Development and characterization of MPGD-based transition radiation detectors

TL;DR

This paper investigates MPGD technologies like GEM, Micromegas, and $ew$RWELL as innovative amplification stages in transition radiation detectors, demonstrating their potential for improved electron identification in high-energy physics experiments.

Contribution

It presents the design, construction, and in-beam testing of novel MPGD-based TRDs, including the first in-beam measurements of Micromegas- and $ew$RWELL-based TRDs, and evaluates their performance.

Findings

GEM-based TRD achieved a pion suppression factor of about 8 at 90% electron efficiency.

Micromegas-based TRD with GEM preamplification showed improved stability and TR photon discrimination.

$ew$RWELL prototype operated stably but with limited gain.

Abstract

Transition Radiation Detectors (TRDs) are useful for electron identification and hadron suppression in high energy nuclear and particle physics experiments. Conventional wire-chamber TRDs face operational limitations due to space charge effects, motivating the replacement of the amplification stage with MicroPattern Gaseous Detectors (MPGDs). This work explores different MPGD technologies - Gas Electron Multiplier (GEM), Micro-Mesh Gaseous Structure (Micromegas), and Resistive Micro-Well ($\mu$RWELL) - as alternative TRD amplification stages. We report on the design, construction, and in-beam characterization of multiple MPGD-based TRD prototypes exposed to 3-20 GeV mixed electron-hadron beams at the Fermilab Test Beam Facility and at the CERN SPS H8 beamline. Each detector consisted of a multi-layered radiator, an approximately 2 cm deep drift region, an MPGD amplification stage optimized for X-ray transition radiation detection in a Xe:CO$_{2}$ (90:10) gas mixture, and a two-dimensional readout. The GEM-based TRD prototype achieved a pion suppression factor of about 8 at 90% electron efficiency, while the Micromegas-based prototype - with an added GEM preamplification layer - demonstrated improved operational stability and clear TR photon discrimination. The $\mu$RWELL prototype achieved stable operation but limited signal gain. Geant4-based studies confirmed the observed trends and highlighted the sensitivity of the TR yield to cathode material and radiator configuration. These studies represent the first in-beam measurements of Micromegas- and $\mu$RWELL-based TRDs, along with discussion of the performance capabilities of a triple-GEM-TRD. The results demonstrate the feasibility of MPGDs as scalable, high-rate amplification structures for next-generation TRD applications.