Measurement of the electric potential and the magnetic field in the shifted analysing plane of the KATRIN experiment

TL;DR

This paper details the calibration of electromagnetic fields in the KATRIN experiment's shifted-analysing-plane to improve neutrino mass measurement sensitivity by reducing background noise.

Contribution

It introduces a novel calibration method using gaseous $^{83m}$Kr conversion electrons to accurately estimate complex electromagnetic fields in the SAP configuration.

Findings

Calibration method successfully estimates electromagnetic fields in SAP.

Field estimation improves background suppression in neutrino mass measurements.

Enhanced calibration supports achieving the targeted sensitivity of below 0.3 eV.

Abstract

The projected sensitivity of the effective electron neutrino-mass measurement with the KATRIN experiment is below 0.3 eV (90 % CL) after five years of data acquisition. The sensitivity is affected by the increased rate of the background electrons from KATRIN's main spectrometer. A special shifted-analysing-plane (SAP) configuration was developed to reduce this background by a factor of two. The complex layout of electromagnetic fields in the SAP configuration requires a robust method of estimating these fields. We present in this paper a dedicated calibration measurement of the fields using conversion electrons of gaseous $^\mathrm{83m}$Kr, which enables the neutrino-mass measurements in the SAP configuration.