Radon measurements with a compact, organic-scintillator-based alpha/beta spectrometer

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

Radiation Measurements, 137, p.106428_1 - 106428_7, 2020/09

https://doi.org/10.1016/j.radmeas.2020.106428

We have developed a compact, organic-scintillator-based alpha/beta spectrometer for radon measurements and have characterized it using a unique, small radon chamber. The spectrometer is composed of a through-silicon via (TSV) silicon photomultiplier (or SiPM) and a 6 mm 6 mm 6 mm stilbene crystal cube. Analog signals from the SiPM are sent to a digitizer. The detector is housed in a light-tight box, with a stacked air filter installed in one side of the box to enable Rn gas to diffuse to the inside. We conducted one experiment with the spectrometer and an AlphaGUARD detector placed in a basement at the University of Michigan, and we conducted other experiments with both detectors placed in a small radon chamber together with Ra sources. By applying a pulse-shape-discrimination technique, we were able to separate the alpha and beta spectra simultaneously and clearly and to measure them quantitatively. We found two peaks in the measured alpha spectrum: a lower-energy peak due to Po and a higher-energy peak due to Po. We found a linear relation between the radon concentration y from AlphaGUARD and the counting rates from the stilbene-SiPM detector. The alpha/beta spectrometer is less than 10 mm thick, and we expect that it will be easy to increase the sensitivity with future device construction. Thus, this compact, organic-scintillator-based alpha/beta spectrometer shows promise for use in novel radon-detection systems.

核物質分布測定装置

森下 祐樹

not registered

JP, 2020-062776  Patent licensing information  Patent publication (In Japanese)

【課題】放射線のバックグラウンド成分を適切に認識することによって核物質の分布を適正に認識する。 【解決手段】位置検出型放射線検出器がα線又はβ線を検出することによって、パルス状の出力信号が発せられる(S1)。解析部は、この波形データから、この出力信号がα線によるものかβ線によるものかを認識し(S2)、認識されたエネルギーと位置情報、検出時刻を、α線、β線毎に区分して記憶部に記憶させる(S3)。測定時間内における全ての検出によって上記の情報が記憶された後、解析部は、β線の検出時刻とα線の検出時刻とが近い組み合わせ(α-β相関イベント)を抽出する(S5)。解析部は、この結果より、222RNに起因したバックグラウンド成分を算出することができる(S7)。検出されたα線の検出強度からこのバックグラウンド成分を差し引いた値を、補正後のα線の検出強度とすることができる(S8)。