Be target. Known and new $\gamma$-ray transitions of the isotope $^{55}$Sc were observed and $\gamma$-rays from $^{57,59}$Sc were identified for the first time. Observed $\gamma$ spectra from $^{55,57,59}$Sc will be presented together with preliminary level schemes. They will be discussed in the framework of the tensor-driven shell evolution.

Supported by BMBF under Grant Nos. 05P19/21RDFN1.

Orateur: Radostina Zidarova (TU Darmstadt)

parallel session

Président de session: Robert Bark (iThemba LABS)

52 Microscopic study of alpha, two-alpha and cluster decays

Using covariant energy density functional approach, it was recently possible to describe alpha decay, on both medium mass and heavy nuclei [1]. Using the same formalism, a new mode of radioactivity was predicted [2]. In such a mode, 2 alpha particles are emitted back-to-back, contrary to a 8Be-like cluster mode. Cluster decay will also be analyzed with this approach [3].
Information brought by such a formalism on the preformation and the localization of the alpha particle in the nuclei will be discussed [4]. Indications on possible favorable candidates to experimentally search for 2 alpha decays with radioactive beams will also be given.

[1] F. Mercier, J. Zhao, R.-D. Lasseri, J. P. Ebran, E. Khan, T. Nikšić, and D. Vretenar, Phys. Rev. C 102, 011301(R) (2020)

[2] F. Mercier, J. Zhao, J.-P.Ebran, E. Khan, T. Nikšić, D. Vretenar, Phys. Rev. Lett. 127, 012501 (2021)

[3] J. Zhao, J. P. Ebran, L. Heitz, E. Khan, F. Mercier, T. Nikšić, and D. Vretenar, arXiv:2211.14135 (2022)

[4] E. Khan, L. Heitz, F. Mercier, J. P. Ebran, Phys. Rev. C 106, 064330 (2022)

Orateur: Elias Khan (IJCLab)

53 Investigation of negative-parity band in $^{130}$Cs

Investigation of negative-parity band in $^{130}$Cs
C. Majumder$^{1}$, Pragya Das$^{1,*}$, H. K. Singh$^{1}$, U. Lamani$^{1}$, B. Bhujang$^{1,\#}$, and V. Pasi$^{1,\dagger}$
$^{1}$Department of Physics, Indian Institute of Technology Bombay, Mumbai, India.
$^{\#}$Present address: Govt. PU College, Shiggaon - 581205, Karnataka, India.
$^{\dagger}$Present address: Feat Educational Ventures Private Limited (Corporate Office) 201, Goregaon (W) - 400104, Mumbai, India.
$^{*}$pragya@phy.iitb.ac.in

Odd-odd Cs isotopes have been extensively studied by means of in-beam $\gamma$-ray spectroscopy, especially the positive-parity band based on $ \pi h_{11/2}\otimes\nu h_{11/2}$ for the chiral symmetry and signature inversion [1,2]. Our present study focuses on a negative-parity band based on $\pi h_{11/2}\otimes\nu g_{7/2}$ valence particle configuration in $^{130}$Cs [3]. We have studied the band structure by measuring lifetimes (in ps) of excited states using Doppler shift attenuation method (DSAM). Our new results on reduced transition probabilities (B(E2) and B(M1)) established the triaxial nature of the band consistent with the total Routhian surface (TRS) calculation.

We utilized the fusion-evaporation reaction $^{124}$Sn($^{11}$B, 5n)$^{130}$Cs to populate the high spin states of $^{130}$Cs. Energetic $^{11}$B beam at 70 MeV was delivered by the Pelletron accelerator facility at the Tata Institute of Fundamental Research, Mumbai, India. We utilized a self-supporting target ($^{124}$Sn) of thickness $\sim$ 2.2 mg/cm$^2$ sufficient to stop most of the recoiling nuclei. The emitted $ \gamma $-rays were detected by the 21 Compton suppressed HPGe Clover detectors of Indian National Gamma Array (INGA) [4]. The valid two- and higher-fold coincident $ \gamma $-events were recorded in list mode using PIXIE-16 based digital data acquisition system. The standard procedure of data analysis was adopted as described in our earlier work [5]. For the concerned negative-parity band, we first confirmed the decay scheme and spins up to 22 $\hbar$ by finding the Directional Correlation ratios. To extract the lifetimes, we fitted the DSAM lineshape profiles using the code LINESHAPE [6] for detectors located at angles of 23$ ^{0} $, 90$ ^{0} $, 157$ ^{0} $.

From our DSAM analysis, we determined the lifetimes of four states (14$^{-}$ to 20$^{-}$) within the range of 0.4 to 1.2 ps, with an average B(E2) value of 0.4 $e^2 b^2 $. There seems to be a slight decrease in B(E2) values with increasing spin. Interestingly, the band exhibits some striking features. Only the even spin states are populated above the bandhead 8$^{-}$, so the M1 transitions are missing. Above the backbend at around $\hbar\omega \simeq$ 0.38 MeV, both signature spins are observed with M1 transitions. However, the M1 is much weaker than the E2 transitions. The band shows the decoupling behaviour up to 16 $\hbar$, with energy spacings similar to the neighboring even-even and odd-even nuclei -- the ground state band of $^{128}$Xe [7] and $ \pi h_{11/2}$ band of $^{129}$Cs [5].

We performed the total Routhian surface (TRS) [8] calculation to study various features of the band. Firstly, we determined the deformation parameters values ($ \beta $, $ \gamma $) for the minimum energy configuration, from the contour plots for the band configuration $ \pi h_{11/2} \otimes \nu g_{7/2}$. In addition, we identified the first band-crossing for the neutron alignment in $h_{11/2}$ orbit from the quasi-particle Routhian diagram. The theoretical crossing frequency (0.40 MeV) was in agreement with the experimental observation. The proton alignment was ruled out because of the high values of the band-crossing frequencies for both positive and negative-parity orbits. Furthermore, we confirmed the neutron alignment by comparing the experimental B(M1) values with those obtained from the geometrical model of Donau and Frauendorf [9,10]. We extracted the experimental B(M1) values from the B(M1)/B(E2) ratios determined from the $\gamma$-ray intensity measurements, and B(E2) estimated from the DSAM analysis. Again, the proton alignment was ruled out by comparing the estimated and experimental B(M1) values.

In summary, we have investigated thoroughly the structure of the negative-parity band through lifetime measurement near and above the band-crossing region. A triaxial nuclear shape was inferred with deformation parameter values $ \beta $ = 0.16 and $ \gamma $ = $-30^{0}$ (in Lund convention) using the total Routhian surface calculation. We also established the neutron alignment with configuration $ \pi h_{11/2} \otimes \nu g_{7/2}(h_{11/2})^{2}$.

[1] E. Grodner $ et. al. $ Phys. Rev. Lett. 97, 172501 (2006).
[2] Y. Liu $ et. al. $ Phys. Rev. C 54, 719 (1996).
[3] R. Kumar $ et. al. $ Eur. Phys. J. A 11, 5 (2001).
[4] R. Palit $et. al.$, Nucl. Instrum. Methods A 680, 90 (2012).
[5] U. Lamani $et. al.$, Nucl. Phys. A 1014, 122220 (2021).
[6] J. C. Wells and N. R. Johnson ORNL report 6689, 44 (1991).
[7] J. N. Orce $ et. al. $ Phys. Rev. C 74, 034318 (2006).
[8] T. Bengtsson, Nucl. Phys. A 512, 124 (1990).
[9] F. Dönau and S. Frauendorf, in Proceedings of the International Conference on High Angular Momentum Properties of Nuclei, Oak Ridge, 1982, edited by N. R. Johnson (Harwood, New York, 1983), p. 143.
[10] F. Dönau, Nucl. Phys. A 471, 469 (1987).

Orateur: Dr Chandrani Majumder (Indian Institute of Technology Bombay)

54 Determination of electromagnetic moments within nuclear DFT

Nuclear electromagnetic moments provide essential information in our understanding of nuclear structure. Observables such as electric quadrupole moments are highly sensitive to collective nuclear phenomena, whereas magnetic dipole moments offer sensitive probes to test our description of microscopic properties such as those of valence nucleons. Although great progress was achieved in the description of electromagnetic properties of light nuclei and experimental trends in certain isotopic chains, a unified and consistent description across the Segré chart of nuclear electromagnetic properties remains an open challenge for nuclear theory.

In our nuclear-DFT methodology, we align angular momenta along the intrinsic axial-symmetry axis with broken spherical and time-reversal symmetries. This allows us to explore fully the self-consistent charge, spin, and current polarizations. Spectroscopic moments are then determined for symmetry-restored wave functions and compared with available experimental data.

We determined the nuclear electric quadrupole and magnetic dipole moments in all one-particle and one-hole neighbours of eight doubly magic nuclei [1]. Such a dataset allowed us to adjust the time-odd mean-field channel of nuclear functionals to experimental data. Without further adjustments, we then determined the electromagnetic moments in paired nuclear states corresponding to the proton (neutron) quasiparticles blocked in the $\pi11/2^-$ ($\nu13/2^+$) intruder configurations [2]. We performed calculations for all deformed open-shell odd nuclei with $63\leq{Z}\leq82$ and $82\leq{N}\leq126$.

We obtained good agreement with data without using effective $g$-factors or effective charges in the dipole or quadrupole operators, respectively. We also showed that the intrinsic magnetic dipole moments, or those obtained for conserved intrinsic time-reversal symmetry, do not represent viable approximations of the spectroscopic ones, see the results plotted in the figure.

In this talk, I will review recent nuclear-DFT results obtained in the unpaired odd near doubly magic nuclei [1], heavy paired odd open-shell nuclei [2], and indium [3], silver [4], and tin [5] isotopes.

References
[1] P.L. Sassarini et al., J. Phys G 49 (2022) 11LT01
[2] J. Bonnard et al., arXiv:2209.09156
[3] A.R. Vernon et al., Nature 607 (2022) 260; A.R. Vernon et al., to be published; L. Nies et al., to be published
[4] R.P. de Groote et al., to be published
[5] T.J. Gray et al., to be published

Acknowledgements
This work was partially supported by the STFC Grant Nos.~ST/P003885/1 and ST/V001035/1, by the Polish National Science Centre under Contract No. 2018/31/B/ST2/02220, by a Leverhulme Trust Research Project Grant, by the Academy of Finland under the Academy Project No. 339243, and by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under award numbers DE-SC0021176 and DE-SC0021179. We acknowledge the CSC-IT Center for Science Ltd., Finland, for the allocation of computational resources. This project was partly undertaken on the Viking Cluster, which is a high performance compute facility provided by the University of York. We are grateful for computational support from the University of York High Performance Computing service, Viking and the Research Computing team.

Orateur: Jacek Dobaczewski (University of York)

Dobaczewski.ARIS2023.230605-06.pdf

55 Harvesting Hf-172 from heavy-ion beam irradiated tungsten beam-blocker for generating Lu-172

During the routine operation of radioactive heavy-ion beam facilities, tremendous quantities of radioisotopes get deposited or produced at multiple sites throughout the accelerator parts and beamline components. This presents an opportunity to harvest the long-lived radioisotopes that have wide ranging applications once these components and parts are decommissioned and often, considerable activities will have built up by then. One such decommissioned component from the National Superconducting Cyclotron Laboratory (NSCL) was the tungsten beam-blocker that acted as the beam-dump for the primary heavy-ion beams while NSCL was in operation. This work elucidates the radioanalytical separation techniques and methodologies used in the extraction and purification of Hf-172 from the tungsten beam-blocker and the other co-embedded radionuclides such as Lu-173, Lu-172, Na-22, Co-56, Co-57, Co-58, Co-60 amongst others. The harvested Hf-172 was used for generating Lu-172 employing the use of an extraction chromatographic resin and radiolabeling studies were carried out with the generated Lu-172.

Orateur: Samridhi Satija (Michigan State University/Facility for Rare Isotope Beams)

56 Mass Measurement of the 123Pd with the Rare-RI Ring in RIKEN

The rapid neutron capture process (r-process) is considered to be responsible for the synthesis of about one-half of the elements heavier than iron up to bismuth and all of thorium and uranium. To model the r-process, nuclear properties of neutron-rich nuclides are needed. Nuclear mass is one of the most important input properties for the r-process calculation. However, some of the neutron-rich nuclides involved in the r-process lie far away from the stability line and are hard to produce in the laboratory. Therefore, r-process calculations have to rely on theoretical mass predictions. Thus, the mass measurements for the neutron-rich nuclei not only provide reliable data for the r-process calculations but also can help validate and improve the theoretical mass models.

The Rare-RI Ring (R3) is a recently commissioned isochronous mass spectrometer dedicated at Radioactive Isotope Beam Factory (RIBF) in RIKEN. Based on the Isotope-Selectable Self-triggered Injection technique, the pre-identified ions can be selected and injected into R3 event by event. The mass precision of 10$^{-6}$ is expected to be achieved within less than 1~ms. In this contribution, the first application of mass measurements with the Rare-RI Ring will be reported. In the experiment, 5 isotones, $^{127}$Sn, $^{126}$In, $^{125}$Cd, $^{124}$Ag, and $^{123}$Pd , were injected into R3 and extracted from it successfully. The mass uncertainty of $^{123}$Pd is improved and the final relative uncertainty is 2.3$\times$10$^{-6}$. The impact of the new $^{123}$Pd mass result on the solar r-process abundances in a neutron star merger event is investigated by performing PRISM reaction network model. The A=122 and A=123 element abundance ratios in twenty r-process trajectories are calculated with varying electron fraction Y$_e$. We found that if our new mass value is used instead of the FRDM value, the r-process abundances at A=122 and A=123 are modified toward being more consistent with solar values.

Orateur: HONGFU LI (Institute of Modern Physics, Chinese Academy of Sciences)

poster session

mercredi 7 juin

plenary 09

Président de session: Magdalena Górska (GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany)

57 Laser spectroscopy of the Heaviest Elements

The heaviest elements are of interest to nuclear and atomic physicists due to their peculiar properties. While nuclear shell structure effects are responsible for their very existence stabilizing them against spontaneous disintegration, the structure of their electronic shells is affected by strong relativistic effects leading to different atomic and chemical properties compared to their lighter homologs. The atomic structure can be probed by laser spectroscopy. This is a powerful tool to unveil fundamental atomic and, from the determination of subtle changes in atomic transitions, nuclear properties. The lack in atomic information on the heavy element of interest, the low production rates, and the rather short half-lives make experimental investigations challenging and demand very sensitive experimental techniques.
Laser spectroscopy of accelerator produced heavy nobelium (No, $Z$=102) isotopes in atom-at-a-time quantities became accessible in the pioneering experiment employing the RAdiation Detected Resonance Ionization Spectroscopy (RADRIS) technique at the velocity filter SHIP at GSI, Darmstadt. More recent measurements with additional advancements of the setup and employing a novel mode of the RADRIS technique, where the desired nuclides are bred by radioactive decay on the capture filament, extended the reach of the method to $^{251,255}$No and, for the first time, to on-line produced fermium (Fm, $Z$=100) isotopes. These on-line experiments are complemented by off-line laser spectroscopy measurements at the RISIKO mass separator at Mainz University on reactor-bred heavy actinides with suitable long lifetimes. Hot-cavity laser spectroscopy on radio-chemically purified samples enabled the investigation of isotopes of the heavy actinides curium (Cm, $Z$=96), californium (Cf, $Z$=98), einsteinium (Es, $Z$=99), and fermium. This experimental endeavor is accompanied by improvements of theoretical atomic calculations enabling the determination of nuclear ground state properties from the extracted atomic observables of isotope shifts and hyperfine structure parameters. This provides insight to the peculiar nuclear nature and especially the deformation of the heaviest elements. The obtained results will be discussed in view of nuclear theory predictions together with the perspectives for laser spectroscopic investigations in even heavier elements.

Orateur: Sebastian Raeder (GSI Darmstadt)

ARIS_Raeder_V1.1.pptx

58 Extremely neutron-rich nuclei beyond the drip line

The limit of the nuclear stability, called neutron drip line, reflects structure of atomic nuclei with extremely proton-neutron asymmetry. It is known that the neutron drip line of oxygen isotope is 24O (Z=8, N=16), while that of fluorine is 31F (Z=9, N=22). This sudden change of the neutron drip line is called oxygen anomaly. Theoretical study [1] suggests that three-nucleon forces play an important role in the binding of the oxygen isotopes especially for N>16. This region is also interesting in terms of the island of inversion. It is well known that the N=20 shell closure disappears for magnesium and neon isotopes in the vicinity of N=20 while the shell structure for fluorine and oxygen is not clear. Recent experimental studies [2,3] suggest that the island of inversion extends to 29F (Z = 9, N = 20). It is a question whether the 28O nucleus, having the canonical magic numbers Z=8 and N=20, shows doubly magic characters or not. In these contexts, experimental study on the neutron-rich oxygen isotopes located beyond the neutron drip line is strongly desired.
Series of experiment for the unbound oxygen isotopes 25-28O has been performed with the SAMURAI setup [4] at RI Beam Factory (RIBF). Results of the experiments and related studies will be presented in the talk.

