Development and operation of a muon detection system under extremely high humidity environment for monitoring underground water table

摘要

In order to investigate the complex nature of landslides triggered byrainfall, dynamic muon radiography of the motion of the underground watertable is planned in a drainage tunnel drilled underneath an estimated faultplane. However, the humidity inside the tunnel is almost 100%. In orderto suppress moisture effects, a scintillation counter with Cockcroft–Waltonphotomultipler tubes (CW-MPT) was developed and tested at the observationsite located in Shizuoka Prefecture, Japan. The counter was stably operatedfor 38 days without gain degrading. Based on the result, we constructed amuon detection system with CW-PMTs at the same site and started operationruns. In this work, the data from borehole-based water gauge measurements ofthe underground water levels were analyzed and discussed. It was confirmedthat the comparison between muon and borehole data would be useful.