Speaker
Description
The Resonance Ionization Laser Ion Source (RILIS) today is a well-established technique for highly efficient and chemically selective radioactive ion beam production at the worldwide leading radioactive ion beam facilities such as CERN-ISOLDE [[1]]. Additionally, these laser ion sources allow for direct optical spectroscopy of exotic nuclei with sub ion-per-second production yields. Nevertheless, in experiments demanding high isotopic beam purity, active suppression of contamination arising from competing ionization processes is often essential. ISOLDE’s Laser Ion Source and Trap (LIST) achieves this by spatial separation of the high temperature vapor transfer line from the cold and clean laser ionization volume of an RFQ ion guide structure positioned immediately downstream.
The LIST has been successfully applied for laser spectroscopy on polonium [[2]] and delivery of a clean magnesium ion beam for decay studies [[3]]. These experiments were previously inhibited by strong francium and sodium fractions, respectively. In the latter experiment in 2018, a contamination suppression factor of 10$^6$ was demonstrated, in contrast to the RILIS/LIST efficiency loss factor of only 25.
During the long shutdown both ISOLDE frontends have been upgraded to support the LIST, also featuring two independent RF supply lines each. This refined infrastructure grants possibilities for RFQ operation alternatives, being tested at the ISOLDE off-line 2 separator: A dedicated transformer circuit at each target unit might be omitted for one fixed unit in the high voltage rack, leading to decreased complexity. Additionally, a square wave-type fast DC voltage switching approach similar to TRIUMF’s IG-LIS [[4]] is explored.
Moreover, following successful off-line campaigns at Mainz University on technetium [[5], [6]], and promethium [[7]], a high-resolution operation mode for the LIST is being implemented at ISOLDE. Based on perpendicular laser – atom beam interaction, the experimental spectral linewidth can be reduced by an order of magnitude to the 100 MHz regime. Hyperfine structure investigation experiments to reveal nuclear structure information e.g. on neutron-rich actinium [[8]], exploiting this new technique in upcoming Run 3, will be presented.
References
1$\quad$V. Fedosseev et al., J. Phys. G: Nucl. Part. Phys. 44 084006 (2017)
2$\quad$D. Fink et al., Phys. Rev. X 5, 011018 (2015)
3$\quad$B. Blank et al., INTC-P-459 (2016)
4$\quad$S. Raeder et al., Rev. Sci. Inst. 85, 033309 (2014)
5$\quad$R. Heinke et al., Hyperfine Interact 238:6 (2017)
6$\quad$T. Kron et al., Phys. Rev. C 102, 034307 (2020)
7$\quad$D. Studer et al., Eur. Phys. J. A 56:69 (2020)
8$\quad$R. Heinke et al., INTC-P-556 (2020)