Optimization of a laser ion source for 163Ho isotope separation

To measure the mass of the electron neutrino, the Electron Capture in Holmium-163 (ECHo) collaboration aims at calorimetrically measuring the spectrum following electron capture in Ho-163. The success of the ECHo experiment depends critically on the radiochemical purity of the Ho-163 sample, which is ion-implanted into the calorimeters. For this, a 30 kV high transmission magnetic mass separator equipped with a resonance ionization laser ion source is used. To meet the ECHo requirements, the ion source unit was optimized with respect to its thermal characteristics and material composition by means of the finite element method thermal-electric calculations and chemical equilibrium simulation using the Gibbs energy minimization method. The new setup provides an improved selectivity of laser ionization vs interfering surface ionization of 2700(500) and an overall efficiency of 41(5)% for the ion-implantation process. Published under license by AIP Publishing.