Tesis doctoral. Óscar Pérez Lázaro (DFTUZ. Área de Física Atómica, Molecular y Nuclear)

Tesis Doctoral

“Development of new ultra-low-background particle detectors based on Micromegas technology for the search of Dark Matter at the low-mass frontier”
Óscar Pérez Lázaro
(Área de Física Atómica, Molecular y Nuclear)

Director: Igor García Irastorza

Abstract:

This PhD thesis is focused on the evolution and latest developments of TREX-DM, a gaseous Time Projection Chamber (TPC) designed to detect low-mass WIMPs through their low-energy nuclear recoils. TREX-DM is equipped with microbulk Micromegas readout planes, a technology well-suited for rare event searches due to its intrinsic radiopurity, potential for low energy thresholds and background discrimination capabilities through 3D event reconstruction.

A central focus of the thesis is background reduction in TREX-DM: through 222Rn mitigation and surface contamination control, background levels have been reduced from around 1000 to 80-100 dru. Surface contamination, primarily from 222Rn progeny, has prompted the development of novel screening tools such as AlphaCAMM, a high-sensitivity surface contamination detector.

The most significant result is the implementation of a Gas Electron Multiplier (GEM) pre-amplification stage on top of the microbulk Micromegas detectors. This yields extra gain factors up to around 100, substantially reducing the energy threshold. A calibration with a 37Ar source (low-energy peaks at 0.27 keV and 2.82 keV) validated this reduction, demonstrating energy thresholds at the level of single-ionisation energies (26 eV in argon).

Future improvements target further background reduction through a modified cathode design, enhanced detector stability via a more robust field cage, and gas mixture optimisation to enhance sensitivity to low-energy nuclear recoils.

Fecha: Jueves 4 de septiembre de 2025
Hora: 11:00
Lugar: Salón de Actos de Matemáticas