Development of a low-background HPGe detector at Kamioka Observatory

TL;DR

This paper reports the development and characterization of a new ultra-low background HPGe detector at Kamioka, achieving a 25% reduction in background count rate compared to a previous model, enhancing sensitivity for rare event detection.

Contribution

The paper introduces a new low-background HPGe detector with improved shielding and background reduction techniques at Kamioka Observatory.

Findings

Background count rate reduced by 25% compared to previous detector

Effective shielding and cleaning procedures implemented

Radioactivity measurements of samples conducted

Abstract

A new ultra-low background high-purity germanium (HPGe) detector has been installed at the Kamioka underground experimental site. The background count rate in the energy range from 40 keV to 2700 keV is about 25% lower than that of the first HPGe detector installed in 2016, which has the same detector specification and similar shielding geometry. This paper describes the shielding configuration, including the cleaning of the material surface, the comparison of calibration data and simulation, the time variation of the background spectra, the sample measurement procedure, and some results of the radioactivity in the selected samples.