References
[1] T. Otsuka et al., Phys. Rev. Lett. 105, 032501 (2010).
[2] P. Doornenbal et al., Phys. Rev. C 95, 041301(R) (2017).
[3] S. Bagchi et al., Phys. Rev. Lett.124, 222504 (2020).
[4] T. Kobayashi et al., Nucl. Instrum. Methods Phys. Res., Sect. B 317, 294 (2013).

Orateur: Yosuke Kondo (Tokyo Institute of Technology)

59 Nuclear collectivity studied with the newly refurbished Miniball spectrometer at HIE-ISOLDE

The Miniball spectrometer has been utilised for the study of collectivity in nuclei for two decades, exploiting post-accelerated radioactive ion beams at the ISOLDE facility. The workhorse technique has been Coulomb excitation, but few-nucleon and multi-nucleon transfer-reactions have also been exploited with the addition of ancillary devices such as the T-REX charged-particle detector.

Miniball came back to life at HIE-ISOLDE in 2022 following the second long shutdown at CERN (2018-2021), during which time it has undergone a total transformation. There has been a refurbishment of the HPGe detectors, including new cryostats, electronics and preamplifiers, as well as a newly developed data acquisition system.

In this talk, I will present some recent physics highlights from Miniball in the HIE-ISOLDE era, focusing on studies of nuclear collectivity and shapes. I will also detail the current status of the spectrometer and show preliminary results from the first experiments of the new era; including the first use of the SPEDE spectrometer for conversion electron spectroscopy in the Coulomb excitation of $^{182}$Hg.

Orateur: Liam Gaffney (University of Liverpool)

ARIS2023_Miniball-182Hg_Gaffney_online.pptx

60 OEDO-SHARAQ system: Its multifaceted performance and recent experimental achievements

The OEDO-SHARAQ system at RIBF in RIKEN was primarily started to promote high-resolution nuclear spectroscopy with radioactive isotope (RI) beams. It was recently upgraded as the world's first beamline characterized by the energy-degrading of RI beams with a followed magnetic spectrometer for fragment analysis.

The high-resolution property of the system was fully demonstrated in the direct atomic mass measurements by using the TOF-B$\rho$ method. We recently reported the atomic masses of $^{55-57}$Ca and $^{58-62}$Ti for the first time using the OEDO-SHARAQ system in RIBF [1,2]. In this talk we would like to discuss the shell evolution in the neutron $p_{1/2}$, $f_{5/2}$ and $g_{9/2}$ orbitals in this region and the similarities or differences to a region around $^{24}$O and $^{32}$Mg.

The energy-degrading operation of the system began experiments in the spring of 2017. This beamline was designed to decelerate the intermediate-energy RI beam produced by the BigRIPS separator down to 10-50 MeV/u. A radio-frequency electric ion-optical element is installed in the beamline, which provides unique ion optics of time-dependent beam focusing [3]. Additionally, an angle-tunable wedge-shaped energy degrader is utilized for the compression of RI-beam energy [4]. The combination of these key equipment enables OEDO to achieve simultaneously good beam focusing and energy compression on the secondary target. Thus, the RI beams provided by the OEDO-SHARAQ system widely cover the energy range for pre-compound, pre-equilibrium, and/or direct reactions.

After OEDO's construction, we performed measurements utilizing such reaction mechanisms. Recent achievements include low-energy cross-section studies of spallation reactions on RIs, especially long-lived fission products (LLFPs) $^{93}$Zr and $^{107}$Pd. The results report the lowest beam energy measurements for these LLFPs and are essential when designing reduction schemes for nuclear waste management [5]. Also, experimental studies on the astrophysical neutron-capture process were done. Amplitudes of neutron-capture processes are essential for nucleosynthesis in explosive sites. OEDO-SHARAQ provides the experimental opportunity to determine survival probabilities from unbound states via a pre-compound neutron-transfer reaction. We recently measured $^{130}$Sn(d,p) and $^{56}$Ni(d,p) reactions to study the neutron captures in $r$- and $\nu p$-processes, respectively. Data analyses are ongoing. We will show here tentative achievements mainly regarding the experimental technique.

This presentation will introduce the multifaceted performances of the OEDO-SHARAQ system in intermediate-energy high-resolution spectroscopy and low-energy inverse-kinematics reaction measurements and report the recent experimental results of the system. We also discuss perspectives about future physics programs.

Orateur: Shin'ichiro Michimasa (Center for Nuclear Study, The University of Tokyo)

10:25 coffee break

plenary 10

Président de session: Gerda Neyens (KU Leuven)

61 Global ab initio calculations for the structure of exotic and heavy nuclei

Breakthroughs in our treatment of the many-body problem and nuclear forces are rapidly transforming modern nuclear theory into a true first-principles discipline. This allows us to address some of the most exciting questions at the frontiers of nuclear structure and physics beyond the standard model.
In this talk I will highlight recent advances which now allow for global converged calculations of open-shell nuclei to the 208Pb region and beyond. In particular, I will focus on key topics in nuclear structure such as predictions of the proton and neutron driplines and evolution of magic numbers throughout the light and medium-mass regions, including new insights on the nature and existence of 28O including continuum degrees of freedom. In addition, I will discuss how correlation of the neutron skin and dipole polarizability in heavy nuclei to 208Pb provide first ab initio constraints on symmetry energy parameters for determining neutron star properties.

Orateur: Dr Jason Holt (TRIUMF)

Holt_ARIS.pdf

62 Determination of the Neutron Dripline at F and Ne and Discovery of the Heaviest Na Isotope: $^{39}$Na

The location of the neutron dripline is crucial to understand the stability of nucleonic many-body systems with extreme neutron-to-proton ratios.
It provides a benchmark for nuclear theories and mass models, and an important key to understand underlying nuclear structure and interactions.
The neutron dripline has been experimentally determined up to oxygen (atomic number $Z$ = 8) as $^{24}$O [1-4] more than 20 year ago, while no experimental confirmation has been reported for $Z$ $\geq$ 9.

We have searched for the neutron driplines, the heaviest new isotopes, of fluorine ($Z$ = 9), neon (10), and sodium (11) by the BigRIPS separator at the RIKEN RI Beam Factory.
The neutron-rich isotopes were produced by projectile fragmentation of a 345-MeV/u 450~500-pnA $^{48}$Ca$^{20+}$ beam impinging on a 20-mm-thick Be target.
No events were observed for $^{32,33}$F, $^{35,36}$Ne, and $^{38}$Na [5].
Comparison with predicted yields excludes the existence of bound states of these unobserved isotopes with high confidence levels, which indicates that $^{31}$F and $^{34}$Ne are the heaviest bound isotopes of fluorine and neon, respectively.
We have confirmed the fluorine and neon neutron driplines for the first time.
We have observed the new isotope of $^{39}$Na, which is the most neutron-rich isotope with $N$ = 28 neutron magic number [6].

The locations of the neutron dripline from oxygen to neon isotopes and the bound nature of $^{39}$Na could be explained by evolution of nuclear deformation.
By the recent large-scale shell-model calculation with $ab$ $initio$ effective $NN$ interaction [7], the oxygen dripline is determined by a new magic number of $N$ = 16, emerging by tensor force and repulsive 3 nucleon forces.
From $Z$ = 9 to 12, quadrupole deformation leads to a larger binding energy for neutrons and affects the location of the driplines.
The discovery of $^{39}$Na suggests that its ground state is deformed and the magicity of $N$ = 28 is lost.

In this talk, the experimental results will be presented to discuss the location of the neutron driplines as well as the underlying nuclear structure.

References:
[1] D. Guillemaud-Mueller $et$ $al$., Phys. Rev. C 41, 937 (1990).
[2] M. Fauerbach $et$ $al$., Phys. Rev. C 53, 647 (1996).
[3] O. B. Tarasov $et$ $al$., Phys. Lett. B 409, 64 (1997).
[4] H. Sakurai $et$ $al$., Phys. Lett. B 448, 180 (1999).
[5] D.S. Ahn, T. Kubo $et$ $al$., Phys. Rev. Lett. 123, 212501 (2019).
[6] D.S. Ahn, T. Kubo $et$ $al$., Phys. Rev. Lett. 129, 212502 (2022).
[7] N. Tsunoda et $al$., Nature (London) 587, 66 (2020).

Orateur: Dr Hiroshi SUZUKI (RIKEN Nishina Center)

63 The AGATA $\gamma$-ray tracking array at the LNL TANDEM-ALPI-PIAVE facility

The AGATA $\gamma$-ray tracking array represents the state-of-the-art of in-beam gamma-ray detection. Its capabilities rely on the high segmentation of its High Purity Germanium detectors to provide position sensitivity and, as a result, the ability to track gamma rays.

In this contribution, we will present an overview of the experiments performed during the first phase of AGATA's installation at the TANDEM-ALPI-PIAVE accelerator complex in the "Laboratori Nazionali di Legnaro" in Italy. The gamma-ray array was initially coupled to the PRISMA magnetic spectrometer, to study the spectroscopy of isotopes produced from multinucleon transfer and fission reactions.

Moreover, part of the experimental campaign was devoted to the study of Coulomb excitation experiments that saw the array coupled to silicon detectors (SPIDER and EUCLIDES).

A brief overview of the performance and recent achievements will be presented, with a future perspective of the spectrometer at Legnaro, also in view of the future delivery of radioactive beams provided by the SPES facility.

Orateur: Daniele Brugnara (University of Padova - LNL INFN)

brugnara_ARIS_2023.pptx

64 Discovery of isotopes and first time broadband measurements of neutron-deficient light lanthanides via high precision mass spectrometry

Approaching the limits of nuclear binding, the structure and properties of drip-line nuclei is of great interest and draws a lot of attention from both, experiment and theory. The nuclear properties in the light lanthanide region are shaped by the interplay between large beta-decay Q-values, low or negative proton separation energies, and the confining effects of the Coulomb barrier. From precise mass values, differential quantities, such as the proton and neutron separation energies, can be determined, and different phenomena, including a variety of beta-delayed particle emission channels, proton radioactivity, and two-proton radioactivity as well as exotic pairing phenomena, can be addressed.
Nuclei in the region of between $^{100}$Sn and $^{150}$Lu were produced at relativistic energies and separated in-flight with the fragment separator FRS at GSI as part of the FAIR Phase-0 experiments. They were identified by their proton number and mass-to-charge ratio in the FRS, before being slowed down, thermalized in the Cryogenic Stopping Cell (CSC) of the FRS Ion Catcher and transported to a Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) for high-resolution mass measurements. In order to calibrate and verify the particle identification at the FRS, a novel method, tagging by high resolution mass spectrometry using the MR-TOF-MS of the FRS Ion Catcher, was successfully applied.
In the experiment, new isotopes towards the proton drip-line, in the region between Nd and Tb, could be identified by the FRS particle identification. For the mass measurements a new technical approach was applied, the so called mean range bunching. The combination of achromatic ion optics of the FRS with a new variable wedge-shaped degrader system at the final focal plane allows to “correct” the range-position dependence, which enables efficient stopping of many nuclides in the CSC simultaneously. This novel technical approach was proven by the simultaneous measurement of more than 35 nuclides in a single setting. It opens up the possibility to cover large regions on the chart of the nuclides in a single measurement with stopped or thermalized nuclides, aside from mass measurements also for decay and laser spectroscopy. The masses of more than 10 nuclides were measured for the first time, and the mass uncertainties of more than 10 nuclides were significantly reduced. These results give an insight into the nuclear structure and for the first time allow tracking of the proton drip line between $^{100}$Sn and $^{150}$Lu. In this contribution, these recent results and the new technical approaches will be reported.

Orateur: Christine Hornung (GSI Helmholtzzentrum für Schwerionenforschung)

12:45 lunch break

plenary 11

Président de session: Paul Fallon (Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA)

65 High-resolution gamma-ray spectroscopy at a neutron beam: news from ILL

Thermal neutron capture gamma-ray spectroscopy and prompt gamma-ray spectroscopy of fission fragments are powerful tools to obtain detailed nuclear structure information for nuclides close to stability and medium mass neutron-rich isotopes. The power of coupling a high-efficiency Ge detector array with an intense pencil-like neutron beam provided by the ILL reactor, has been recently demonstrated by the success of the EXILL (EXogam at ILL) campaign. This success led to the installation of permanent setup at ILL, the new instrument FIPPS (FIssion Product Prompt Spectrometer). In its first phase, it consists of a halo-free pencil neutron beam incident on a target surrounded by an array of 8 HPGe clovers. This setup has recently been exploited for a variety of (n,$\gamma$) experiments on stable (rare) and radioactive targets. Additional HPGe clovers from IFIN-HH were added during the last year allowing for a higher efficiency and granularity. Recently, targets consisting of $^{235,233}$U diluted in a liquid scintillator has been used to study the spectroscopy of neutron-rich nuclei with a fission tag. In a second phase, the instrument will be complemented with a fission-fragment identification setup, based on diamond detectors. This will increase the sensitivity and selectivity for nuclear spectroscopy of fission products and enable fission studies of the correlation between excitation energy, angular momentum and kinetic energy.

After a general introduction to the nuclear physics activity at ILL, the details of the FIPPS instrument, its performance and first physics results will be shown. An overview on the physics cases investigated in last years, together with the techniques used, will be given. The future developments foreseen, in particular for fission studies, will be also reported.

Orateur: Dr Caterina Michelagnoli (Institut Laue-Langevin)

66 High-resolution in-beam $\gamma$-ray spectroscopy at RIBF

In-beam gamma-ray spectroscopy experiments have been actively performed at Radioactive Isotope Beam Factory (RIBF) of the RIKEN Nishina Center owing to the high secondary beam intensities from the BigRIPS fragment separator [1]. These experiments mostly employed the DALI2 NaI array with the very high $\gamma$-ray detection efficiency [2], and the Zero Degree Spectrometer [1] and the SAMURAI spectrometer [3] for reaction product identifications. Among the abundant scientific achievements from in-beam $\gamma$-ray spectroscopy experiments, the first spectroscopy of $^{54}$Ca [4], $^{78}$Ni [5], and $^{70}$Kr [6] are examples of the capability of the RIBF facility.
Despite the notable accomplishments, experiments have been mostly limited to even-even nuclei in the vicinity of shell closures due to the moderate energy resolution of the DALI2 array. For the new capability in spectroscopy, a germanium-based high-resolution $\gamma$-ray detector array was constructed in 2019 under the High-resolution Cluster Array at RIBF (HiCARI) project [7]. The HiCARI array was comprised of several different types of high-purity germanium detectors, six segmented triple clusters from the Miniball collaboration, four segmented Clover detectors from the IMP, a quad-type tracking detector from the RCNP, and a triple-cluster tracking detector P3 from the LBNL. Through the improved position and energy resolution, the spectroscopy capabilities could be extended to further regions of interest such as odd-mass and deformed nuclei. Moreover, the HiCARI array was capable to measure level lifetimes based on the line-shape method [8].
In 2020 and 2021, 8 experiments were successfully carried out during 31.5 day of beam times with $^{238}$U and $^{70}$Zn primary beams. The campaign included a wide range of exotic neutron-rich nuclei covering various physics motivations, such as shell and shape evolutions. An overview of the HiCARI project and first preliminary results from the rich physics program will be presented.

[1] T. Kubo et al., Prog. Theor. Exp. Phys. 2012, 03C003 (2012).
[2] S. Takeuchi et al., Nucl. Instrum. And Methods Phys. Res. A 763, 596 (2014).
[3] T. Kobayashi et al., Nucl. Instrum. And Methods Phys. Res. B 317, 294 (2013).
[4] D. Steppenbeck et al., Nature 502, 207 (2013).
[5] R. Taniuchi et al., Nature 569, 52 (2019).
[6] K. Wimmer et al., Phys. Lett. B 785, 441 (2018).
[7] K. Wimmer et al., RIKEN Accel. Prog. Rep. 54, S27 (2021).
[8] P. Doornenbal et al., Nucl. Instrum. Methods Phys. Res. A 613, 218 (2010).

