Accurate gamma and MeV-electron track reconstruction with an ultra-low diffusion Xenon/TMA TPC at 10 atmospheres

TL;DR

This paper demonstrates the use of a high-pressure Xenon/TMA TPC with ultra-low diffusion for precise 3D tracking of MeV-electrons and gamma-rays, advancing detector capabilities for rare event searches.

Contribution

It introduces a Xenon/TMA gas mixture at 10 atm with low electron diffusion, combined with advanced readout technology for accurate 3D electron track reconstruction.

Findings

Achieved low electron diffusion of 1.3 mm longitudinally and 0.8 mm transversely.

Operated continuously for 100 days with stable performance.

Provided detailed 3D topological information of MeV-electron tracks.

Abstract

We report the performance of a 10 atm Xenon/trimethylamine time projection chamber (TPC) for the detection of X-rays (30 keV) and gamma-rays (0.511-1.275 MeV) in conjunction with the accurate tracking of the associated electrons. When operated at such a high pressure and in 1%-admixtures, trimethylamine (TMA) endows Xenon with an extremely low electron diffusion (1.3 +-0.13 mm-sigma (longitudinal), 0.8 +-0.15 mm-sigma (transverse) along 1 m drift) besides forming a convenient Penning-Fluorescent mixture. The TPC, that houses 1.1 kg of gas in its active volume, operated continuously for 100 live-days in charge amplification mode. The readout was performed through the recently introduced microbulk Micromegas technology and the AFTER chip, providing a 3D voxelization of 8mm x 8mm x 1.2mm for approximately 10 cm/MeV-long electron tracks. This work was developed as part of the R&D program of the NEXT collaboration for future detector upgrades in the search of the 0bbnu decay in 136Xe, specifically those based on novel gas mixtures. Therefore we ultimately focus on the calorimetric and topological properties of the reconstructed MeV-electron tracks.