TREX-DM: a low-background Micromegas-based TPC for low-mass WIMP detection

TL;DR

TREX-DM is a low-background, Micromegas-based TPC designed to detect low-mass WIMPs with very low energy thresholds, potentially surpassing current limits for WIMPs of 2-8 GeV.

Contribution

This paper introduces TREX-DM, a novel low-background gaseous TPC with Micromegas readouts optimized for low-mass WIMP detection, demonstrating its design and initial performance.

Findings

Achieved an energy threshold below 0.4 keVee

Designed for an active mass of 0.300 kg of Ar or 0.160 kg of Ne at 10 bar

Preliminary background model indicates promising low-background performance

Abstract

If Dark Matter is made of Weakly Interacting Massive Particles (WIMPs) with masses below $\sim$20 GeV, the corresponding nuclear recoils in mainstream WIMP experiments are of energies too close, or below, the experimental threshold. Gas Time Projection Chambers (TPCs) can be operated with a variety of target elements, offer good tracking capabilities and, on account of the amplification in gas, very low thresholds are achievable. Recent advances in electronics and in novel radiopure TPC readouts, especially micro-mesh gas structure (Micromegas), are improving the scalability and low-background prospects of gaseous TPCs. Here we present TREX-DM, a prototype to test the concept of a Micromegas-based TPC to search for low-mass WIMPs. The detector is designed to host an active mass of $\sim$0.300 kg of Ar at 10 bar, or alternatively $\sim$0.160 kg of Ne at 10 bar, with an energy threshold below 0.4 keVee, and is fully built with radiopure materials. We will describe the detector in detail, the results from the commissioning phase on surface, as well as a preliminary background model. The anticipated sensitivity of this technique may go beyond current experimental limits for WIMPs of masses of 2-8 GeV.