Orateur: Byul Moon (Center for Exotic Nuclear Studies, Institute for Basic Science)

67 Super-allowed alpha decay to doubly-magic $^{100}$Sn

The proton-rich doubly-magic self-conjugate nucleus $^{100}$Sn and neighboring nuclei are a site of unique nuclear phenomena and a test bed for modern nuclear models. The $^{100}$Sn nucleus is one of the fastest known Gamow-Teller $\beta$ emitters. Due to close proximity of the proton drip line, nuclei with Z>50 and N>50 near $^{100}$Sn form an island of $\alpha$ and proton emitters which decay towards $^{100}$Sn. Alpha decays of proton-rich Te isotopes were proposed to terminate the astrophysical rp-process. Consequently, despite small production cross sections, this region of nuclear chart has been an aim of numerous experimental studies.
In an experiment with the Fragment Mass Analyzer at ATLAS, the super-allowed $\alpha$-decay chain $^{108}$Xe-$^{104}$Te to doubly-magic $^{100}$Sn was observed [1] using the recoil-decay correlation technique. This was the first time that evidence was found for production of $^{100}$Sn in a fusion-evaporation reaction. This observation is an important stepping-stone towards developing a microscopic model of $\alpha$ decay, since it is only the second case of $\alpha$ decay to a doubly-magic nucleus besides the benchmark $^{212}$Po $\alpha$ decay to $^{208}$Pb, and it triggered a flurry of theoretical activity. The decay properties of $^{108}$Xe and $^{104}$Te indicate that in at least one of them the reduced $\alpha$-decay width is a factor of 5 larger than in $^{212}$Po, which confirms their super-allowed character. This could be explained by an enhanced $\alpha$-particle preformation probability due to a stronger interaction between protons and neutrons, which occupy the same orbitals in N=Z nuclei. The Q$_\alpha$-values deduced for the very exotic $^{108}$Xe and $^{104}$Te nuclei are consistent with the doubly-magic nature of $^{100}$Sn. Interestingly, a weak proton-decay branch in $^{108}$I was found in the same experiment. The deduced $^{104}$Sb Q$_p$ value rules out the formation of the Sn-Sb-Te cycle at $^{103}$Sn.
Further experiments to observe more $^{108}$Xe-$^{104}$Te $\alpha$-decay chains and to better characterize the properties of other $\alpha$ emitters in the $^{100}$Sn region are planned. Tests with the recently constructed Argonne Gas-Filled Analyzer, which offers much higher efficiency, will be discussed.

[1] K.Auranen, D.Seweryniak, M.Albers, A.D.Ayangeakaa, S.Bottoni, M.P.Carpenter, C.J.Chiara, P.Copp, H.M.David, D.T.Doherty, J.Harker, C.R.Hoffman, R.V.F.Janssens, T.L.Khoo, S.A.Kuvin, T.Lauritsen, G.Lotay, A.M.Rogers, J.Sethi, C.Scholey, R.Talwar, W.B.Walters, P.J.Woods, and S.Zhu, Phys. Rev. Lett. 121, 182501 (2018)

This material is based upon work supported by the U.S Department of Energy, Office of Science, Office of Nuclear Physics, under contract number DE-AC02-06CH11357. This research used resources of ANL's ATLAS facility, which is a DOE Office of Science User Facility.

Orateur: Dariusz Seweryniak (Argonne National Laboratory)

superallowed aris final seweryniak.pptx

68 Studies of exotic isotopes using laser ionization techniques and trapped ion techniques

Laser spectroscopy techniques provide nuclear-model independent access to nuclear electromagnetic moments, spins and charge radii. Advances in radioactive ion beam instrumentation and laser technologies have enabled the study of a wide range of elements and isotopes, pushing out far from the valley of stability towards the drip lines. In this contribution, I will present experimental progress along two important frontiers. I will discuss the use of methods based on laser ionization spectroscopy and how they have allowed us to reach exotic nuclei such as 94Ag 52K. Crucially, these measurements relied on the use of decay detection or ultra-selective mass separation tools to provide low-background measurement conditions.
Besides using efficient laser ionization and particle detection methods, another important area of research relies on the use of ion traps. I will show a recent example of how ions trapped in a linear Paul trap can be optically pumped into a beneficial metastable state. In particular, I will show how this approach enabled fluorescence spectroscopy of neutron-deficient singly-charged cobalt isotopes. Finally, I will conclude with a discussion on the next logical step, which entails doing optical and radiofrequency spectroscopy of radioactive ions while they are trapped in a linear Paul trap. I will discuss the status of a new setup currently under construction at the KU Leuven.

Orateur: Prof. Ruben de Groote (KU Leuven)

16:15 coffee break

plenary 12

Président de session: Iris Dillmann

69 What are the fingerprints of nucleosynthesis?

Disentangling the different components and astrophysical sites of various nucleosynthesis processes is challenging for many reasons. Observations of metal-poor stars currently provide some of the cleanest signatures of the rapid neutron-capture process (r-process) but are sparse. Isotopic analyses of presolar grains originating from Asymptotic Giant Branch (AGB) stars give strong insight into the slow neutron-capture process (s-process) but rely on assumptions that the grains are unaltered between formation and laboratory analysis. To correctly interpret such observations, the nuclear physics in nucleosynthesis models need to be accurate and of high enough precision. Currently the characteristic fingerprints of different processes only loosely constrain the astrophysical conditions under which the elements form. In the recent past, significant advancements in constraining the nuclear physics uncertainties, together with increased availability of ‘ground-truth’ data have improved our understanding of how the elements are made in the cosmos.

Orateur: Wei Jia Ong (Lawrence Livermore National Laboratory)

70 Axial Shape Asymmetry and Configuration Coexistence in Neutron-Rich 74Zn

Results from recent experiments studying nuclei in the $^{78}$Ni region suggest that the $N=50$ shell closure persists, in agreement with state-of-the-art shell model calculations. However, how collectivity manifests and evolves in this region of the Segrè chart is still an open question, particularly concerning phenomena such as vibrational modes, triaxiality and shape coexistence. This is especially true in the Zn isotopic chain in the neutron-rich region, in which even definitive spin assignments are unavailable except for the very low-lying states.

In this talk, I will present the results of a recent experiment performed at the TRIUMF laboratory (Vancouver, Canada) using the GRIFFIN $\gamma$-ray spectrometer. The excited states of $^{74}$Zn were investigated via $\gamma$-ray spectroscopy following $^{74}$Cu $\beta$-decay. By exploiting $\gamma$-$\gamma$ angular correlation analysis, the $2_2^+$, $3_1^+$, $0_2^+$ and $2_3^+$ states in $^{74}$Zn were firmly identified. The $\gamma$-ray branching and $E2/M1$ mixing ratios for transitions de-exciting the $2_2^+$, $3_1^+$ and $2_3^+$ states were measured, allowing for the extraction of relative $B(E2)$ values. In particular, the $2_3^+ \to 0_2^+$ and $2_3^+ \to 4_1^+$ transitions were observed for the first time. The levels observed were organized into rotational-like bands and the results were compared with large-scale shell-model calculations from which the shapes of individual states were determined. Enhanced axial shape asymmetry (triaxiality) is suggested to characterize $^{74}$Zn in its ground state. Furthermore, an excited $K=0$ band with a different shape is identified. A shore of the $N=40$ island of inversion appears to manifest above $Z=28$, previously thought as its northern limit in the nuclide chart.

Orateur: Marco Rocchini (INFN - Firenze division)

rocchini-ARIS2023.pdf

71 Recent progress of mass measurements for short-lived nuclides at CSRe-Lanzhou

Accurate nuclear masses not only provide indispensable information on nuclear structure, but also deliver important input data for applications in nuclear astrophysics. The challenge today is to obtain accurate masses of nuclei located far away from the valley of stability. In the past few years, we have devoted to the mass measurements of exotic nuclei below A=100 using the isochronous mass spectrometry (IMS) at the heavy ion storage ring CSRe in Lanzhou. New mass values have been obtained including $^{27}$P, $^{29}$S [1], $^{407}$Ti, $^{44}$Cr, $^{46}$Mn, $^{48}$Fe, $^{50}$Co, $^{52}$Ni [2], $^{44g,m}$V, $^{46}$Cr, $^{48}$Mn, $^{50}$Fe, $^{52g,m}$Co, $^{54}$Ni, $^{56}$Cu [3,4], $^{79}$Y, $^{81,82}$Zr, $^{83,84}$Nb [5], $^{101g,m}$In [6], $^{87m}$Mo, $^{91m}$Ru, $^{95m}$Pd, $^{103}$Sn [7]. Some physics issues have been addressed using our new and improved mass data. In this talk, the experiment details and some selected topics in nuclear structure and in nuclear astrophysics are presented and discussed. We also outline the plans and the technique improvements in our future experiments.

References:
[1] C. Y. Fu et al., Phys, Rev. C 98, 014315 (2018)
[2] C. Y. Fu et al., Phys, Rev. C 102, 04311 (2020)
[3] Y. H. Zhang et al., Phys, Rev. C 98, 014319 (2018)
[4] M. Wang et al., Phys, Rev. C 106, L051301 (2022)
[5] Y. M. Xing et al., Phys. Lett. B 781, 358 (2018)
[6] X. Xu et al., Phys, Rev. C 100, 051303(R) (2019)
[7] Y. M. Xing et al., Phys, Rev. C 107, 014304 (2023)

Orateur: Dr Meng Wang

poster session

jeudi 8 juin

plenary 13

Président de session: Prof. Piet Van Duppen (KU Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200D, 3001 Leuven, Belgium)

72 Studies of astrophysically important reactions using rare isotope beams at TRIUMF

Determining the stellar origin of the elements observed in our Galaxy today poses one of the key challenges in the field of nuclear astrophysics. Thus, we seek to understand the nuclear processes involved in stellar evolution, as their details give us insight into the fusion pathways and routes to the synthesis of heavy elements. The investigation of radiative capture reactions involving the fusion of hydrogen or helium is crucial for the understanding of said nucleosynthesis pathways as these reactions govern nucleosynthesis and energy generation in a large variety of astrophysical burning and explosive scenarios. However, direct measurements of the associated reaction cross sections at astrophysically relevant low energies are extremely challenging due to the vanishingly small cross sections in this energy regime. Continuous advances in the production of accelerated rare isotope beams provide an opportunity to simulate and study the reactions occurring inside stars. However, many astrophysically important reactions involve radioactive isotopes, which still pose challenges for beam production and background reduction.

To overcome these challenges, dedicated facilities, such as the DRAGON (Detector of Recoils And Gammas Of Nuclear reactions) recoil separator, SONIK (Scattering Of Nuclei in Inverse Kinematics), TUDA, the TRIUMF UK Detector Array for charged particle detection as well as the EMMA (ElectroMagnetic Mass Analyser) recoil mass spectrometer at the TRIUMF-ISAC Radioactive Ion Beam Facility have been designed to experimentally determine nuclear reaction rates of interest for nuclear astrophysics in inverse kinematics.

In this contribution, I will introduce the experimental facilities - with focus on the DRAGON recoil separator - before presenting recent experimental highlights involving the use of radioactive and high-intensity stable ion beams. Finally, I will report on recent and future facility upgrades to extend the experimental capacities and versatility.

Orateur: Annika Lennarz (TRIUMF)

ARIS2023_Lennarz.pdf

73 Latest results from MARA

J. Uusitalo,
for the nuclear spectroscopy group collaboration

Accelerator Laboratory, Department of Physics, University of Jyväskylä, FI-40014, Jyväskylä, Finland
Department of Physics, Oliver Lodge Laboratory,
University of Liverpool, Liverpool, L69 7ZE, United Kingdom

A new vacuum-mode separator, MARA (Mass Analyzing Recoil Apparatus) [1, 2], has been completed and has extended the research possibilities whit the existing gas-filled recoil separator, RITU [3] at JYFL-ACCLAB. The ion-optical configuration of MARA is QQQDEDM, differing significantly from the other existing in-flight separators around the world. MARA has turned out be a very reliable separator and easy to operate. The studied nuclei of interest have been produced using fusion-evaporation reactions, mainly employing symmetric or inverse kinematics. In-beam studies, isomeric studies as well as production of new isotopes have been performed at and beyond the proton dripline starting from a mass number 66 up to a mass number 180.
In this work some highlights of the latest results using the JYFL in-flight separator MARA will be given.
[1] J. Uusitalo et al., Acta Physica Polonica B 50 (2019) 319
[2] J. Sarén et al., Research Report No. 7/2011, University of Jyväskylä
[3] M. Leino et al., NIMB 99 (1995), 653

Orateur: Dr Juha Uusitalo (University of Jyväskylä)

74 From Tensor Currents to Solar Neutrinos: Precision Beta-Decay Studies of $^8$Li and $^8$B

The $\beta$-decays of $^8$Li and $^8$B provide an important playground to search for physics beyond the Standard Model, and, additionally, a detailed study of $^8$B $\beta$-delayed $\alpha$-particles provides key insights needed to constrain the spectrum of high energy neutrinos emitted by the Sun. To accomplish both these aims, the $\beta$-decays of $^8$Li and $^8$B were studied with the Beta-decay Paul Trap (BPT) at the ATLAS facility of Argonne National Laboratory. The BPT traps a cloud of ions at rest in a volume of ~1 mm$^3$ for extended periods of time, allowing for a backing-free measurement of the emitted particles. The trapping volume is surrounded by segmented, 1 mm thick DSSDs, from which the decay kinematics can be fully constrained by a $\beta$-$\alpha$-$\alpha$ triple coincidence measurement. This enables both a nearly background-free measurement of the $\beta$-$\nu$ angular correlation coefficient $a_{\beta \nu}$, while a $\alpha$-$\alpha$ double coincidence measurement enables a determination of the $^8$B neutrino energy spectrum.

We will present (1) recent results in $^8$Li, showing the most precise measurement of $a_{\beta \nu}$ in a GT decay and highlighting both the possibility of a ~9 MeV $2^+$ “intruder state” in $^8$Be and the importance of accurate values for the recoil-order terms, (2) the first measurement of $a_{\beta \nu}$ in $^8$B and a method to constrain $C_T$ and $C_T'$ in the decay of mirror systems, and (3) the preliminary analysis of a high statistics $^8$B dataset to determine $a_{\beta \nu}$, and a new determination of the neutrino spectrum following $^8$B $\beta$-decay, which is important for the next generation of solar neutrino experiments.

We acknowledge the U.S. DOE Contract No. DE-AC02-06CH11357 [ANL] and DE- AC52-07NA27344 [LLNL], the Argonne National Laboratory ATLAS facility, which is a DOE Office of Science User Facility, and NSERC, Canada, Contract Nos. SAPPJ-2015- 00034 and SAPPJ-2018-00028.

Orateur: Aaron Gallant (Lawrence Livermore National Laboratory)

ARIS23_AGallant_v1.pptx

75 Doubly magic 78Ni as a beta-delayed neutron precursor

78Ni is a unique doubly magic nucleus far from beta stability line, the only one decaying with β-delayed neutron emission channel. Its decay properties influence the early r-process nucleosynthesis and the beta decays of exotic nuclei north-east of Z=28 and N=50. Nuclei in the 78Ni region were created with the 345 MeV/u 238U beam reaching nearly 70 part*nanoAmp. Fragmentation products were separated by means of BigRIPS spectrometer at RIKEN (Wako, Japan). The spectroscopy of radiation emitted by beta-delayed neutron precursors was performed using BRIKEN 3He array [1] modified to achieve larger gamma efficiency [2]. ORNL contributions included 87% of 3He neutron detection volume and two Ge clovers. The fragment implantation and decay array were consisting of four smaller double-sided Si-strip counters of WASABI complemented by a position sensitive YSO scintillator developed at the UTK. The BigRIPS setting was maximized for the transmission of 82Cu. Isotopes between 61V-69V up to 95Br-97Br were produced and identified. The total rate of identified 78Ni ions was around 65,000, with about 40,000 ions implanted for decay study. Beta-gamma and beta-neutron-gamma decay channels were identified for 78Ni precursor. The P1n branching ratio of about 27(4)% was determined from the analysis [3] of β-1n decay pattern. New levels in 78Cu as well as new level associated with proton p3/2 state in Z=29 77Cu were observed. The accepted proposal to study 78Ni decay with the recently commissioned ORNL’s Modular Total Absorption Spectrometer at the Facility for Rare Isotopes Beams will be briefly presented.

[1] A. Tarifeño-Saldivia et al., Jour. of Instrum. 12, P04006 (2017).
[2] R. Yokoyama et al., Phys. Rev. C 100, 031302(R) (2019).
[3] B. C. Rasco et al., Nucl. Instrum. Methods. Phys. Res. A 911, 79 (2018).

