Initial performance of the high sensitivity alpha particle detector at the Yangyang underground laboratory

TL;DR

This paper reports the initial performance and calibration results of the UltraLo-1800 alpha particle detector at a deep underground laboratory, demonstrating its capability to distinguish surface and bulk contamination using pulse discrimination and likelihood analysis.

Contribution

It introduces the first performance evaluation of the UltraLo-1800 detector at a deep underground site, including calibration, low-activity sample measurements, and a novel likelihood analysis for contamination depth separation.

Findings

Successful calibration of the detector at 700 m depth

Effective pulse discrimination and hardware veto implemented

Separation of surface and bulk contamination components achieved

Abstract

Initial performance of the UltraLo-1800 alpha particle detector at the 700 m deep Yangyang underground laboratory in Korea is described. The ionization detector uses Argon as a counting gas for measuring alpha events of a sample. We present initial calibration results and low-activity sample measurements based on the detector's pulse discrimination method and a hardware veto. A likelihood analysis that shows a separation of a bulk component from a surface component with a contamination depth from $^{210}$Po alpha particles using simulated models is presented.