In this work we present a systematic study of Micromegas detectors in high pressure gaseous Xenon using trimethylamine (TMA) as quencher gas. Gas gains and energy resolutions for 22.1 keV X-rays are measured for pressures between 1 and 10 bar and various relative concentrations of TMA from 0.3 % to 15 %. We observe stable operation at all pressures, and a strongly enhanced gas gain, suggestive of Penning-like energy-transfer processes. The effect is present at all pressures and it is strongest at TMA concentrations ranging from 1.5 % to 3 %. Operating in this concentration range, the maximum gain reached values as high as x10^3 (x10^2) at 1 (10) bar. Besides, the energy resolution achievable for 22.1 keV X-rays is substantially better than the one previously obtained in pure Xe, going down to 7.3 % (9.6 %) FWHM for 1 (10) bar. These results are of interest for calorimetric applications of high pressure gas Xe TPCs, in particular for the search of the neutrinoless double beta decay of Xe-136. The resolutions achieved would extrapolate into 0.7 % (0.9 %) FWHM at the Qbb value of Xe-136 for 1 (10) bar.
@article{arxiv.1210.3287,
title = {Micromegas-TPC operation at high pressure in xenon-trimethylamine mixtures},
author = {S. Cebrián and T. Dafni and E. Ferrer-Ribas and I. Giomataris and D. Gonzalez-Diaz and H. Gómez and D. C. Herrera and F. J. Iguaz and I. G. Irastorza and G. Luzon and A. Rodríguez and L. Segui and A. Tomás},
journal= {arXiv preprint arXiv:1210.3287},
year = {2015}
}