Thick GEM versus thin GEM in two-phase argon avalanche detectors

TL;DR

This study compares thick and thin GEM multipliers in two-phase argon avalanche detectors, demonstrating their performance, stability, and noise characteristics for potential use in rare-event physics experiments.

Contribution

It provides the first direct comparison of thick and thin GEMs in two-phase argon detectors, highlighting the stable operation of G10-THGEMs and noise reduction techniques.

Findings

G10-THGEM achieved stable operation with gains up to 3000.

Double-THGEM and triple-GEM operated at low detection thresholds of 20 and 4 electrons.

Pulse-shape analysis effectively reduced noise levels to 0.007 Hz per cm².

Abstract

The performance of thick GEMs (THGEMs) was compared to that of thin GEMs in two-phase Ar avalanche detectors, in view of their potential application in coherent neutrino-nucleus scattering, dark-matter search and in other rare-event experiments. The detectors comprised a 1 cm thick liquid-Ar layer followed by either a double-THGEM or a triple-GEM multiplier, operated in the saturated vapor above the liquid phase. Three types of THGEMs were studied: those made of G10 and Kevlar and that with resistive electrodes (RETHGEM). Only the G10-made THGEM showed a stable performance in two-phase Ar with gains reaching 3000. Successful operation of two-phase Ar avalanche detectors with either thin- or thick-GEM multipliers was demonstrated at low detection thresholds, of 4 and 20 primary electrons respectively. Compared to the triple-GEM the double-THGEM multiplier yielded slower anode signals; this allowed applying a pulse-shape analysis to effectively reject noise signals. Noise rates of both multipliers were evaluated in two-phase Ar; with detection thresholds of 20 electrons and applying pulse-shape analysis noise levels as low as 0.007 Hz per 1 cm2 of active area were reached.