Optimization of a laser ion source for $^{163}$Ho isotope separation

TL;DR

This paper details the optimization of a laser ion source for isotope separation of $^{163}$Ho, enhancing selectivity and efficiency crucial for neutrino mass measurement experiments.

Contribution

It introduces a new optimized laser ion source setup with improved selectivity and efficiency for $^{163}$Ho isotope separation.

Findings

Selectivity improved to 2700(500) times over surface ionization.

Overall efficiency of 41(5)% achieved.

Finite element and Gibbs energy simulations guided optimization.

Abstract

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 $^{163}$Ho. The success of the ECHo experiment depends critically on the radiochemical purity of the $^{163}$Ho sample, which is ion-implanted into the calorimeters. For this, a $30 \, \textrm{kV}$ 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 finite element method (FEM) thermal-electric calculations and chemical equilibrium simulation using the Gibbs energy minimization method. The new setup provides a much improved selectivity in laser ionization versus interfering surface ionization of $2700(500)$ and a superior overall efficiency of $41(5) \, \textrm{%}$ for the ion-implantation process.