Supported by the U.S. DOE Office of Nuclear Physics under contracts DE-AC05-00R22725 (ORNL) and DE-FG02-96ER40983 (UTK)

Orateur: Dr Krzysztof Rykaczewski (Oak Ridge National Laboratory)

10:25 coffee break

parallel session

Président de session: Klaus Wendt (Johannes Gutenberg University Mainz)

76 Measurement of the bound-state beta decay of highly charged ions 205Tl81+

Neutrinos are produced as a result of the nuclear fusion reactions happening inside the Sun. Precise measurement of the solar neutrino flux is crucial for a better understanding of the various nuclear reactions taking place in the Sun but also gives us important information about the Sun's core [1]. The geochemical experiment LOREX (LORandite EXperiment) [2], proposed by Freedman and collaborators aims to determine the long-time average (over ~4.3 million years) of the solar pp-neutrino flux Φν through the neutrino-capture reaction. The interaction cross-section of νe and 205Tl nucleus is important for the determination of the neutrino flux in the LOREX project. To determine the interaction cross-section, the half-life of bound state β- decay of bare 205Tl81+ nuclei is required as the two processes share the identical nuclear matrix element.
In this talk, we report on the first direct measurement of the bound-state beta decay of 205Tl81+ ions [3]. The experiment was performed at GSI, Darmstadt in 2020, wherein the entire accelerator chain was employed. Highly charged ions 205Tl81+ ions were produced with the projectile fragmentation of 206Pb primary beam on 9Be target, separated in the fragment separator (FRS), accumulated, cooled, and stored for different storage times (up to 10 hours) in the experimental storage ring (ESR). The experimentally measured half-life value agrees with the theoretically predicted values by E. Braun [3] and deviates from the theoretically predicted values [4,5]. The interaction cross-section between neutrino and 205Tl nucleus is determined. The impact of our result on LOREX project will be discussed in this talk.
This research has been conducted in the framework of the SPARC, ILIMA, LOREX, NucAR collaborations, experiment E121 of FAIR Phase-0 supported by GSI. The authors received support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 682841 “ASTRUm”).

[1] Wurm, Michael: Solar neutrino spectroscopy. Physics Reports 685, 1-52 (2017). 10.1016/j.physrep.2017.04.002
[2] Melvin S. Freedman et al., Solar Neutrinos: Proposal for a New Test. Science 193, 4258: p. 1117 (1976).
[3] Ragandeep Singh Sidhu, Ph.D. Thesis, Ruprecht-Karls-Universität, 2021.
[4]1986, Proceedings of the International Symposium, Weak and Electromagnetic Interactions in Nuclei, Heidelberg, edited by H. V. Klapdor (Springer, Berlin), p. 47.
[5] K. Takahashi et al., Phys. Rev. C, 36, 1522, 1987.
[6] S. Liu et al., Phys. Rev. C, 104, 024304, 2021.

Orateur: Rui-Jiu Chen (GSI)

77 Nuclear structure of Pd isotopes via optical spectroscopy

High-resolution laser spectroscopy has been proven to be a powerful tool to extract nuclear structure data in an nuclear-model-independent manner. The isotope shift which can be extracted from the hyperfine spectra gives direct access to changes in mean-square charge radii, while the extracted hyperfine parameters give access to the nuclear spin, nuclear magnetic dipole moment and electric quadrupole moment. All this provides information on e.g. deformation and shape coexistence, proton-neutron pairing correlations, evolution of nuclear shells and the presence of shell closures. In recent years, measurements of nuclear ground state properties have also been proven exceptionally potent in testing state-of-the-art nuclear Density Functional Theory (DFT) and ab-initio approaches.

The Pd isotopes are located in a transitional area in between chains which display smooth parabolic trends in the changes in mean-square charge radii (Sn, In, Cd and Ag), and a region where the changes in mean-square charge radii and corresponding electric quadrupole moments show evidence of a dramatic shape change at N=60, maximized and centred around the yttrium system. In the transitional area between both regions however, i.e. the Tc, Ru, Rh and Pd isotopes, no optical spectroscopic information has been available for radioactive nuclei so far. This is in part due to the refractory character of these nuclei, which makes their production challenging for many facilities, but also due to their complex atomic structure.

At the IGISOL facility, these difficulties were overcome thanks to the chemically insensitive production method, and the installation of a charge-exchange cell and addition of a cw Ti:sapphire laser. Collinear laser spectroscopy was performed on unstable Pd isotopes, which are known to be deformed from decay spectroscopy studies, although there is disagreement on the origin and character of the (possible) change in deformation. The measured nuclear charge radii [1], spins and nuclear moments [2] will be presented in this contribution, and the implication on the deformation/shape of the isotopes will be discussed. In addition, the results will be compared to state-of-the-art DFT calculations using Fayans Energy Density Functionals (EDFs), and using Gogny EDF including beyond mean-field calculations within the Symmetry Conserving Configuration Mixing (SCCM) framework. As all recent benchmarks of nuclear DFT were performed on spherical systems, close to (doubly-)magic systems, this presents the first test of the performance of the Fayans functionals for well-deformed isotopes.

[1] S. Geldhof et al., Phys. Rev. Lett. 128, 152501 (2022).
[2] A. Ortiz-Cortes et al., to be submitted.

Orateur: Sarina Geldhof (GANIL)

ARIS-Geldhof.pptx

78 Laser Spectroscopy of the Hyperfine Splitting in $^{208}$Bi$^{82+}$

We present results of a laser spectroscopy experiment on the hyperfine splitting of hydrogen-like $^{208}$Bi$^{82+}$ at the Experimental Storage Ring (ESR) at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt. This is the first time that an artificially produced isotope is successfully targeted by laser spectroscopy in a storage ring.
During the campaign in May 2022, the ions of the radioactive isotope were produced in-flight before injection into the ESR. After isotope separation, a few 10$^{5}$ $^{208}$Bi$^{82+}$-ions were stored with β = 0.72 (E$_\mathrm{ion}$ = 408$\,$MeV/u). To excite the hyperfine transition ($\lambda_0$ = 221$\,$nm) the ion beam was superimposed with a counterpropagating beam of a pulsed dye laser at $\lambda_\mathrm{lab}$ = 548$\,$nm. Fluorescence detection was realized spatially separated from the laser interaction with a new detection region to obtain the required low background.
The result is compared to the theoretical and semi-empirical predictions in [1]. It will later be combined with a measurement on lithium-like $^{208}$Bi$^{80+}$, which is in preparation, to provide the so-called specific difference between the two hyperfine splittings [2,3]. This will constitute the most stringent test of QED in strong magnetic fields.
[1]: S. Schmidt, et al., Phys. Lett. B, 779, 324 (2018).
[2]: V. M. Shabaev, et al., Phys. Rev. Lett. 86, 3959 (2001).
[3]: Ullmann et al., Nat. Comm., 8, 15484 (2017).

Funding by BMBF under contract 05P21RDFA1 is acknowledged.

Orateur: Max Horst (TU Darmstadt, HFHF Darmstadt)

79 High-precision collinear laser spectroscopy - An all-optical nuclear charge radius of $^{12}$C

The size of an atomic nucleus is a fundamental observable and can be used to benchmark nuclear structure theory and therefore test our fundamental knowledge of matter. In contrast to matter and neutron radii, the nuclear charge radius can be probed through the well-known electromagnetic interaction. Typically, charge radii of stable nuclei are extracted from elastic electron scattering or muonic atom spectroscopy, and collinear laser spectroscopy resonance ionization spectroscopy are used to measure differential charge radii of radioactive isotopes relative to a stable reference nucleus. In a few cases, the uncertainty of the charge radius of the stable isotope limits the uncertainties of the radioactive species. To overcome this limit in light mass nuclei like $^{10, 11}$B, an all-optical approach for the charge radius determination purely from laser spectroscopy measurements and non-relativistic QED calculations [1] was tested with the well-known nucleus of $^{12}$C. Thereby, helium-like $^{12}$C$^{4+}$ was laser excited from the metastable $1s2s\,^3$S$_1$ state with a lifetime of 21 ms to the $1s2p\,^3$P$_J$ states and the respective transition frequencies were determined with less than 2 MHz uncertainty. The high-precision collinear laser spectroscopy was performed at the Collinear Apparatus for Laser Spectroscopy and Applied Science (COALA), situated at the Institute for Nuclear Physics at the TU Darmstadt.
This contribution will present the first high-precision laser spectroscopy in the isotopic chain of carbon and the first all-optical nuclear charge radius determination of $^{12}$C. This project is supported by the German Research Foundation (Project-ID 279384907 – SFB1245).
[1] V.A. Yerokhin et al., Phys. Rev. A 106, 022815 (2022)

Orateur: Phillip Imgram (Institute for Nuclear Physics, Technical University Darmstadt)

80 Production of medical grade Ac-225 with resonant laser ionization and mass separation at CERN MEDICIS

The medical radioisotope Ac-225 is produced at a handful of accelerator facilities by high energy proton irradiation of thorium-based targets. The current standard separation protocol of this isotope and its generator parent Ra-225 from irradiated targets is based on radiochemistry. This method can recover Ac-225 and Ra-225 with high radiochemical yields of >90%. Nonetheless, a major issue is that the recovered Ac solutions contain the long-lived Ac-227 with an activity potentially unsafe for medical use. In order to address this, the method of resonant laser ionization and mass separation can instead be performed on Ac-225-containing samples including irradiated ThO2 matrices, or as solutions dried on refractory foils. This contribution will provide a comprehensive overview of the multiple collections of Ac-225 that have been performed with this method at CERN MEDICIS from different starting samples. For each collection, the total separation efficiency as measured by complementary alpha- and gamma-spectroscopy techniques will be reported and discussed. Furthermore, the separation factor of Ac-225 compared to Ac-227 through this method and hence its suitability for producing medically relevant Ac-225 samples will be reported where applicable. During the discussion, emphasis will be placed on the systematics of the laser ionization efficiency, as well as Ac-225 release as a function of its chemical environment and temperature. The contribution will conclude by recommending an optimum method for separating medical grade Ac-225 from thorium-based targets irradiated with protons.

Orateur: Jake Johnson (KU Leuven)

81 Measurements of β-delayed one and two neutron emission probabilities south-east of 132Sn within the BRIKEN project at RIKEN

Recent observations of metal-poor star elemental and isotopic abundances [Roe22, Wen18] have sparked new interest in the nucleosynthesis of elements around the second r-process abundance peak, as it may shed light on the r-process conditions. To understand the r-process conditions and link these observations to astrophysical models, it is crucial to have information on the nuclear properties of the radioactive progenitors of the second r-process peak.
Following r-process freezeout, the final abundances of the second peak are the result of various competing reactions, such as neutron capture, photodisintegration, fission, and β-delayed neutron emission. The latter has been the main focus of our experiment, conducted within the BRIKEN project [Tol19] at the RIBF facility of RIKEN (Japan).
In the present contribution, we will present new experimental results on β-delayed one and two neutron emission probabilities of very neutron-rich nuclei located south-east of ¹³²Sn [Pho20] and compare them with recent macroscopic-microscopic and self-consistent global models with the inclusion of the statistical treatment of neutron and γ emission [Kaw08, Min21]. The impact of our results on the odd-even staggering of the final r-process abundance around the second r-process peak, as well as the observed odd-mass isotopic fractions of Ba in metal-poor stars [Wen18] will be presented. Continuing our experimental program on r-process nuclei, we will present a new experimental setup that will allow β-decay and β-delayed neutron spectroscopy studies to be conducted in parallel with MR-TOF mass measurements program at RIKEN RIBF.

References
[Roe22] I. U. Roederer et al., Astrophys. J. Suppl. Ser. 260, 27 (2022).
[Wen18] C. Wenyuan et al., Astrophys. J. 854, 131 (2018).
[Pho20] V. H. Phong, Phys. Rev. Lett. 129, 172701 (2022)
[Tol19] A. Tolosa-Delgado et al., Nucl. Instr. And Methods A, 925, 133 (2019)
[Kaw08] T. Kawano, P. Möller, and W. B. Wilson, Phys. Rev. C 78, 054601 (2008).
[Min21] F. Minato et al., Phys. Rev. C 104, 044321 (2021).
[Ros22] M. Rosenbusch et al., Nucl. Instr. And Methods A, 1047, 167824 (2023)

Orateur: Dr Phong Vi (RIKEN Nishina Center, Japan and University of Science, Vietnam National University, Hanoi, Vietnam)

82 Nuclear and molecular physics studies with laser spectroscopy of radioactive molecules

The research potential of radioactive molecules for both fundamental and applied science has recently been recognized [1,2] and significant progress has been marked at ISOLDE on both the production [3] and the spectroscopy [4-7] of radioactive molecules.

In addition to the first laser spectroscopy of RaF at the collinear resonance ionization spectroscopy (CRIS) experiment [4,5] and its subsequent high-resolution study [6], the CRIS collaboration recently performed the first laser spectroscopy of AcF [8]. AcF has been proposed as a promising system for the first measurement of a nuclear Schiff moment across the nuclear chart, which is a symmetry-violating property that is predicted to be easier to measure in AcF than in RaF, YbF, ThO, and other diatomic molecules that are currently under investigation in the search for an electron electric dipole moment.

Simultaneously, experimental and theoretical progress in the excited electronic states of RaF [7] and the manifestation of nuclear observables in molecular spectra [9] carried out by members of the CRIS collaboration has highlighted the potential of laser spectroscopy of radioactive molecules at radioactive ion beam facilities to probe nuclear and molecular observables that are not easily accessible by other methods and systems.

In this talk, recent results by the CRIS collaboration on the laser spectroscopy of RaF and AcF will be presented, along with the spectroscopy of lighter radioactive molecules that can provide access to nuclear and molecular observables that cannot be studied via other methods. The future directions of laser-spectroscopic studies of radioactive molecules at CRIS will also be discussed.

[1] Opportunities for Fundamental Physics Research with Radioactive Molecules, In preparation (2023)
[2] M. Athanasakis, S. G. Wilkins, G. Neyens, Radioactive molecules at ISOLDE, Letter of Intent to the ISOLDE and n_ToF Committee at CERN. No. CERN-INTC-2021-017 (2021)
[3] M. Au et al., In-target, in-source, and in-trap formation of molecular ions in the actinide mass range at CERN-ISOLDE, Submitted to NIM B (2023)
[4] R. F. Garcia Ruiz et al., Spectroscopy of short-lived radioactive molecules, Nature 581, 396 (2020)
[5] S. M. Udrescu et al., Isotope Shifts of Radium Monofluoride Molecules, Physical Review Letters 127, 033001 (2021)
[6] S. M. Udrescu, S. G. Wilkins et al., Precision spectroscopy and laser cooling scheme of a radium-containing molecule, Under review at Science (2023)
[7] M. Athanasakis-Kaklamanakis, S. G. Wilkins, L. V. Skripnikov et al., Pinning down electron correlations in RaF towards searches for new physics, In preparation (2023)
[8] M. Athanasakis-Kaklamanakis et al., Laser ionization spectroscopy of AcF, Proposal to the ISOLDE and n_ToF Committee at CERN. No. CERN-INTC-2021-053 (2021)
[9] M. Athanasakis-Kaklamanakis, S. G. Wilkins, A. A. Breier, and G. Neyens, King-plot analysis of isotope shifts in simple diatomic molecules, Accepted at Physical Review X (2023)

Orateur: Michail Athanasakis-Kaklamanakis (CERN)

mak_ARIS2023.pptx

parallel session

Président de session: Daniel Bazin (MSU-FRIB)

83 First results with the Advanced Rare Isotope Separator (ARIS) at FRIB

Commissioning of the Facility for Rare Isotope Beams (FRIB) in-flight separator system Advanced Rare Isotope Separator, ARIS, began in early 2022. The system consists of up to three stages of achromatic separation based on large superconducting magnets and can deliver beams to various experimental stations for nuclear and astrophysics studies, as well as other societal needs. ARIS is designed to be able to work with 400kW of primary beam power. The conceptual design and the comparison to commissioning studies will be presented.

In this contribution we summarize first results of rare beam isotopes production, and then to focus on high Z isotopes production in the recent commissioning experiment, that demonstrates ARIS abilities to separate and identify isotopes produced in the energy range of 100-200 MeV/u. Isotope production results and comparison with production models will be presented.

Funding Agency:
Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University.

