Low X-ray bakground measurements at the Underground Canfranc Laboratory

TL;DR

This study demonstrates that Micromegas detectors, when properly shielded and used underground, achieve extremely low X-ray background levels, enhancing their suitability for rare event searches.

Contribution

The paper reports the first underground measurements of Micromegas detector background levels and compares them with simulations to optimize shielding.

Findings

Background levels up to 2 x 10^{-7} keV^{-1}s^{-1}cm^{-2} achieved underground

Shielding configurations significantly reduce background noise

Simulations help understand background origins and improve shielding design

Abstract

Micromegas detectors, thanks to the good spatial and temporal discrimination capabilities, are good candidates for rare event search experiments. Recent X-ray background levels achieved by these detectors in the CAST experiment have motivated further studies in the nature of the background levels measured. In particular, different shielding configurations have been tested at the Canfranc Underground Laboratory, using a microbulk type detector which was previously running at the CAST experiment. The first results underground show that this technology, which is made of low radiative materials, is able to reach background levels up to $2 \times 10^{-7}$keV$^{-1}$s$^{-1}$cm$^{-2}$ with a proper shielding. Moreover, the experimental background measurements are complemented with Geant4 simulations which allow to understand the origin of the background, and to optimize future shielding set-ups.