# Micromegas with GEM preamplification for enhanced energy threshold in low-background gaseous time projection chambers

## TL;DR

Researchers improved a detector design for dark matter experiments by adding a preamplification stage, which could make the detector more sensitive to low-mass dark matter particles.

## Contribution

The novel use of a GEM preamplifier with a Micromegas readout increases gain and lowers energy thresholds for dark matter detection.

## Key findings

- GEM preamplification achieved gain factors of 90, 50, and 20 at different gas pressures.
- The setup was tested in a full-scale TREX-DM replica, showing potential for a 50 eV energy threshold.
- This improvement enhances sensitivity to low-mass WIMPs in dark matter searches.

## Abstract

We develop the concept of a Micromegas readout plane with an additional GEM preamplification stage placed a few millimetres above it to increase the maximum effective gain of the combined readout.

We implement it and test it in realistic conditions for its application to low-background dark matter searches like the TREX-DM experiment. For this, we use a Micromegas of microbulk type, built with radiopure materials.

We report on GEM effective extra gain factors of about 90, 50 and 20 in 1, 4 and 10 bar of Ar-1%iC
4H
10. These results are obtained in a small test chamber allowing for systematic scanning of voltages and pressures. In addition, a TREX-DM full-scale set-up has also been built and tested, featuring a replica of the fully-patterned TREX-DM microbulk readout.

The results here obtained show promise to lower the threshold of the experiment down to 50 eV

ee
, corresponding to substantially enhanced sensitivity to low-mass WIMPs.