Orateur: Oleg Tarasov (FRIB /MSU)

84 Evolution of the neutron $1d$ spin-orbit splitting in $^{35}$S and $^{39}$Ca

Nuclei along N=20 provide an excellent region to investigate the change in nuclear structure and interactions. From their evolution from the doubly magic nucleus $^{40}$Ca through to the Z=16 and Z=14 nuclei $^{36}$S and $^{34}$Si, respectively, to $^{32}$Mg with a deformed $2p-2h$ intruder ground state [1]. The mechanism responsible for the change in shell structure is not well understood and is suspected to be a subtle combination of the different components of the nuclear force namely the central, spin-orbit (SO), and tensor parts. A significant reduction of the neutron $d_{5/2}$ and $d_{3/2}$ spin-orbit splitting between $^{40}$Ca and $^{36}$S, as protons are removed from the $d_{3/2}$ orbital, would be indicative of the proton-neutron tensor force. By comparing the neutron $d_{5/2}$ hole strength between these nuclei, the strength of the tensor force is probed in an unprecedented manner.

The centroids of the hole states in $^{35}$S have been inferred from a $^{36}$S(p,d)$^{35}$S experiment performed at iThemba LABS. A $^{36}$S(p,d)$^{35}$S reaction is a useful tool to probe the neutron spin-orbit splitting in $^{36}$S, provided a reliable $^{36}$S target is available. This was achieved by specifically developing a new target system at iThemba LABS which allows for a cost-effective $^{36}$S target without heavy contaminants to be used. This novel target encapsulates sulfur between two Mylar foils and has been shown to be an effective way to produce targets with a significant amount of material (0.5-1 mg/cm$^2$).
Using this moving $^{36}$S target with 66 MeV incident protons, states in $^{35}$S were measured with the K600 magnetic spectrometer at iThemba LABS. States up to 20 MeV were observed, identifying the neutron single-particle strength below and above the Fermi surface using the detection of the deuterons at the focal plane of the K600 spectrometer with an energy resolution of approximately 30 keV [2]. The results from the $^{36}$S(p,d)$^{35}$S experiment were compared to the $^{40}$Ca(p,d)$^{39}$Ca study by Matoba et al. [3]. The results show an increase of the neutron $1d_{5/2}$ - $1d_{3/2}$ SO
splitting between $^{35}$S and $^{39}$Ca by 0.411 MeV. This is contrary to the universal trend of SO splitting with increasing mass number which would predict a decrease of $\sim$ 0.450 MeV. This deviation is highly indicative of the effect of tensor forces. At present, the tensor force is not implemented in the vast majority of the available mean field and relativistic mean field calculations, whereby the amplitude of the SO
splitting is solely attributed to the spin-orbit force. This study provides an unambiguous result indicating the role of the tensor force. It is shown that the strength of the tensor force is, however, lower than predicted by the shell model and ab-initio theory.

[1] O. Sorlin and M.-G. Porquet, Progress in Particle and Nuclear Physics 61,
602 (2008), ISSN 0146-6410
[2] R. Neveling, H. Fujita, et. al Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and
Associated Equipment 654, 29 (2011), ISSN 0168-9002
[3] M. Matoba, et. al Phys. Rev. C 48, 95 (1993)

This work is supported by the National Research Foundation of South Africa grant 118846.

Orateur: Sandile Jongile

Sandile_Aris_presentation_8June.pdf

85 Evolution of single-particle structure along the Mg isotopic chain: the d(30Mg,p)31Mg reaction measured with the ISOLDE Solenoidal Spectrometer

The $N=20$ "island of inversion" is a neutron-rich region of the nuclear chart which is of particular importance for understanding the evolution of nuclear structure. In this region, deformed intruder configurations (particle-hole excitations) dominate at ground-state and low-excitation energies which is facilitated by the weakening of the $N=20$ shell closure. Additionally this shell gap weakens as protons are removed, leading to a new shell closure emerging at $N=16$, which produces doubly-magic properties in $^{24}$O.

The magnesium isotopes exhibit a swift transition into the island between $^{30}$Mg and $^{31}$Mg, and thus are a useful measure of how single-particle structure evolves into the island. Data on isotopes in this region can be used to test the validity of current nuclear models, and be used to further refine them for other nuclei in the island.

The ISOLDE Solenoidal Spectrometer (ISS) collaboration published results on the nuclear structure of $^{29}$Mg recently [1], measuring its neutron occupancies from the $d$($^{28}$Mg,$p$)$^{29}$Mg reaction (9.47 MeV/u) performed before CERN's long shutdown. An analagous $d$($^{30}$Mg,$p$)$^{31}$Mg reaction (8.52 MeV/u) has been performed at the ISS to examine the neutron occupancies of $^{31}$Mg, which can be compared to the measurement of $^{29}$Mg to understand this transition into the island. This measurement was performed with a new on-axis silicon developed specifically for ISS. Preliminary results from this new measurement will be presented, with reference to the previous measurement on $^{29}$Mg.

[1] P. T. MacGregor et al., Phys. Rev. C 104, L051301, Nov 2021

Orateur: Dr Patrick MacGregor (CERN)

2023_aris_ptm.pdf

86 Medical Radioisotope Production Using Inverse Kinematics

A novel approach to produce medically important radionuclides using inverse kinematics [1-3] has been developed at the Cyclotron Institute at Texas A&M University. The methodology involves a heavy-ion beam of appropriate energy impinging on a light gas target (e.g., $H_{2}$, $D_{2}$, $^{3-4}$He, …) and collecting the isotope of interest, focused along the beam direction, on a foil catcher after the target. In addition, secondary emitted particles such as neutrons from the primary nuclear reaction can be used to irradiate a secondary target for further radionuclide production. As the quantity of the material required to prepare the heavy-ion beam is considerably smaller than that used in the standard solid target approach, material costs are expected to be reduced via this methodology. The theranostic radionuclide $^{67}Cu$ ($T_{1/2} = 62 h$) was produced through the reaction of a $^{70}Zn$ beam at 15 MeV/nucleon with a hydrogen gas target [1-2]. The $^{67}Cu$ radionuclide alongside other coproduced isotopes, was collected after the gas target on an aluminum catcher foil. Their radioactivity was measured by off-line $\gamma$ -ray analysis. In addition, the forward-focused neutrons from the primary reaction were used to irradiate a $^{nat}Zn$ target in order to produce more $^{67}Cu$. Pursuing this initial investigation, the well-known $^{99}Mo/^{99m}Tc$ generator system [3] was also investigated with a beam of $^{100}Mo$ at 12MeV/nucleon on $^{4}$He gas cell target for three different gas pressures. The methodology was tested with success. The production of the $^{67}Cu$ and $^{99}Mo$ were predominant in comparison with the various radio-impurities. In order to achieve production appropriate for preclinical studies, high-intensity heavy-ion primary beams are necessary.

References
[1] Souliotis, G. et al. A novel approach to medical radioisotope production using inverse kinematics: A successful production test of the theranostic radionuclide $^{67}Cu$. Applied Radiation Isotopes 149, 89–95, DOI: https://doi.org/10.1016/j.apradiso. 2019.04.019 (2019).
[2] Rodrigues, M.R.D. et al. A novel approach to medical radioisotope production using inverse kinematics, EPJ Web of Conferences 252, 08002, DOI: https://doi.org/10.1051/epjconf/202125208002 (2021).
[3] Mabiala J. et al. Enhanced production of $^{99}$Mo in inverse kinematics heavy ion reactions, EPJ Web of Conferences 252, 08003. DOI: https://doi.org/10.1051/epjconf/202125208003 (2021).
[4] Rodrigues M.R.D. et al., Radiation Physics and Chemistry submitted.

Orateur: Dr Marcia Dias Rodrigues (Cyclotron Institute, Texas A&M University, USA)

87 Light-exotic nuclei studied with the (t,p) reaction in inverse kinematics using HELIOS

We report on studies of `$^{14}$B and $^{10}$Li using the (t,p) reaction in inverse kinematics with HELIOS at Argonne National Laboratory. Two-neutron transfer provides information complementary to that obtained with one-neutron transfer. The selective nature of (t,p) is ideal for studying neutron pairing, configuration mixing and shape-coexistence, effects necessary to understand regions where the shell-model orbitals are changing rapidly with N/Z. Here, we have studied the $^{12}B$(t,p)$^{14}$B and $^8$Li(t,p)$^{10}$Li reactions. In $^{14}$B, data for $^{14}$Be beta-decay [1] and the $^{14}$Be(p,n)$^{14}$B reaction [2] suggest a 1$^+$ excitation at E$_X$($^{14}$B)=1.27 MeV interpreted as a low-lying intruder state with strong $\nu$(1s$_{1/2})^2$ character. The properties of this and other $\nu$(sd)$^2$ states in $^{14}$B that can be populated in (t,p) provide information about the changing nature of the p-sd splitting in this mass region that is important, for example, in understanding the disappearance of the N=8 shell gap suggested in $^{12}$Be. In $^{10}$Li, the nature of the low-lying structure remains controversial with conflicting interpretations of data from the $^9$Li(d,p)$^{10}$Li reaction[3,4] suggesting the dominance of either s-wave or p-wave excitations. The selectivity of (t,p) can shed more light on this behavior, but also identify two-neutron (sd)$^2$ excitations that, due to their small overlap with $^9$Li$_{g.s.}$+n, may be narrow despite $^{10}$Li being unbound. The properties of such states in $^{10}$Li can provide information that is important for a detailed understanding of the two-neutron halo structure of $^{11}$Li.

Secondary $^{12}$B and $^8$Li beams produced using the RAISOR separator at the ATLAS facility at Argonne National Laboratory bombarded a $^3$H target consisting of $^3$H adsorbed into a 450 $\mu$g/cm$^2$ Ti foil. Protons transported by the HELIOS uniform magnetic field were detected using an array of position-sensitive silicon detectors, and recoiling beam-like reaction products were detected at forward angles using a set of E-E silicon-detector telescopes. We will present the results of first measurements of the $^{12}$B(t,p)$^{14}$B and $^8$Li(t,p)$^{10}$Li reactions, and compare the observations with predictions of shell-model calculations for two-neutron transfer leading to states in $^{14}$B and $^{10}$Li.

This research was supported by the US Department of Energy, Office of Nuclear Physics, under Grants No. DESC0014552, (UConn), No. DE-FG02-96ER40978 (LSU), and No. DE-AC02-06CH11357 (ANL).
[1] N. Aoi et al., Phys. Rev. C 66, 014301 (2002).
[2] Y. Satou et al., Phys. Lett. B 697, 459 (2011).
[3] H. B. Jeppesen et al., Phys. Lett. B 642, 449 (2006).
[4] M. Callavaro et al., Phys. Rev. Lett. 118, 012701 (2017).

Orateur: Alan Wuosmaa (University of Connecticut)

wuosmaa avignon 2023.pdf

88 Spectroscopy of heavy neutron-rich N > 126 nuclei at RIKEN

The experimental information available to test shell-model calculations south of 208Pb is almost non-existent at present due to the challenges in accessing the exotic neutron-rich region around and beyond N=126. Such information are essential not only for understanding how the shell structure evolves below and beyond N=126, and if deformation or new shell gaps develop in the region, but to calculate more complex configurations in the more exotic, inaccessible nuclei on the r-process pathway towards the trans-bismuth fissile elements [Hol19].

In the present contribution, we will show for the first time new isomeric transitions observed in the “south-east” quadrant of 208Pb in an experiment carried out during the 2021 spring campaign of the BRIKEN collaboration at the RIBF factory in RIKEN (Japan) [Wu17,Tol19]. The level schemes will be discussed in terms of the latest shell-model calculations in the region [Yuan22]. Future perspectives to continue with the investigation of isomerism around and beyond 208Pb exploiting the BigRIPS spectrometer at RIKEN will be discussed as well.

References
[Hol19] E.M. Holmbeck et al., Ap. J. 870, 23 (2019)
[Tol19] A. Tolosa-Delgado et al., Nucl. Instr. And Methods A, 925-133 (2019)
[Wu17] J. Wu et al., β-decay spectroscopy in the vicinity of the N=126 closed shell. RIBF NP-PAC Proposal NP1712-RIBF158
[Yuan22] Cenxi Yuan et al., Phys. Rev. C 106, 044314 (2022)

Orateur: Anabel Morales López (IFIC (CSIC-UV))

89 Precision Lifetime Measurements of Excited States in 38Si and 36Si

Rapid shape transitions are predicted by the shell model calculations as a result of the nuclear shell structure significantly evolving in the neutron-rich region at the traditional magic numbers N=20 and 28. The energy ratios between the first 2+ and 4+ states in the even-even silicon isotopes from N=20 to 28 suggest a variety of collectivity evolving from vibrational, to possible triaxial, to rotational modes. The systematic behavior of the level schemes along the silicon isotopic chain suggests 38Si as the turning point in this transition. The lifetime measurements of 38Si and 36Si were performed at the National Superconducting Cyclotron Laboratory based on the Recoil-Distance Method using the Gamma-Ray Energy Tracking In-Beam Nuclear Array (GRETINA). The data was used to extract the B(E2) ratios for the yrast 2+ and 4+ states in 38Si and the yrast 4+ and 6+ states in 36Si. These ratios were then compared to theoretical models.

Orateur: Mara Grinder (Rutgers University)

12:45 lunch break

parallel session

Président de session: Michael Block (GSI/HIM/JGU)

90 Developments in muonic x-ray spectroscopy

Muonic x-ray spectroscopy is a technique that utilizes the properties of the muon to obtain information about the structure of the atom and the nucleus. When a muon interacts with an atom, it can be captured in a high principal atomic quantum number state, after which it will fall towards the ground state emitting high energy characteristic x rays. Due to the heavy mass of muons compared to that of electrons ($m_{\mu} \approx 207 m_e$, the muon’s orbitals are closer to the nucleus with that same factor. Hence, the muonic energy levels are more sensitive to nuclear effects. In particular, the finite size correction is increased by a factor close to $10^7$. Consequently, muonic x rays can provide valuable input for laser spectroscopy in the form of high-precision absolute charge radii ($10^{-3}$ relative precision).

While muonic x rays have been extensively studied at the end of the twentieth century, it was limited to target quantities above 10 mg. However, in 2017, our collaboration investigated the use of a high-pressure hydrogen cell with a small deuterium admixture in order to enhance the transfer of the muon to the target atom of interest [1]. With this advancement, measurements on targets of ~5 µg became possible, opening the door to long-lived radioactive isotopes (>20 years) [2]. At low-to-medium atomic numbers, a high isotopic purity is required in order to reliably extract the nuclear charge radius. This purity can only be obtained by using magnetic mass separation for certain isotopes. Therefore, we investigated the feasibility of using implanted targets during a beamtime in September 2022. Besides measurements on implanted targets, the attenuation of the muonic x-ray signal through graphite was quantified. These advancements will allow for absolute charge radii measurements of medium-Z elements that are not available in sufficiently large quantities and/or isotopic purity.

In this contribution, we will report on the recent advancements of the muX collaboration as well as their implications for future research.

[1] Knecht, Andreas, Alexander Skawran, and Stergiani Marina Vogiatzi. "Study of nuclear properties with muonic atoms." The European Physical Journal Plus 135.10 (2020): 1-18.
[2] Adamczak, A., et al. "Muonic atom spectroscopy with microgram target material." EPJA in print (2023).

Orateur: Michael Heines (IKS, KU Leuven, Belgium)

muX_talk_ARIS.pptx

91 Study of alpha particle production in the 6He+9Be collision

A study of reaction mechanisms involved in the production of alpha particles in reactions induced by a 6He radioactive beam on a 9Be target nuclei is presented. Experimental data [1] was obtained using the RIBRAS (Radioactive Ion Beams in Brasil) facility of the Institute of Physics of the University of São Paulo, Brazil [2-4]. It is the first RIB facility in the southern hemisphere and is presently the only experimental equipment in South America capable of producing secondary beams of rare isotopes. The RIBRAS system consists of two superconducting solenoids used to select and focus light secondary beams of nuclei out of the stability valley. 6He+9Be angular distributions were measured at Elab=16.2MeV and Elab=21.3 MeV bombarding energies. A large yield of alpha particles was observed, that is absent with gold target measurements, indicating that they come from reactions with the 9Be target. The 6He secondary beam had many kind of particles (cocktail beam) like 7Li and light particles such as α, p and t. In particular, these 7Li and α-particles can also contribute to the production of the observed alpha particles, in addition to the breakup of the 9Be target, since the 9Be nucleus has (α+α+n) cluster configuration with binding energy of 1.564 MeV. Energy and angular distributions of those events were obtained taking into account these alpha particle production possibilities. The results were compared with theoretical calculations performed using the Continuum Discretized Coupled Channel (CDCC), the Ichimura-Austern-Vincent (IAV) formalisms [5,6], in addition to the fusion-evaporation calculations.

