Development of an Electrostatic Ion Beam Trap for Laser Spectroscopy of Short-lived Radionuclides

Due to its high accuracy and resolution, collinear laser spectroscopy (CLS) is a powerful tool to measure nuclear ground state properties such as nuclear spins, electromagnetic moments and mean-square charge radii of short-lived radionuclides. Performing CLS with fast beams (>30 keV) provides an excellent spectral resolution approaching the natural linewidth. However, its fluorescence-light detection limits its successful application to nuclides with yields of more than several 100 to 10,000 ions/s, depending on the specific case and spectroscopic transition. To extend its reach to the most exotic nuclides with very low production yields far away from stability, more sensitive methods are needed. For this reason, the novel Multi Ion Reflection Apparatus for CLS (MIRACLS) is currently under development at ISOLDE/CERN. This setup aims to combine the high resolution of conventional fluorescence based CLS with a high experimental sensitivity, enhanced by a factor of 30 to 700 depending on the mass and lifetime of the studied nuclide. By repetitively reflecting the ion beam between the electrostatic mirrors of an electrostatic ion beam trap, often also called Multi-Reflection Time of Flight (MR-ToF) device, the laser beam probes the ion bunch during each revolution. Therefore, the observation time is extended and the experimental sensitivity is enhanced compared to conventional single-passage CLS. As part of this thesis, a MIRACLS proof-of-principle apparatus has been constructed around an MR-ToF system, operating at ~1.5 keV beam energy, which has been upgraded for the purpose of CLS. The goal of this setup is to demonstrate the potential of the MIRACLS concept, to benchmark simulations that are employed to design a future device operating at 30 keV, and to further develop the technique. For this purpose, CLS measurements with ions of stable magnesium and calcium isotopes are performed. This data serves to characterise the performance of the new method, especially in terms of gain in sensitivity and measurement accuracy.