Background studies and shielding effects for the TPC detector of the CAST experiment

TL;DR

This paper analyzes background radiation and designs shielding for the CAST TPC detector, significantly reducing background noise and improving measurement homogeneity in the 1-10 keV range.

Contribution

It presents a detailed background analysis and a novel shielding design that effectively reduces background noise in the CAST TPC detector.

Findings

Background reduced by a factor of ~4 with shielding

Shielding improves background homogeneity

Effective in the 1-10 keV energy range

Abstract

Sunset solar axions traversing the intense magnetic field of the CERN Axion Solar Telescope (CAST) experiment may be detected in a Time Projection Chamber (TPC) detector, as X-rays signals. These signals could be masked, however, by the inhomogeneous background of materials in the experimental site. A detailed analysis, based on the detector characteristics, the background radiation at the CAST site, simulations and experimental results, has allowed us to design a shielding which reduces the background level by a factor of ~4 compared to the detector without shielding, depending on its position, in the energy range between 1 and 10 keV. Moreover, this shielding has improved the homogeneity of background measured by the TPC.