On-site underground background measurements for the KASKA reactor-neutrino experiment

TL;DR

This study conducted underground background measurements at the KASKA reactor site to inform the design of a neutrino oscillation experiment, focusing on natural radioactivity and cosmic muon rates at various depths.

Contribution

It provides detailed on-site measurements of natural radioactivity and cosmic muon fluxes at different depths, crucial for optimizing the KASKA neutrino experiment design.

Findings

Quantified natural radioactive element abundance in surrounding soil.

Measured cosmic muon rates at various underground depths.

Data will inform shielding and detector placement for KASKA.

Abstract

On-site underground background measurements were performed for the planned reactor-neutrino oscillation experiment KASKA at Kashiwazaki-Kariwa nuclear power station in Niigata, Japan. A small-diameter boring hole was excavated down to 70m underground level, and a detector unit for $\gamma$-ray and cosmic-muon measurements was placed at various depths to take data. The data were analyzed to obtain abundance of natural radioactive elements in the surrounding soil and rates of cosmic muons that penetrate the overburden. The results will be reflected in the design of the KASKA experiment.