Development of Ti:sa laser ion sources for S3-LEB at SPIRAL2-GANIL

by Jekabs ROMANS

Abstract: At GANIL-SPIRAL2 and LPC Caen [1,2] the Super Separator Spectrometer-Low Energy Branch (S³-LEB) [4,5] project is under development to study exotic nuclei by In-Gas Laser Ionization Spectroscopy (IGLIS) [3] in order to extract their ground-state properties, such as nuclear mean-square charge radii δ<r²>, magnetic dipole μ and electrical quadrupole Q moments, and nuclear spins I. Nuclides will be created by fusion-evaporation reactions with high intensity and energy primary beams allowing access to refractory elements, N=Z and proton drip line nuclei, as well as heavy actinides. The reaction products will be in-flight separated from the primary beam and contaminants by the S³ and subsequently enter S³-LEB [4,5,6]. The in-gas-jet laser spectroscopy method will combine high efficiency and high spectral resolution due to minimized broadening mechanisms [7]. 

Working principle of the setup will be presented and explained. However, this presentation will focus on the laser system, which is a crucial aspect of the S³-LEB setup. Over the past three years it has been extensively developed at GISELE offline laser laboratory to be capable of performing high resolution spectroscopy [8]. In order to extract the nuclear properties of the nuclei, one has to be able to resolve the hyperfine structure features of the atomic spectrum, which requires wide scanning range capabilities, narrow emission spectrum linewidths and adequate excitation/ionization laser pulse temporal and spatial overlap and reliable emission spectrum recording. The progressive development of the titanium:sapphire (Ti:sa) laser systems in GISELE laboratory has led to successful S³-LEB Day 1 physics case element measurements like erbium, tin and palladium, which will be presented. 

[1] Grand Accélérateur National d’Ions Lourds, URL: https://www.ganil-spiral2.eu/en/
[2] Laboratoire de physique corpusculaire – Caen, URL: https://www.lpc-caen.in2p3.fr/en/home-en/
[3] R. Ferrer et al. Nucl. Instrum. Meth. B 317, pp: 570-581 (2013). doi: 10.1016/J.NIMB.2013.07.028 
[4] F. Déchery et al, Nucl. Instrum. Meth. B 376, 125 (2016). doi: 10.1016/j.nimb.2016.02.036
[5] F. Déchery et al., Eur. Phys. J A 51, 66 (2015). doi: 10.1140/epja/i2015-15066-3
[6] P. Chauveau et al. Nucl. Instrum. Meth. B 376 (2016), pp: 211-215. doi: 10.1016/J.NIMB.2016.01.025
[7] R. Ferrer et al. Nat. Commun. 8, 14520 (2017). doi: 10.1038/ncomms14520
[8] J.Romans et al., Atoms 10(1), 21 (2022), doi: 10.3390/atoms10010021