References
[1] K. C. C. Pires et al. Phys. Rev. C83, 064603, (2011).
[2] R. Lichtenthäler Filho, et al. Eur. Jour. of Phys., 25, 733, (2005).
[3] A. Lépine-Szily, et al. Nuclear Physics News, v. 23, p. 5-11, (2013).
[4] R. Lichtenthäler, et al. Eur. Phys. J. A57, 92 (2021).
[5] Jin Lei, A. M. Moro. Phys. Rev. C92, 044616 (2015).
[6] O. C. B. Santos et al. Phys. Rev. C103, 064601 (2021).

Orateur: Kelly C. C. Pires (Universidade de São Paulo)

92 Recent Nuclear Structure Studies at N=50 Through Masses of Isomeric States

The nuclear binding energy arises from various effects that govern nuclear properties. Different nucleon configurations within nuclear isomers lead to modified binding energies, often resulting in mass differences of tens to hundreds of kilo-electronvolts. These isomeric excitation energies can be directly accessed by measuring the difference in atomic masses of ground and isomeric states. Here, we present such measurements performed through mult-reflection time-of-flight [1] and ion-cyclotron resonance mass spectrometry [2]. By evaluating the excitation energies of neutron-deficient indium isotopes down to the shell closure at N=50 against state-of-the-art shell model, DFT, and ab initio calculations, we contrast the performance of these theories applied to several nuclear properties [3,4]. We further present evidence for shape-coexistences close to N=50 through independent excitation energy measurements of the 1/2$^+$ state in $^{79}$Zn with JYFLTRAP at IGISOL and ISOLTRAP at ISOLDE, supported by accurate large-scale shell model calculations [5].

[1] Wienholtz, F. et al. (2013). Masses of exotic calcium isotopes pin down nuclear forces. Nature, 498(7454), 346–349. https://doi.org/10.1038/nature12226
[2] Dilling, J., Blaum, K., Brodeur, M., & Eliseev, S. (2018). Penning-Trap Mass Measurements in Atomic and Nuclear Physics. Annual Review of Nuclear and Particle Science, 68, 45–74. https://doi.org/10.1146/ANNUREV-NUCL-102711-094939
[3] Mougeot, M. et al. (2021). Mass measurements of 99–101In challenge ab initio nuclear theory of the nuclide 100Sn. Nature Physics, 17(10), 1099–1103. https://doi.org/10.1038/S41567-021-01326-9
[4] L. Nies et al., Isomeric excitation energy for 99mIn from mass spectrometry reveals contrasting trends next to doubly magic 100Sn, submitted
[5] L. Nies et al., in preparation

---

L. Nies, A. Kankainen, K. Blaum, D. Lunney, L. Schweikhard for the JYFLTRAP and ISOLTRAP collaborations

Orateur: Lukas Nies (CERN / University of Greifswald (DE))

2023_06_02_ARIS_LUKAS_NIES_ISOLTRAP.pdf

93 Combined Mass and Half-life Measurements with TITAN's MR-TOF-MS

TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN) operates several ion traps for high-precision mass measurements and spectroscopy. Among these traps is a Multi-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) for mass measurement and isotope selective cleaning of beam for other traps. TITAN's MR-TOF-MS has demonstrated excellent dynamic range ($\sim10^8$) and high-precision ($\frac{\delta m}{m} \approx 10^{-7}$) allowing for measurement of very exotic isotopes. Presented here are a set of mass measurements clarifying the nuclear structure near N=34 in potassium.

Recently we developed new techniques enabling the measurement of half-lives using the MR-TOF-MS. This has allowed for half-life measurements of isotopes ranging from $\sim$10 ms and $\sim$5 min. In addition to providing supplementary data for identification of species, this new measurement technique has allowed for several first time half-life measurements and improved half-life uncertainties. The TITAN MR-TOF-MS's re-trapping and ion by ion mass and decay measurement abilities have proven to be powerful tools for half-life and mass measurements of exotic low rate species in a high background environment. The implications of these and future half-life measurements for nuclear structure and nucleosynthesis will be discussed.

Orateur: M. Coulter Walls (University of Manitoba)

ARIS 2023 Coulter Walls - final(1).pptx

94 Recent highlights from high-precision atomic mass measurements using MRTOF-MS at RIKEN/RIBF

Multi-reflection time-of-flight (MRTOF) mass spectrometry [1] has become a new powerful tool for fast and precise measurements of atomic masses. It is a breakthrough-technology considering the required duration of a measurement and the small number of rare events needed to reach a relative mass precision of $\delta m/m \leq 10^{-7}$. This mass spectrometry technology has been developed at RIKEN's RIBF facility for about two decades. Presently, three independent systems are running at different access points to radioisotopes, where gas cells built the essential hub for low-energy access. Recent achievements like high mass resolving power [2] and installations like $\alpha/\beta$-TOF detectors [3] and in-MRTOF ion selection have tremendously increased the selectivity of the systems and improved the reduction of background. This makes us capable to distinguish between a rare radioactive ions and unwanted molecules or dark counts.
In this contribution, I will give an overview about recent MRTOF atomic mass measurement highlights achieved at RIBF. Among other measurements presented, these results include new mass values for neutron-rich titanium and vanadium isotopes revealing a vanishing of the empirical two-neutron shell gap at $N = 34$, which is known to be pronounced in Ca isotopes [4]. Furthermore, I will present the discovery of the isotope $^{241}$U using the KISS facility [5], and the present status of MRTOF mass measurements of superheavy nuclides using the MRTOF setup at the GARIS-II separator [6].

References:
[1] H. Wollnik, M. Przewloka, Int. J. Mass Spectrom. Ion Proc. 96, 267 (1990).
[2] M. Rosenbusch et al., Nucl. Instrum. Meth. A 1047, 167824 (2023).
[3] T, Niwase et al., Theo. Exp. Phys. 2023(3), 031H01 (2023).
[4] S. Iimura et al., Phys. Rev. Lett. 130, 012501 (2023).
[5] T. Niwase et al., Phys. Rev. Lett. 130, 132502 (2023).
[6] P. Schury et al., Phys. Rev. C 104, L021304 (2021).

Orateur: Dr Marco Rosenbusch on behalf of the RIBF-MRTOF collaboration and the KISS collaboration (RIKEN, KEK-WNSC)

95 High-precision mass measurements of ground and isomeric states of (super)heavy nuclides with SHIPTRAP

Quantum shell effects stabilize heavy nuclei against spontaneous fission, making the existence of superheavy elements possible. Direct mass measurements performed with Penning traps provide information on the nuclear shell structure via binding energies, as well as excitation energies of low-lying, long-lived isomers obtained from the directly measured masses.

The SHIPTRAP experiment is devoted to the study of heavy and superheavy nuclei produced via fusion-evaporation reactions at rates well below one particle per hour. Thanks to the Phase-Imaging Ion-Cyclotron-Resonance technique, the resolving power has been increased beyond 10⁷, bringing many low-lying isomeric states within reach for mass spectrometry. In this contribution the latest results, obtained as part of the FAIR Phase-0 campaign, will be discussed. These encompass ground-state masses and isomeric-state-energy measurements of several nuclides, ranging from ²⁴¹Cf to ²⁵⁸Db. The alpha-decay chain ²⁰⁶Fr-²⁰²At-¹⁹⁸Bi was also studied, with the aim to pin down the excitation energies of several isomers for the first time.

Orateur: Manuel J. Gutiérrez (GSI Darmstadt / HIM Mainz)

96 The new Atomic Mass Evaluation (AME2020)

Systematic study of the masses of exotic nuclei far from the valley of stability reveals interesting phenomena such as new decay models, disappearance of traditional shell gaps and emergence of new magic numbers, and breakdown of isospin symmetry. With the advent of the new radioactive ion beam facilities built worldwide, numerous projects of mass measurements of short-lived nuclei have been carried out and reshape our understanding of how nuclei are formed. The latest Atomic Mass Evaluation (AME2020) [1,2] was recently published, which provides the most up-to-date knowledge for nuclear masses. In this conference, the evaluation procedure will be briefly reviewed and the main influence of new mass data on the AME will be discussed. Some mass data deviating from the smooth trends of the mass surface will also be mentioned and pertinent experiments are called for.

[1] W.J. Huang, M. Wang, F.G. Kondev, G. Audi, S. Naimi, Chin. Phys. C 45, 030002 (2021)
[2] M. Wang, W.J. Huang, F.G. Kondev, G. Audi, S. Naimi, Chin. Phys. C 45, 030003 (2021)

This work is supported in part by the National Key Research and Development Program of China (Grant No.2016YFA0400504), the Strategic Priority Research Program of Chinese Academy of Sciences (CAS, Grant No.XDB34000000), the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract No.DE-AC02-06CH11357 and the RIKEN Pioneering Project Funding (SN).

Orateur: Wenjia Huang (Institute of Modern Physics, Chinese Academy of Sciences)

ARIS2023-Wenjia Huang.pptx

parallel session

Président de session: Filip Kondev

97 Possible Existence of Extremely Neutron-Rich Superheavy Nuclei in Neutron Star Crusts Under a Superstrong Magnetic Field

We investigate outer crust compositions for a wide range of pressures (densities) and magnetic-field strengths, adopting the latest experimental masses (AME2020) supplemented with various theoretical mass models. By exploring the optimal composition of nuclei in the entire nuclear chart, we find emergence of neutron-rich heavy nuclei, which are much heavier than previously thought (that was at most $Z\approx50$), mainly because of the increasing electron density with the magnetic field strength, which allows nuclei to exist at higher densities without leakage of neutrons. We point out a clear manifestation of neutron magic numbers, e.g. $N=50, 82, 126$, as well as $184$, and possibly those around the next spherical magic number $N\approx 258$. Furthermore, surprisingly enough, for $B\geq4\times10^{18}$ G, we find that superheavy nuclei with $Z>110$, including the unknown element $119$, naturally emerge as optimal compositions that minimize the Gibbs energy. In this talk, we will explain the aforementioned findings and discuss possible consequences.

Orateur: Dr Kazuyuki Sekizawa (Tokyo Institute of Technology)

98 Ab initio calculation of the $^3$He$(\alpha,\gamma)^7$Be astrophysical $S$ factor

The $^3$He$(\alpha,\gamma)^7$Be reaction is an important part of ongoing processes occurring in stars like our very own sun. In the fusion reaction network of the sun, the $^3$He$(\alpha,\gamma)^7$Be reaction is key to determining the $^7$Be and $^8$B neutrino fluxes resulting from the pp-II chain . In standard solar model (SSM) predictions of these neutrino fluxes, the low-energy $^3$He$(\alpha,\gamma)^7$Be $S$ factor, $S_{34}(E)$, is the largest source of uncertainty from nuclear input. The SSM uses $S_{34}(E)$ near the Gamow peak energy, roughly 18 keV, which cannot be experimentally measured since the Coulomb force between $^3$He and $^4$He suppresses the fusion reaction at such low energies. Theoretical calculations are needed to guide the extrapolation to the solar energies of interest. To this end, I will present ab initio calculations of the $^3$He$(\alpha,\gamma)^7$Be reaction using the no-core shell model with continuum starting from two- and three-nucleon chiral interactions. To demonstrate that the NCSMC provides an accurate $S$ factor, I will also compare NCSMC $^{3}$He + $^{4}$He elastic-scattering cross sections with those recently measured by the SONIK collaboration.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC.

Orateur: Mack Atkinson (Lawrence Livermore National Laboratory)

atkinson-aris-2023.pdf

99 Is there a dark decay in ⁶He ?

The neutron lifetime discrepancy between beam and bottle experiments of 4$\sigma$ could be interpreted as a possible sign of the neutron into dark particles [1]. If such a decay exists, it could also occur in unstable nuclei with sufficiently low neutron binding energy, a quasi-free neutron decay into a dark matter particle $\chi$; as is the case of $^6$He with S$_{2n} = 975.45keV < m_n - m_{\chi}$ [2]. This quasi-free neutron dark decay would be as followed $^6He \rightarrow ^4He + n + \chi$ which is the only way to have the emission of a free neutron in the decay of $^6$He. The SPIRAL1 facility at GANIL was used in June 2021 in order to produce a pure $^6$He$^{1+}$ radioactive beam at 25keV to observe an excess of neutrons in the decay of $^6$He which would be a unique signature for dark matter creation. In this presentation, we report the (preliminary) results of this experiment to set an upper limit for this dark decay mode in $^6$He.

[1] Bartosz Fornal and Benjam ́ın Grinstein. “Dark Matter Interpretation of the Neutron Decay Anomaly”.
In: Phys. Rev. Lett. 120 (19 May 2018), p. 191801. doi: 10.1103/PhysRevLett.120.191801. url:
https://link.aps.org/doi/10.1103/PhysRevLett.120.191801.
[2] M. Pf ̈utzner and K. Riisager. “Examining the possibility to observe neutron dark decay in nuclei”.
In: Phys. Rev. C 97 (4 Apr. 2018), p. 042501. doi: 10 . 1103 / PhysRevC . 97 . 042501. url: https://link.aps.org/doi/10.1103/PhysRevC.97.042501

Orateur: Marius Le Joubioux (GANIL)

Is there a dark decay of neutrons in ⁶He .pptx

100 A systematic analysis of nucleon emission in deuteron-induced reactions

Considering its weakly-bound nature, a complete description of deuteron-induced reactions remains a challenging problem for theoretical studies. To examine this problem, we perform a systematic analysis of inclusive nucleon emission cross sections for deuterons incident on a wide range of nuclei at different energies up to 100 MeV. The local-energy approximation to the post form DWBA is used to calculate the elastic and nonelastic breakup cross sections [1,2]. The breakup cross sections are integrated into the EMPIRE nuclear reaction code [3] in order to take into account the pre-equilibrium and equilibrium decay of the three compound nuclei formed in the reaction. Theoretical double differential and integrated nucleon emission cross sections are compared with the experimental ones. Our investigations demonstrate a general good agreement between the theoretical and experimental integrated cross sections. The comparisons of the experimental data with the calculated double differential cross sections show that the general behavior of the experimental spectra is reproduced at small angles and for the lighter systems, but that systematic discrepancies between the calculations and the data occur for heavier targets. Possible reasons for the disagreements are discussed.

References
[1] M. Ichimura, N. Austern, and. C. M. Vincent, Phys. Rev. C 32, 431 (1985).
[2] N. Austern, Y. Iseri, M. Kamimura, M. Kawai, G. Rawitscher, M. Yahiro, Phys. Rep. 154, 125 (1987).
[3] M. Herman, R. Capote, B. V. Carlson, P. Oblozinský, M. Sin, A. Trkov, H. Wienke, V. Zerkin, Nucl. Data Sheets 108, 2655 (2007).

Orateur: Brett Carlson (Instituto Tecnológico de Aeronáutica)

101 Spectroscopic Factor Investigation in the N=40 Island of Inversion

The focus of this work is on the Fe and Mn neutron-rich isotopes with $N\sim40$, which lie within one of the so-called Islands of Inversion. Here, a quenching of the $N=40$ shell gap allows deformation to develop in the ground-state configurations. Limited spectroscopic information is available in the region of $N\sim40$ below the Ni isotopes. For the even-even nuclei, this consists of systematics of 2$^+_1$ and 4$^+_1$ state energies and, for the Fe and Cr isotopes, of $B(E2; 2^+_1\rightarrow 0^+_1)$ values up to $^{68}$Fe and $^{64}$Cr. Large-scale shell-model calculations well reproduce the energy systematics of the observed low-lying states of the even-even Fe and Cr isotopes around $N=40$. A good agreement is found also within the rotational Nilsson model. Such two descriptions, however, provide different predictions for proton spectroscopic factors. A measurement of such quantity would thus allow us to probe the validity of the considered models.
In this context, proton knockout reactions on the neutron-rich $N=38$ and $N=40$ isotopes $^{64,66}$Fe and $^{63,65}$Mn have been performed to investigate the proton spectroscopic factors of the parent nuclei. The experiment took place at the NSCL laboratory in the US and exploited the $\gamma$-ray tracking array GRETINA coupled to the S800 spectrograph to perform an in-beam $\gamma$-ray spectroscopic study. Preliminary results of the data analysis will be presented.

