Micromegas-TPC operation at high pressure in Xenon-trimethylamine mixtures

TL;DR

This study demonstrates that using xenon-trimethylamine mixtures in Micromegas-TPCs significantly enhances gain and energy resolution at high pressures, benefiting neutrino-less double beta decay searches.

Contribution

It introduces the use of Xe-TMA mixtures in Micromegas-TPCs, showing improved gain, energy resolution, and maximum achievable gain compared to pure xenon.

Findings

Gain increase up to 100 times at constant field.

Energy resolution improved by up to a factor of 3.

Maximum gain up to 400 at 10 bar in Xe-TMA mixture.

Abstract

We present in this work measurements performed with a small Micromegas-TPC using a xenon-trimethylamine (Xe-TMA) Penning-mixture as filling gas. Measurements of gas gain and energy resolutions for 22.1 keV X-rays are presented, spanning several TMA concentrations and pressures between 1 and 10 bar. Across this pressure range, the best energy resolution and largest increase in gain at constant field (a standard figure for characterizing Penning-like energy transfers) is observed to be in the 1.5%-2.5% TMA region. A gain increase (at constant field) up to a factor 100 and a best energy resolution improved by up to a factor 3 with respect to the one previously reported in pure Xe -operated Micromegas, can be obtained. In virtue of the VUV-quenching properties of the mixture, the overall maximum gain achievable is also notably increased (up to 400 at 10bar), a factor x 3 higher than in pure Xe. In addition, preliminary measurements of the electron drift velocity in a modified setup have been performed and show good agreement with the one obtained from Magboltz. These results are of great interest for calorimetric applications in gas Xe TPCs, in particular for the search of the neutrino-less double beta decay of Xe-136.