Operating a large-diameter dual-phase liquid xenon TPC in the unshielded PANCAKE facility

TL;DR

This study demonstrates the stable operation of a large dual-phase liquid xenon TPC in an unshielded environment, showing its potential for testing large components for rare event detection despite high background noise.

Contribution

First successful operation of a large-diameter dual-phase LXe TPC in an unshielded setting, enabling testing of large-scale xenon detectors in realistic conditions.

Findings

Stable operation in high-background environment

LXe purity and electron drift velocity measured

TPC threshold around 15 keV for electronic recoils

Abstract

Future liquid-xenon (LXe) based observatories for rare processes, such as XLZD, require testing of large components and sub-assemblies in cryogenic liquid or gaseous xenon environments. Here we present results from the stable operation of a shallow dual-phase LXe TPC with an inner diameter of 133.4\,cm and a height of 3.1\,cm in the unshielded PANCAKE platform, without underground suppression of cosmic-ray backgrounds. A total of 340\,kg of xenon was used in the experiment, of which 127\,kg constituted the active TPC mass. Measurements of the LXe purity-dependent electron lifetime and the electron drift velocity in LXe demonstrate that sensitive measurements to characterize the TPC performance are possible in a high-background environment, even with a very basic PMT-based light detection system. Improving this will straightforwardly reduce the TPC threshold, which was observed to be around 15\,keV for electronic recoils in TPC operation.