Progress on the ALETHEIA project and a new approach to mitigate events overlap

TL;DR

This paper reports significant progress in developing liquid helium TPCs for dark matter detection, demonstrating that operating near 1.0 K mitigates event overlap issues due to increased electron mobility.

Contribution

The study introduces a new approach to mitigate event overlap in LHe TPCs by operating at 1.0 K, showing technological feasibility of single-phase LHe TPCs for dark matter searches.

Findings

LHe TPC development has advanced significantly since 2020.

Operating near 1.0 K eliminates event overlap issues.

Electron mobility at 1.0 K is three orders of magnitude higher.

Abstract

The ALETHEIA project aims to search for low-mass dark matter using liquid helium (LHe)-filled time projection chambers (TPCs). While liquid argon and liquid xenon TPCs have been extensively employed in the field of direct dark matter detection, successful development of LHe TPCs has not yet been achieved. Launched in 2020, our project has made significant progress since then. These advancements have convinced us that a single-phase LHe TPC is technologically feasible. Compared to liquid xenon and liquid argon TPCs, one of the unique challenges for LHe TPCs is event overlap caused by the 13-second lifetime scintillation. We will demonstrate that this overlap can be entirely mitigated when the LHe temperature is maintained near 1.0 K. At this temperature, electron mobility is three orders of magnitude higher than at approximately 4.0 K, which is the temperature we initially proposed for the LHe TPC.