Orateur: Carlotta Porzio (Lawrence Berkeley National Laboratory)

CPorzio_ARIS2023.pdf

102 Measurement of the Fierz interference term in 20F decay

(1) Department of Physics and Astronomy, Michigan State University, East-Lansing, MI, USA
(2) National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI, USA
(3) Department of Physics, Wittenberg University, Springfield, OH, USA
(4) Department of Chemistry, Michigan State University, East Lansing, MI, USA
(5) Facility for Rare Isotope Beams, Michigan State University, East Lansing, MI, USA
(6) LPC-Caen, ENSI-CAEN, CNRS-IN2P3, Universite de Caen Normandie, Caen, France

Precision measurements in nuclear beta decay offer a sensitive means to search for new physics beyond the standard electroweak model. The new physics signatures are parametrized in terms of exotic phenomenological scalar and tensor interactions, which induce deviations on observables relative to their standard model predictions. It has been recognized that the Fierz interference term is the most sensitive parameter to probe the presence of exotic couplings since it depends linearly on them. This term can directly be accessed through measurements of the beta-particle energy spectrum. These are notoriously difficult to perform with high precision due to distortions generally induced by back- and out-scattering of beta particles.

We report here on the measurement of the energy spectrum of beta particles emitted in 20F decay to extract the Fierz term in this decay for the first time. A 132 MeV/nucleon 20F beam was implanted in a CsI(Na) detector and beta-gamma coincidences were recorded between the implantation detector and four other CsI(Na) surrounding detectors. This configuration enabled us to implement a calorimetry technique such that the dominant distortion of the beta-energy spectrum was due to the bremsstrahlung radiation escaping the implantation detector. The measured decay is the 99.9913(8)% Gamow-Teller branch and the Fierz term is sensitive to exotic tensor couplings.

This contribution will describe the experimental conditions and will provide details on the systematic effects in the data analysis of the spectrum shape. It will also discuss the role of the weak magnetism form factor in the extraction of the Fierz interference term.

This work was supported in part by the US National Science Foundation under grants PHY-1102511, PHY-1506084, PHY-1565546, and PHY-2013557, and by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, and used resources of the Facility for Rare Isotope Beams (FRIB), which is a DOE Office of Science User Facility, operated by Michigan State University, under Award Number DE-SC0000661.

(*) Present address: Max Planck Institute for Physics, Munich, Germany
(%) Present address: College of Engineering, Michigan State University, East Lansing, MI, USA
(#) Permanent address: LeoLabs Inc., Menlo Park, CA, USA
(&) Permanent address: XIA LLC, Knoxville, TN, USA

Orateur: O. Naviliat-Cuncic (1,2,5,6)

103 Decay spectroscopy around neutron-rich 33Mg to probe an ‘island of inversion’

The term ‘island of inversion’ is used to refer to a region of the nuclear landscape in which deformed intruder configurations dominate nuclear ground states over the spherical configurations naively expected from the shell model. Theoretical models of the inversion mechanism can be tested through detailed studies of the nuclear structure of transitional nuclei, in which the normal and intruder configurations compete. One such transition occurs along the N = 20 isotones, where neutron-rich $^{32}$Mg is known to have a deformed ground-state configuration, while $^{34}$Si displays a normal ground state configuration. Previous studies of the intermediate N = 20 isotone $^{33}$Al have yielded conflicting results regarding its structure. In the present work, $^{33}$Al was studied through the $\beta$-decay of $^{33}$Mg to clarify these discrepancies. A low-energy radioactive beam of $^{33}$Mg was delivered at a rate of 10e3 ions/s by the Isotope Separator and Accelerator (ISAC-I) facility at TRIUMF. Data were collected with the GRIFFIN high-purity germanium $\gamma$-ray spectrometer coupled with the SCEPTAR plastic scintillator array and the ZDS (zero degree) $\beta$ particle detectors. The majority of the data were collected in a cycled mode (with a period of 2 s beam on, 1.5 s beam off) to provide sensitivity to all of the $^{33}$Mg, $^{33}$Al, $^{32}$Al ($\beta$-n daughter) and $^{33}$Si half-lives. The high efficiency of the GRIFFIN detector provided new $\gamma$-$\gamma$ coincidences to elucidate the excited state structure of $^{33}$Al, and the capability of GRIFFIN to detect weak transitions has provided more complete $\beta$-decay branching ratios for the $^{33}$Mg--$^{33}$Al--$^{33}$Si decay chain. Results following the $\beta$-decay of neutron-rich $^{33}$Mg are presented. Approximately 10$^{8}$ $\gamma$-$\gamma$ coincidences were used to build level schemes for $^{33}$Al and $^{32}$Al. The $\gamma$-gated time spectra were fit to calculate half-lives of $^{33}$Mg, $^{32, 33}$Al and $^{33}$Si, $\beta$ counts were used to calculate $\beta$-feeding to the levels of the scheme of $^{33}$Al, including the ground state. Clarification of $^{33}$Al level scheme, and expansion of $^{32}$Al are presented.

Orateur: Tammy Zidar (University of Guelph)

16:15 coffee break

parallel session

Président de session: Wilfried Nörtershäuser (TU Darmstadt)

104 The ISOLDE RILIS at 30

The Resonance Ionization Laser Ion Source (RILIS) has been the principal ion source at ISOLDE for the majority of the past three decades. Unmatched selectivity, coupled to high efficiency, has been the main reason for RILIS being requested in more than half of the proposals submitted for review to the ISOLDE scientific committee (INTC). What started as a home-made system of 3 tunable dye lasers pumped by a single Copper vapor laser system with a Master oscillator/ Power amplifier configuration has now become a suite of state-of-the-art collection of >13 lasers: Ti:Sapphire and commercial dye lasers pumped by industrial solid state lasers. Over 35 chemical elements have been ionised within a variety of specially-designed laser ion source configurations and simultaneous operation at both ISOLDE front-ends is possible.
I will talk about the changes made over the past years to get to the modern RILIS system we use today and deliver a performance review. In addition I will give a summary of ongoing developments and how they might improve RILIS efficiency, applicability and selectivity further. I will conclude by presenting the work towards making RILIS a viable option for high-resolution laser spectroscopy, future-proofing the highly sensitive in-source laser spectroscopy method at ISOLDE.

Orateur: Katerina Chrysalidis (CERN)

ARIS2023_chrysalidis.pptx

105 The PUMA experiment at CERN

Frank Wienholtz for the PUMA collaboration
The main goal of the PUMA [1] (antiProton Unstable Matter Annihilation) experiment is to use antiprotons as a tool to investigate properties of exotic nuclei. For this, antiprotons produced at the AD/CERN and decelerated by the ELENA storage ring will be captured, cooled and transported to the ISODLE facility where the antiprotons will be mixed with short lived isotopes. During this process, an antiproton can be captured by the nucleus and will subsequently annihilate with a neutron or a proton at the surface of the nucleus itself. The fingerprint of this annihilation will be measured using a time-projection-chamber. With this knowledge of the ratio of protons to neutrons on the outermost part of the nuclei distribution, phenomena like a neutron or a proton halo or neutron or proton skins can be investigated.
This contribution will give an overview of the PUMA experiment, present its status and highlight some of the main physics goals.

[1] Aumann et al., Eur. Phys. J. A (2022) 58: 88

Orateur: Frank Wienholtz (TU Darmstadt)

106 First beta-delayed spectroscopy of neutron-rich Cl isotopes with FDSi

The first experimental campaigns with FRIB Decay Station Initiator [1] at FRIB focused on the spectroscopy of very neutron-rich isotopes. They provided a wealth of data on beta-delayed neutron emitters. We will present the first results on the beta-delayed neutron emission spectroscopy near N=28 shell closure, such as ${}^{45,46,47}$Cl. Using a combination of neutron and gamma-ray data, we extracted the beta decay strength distribution to neutron unbound states and compared the results with the large-scale shell model calculations by Yoshida et al. [2], providing the first test of these predictions for the dominant Gamow-Teller transitions in this region. We also extracted the neutron-emission branching ratios to excited states in Ar isotopes and compared them with those predicted by the statistical model [3]. The importance of the discrepancies between model predictions and experimental data will be discussed.

[1] https://fds.ornl.gov/initiator/
[2] T. Kawano et al., Journal of Nuclear Science and Technology, 47(5),462, (2010), .
[3] S. Yoshida, Y. Utsuno, N. Shimizu, and T. Otsuka, Phys. Rev. C 97, 054321 (2018).

Orateur: Ian Cox (University of Tennessee, Knoxville)

aris2023Cox.pdf

107 First beta-delayed neutron spectroscopy of doubly-magic $^{24}O$.

Located at the neutron drip-line, $^{24}O$ is the heaviest doubly-magic isotope of the oxygen isotopic chain. As the $Q_\beta$ value increases and the neutron separation energy in the daughter nucleus decreases for the neutron-rich nucleus, beta-delayed neutron emission becomes a dominant decay mode, and neutron energy measurement is vital in studying the beta decay to the neutron unbound states. Also, spectroscopy of such drip-line nuclei may provide important information regarding the effects of nuclear interactions and many-body correlations in determining the limits of nuclear stability [1].

The neutron energy spectrum measurement of the beta-delayed neutron precursor $^{24}O$ was performed for the first time at National Superconducting Cyclotron Laboratory (NSCL) using a neutron time-of-flight array (VANDLE[2]) accompanied by gamma spectroscopy setup. New half-life and beta decay branching ratios are extracted. The beta-gamma and beta-delayed neutron measurements following the decay of $^{24}O$ provided the excitation energies and beta decay strength distribution to both neutron-bound and unbound states in $^{24}F$. The decay of "doubly-magic" $^{24}O$ is an excellent case to test the quality of the state-of-the-art calculations of the beta-decay strength distribution near the neutron drip line. The experimental results are compared with the shell model calculation using the standard, empirical USDB interaction, and state-of-the-art ab initio calculations such as those using the valence-space in-medium similarity renormalization group (VS-IMSRG), coupled cluster model or shell-model embedded in the continuum.

[1] T. L. Tang et al. Phys. Rev. Lett. 124, 212502 (2020).
[2] W. A. Peters et al., Nucl. Instrum. Methods Phys. Res. A 836, 122 (2016).

Orateur: Shree Neupane (University of Tennessee)

ARIS_Shree.pptx

108 Study of the $^{10}$Be(t,p)$^{12}$Be reaction with the SOLARIS spectrometer

The $^{10}$Be(t,p)$^{12}$Be reaction has been studied with the SOLARIS solenoidal spectrometer. This measurement was carried out in inverse kinematics using a 9.6 MeV/u $^{10}$Be beam provided by the ReA6 re-accelerator in stand-alone mode. SOLARIS provides excellent resolution (about 150 keV FWHM) and background rejection capabilities via recoil detection. A titanium tritide target was used. The advantages of this approach, contrasted to the classic study of this reaction in normal kinematics, are higher bombarding energies coupled with recoil detection, allowing for a clean Q-value spectrum and insights into the decay of unbound states in $^{12}$Be. We observed the well-known bound states of $^{12}$Be and known states above the one- and two-neutron separation energies along with some additional, weakly populated states. Using angular distributions and coincident recoils ($^{10}$Be, $^{11}$Be), we favor spin-parity assignments of 3- and 4+ for the states at 4.58 and 5.72 MeV, respectively. We observe states at approximately 5.0 MeV and 5.4 MeV which have not been clearly observed before. The SOLARIS device, the analysis procedure, and the preliminary results are discussed.

This material is based upon work supported by NSF’s National Superconducting Cyclotron Laboratory which is a major facility fully funded by the National Science Foundation under award PHY-1565546; the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract Number DE-AC02-06CH11357 (Argonne) and under Award Number DE-SC0014552 (UConn); the Spanish Ministerio de Economía y Competitividad through the Programmes “Ramón y Cajal” with the grant number RYC2019-028438-I; the UK Science and Technology Facilities Council (Grant No. ST/P004423/1); and the International Technology Center Pacific (ITC-PAC) under Contract No. FA520919PA138. SOLARIS is funded by DOE Office of Science under the FRIB Cooperative Agreement DE-SC0000661. The Paul Scherrer Institut is acknowledged for their provision of the $^{10}$Be isotope.

Orateur: Alicia Muñoz Ramos (IGFAE-USC)

ARIS_AliciaMR.pdf

parallel session

Président de session: Rafael Ferrer (Instituut voor Kern- en Stralingsfysica, KU Leuven)

109 KDK: first measurement of the rare electron-capture decay of 40K to the ground state of 40Ar

Potassium-40 (40K) is a naturally-occurring radioactive isotope. It is a background in searches for exotic subatomic particles, plays a role in geochronology, and has a nuclear structure of interest to theorists. This radionuclide decays mainly by beta emission to calcium, and by electron-capture to an excited state of argon. The electron-capture decay of 40K directly to the ground state of argon has never been measured, and predicted intensities are highly variable (0–0.22%). This poorly understood intensity may impact the interpretation of a controversial claim of dark matter discovery [1]. The KDK (potassium decay) experiment has carried out the first measurement of this electron-capture branch, using a novel setup at Oak Ridge National Labs [2]. KDK deployed a very sensitive inner detector to trigger on the ~keV radiation emitted by both forms of electron capture, surrounded by a very efficient veto to distinguish between the decays to ground state and those to the excited state. We present result of the experiment [3] and implications for various fields.

[1] Pradler et al, Physics Letters B 720 (2013) 399–404, http://dx.doi.org/10.1016/j.physletb.2013.02.033

[2] Stukel et al, Nuclear Inst. and Methods in Physics Research, A 1012 (2021) 165593, https://doi.org/10.1016/j.nima.2021.165593

[3] Stukel et al, https://doi.org/10.48550/arXiv.2211.10319

Orateur: Philippe Di Stefano (Queen's)

110 Onset of deformation in the neutron-rich krypton isotopes via transfer reactions with the ISOLDE Solenoidal Spectrometer

In the A = 100 region, the dramatic shape change observed for Zr [1-3] and Sr [4-7] (Z = 40 and 38, respectively) is not present in Kr (Z = 36) isotopes [8-10]. The $2_{1}^+$ energies and the B(E2; $2_{1}^+$→ $0_{1}^+$) values vary smoothly across the Kr isotopes but Sr and Zr isotopes display a large jump at N = 60, indicating a significant increase in the ground state deformation of these isotopes. The ν$g_{7/2}$ orbital is filled in the ground states of the krypton isotopes around N = 59 and is thought to lower the energy of the π$g_{9/2}$ orbital and help to drive deformation in this region.
Previous studies in this region have shown a smooth onset of deformation in Kr isotopes at N = 60 [9,10] and evidence of a new oblate structure coexisting with the prolate ground state [11]. Accurately predicting ground-state spins and parities of odd-mass isotopes in this region is challenging due to the large valence space, and lack of ESPE data and accurate shell-model interactions. The single-particle energy differences and spectroscopic factors extracted from neutron adding reactions will provide a more complete experimental picture of the underlying single-particle configurations, which will allow for comparison to modern shell-model calculations [12] that try to describe the onset of deformation around A = 100.
The evolution of neutron single-particle properties and their role in the onset of deformation towards N = 60 in the neutron-rich Kr isotopes has been studied via the one-neutron transfer reactions $^{92,94}$Kr (d,p). These were performed in inverse kinematics at an energy of 7.5 MeV/u using the ISOLDE Solenoidal Spectrometer at ISOLDE, CERN. The main goals are to determine the energy difference between the 2ν$s_{1/2}$ and 0ν$g_{7/2}$ orbitals below N = 60 using the $^{92,94}$Kr (d,p) reactions to identify the likely Δ$\ell$ = 4 transfer to the 7/2$^+$ state. Preliminary results obtained from the October 2022 experiment will be presented.

References:
[1] F. Browne et al., Phys. Lett. B 750, 448 (2015).
[2] J. E. García-Ramos and K. Heyde, Phys. Rev. C 100, 044315 (2019).
[3] P. Spagnoletti et al., Phys. Rev. C 100, 014311 (2019).
[4] F. Buchinger et al., Phys. Rev. C 41, 2883 (1990).
[5] E. Clément et al., Phys. Rev. Lett. 116, 022701 (2016).
[6] A. Chester et al., Phys. Rev. C 96, 011302 (2017).
[7] S. Cruz et al., Phys. Rev. C 100, 054321 (2019).
[8] M. Keim et al., Nucl. Phys. A 586, 219 (1995).
[9] M. Albers et al., Phys. Rev. Lett. 108, 062701 (2012).
[10] M. Albers et al., Nucl. Phys. A 899, 1 (2013).
[11] T. R. Rodríguez, Phys. Rev. C 90, 034306 (2014).
[12] T. Togashi et.al., Phys. Rev. Lett. 117, 172502 (2016).

