Performance of different photocathode materials in a liquid argon purity monitor

TL;DR

This study compares the performance of various photocathode materials, including silver, titanium, aluminium, and gold, in liquid argon purity monitors, revealing silver's superior signal strength over gold.

Contribution

It provides the first comparative analysis of multiple photocathode materials in liquid argon purity monitors, highlighting silver's enhanced signal performance.

Findings

Silver produces about three times stronger signals than gold in liquid argon.

Titanium and aluminium perform worse than gold in vacuum conditions.

Silver's performance suggests potential for improved purity monitoring in noble gas detectors.

Abstract

Purity monitor devices are increasingly used in noble gas time projection chambers to measure the lifetime of drifting electrons. Purity monitors work by emitting electrons from a photocathode material via the photoelectric effect. The electrons are then drifted towards an anode by means of an applied electric drift field. By measuring the difference in charge between the cathode and the anode, one can extract the lifetime of the drifting electrons in the medium. For the first time, we test the performance of different photocathode materials-- silver, titanium, and aluminium--and compare them to gold, which is the standard photocathode material used for purity monitors. Titanium and aluminium were found to have a worse performance than gold in vacuum, whereas silver showed a signal of the same order of magnitude as gold. Further tests in liquid argon were carried out on silver and gold with the conclusion that the signal produced by silver is about three times stronger than that of gold.