First steps of the ECHo experiment: Penning-trap mass measurements of the 163Ho electron capture process and implantation of ultrapure Ho into microcalorimeter arrays
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Abstract
The ECHo experiment (Electron Capture of 163Ho) has been initiated as an approach to measure the mass of the electron neutrino by analysis of the electron capture decay spectrum of 163Ho using metallic magnetic calorimeters. The radioisotope 163Ho has been produced from enriched 162Er in a high flux nuclear reactor and was isolated from the target by high performance liquid chromatography. Dominant remaining contaminants are stable 165Ho and the long lived isomer 166mHo. Within this work, two important preparatory tasks for the ECHo experiment have been carried out: Penning-trap mass measurements of 163Ho and 163Dy were performed as prerequisite for a high precision determination of the decay energy QEC. By employing the time-of-flight ion cyclotron resonance technique the uncertainties of the masses of 163Ho and 163Dy could be decreased by a factor of two in comparison to former literature data. Furthermore, the embedding of ultra-pure 163Ho into microcalorimeters by ion beam implantation in a mass separator has been developed and characterized. The highly efficient and selective process of resonant laser ionization combined with mass separation in a sector field magnet and newly installed post-focusing optics facilitated the implantation of 163Ho with less than 10-8 parts of radioactive contaminants.