Neutral tritium gas reduction in the KATRIN differential pumping sections

TL;DR

This paper reports on the measurement of tritium gas reduction in the KATRIN experiment's differential pumping sections, crucial for maintaining low tritium levels in the spectrometer to ensure accurate neutrino mass measurements.

Contribution

It provides the first experimental measurement of the reduction factor of the differential pumping section using high purity tritium gas, validating simulation models and meeting KATRIN's stringent requirements.

Findings

Measured reduction factor of the differential pumping section.

Comparison with simulation results shows good agreement.

Reduction exceeds the required 14 orders of magnitude.

Abstract

The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to measure the effective electron anti-neutrino mass with an unprecedented sensitivity of $0.2\,\mathrm{eV}/\mathrm{c}^2$, using $\beta$-electrons from tritium decay. The electrons are guided magnetically by a system of superconducting magnets through a vacuum beamline from the windowless gaseous tritium source through differential and cryogenic pumping sections to a high resolution spectrometer and a segmented silicon pin detector. At the same time tritium gas has to be prevented from entering the spectrometer. Therefore, the pumping sections have to reduce the tritium flow by more than 14 orders of magnitude. This paper describes the measurement of the reduction factor of the differential pumping section performed with high purity tritium gas during the first measurement campaigns of the KATRIN experiment. The reduction factor results are compared with previously performed simulations, as well as the stringent requirements of the KATRIN experiment.