Electron Emissions and Hot spots in Dual-Phase LXe TPCs

TL;DR

This paper explains persistent electron emissions and hot spots in dual-phase LXe TPCs as caused by photon-triggered electron emission from resistive oxide films on wires, influenced by ion landing and material properties.

Contribution

It introduces a materials physics-based explanation for persistent emissions in LXe TPCs, highlighting the role of resistive oxide films and their long RC time constants.

Findings

Photon-triggered single-electron emission from resistive oxides explains persistent signals.

Material properties of oxides influence emission time scales (~1 second).

Damaged regions with enhanced quantum efficiency cause hot spots.

Abstract

Persistent photon and single-electron emissions - in the form of "electron trains" and localized "hot spots" - have been observed in multiple dual-phase liquid xenon (LXe) time projection chambers (TPCs), often persisting long after ionizing events. We show that these phenomena are naturally explained by photon-triggered single-electron emission from resistive mixed-oxide films on stainless-steel wires, which behave as leaky capacitors with long RC time constants at LXe temperature. Positive ions landing on these oxides can further enhance local fields and drive Malter-like electron emission. We outline the materials physics (Cr2O3 / Cr2O3-x / Cr(OH)3 mosaics), quantify expected time scales (~1 second under illumination), and demonstrate how small damaged regions with enhanced QE can produce persistent hot spots.