Highly efficient isotope separation and ion implantation of $^{163}$Ho for the ECHo project

The effective electron neutrino mass measurement at the ECHo experiment requires high purity $^{163}$Ho, which is ion implanted into detector absorbers. To meet the project specifications in efficiency and purity, the entire process chain of ionization, isotope separation, and implantation of $^{163}$Ho was optimized. A new two-step resonant laser ionization scheme was established at the $30\, kV$ magnetic mass separator RISIKO. This achieved ionization and separation efficiencies with an average of $69(5)_\textrm{stat}(4)_\textrm{sys}\,\%$ using intra-cavity frequency doubled Ti:sapphire lasers. The implantation of a $^{166\textrm{m}}$Ho impurity is suppressed about five orders of magnitude by the mass separation. A dedicated implantation stage with focusing and scanning capability enhances the geometric implantation efficiency into the ECHo detectors to $20(2)\,\%$.