Development of large Micromegas readout planes for experiments searching for rare events

TL;DR

This paper reports on the development and testing of large Micromegas readout planes for rare event experiments like neutrinoless double beta decay and WIMP searches, including tiled mosaics and GEM-Micromegas systems.

Contribution

It introduces new large-scale Micromegas readout plane designs, including tiled mosaics and integrated GEM-Micromegas systems, tailored for high-pressure gaseous TPCs in rare event detection.

Findings

Successful development of a tiled Micromegas readout plane for PandaX-III.

Implementation of a 25x25 cm² Micromegas readout in TREX-DM.

Design and testing of a GEM-Micromegas system to lower energy thresholds.

Abstract

The use of Time Projection Chambers (TPCs) in particle physics experiments has been growing since their invention, reaching sizes equivalent to buildings (ALICE or ATLAS at CERN). However, their application in another class of experiments, commonly referred to as rare event experiments, has been more recent. This work focuses on two such experiments aimed at searching for rare events: the search for neutrinoless double beta decay (PandaX-III experiment) and the search for WIMPs (TREX-DM experiment). Both utilize a large-sized gaseous TPC, necessitating that the corresponding readout plane is also large. Both also employ microbulk Micromegas readout planes. This technology has become established in recent years and is continuously improving. Due to the size limitation during manufacturing and the concurrent increase in the size of double beta experiments, there arose a need to develop a tiled readout plane, using a mosaic of modules with microbulk Micromegas, conforming the first part of this thesis, in the context of the PandaX-III experiment. The second part, featuring a single readout plane of 25 x 25 cm2 installed in TREX-DM, focuses on the specifications that define a Micromegas and its response in a high-pressure gaseous detector. Additionally, during the work on TREX-DM, the need to reduce the energy threshold of the experiment emerged, leading to the development of another composite readout plane, the GEM-Micromegas system, in which a GEM specifically manufactured for this system was installed above the Micromegas. Finally, leveraging the development of the Micromegas for TREX-DM, a new gaseous detector for the detection of surface alpha particles, called AlphaCAMM, is planned, designed, and implemented, addressing all the requirements of a low-background detector with a projection beyond the TREX-DM experiment.