Suppression of Penning discharges between the KATRIN spectrometers

TL;DR

This paper discusses the design and successful implementation of electron catchers in the KATRIN experiment to suppress Penning discharges, thereby reducing background noise and protecting the spectrometers.

Contribution

It introduces a novel electron catcher system that effectively intercepts stored electrons in the Penning trap, improving experimental stability and background suppression.

Findings

Electron catchers significantly reduce background electron counts.

The system can be moved quickly to intercept electrons along their paths.

Implementation enhances the safety and accuracy of the KATRIN experiment.

Abstract

The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to determine the effective electron (anti)neutrino mass with a sensitivity of $0.2\textrm{ eV/c}^2$ (90$\%$ C.L.) by precisely measuring the endpoint region of the tritium $\beta$-decay spectrum. It uses a tandem of electrostatic spectrometers working as MAC-E (magnetic adiabatic collimation combined with an electrostatic) filters. In the space between the pre-spectrometer and the main spectrometer, an unavoidable Penning trap is created when the superconducting magnet between the two spectrometers, biased at their respective nominal potentials, is energized. The electrons accumulated in this trap can lead to discharges, which create additional background electrons and endanger the spectrometer and detector section downstream. To counteract this problem, "electron catchers" were installed in the beamline inside the magnet bore between the two spectrometers. These catchers can be moved across the magnetic-flux tube and intercept on a sub-ms time scale the stored electrons along their magnetron motion paths. In this paper, we report on the design and the successful commissioning of the electron catchers and present results on their efficiency in reducing the experimental background.