Orateur
Description
The SPIRAL2 facility in GANIL will extend the capabilities of studying exotic nuclei by producing beams of radioactive isotopes with very high intensities [1]. The Super Separator Spectrometer (S$^{3}$) will select the short-lived nuclei produced by fusion-evaporation reactions, and the S$^{3}$-Low Energy Branch (S$^{3}$-LEB), installed at the focal plane of S$^{3}$, will be dedicated to the study of ground- and isomeric-state properties using resonance laser ionization, yielding high efficiency and selectivity [2,3].
The key feature of S$^{3}$-LEB is the application of in-gas laser ionization and spectroscopy (IGLIS) in the hypersonic gas-jet [4], which reduces the Doppler and pressure broadening by at least an order of magnitude compared to the gas cell-based spectroscopy [5]. Laser spectroscopy with S$^{3}$-LEB will offer improved spectral resolution ($\approx 200$ MHz) while maintaining high efficiency. Measurements of isotope shifts and hyperfine constants at this resolution will provide access to key properties of exotic nuclei, such as nuclear spins, electromagnetic moments and changes in mean-squared charge radii even in the N=Z region of the nuclear chart [6].
Once the atoms of interest are ionized, they are guided through multiple radiofrequency quadrupole for their cooling and bunching, before being sent to the multi-reflection time-of-flight mass spectrometer, PILGRIM. In the first commissioning tests, the ions were continuously accumulated in the buncher up to the moment of their extraction, leading to a mixture of ions with different cooling times in the extracted bunch. To improve bunching, ions can be accumulated before their arrival in the buncher in order to homogenise their cooling. In this contribution, details about this new technique will be presented, and compared with detailed SIMION simulations of the S$^{3}$-LEB setup.
References
[1] F. Déchery et al., Eur. Phys. J. A 51, 66 (2015)
[2] A. Ajayakumar, et al., Nucl. Instrum. Meth. B 539, 102 (2023)
[3] J. Romans, et.al., NIM B, 536, 72 (2023)
[4] R. Ferrer. et.al., NIMS B, 317570 (2013)
[5] R. Ferrer et al., Nature Communications, 8:14520, (2017)
[6] X.F. Yang, et al., Prog. Part. Nucl. Phys. 129 (2023)