Orateur
Description
PISTA@VAMOS: Upgrade of the Fission Program in Inverse
Kinematics at GANIL
D. Ramos 1 , A. Lemasson 1 , M.Rejmund 1 , P. Morfouace 2 , J. Taieb 2 , e849 collaboration, and e850 collaboration
1 GANIL,CEA/DRF-CNRS/IN2P3, Caen, France
2 CEA,DAM, DIF, Arpajon, France
The fission process has intrigued physicist for a long time from both, experimental and theoretical approaches. From a qualitative point of view, it is well known that nuclear structure dominates the production of fission fragments at low excitation energy [1, 2]. However, the large deformation reached by the system and the fission dynamics that drives the system from one single object to two separated fragments prevent, so far, from a quantitave microscopic description of the problem. A great effort has been made in the last decades in order to modeling the fission process [3, 4, 5], but the accuracy of these models could not be experimentally endorsed because of the limited number of avaliable systems as well as a reduced number of physical observables.
The GANIL facility and the VAMOS magnetic spectrometer offer a unique opportunity for fission studies. The high-intensity ${}^{238}$U and $^{232}$Th beams produced at GANIL at Coulomb energies make it possible to explore exotic actinides through multi-nucleon transfer and fusion reactions in inverse kinematics, with minimal angular and energy straggling. The combination of these beams with the VAMOS++ magnetic spectrometer provides a powerful tool to directly measure the full isotopic distribution of fission fragments and to reconstruct the reaction kinematics [6, 7, 8, 9, 10].
In addition, information about the entrance channel including isotopic identification of the fissioning system, reconstruction of the initial excitation energy, and measurements of the fission barrier is obtained by placing a high-granularity silicon telescope downstream of the target. This setup detects the target-like residues produced in the multinucleon transfer reaction [11]. Moreover, transfer and fusion reactions create fissioning systems with a wide range of initial excitation energies, from near the fission barrier threshold up to intermediate energies around ∼50 MeV. This variation enables the study the evolution of structural effects in the nascent fragments.
The fission-fragment identification capabilities of the VAMOS spectrometer have significantly improved in recent years, thanks to new technical and analytical developments [12, 13], as well as the development of a new silicon telescope PISTA —Particle Identification Silicon Telescope Array— [14] with enhanced performance for entrance-channel identification. This effort, led by the GANILCEA/DAM collaboration, enables a better characterization of the fissioning system. The newly combined setup provides unprecedented resolution.
A global overview of the experimental setup and a selection of relevant results recently achieved will be presented.
References
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[3] K.-H. Schmidt et al, Nucl. Data Sheets 131, 107 (2016).
[4] G. Scamps and C. Simenel, Nature 564, 382 (2018).
[5] A. Bulgac et al., Phys. Rev. Lett. 116, 122504 (2019).
[6] M. Caamao et al., Phys. Rev. C 88, 024605 (2013).[7] M. Caamano et al., Phys. Rev. C 92, 034606 (2015).
[8] D. Ramos et al., Phys. Rev. C 97, 054612 (2018).
[9] D. Ramos et al., Phys. Rev. Lett. 123, 092503 (2019).
[10] D. Ramos et al., Phys. Rev. C 107, L021601 (2023).
[11] C. Rodrguez-Tajes et al., Phys. Rev. C 89, 024614 (2014).
[12] A. Lemasson and M. Rejmund, Nucl. Instrum. Methods Phys. Res. A 1054, 168407 (2023).
[13] M. Rejmund and A. Lemasson, Nucl. Instrum. Methods Phys. Res. A 1076, 170445 (2025).
[14] arXiv:2601.20907, https://arxiv.org/abs/2601.20907