Detection of β-ray from ³H with back illuminated sCMOS imager

Tritium occurs in nuclear power plants. The energy of beta-rays from tritium is so low that detecting the beta-rays is challenging. Therefore, method of measuring tritium surface contamination is required. Liquid scintillators are generally used to measure the beta-rays. However, this method is complicated to use on-site. To measure tritium surface contamination on-site, we attempted to detect tritium using the GSENSE2020BSI back-illuminated sCMOS imager. We used a tritium areal radiation source to validate the detection of beta rays from tritium. The beta-rays cause bright spots in images and spread to multipixel. The average number of the pixels by the beta-rays was 4.6 and covered within a 3x3 pixel region. The energy spectrum from 10,000 images with 3x3 binning patterns showed a continuous shape spectrum. The spectra shape was characteristic of beta-ray spectra, demonstrating that the energy spectrum could be obtained with low-energy beta rays from tritium using the back-illuminated sCMOS image sensor. The spectral shape was produced from a radiation simulation using Geant4. From the simulation, the sCMOS sensor was able to measure tritium contamination of 10 becquerels (Bq)/cm² within 100 s and 4 Bq/cm² within 480 s.