Ultra-stable implanted 83Rb/83mKr electron sources for the energy scale monitoring in the KATRIN experiment

TL;DR

This paper demonstrates the development of ultra-stable implanted 83Rb/83mKr electron sources that provide precise, continuous calibration of the energy scale in the KATRIN neutrino mass experiment, ensuring sub-ppm stability.

Contribution

It introduces a novel implanted 83Rb/83mKr source that achieves the required energy stability for KATRIN's calibration needs.

Findings

The 83mKr conversion line maintains +/-1.6 ppm/month stability.

The source provides a 17.8 keV line with 2.7 eV width.

Potential for use in other high-precision calibration applications.

Abstract

The KATRIN experiment aims at the direct model-independent determination of the average electron neutrino mass via the measurement of the endpoint region of the tritium beta decay spectrum. The electron spectrometer of the MAC-E filter type is used, requiring very high stability of the electric filtering potential. This work proves the feasibility of implanted 83Rb/83mKr calibration electron sources which will be utilised in the additional monitor spectrometer sharing the high voltage with the main spectrometer of KATRIN. The source employs conversion electrons of 83mKr which is continuously generated by 83Rb. The K-32 conversion line (kinetic energy of 17.8 keV, natural line width of 2.7 eV) is shown to fulfill the KATRIN requirement of the relative energy stability of +/-1.6 ppm/month. The sources will serve as a standard tool for continuous monitoring of KATRIN's energy scale stability with sub-ppm precision. They may also be used in other applications where the precise conversion lines can be separated from the low energy spectrum caused by the electron inelastic scattering in the substrate.