Low Energy Electronic Recoils and Single Electron Detection with a Liquid Xenon Proportional Scintillation Counter

TL;DR

This paper demonstrates a liquid xenon proportional scintillation counter capable of detecting low-energy electronic recoils and single electrons, with potential applications in neutrino detection.

Contribution

The study introduces a novel single-phase liquid xenon detector design that directly produces electroluminescence in liquid, enabling efficient low-energy recoil detection.

Findings

Detects electronic recoils down to ~1 keV

Observes single electrons with 1.8 PE gain

Potential for reactor neutrino detection via CEvNS

Abstract

Liquid xenon (LXe) is a well-studied detector medium to search for rare events in dark matter and neutrino physics. Two-phase xenon time projection chambers (TPCs) can detect electronic and nuclear recoils with energy down to kilo-electron volts (keV). In this paper, we characterize the response of a single-phase liquid xenon proportional scintillation counter (LXePSC), which produces electroluminescence directly in the liquid, to detect electronic recoils at low energies. Our design uses a thin (10 - 25 $\mu$m diameter), central anode wire in a cylindrical LXe target where ionization electrons, created from radiation particles, drift radially towards the anode, and electroluminescence is produced. Both the primary scintillation (S1) and electroluminescence (S2) are detected by photomultiplier tubes (PMTs) surrounding the LXe target. Up to 17 photons are produced per electron, obtained with a 10 $\mu$m diameter anode wire, allowing for the highly efficient detection of electronic recoils from beta decays of a tritium source down to roughly 1 keV. Single electrons, from photo-emission of the cathode wires, are observed at a gain of 1.8 photoelectrons (PE) per electron. The delayed signals following the S2 signals are dominated by single-photon-like hits, without evidence for electron signals observed in the two-phase xenon TPCs. We discuss the potential application of such a LXePSC for reactor neutrino detection via Coherent Elastic Neutrino Nucleus Scattering (CE$\nu$NS).