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

## TL;DR

This paper presents a highly efficient method for isotope separation and ion implantation of $^{163}$Ho, crucial for the ECHo neutrino mass measurement, achieving high purity and implantation efficiency through optimized laser ionization and separation techniques.

## Contribution

The study introduces a new two-step resonant laser ionization scheme and an optimized implantation process, significantly improving isotope purity and implantation efficiency for $^{163}$Ho.

## Key findings

- Ionization and separation efficiency of 69% achieved.
- Impurity suppression of $^{166m}$Ho by five orders of magnitude.
- Implantation efficiency into detectors is 20%.

## Abstract

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 $20(2)\,\%$.