Orateur: Annie Dolan (University of Liverpool)

111 Radiation-detected NMR for chemistry and life-science studies using unstable nuclei

Radiation-detected Nuclear Magnetic Resonance (RD-NMR), especially in the form of beta-NMR in solids hosts, is an extremely sensitive NMR approach, which has been used in nuclear structure studies over the last few decades, allowing to determine magnetic and quadrupole moments of selected unstable nuclei.
RD-NMR applications in chemistry, biology, or medical diagnosis – performed on short-but also long-lived spin-polarised nuclei in liquid or gaseous samples – are much more recent but growing. Such studies are performed by our ISOLDE team as part of interdisciplinary collaborations with colleagues from other institutes. Beta-NMR on laser polarised short-lived sodium and potassium nuclei has already allowed us to study the arrangement of low-vapour ionic liquids which might be suitable for car-battery material and is being used to investigate binding of DNA G-quadruplex structures around alkali metals. A development of beta-NMR on longer-lived isotopes polarised using chemical methods known in conventional NMR in zero-to-ultra-low fields (ZULF) might lead to ultrasensitive and highly portable NMR devices. Finally gamma-detected MRI signals after spin-exchange optical pumping of long-lived Xe isomers might be used as a new medical imaging modality.
This contribution will cover the principles of RD-NMR, followed by the description of selected experimental setups and examples of ongoing studies from across the fields.

Orateur: Magdalena Kowalska (CERN)

112 Structure of A=22 analogue states revealed through mirrored-transfer

The isospin formalism describes protons and neutrons as two projections of the nucleon and provides a powerful tool for identifying and classifying states in the vicinity of the line of $N=Z$. Under the assumption that isospin is a good quantum number, a number of relations arise to describe isobaric analogue states their properties. This provides access wealth of information, from tests of the isospin-symmetry conserving nature of the nuclear interaction, to applications in nuclear astrophysics. In truth, however, this assumption is known to be false, broken by the Coulomb interaction and components of the nucleon-nucleon interaction.

Here, we employ mirrored transfer reactions using beams of radioactive $^{21}$Na and stable $^{21}$Ne delivered by the ISAC-II facility at TRIUMF. These are used to populate isobaric analogue states in $^{22}$Na and $^{22}$Ne, respectively, through (d,p). Making use of proton-$\gamma$ coincidences, we are able to selectively probe the single-particle nature of individual states, and probe their isospin purity. I will present initial findings, focusing on the role of isospin mixing in $2^+$ states through single-particle transfer, as well as future directions involving (d,n) data taken simultaneously to the (d,p).

Orateur: Jack Henderson (University of Surrey)

113 Constraining the electron-capture rates of neutron-rich nuclei with the $(d,{ }^{2}\text{He})$ reaction in inverse kinematics.

Nuclear charge-exchange reactions can be used to estimate the electron-capture rates which are key quantities in various astrophysical scenarios, such as the final evolution of intermediate-mass stars, core-collapse supernovae (CCSN), cooling of the neutron star crust, and nucleosynthesis in thermonuclear supernovae. Over the past decades, great progress has been made to constrain electron-capture rates on stable nuclei by using reactions in forward kinematics. However, the unstable neutron-rich nuclei that play an important role during, for example, the core-collapse supernovae (N≈50, Z≳28), remained inaccessible. The use of the $(d,{ }^{2}\text{He})$ charge-exchange reaction in inverse kinematics with the Active-Target Time-Projection Chamber and the S800 Spectrograph was developed at NSCL/FRIB, for extracting Gamow-Teller strengths in the β+ direction on unstable nuclei. This makes it possible, for the first time, to constrain electron-capture rates on neutron-rich nuclei. In this talk I will discuss recent results of the pilot $^{14}\text{O}(d,{ }^{2}\text{He})$ experiment.

This work is supported by the National Science Foundation under Grants PHY-2209429, “Windows on the Universe: Nuclear Astrophysics at FRIB”

Orateur: M. Zarif Rahman (MSU-FRIB)

aperitif on the Pont Benezet

ARIS conference dinner

vendredi 9 juin

Friday: plenary 16

Président de session: Maria J G. Borge (ISOLDE-CERN)

114 $\beta$-decay studies of neutron-rich isotopes in the region around double-magic $^{132}$Sn

In a simple picture, nuclei in the vicinity of double magic isotopes are of great interest from both experimental and theoretical points of view. Such nuclei have a spherical shape and the excitations-energy spectrum is dominated by single-particle excitation. This simple approach may need to be revised for nuclei that are significantly off the stability path on the neutron-rich side. The study of the evolution of single-particle states, interaction energies and $\beta$-decay properties (half-lives, $\beta$-decay strength, and $\beta$-delayed neutron emission probability) are important for understanding the structure of such exotic nuclei, as well as for its relevance in understanding the astrophysical r-process.

In this particular, understanding the nuclear structure near the doubly-magic $^{132}$Sn is important for validating theoretical models that predict properties of more exotic nuclei, which are not experimentally accessible. In the specificity, the single-particle energy of the neutron state i$_{13/2}$ is still not firmly established [1,2] and it was suggested that nuclear structure affects the neutron versus $\gamma$-ray competition in the decay of neutron-unbound states [3]. The $n$-$\gamma$ competition in the de-excitation of excited states of these nuclei is relevant in the framework of the astrophysical r-process, since $^{135}$In is a so-called waiting point [4]. $\beta$-decay studies of neutron-rich indium isotopes provide excellent conditions to investigate such effects since their decays are characterized by large energy windows for the population of neutron-unbound states ($Q_{\beta n} >$ 10 MeV).

Excited states in $^{132-135}$Sn were investigated via $\beta$ decay of the respective precursors, $^{133-135}$In, at ISOLDE Decay Station [5,6]. Isomer-selective ionization using the Resonance Ionization Laser Ion Source enabled the $\beta$ decays of $^{133g}$In (I$^{\pi}$=9/2$^+$) and $^{133m}$In (I$^{\pi}$=1/2$^-$) to be studied independently for the first time [5]. Owing to the large spin difference of those two $\beta$-decaying states, it is possible to investigate separately the lower- and higher-spin states in the daughter $^{133}$Sn and therefore to probe independently different single-particle transitions relevant in the $^{132}$Sn region. The single-particle i$_{13/2}$ neutron state was tentatively identified in the decay of $^{134}$In and $^{135}$In.
A review of the most recent results will be given and discussed in the framework of state-of-the-art shell model computations.

$[1]$ P. Hoff et al., Phys. Rev. Lett. 77, (1996) 1020.
$[2]$ A. Korgul et al., Phys. Rev. C 91, (2015) 027303.
$[3]$ V. Vaquero et al., Phys. Rev. Lett. 118, (2017) 202502.
$[4]$ I. Dillmann et al., Eur. Phys. J. A 13, (2002) 281.
$[5]$ M. Piersa, A. Korgul et al., Phys. Rev. C 99, (2019) 024304.
$[6]$ M. Piersa, A. Korgul et al., Phys. Rev. C 104, (2021) 044328.

Orateur: Agnieszka Korgul (Faculty of Physics, University of Warsaw, Poland)

115 Materials Science with radioactive isotopes – results from emission Mössbauer Spectroscopy

The intentional incorporation of foreign atoms in semiconductors, with the aim to realize new and/or novel functionalities with potential applications in optoelectronic and spintronic devices, gives rise to structural changes that profoundly affect their electronic, magnetic, and optical properties. Consequently, information on material properties and on dynamic processes such as dopants diffusion and relaxation processes are necessary and can be determined using a wide variety of techniques. Of particular importance are techniques employing radioactive isotopes implanted in materials as probes as they combine a two-fold function: (a) material modification and (b) material characterization at the atomic level. The latter is achieved through utilizing the isotopes mainly as “spies” via the radiation/particles they emit in their decay. This provides knowledge on lattice sites of desired daughter dopants, lattice location changes with thermal annealing, and the defects/complexes formed with host atoms.

Mössbauer Spectroscopy (MS) is a very sensitive technique capable of detecting minor shifts in energy levels that emanate from hyperfine interactions between the nuclear moments of the probe/dopant and any local electric and magnetic fields in their immediate environment. A novel extension is emission Mössbauer Spectroscopy (eMS) employing short-lived radioactive isotopes developed at ISOLDE, CERN. eMS studies have been undertaken mainly using $^{57}$Mn$^{*}$ ($t_{1/2}$ = 1.5 min) which is produced via proton-induced fission in a UC$_{2}$ target followed by multistage laser ionization[1], mass separation and acceleration to 40-60 keV. In addition, other precursor isotopes such as $^{57}$Co$^{*}$ ($t_{1/2}$ = 272 days) and $^{119}$In$^{*}$ ($t_{1/2}$ = 2.4 min) have also been applied for offline $^{57}$Fe studies and for online $^{119}$Sn measurements, respectively.

Over the years, eMS has been applied in several different material systems at ISOLDE, with investigations initially on the role of Fe in silicon to recent studies on the nature and origin of magnetic effects observed in transition metal doped semiconductors[2-5] envisaged for spintronic applications. Special features of the technique will be presented and discussed, together with representative results in binary[4] and ternary III-nitrides. The results will mainly focus on investigations of the lattice sites of the probes, their charge and spin states, and the magnetic interactions of dopants in ternary-nitrides (virgin and Mn pre-doped)[6] and metal halides[7].

[1] Fedoseyev et al., Nucl. Instrum. Meth. B, 126 (1997) 88.
[2] Gunnlaugsson et al., Appl. Phys. Lett. 97 (2010) 142501.
[3] Mølholt et al., Phys. Scr. T148 (2012) 014006.
[4] Masenda et al. J. Magn. Magn. Mater. 401 (2016)1130.
[5] Mantovan et al. Adv. Electron. Mater. 1 (2015) 1400039.
[6] Masenda et al. New J. Phys. 24 (2022) 103007.
[7] Gunnlaugsson et al., Phys. Rev. B 106 (2022) 174108.

Orateur: Hilary Masenda (University of the Witwatersrand)

ARIS 2023-eMS.hm.pptx

116 Probing Nuclear and Particle Physics Phenomena with Radioactive Molecules

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Orateur: Ronald Garcia Ruiz (MIT)

117 CERN-MEDICIS: a unique facility for the production of non-conventional radionuclides for medical research

The MEDICIS facility is a unique facility located at CERN dedicated to the production of non-conventional radionuclides for research and development in medical imaging, diagnostics and radiation therapy. Located in a laboratory equipped to safely handle unsealed radioactive samples, it comprises a dedicated isotope separator beam line, a target irradiation station at the 1.4 GeV Proton Synchroton Booster (PSB), or alternatively receives activated targets from external institutes e.g. during CERN Long Shut-Downs. The target is heated up at high temperatures to allow for the diffusion and effusion of the produced atoms out of the target that are subsequently ionized. The ions are accelerated and sent through an off-line mass separator. The radionuclide of interest is mass-separated and implanted into a thin metallic collection foil. After collection, followed by a radiochemistry process when necessary, the batch is prepared to be dispatched to a research center for further processing and usage. Since its commissioning in December 2017, the facility has provided novel radionuclides including, but not limited to, Ba-128/Cs-128, Tb-149, Sm-153, Tb-155, Tm-165/Er-165, Er-169, Yb-175 and Ac-225 with high specific activity values, some for the first time, to research institutes part of the collaboration. CERN-MEDICIS’ research and development around the topics of production, extraction and mass-separation is in constant evolution. The facility also contributes in the education and training of young researchers. Moreover, MEDICIS is one of the pillars of PRISMAP, a network of world-leading European facilities including nuclear reactors, medium- and high-energy accelerators, radiochemical laboratories and biomedical facilities. PRISMAP acts as a European platform for medical radionuclides and supports the ongoing research on nuclear therapy and molecular imaging by providing immediate access to novel radionuclides.

Orateur: CHARLOTTE DUCHEMIN (CERN, Meyrin, Switzerland)

10:25 coffee break

Friday: plenary 17

Président de session: Prof. Yuhu Zhang (IMP-Lanzhou)

118 Accessing nuclear structure with high-energy nuclear collisions (presentation sponsored by NUPECC)

High-energy nuclear collisions are conducted in the world’s largest accelerators, the BNL RHIC and the CERN LHC, to characterize the hot phase of strong-interaction matter, the quark-gluon plasma. Following two decades of phenomenological studies and the availability of data from several different species, a picture has been established according to which high-energy nuclear scattering works as an imaging process giving access to spatial distributions of nucleons in the ground states of the colliding ions. These experiments provide, thus, complementary evidence of nuclear deformations, as well a new means to determine neutron skins.

I present recent activities that have gathered together low-energy nuclear structure physicists and high-energy heavy-ion physicists to address these issues, and I highlight the advances that they have brought for both communities. I discuss the prospects for future experimental and theoretical studies at the intersection of these two areas aimed at improving our knowledge of the strong nuclear force across energy scales.

Orateur: Giuliano Giacalone (Universität Heidelberg)

GG_Aris2023.pdf

119 Present status and future prospect of the SCRIT electron scattering facility

The SCRIT (Self-Confining RI Ion Target) electron scattering facility [1] was constructed to realize electron scattering from short-lived unstable nuclei at RIKEN in Japan. Electron scattering is one of the most powerful tools for structure studies of atomic nuclei because of the well-understood mechanism of electromagnetic interaction. It has, however, never been applied to short-lived unstable nuclei because of the difficulty in preparing thick target although it has been long-desired to investigate exotic features of unstable nuclei by electron scattering [2].
Recently, we succeeded in realizing the world's first electron scattering from online-produced unstable nuclei at the SCRIT facility after years of developments. Caesium nuclides were produced via photo-fission of uranium by irradiating 28-g uranium with 15-W electron beam and were ionized with the surface ionization type ion source at an ISOL system [3]. Thanks to a high production rate of caesium nuclides and the development of beam stacking methods in the ISOL and a Cooler-Buncher [4] systems, approximately $10^7$ of $^{137}$Cs ions/pulse beams were delivered into the SCRIT system, the averaged luminosity of $0.9\times10^{26}$ cm$^{-2}$s$^{-1}$ was achieved. The obtained angular distribution of elastically scattered electrons is consistent with a calculation. This experiment perfectly mimics the experiment of electron scattering from short-lived unstable nuclei produced online after the power of the ISOL driver is upgraded.
In this contribution, we will report recent results and future prospect of the SCRIT electron scattering facility.
[1] M. Wakasugi et al., Phys. Rev. Lett. 100, 164801 (2008)
[2] T. Suda and H. Simon, Prog. Part. Nucl. Phys. 96, 1 (2017)
[3] T. Ohnishi et al., Nucl. Instr. Meth. B317 (2013) 357
[4] M. Wakasugi et al., Rev. Sci. Instrum. 89 (2018) 095107

Orateur: Kyo Tsukada (Kyoto University, ICR)

ARIS2023_KT_ver3.pptx

120 The Future of the GANIL facility

The first experiment performed at GANIL (Grand Accélérateur National d'Ions Lourds) was scheduled 40 years ago to study the reactions induced by a 44 MeV/u Ar beam on Ni and Au targets through the mass, charge and energy distributions of the fragments. The projectile fragmentation was found to be the dominant process at this intermediate energy and this pioneer work paved the way to the successful studies of exotic nuclei performed at GANIL in the domain of halo nuclei, magic numbers, exotic radioactivities among others…
In the years 2000, the SPIRAL1 facility gave access to ISOL type beams mainly for light and medium masses nuclei whereas the new SPIRAL2 facility will, in the coming years with S3 and DESIR, open unique opportunities for the study of medium and heavy N=Z nuclei and superheavy nuclei. In addition to nuclear physics experiments, many studies are performed in the domain of interdisciplinary researches such as atomic physics, material science, medical science, biology… Part of the beam time is also dedicated to industrial applications.
In 2020, the GANIL scientific community participated to the national prospectives that produced the "French roadmap for Nuclear, Particle and Astroparticle physics, and associated technical developments and applications". In the framework of the national landscape, particular focus was done on the future of the GANIL facility that has also been afterwards intensively discussed in the frame of a committee of international experts. Four major objectives have been expressed: i- the study of neutron rich fission fragments requiring to construct a dedicated production building; ii- a post-acceleration for the radioactive ions up to 150 MeV/u; iii- the study of electron scattering on radioactive ions and iv- the increase of beamtime for the interdisciplinary activities and industrial applications. We are now in the process of starting a preliminary project in order to define possible scenarios that will account for the four aforementioned objectives. The ARIS conference will be a unique occasion to discuss these objectives with international experts.

Orateur: Dr Stéphane Grévy (CENBG)

NUPECC poster prizegiving

Président de session: Marek Lewitowicz (GANIL)

aris23_poster_awards.pdf

NuPECC Poster Ceremony ARIS.pptx

next ARIS ?

Président de session: Wolfram Korten (CEA)