Study of dielectric breakdown in liquid xenon with the XeBrA experiment

TL;DR

This study investigates the factors influencing electrical breakdown in liquid xenon for noble liquid TPCs, highlighting the roles of electrode area and surface finish, and providing insights for designing more robust high-voltage systems.

Contribution

The paper presents experimental results on breakdown mechanisms in liquid xenon, including the effects of electrode surface finish, area, and other parameters, with implications for future TPC design.

Findings

Area scaling and surface finish significantly affect breakdown.

No notable impact from pressure or ramp speed.

Breakdowns show a rise in current and photon rate before occurrence.

Abstract

Maintaining the electric fields necessary for the current generation of noble liquid time projection chambers (TPCs), with drift lengths exceeding one meter, requires a large negative voltage applied to their cathode. Delivering such high voltage is associated with an elevated risk of electrostatic discharge and electroluminescence, which would be detrimental to the performance of the experiment. The Xenon Breakdown Apparatus (XeBrA) is a five-liter, high voltage test chamber built to investigate the contributing factors to electrical breakdown in noble liquids. In this work, we present the main findings after conducting scans over stressed electrode areas, surface finish, pressure, and high voltage ramp speed in the medium of liquid xenon. Area scaling and surface finish were observed to be the dominant factors affecting breakdown, whereas no significant changes were observed with varying pressure or ramp speed. A general rise in both anode current and photon rate was observed in the last 30 seconds leading up to a breakdown, with a marked increase in the last couple of seconds. In addition, the position of breakdowns was reconstructed with a system of high-speed cameras and a moderate correlation with the Fowler-Nordheim field emission model was found. Tentative evidence for bubble nucleation being the originating mechanism of breakdown in the liquid was also observed. We deem the results presented in this work to be of particular interest for the design of future, large TPCs, and practical recommendations are provided.