Wideband precision stabilization of the -18.6 kV retarding voltage for the KATRIN spectrometer

TL;DR

This paper presents a high-precision, wideband stabilization system for the -18.6 kV retarding voltage in the KATRIN spectrometer, achieving stability well within the required ppm level to enhance neutrino mass measurements.

Contribution

It introduces a custom high-voltage regulation system that maintains voltage stability at the ppm level for the KATRIN experiment, surpassing previous specifications.

Findings

Voltage stability within 2 ppm demonstrated

System effectively mitigates interference without electric shielding

Achieves stability across multiple time scales

Abstract

The Karlsruhe Tritium Neutrino Experiment (KATRIN) measures the effective electron anti-neutrino mass with an unprecedented design sensitivity of 0.2 eV (90 % C.L.). In this experiment, the energy spectrum of beta electrons near the tritium decay endpoint is analyzed with a highly accurate spectrometer. To reach the KATRIN sensitivity target, the retarding voltage of this spectrometer must be stable to the ppm level and well known on various time scales ($\mu s$ up to months), for values around -18.6 kV. A custom-designed high-voltage regulation system mitigates the impact of interference sources in the absence of a closed electric shield around the large spectrometer vessel. In this article, we describe the regulation system and its integration into the KATRIN setup. Independent monitoring methods demonstrate a stability within 2 ppm, exceeding KATRIN's specifications.