Radon measurements in a small chamber using compact organic scintillator-based alpha/beta spectrometer

有機シンチレータベースの小型コンパクト/スペクトロメータを用いたラドン測定

森下 祐樹  ; Ye, Y.*; Mata, L.*; Pozzi, S.*; Kearfott, K.*

Morishita, Yuki; Ye, Y.*; Mata, L.*; Pozzi, S.*; Kearfott, K.*

コンパクトな有機シンチレータベースのスペクトロメータを開発し、ラドン測定を行った。pulse shape discrimination技術を使って線と線のスペクトルを同時に得ることができた。スペクトルを見るとラドン子孫核種であるPoとPoのピークが確認された。市販のラドン測定器とも直線的な関係を示した。開発したスペクトロメータは厚みも薄く、小型である。そのため感度は低いが、複数並べることで感度を向上させることも可能である。そのため、開発したスペクトロメータは、新しいラドン検出器としての可能性を有している。

A compact organic scintillator-based spectrometer was developed and tested for radon measurements. The spectrometer was composed of a Through Silicon Via (TSV) silicon photomultiplier or SiPM and a 6 mm 6 mm 6 mm stilbene cube crystal. Analog signals from the SiPM were sent to a digitizer. The detector was placed in a light-tight box and a stacked air filter was embedded on the side surface of the light-tight box. A continuous radon monitor, the AlphaGUARD, and Ra sources were placed in a small radon chamber constructed using a cylindrical 0.57 m diameter, 0.88 m tall steel drum. By applying a pulse shape discrimination technique, alpha and beta spectra were simultaneously clearly separated and quantitatively measured. Two peaks were registered in the measured alpha spectrum: Po was registered in the lower peak and Po was registered in the higher peak. A linear relationship was observed between radon counts from the AlphaGUARD and count-rates from the stilbene-SiPM detector. The thickness of the stilbene-SiPM detector was less than 10 mm, thus easy increases insensitivity should be possible with future construction. Thus, the compact organic scintillator-based alpha/beta spectrometer shows promise for use in novel radon detection systems.