Material Screening with HPGe Counting Station for PandaX Experiment

TL;DR

This paper describes the development and performance of a high-purity germanium detector-based gamma counting station designed for material screening in the PandaX dark matter experiment, achieving low background rates and high sensitivity.

Contribution

It introduces a well-designed HPGe gamma counting station with enhanced sensitivity and low background, tailored for material screening in underground dark matter experiments.

Findings

Achieved a gamma background rate of 2.6 counts/min in the 20-2700 keV range.

Reaches detection sensitivities at the mBq/kg level for key isotopes.

Provides detailed radioactivity measurements for PandaX materials.

Abstract

A gamma counting station based on high-purity germanium (HPGe) detector was set up for the material screening of the PandaX dark matter experiments in the China Jinping Underground Laboratory. Low background gamma rate of 2.6 counts/min within the energy range of 20 to 2700 keV is achieved due to the well-designed passive shield. The sentivities of the HPGe detetector reach mBq/kg level for isotopes like K, U, Th, and even better for Co and Cs, resulted from the low-background rate and the high relative detection efficiency of 175%. The structure and performance of the counting station are described in this article. Detailed counting results for the radioactivity in materials used by the PandaX dark-matter experiment are presented. The upgrading plan of the counting station is also discussed.