在线环境氡浓度测量的离子脉冲电离室研制

Ion pulse ionization chamber for online measurements of the radon activity concentration

氡(Rn)及其子体对人体呼吸器官有严重危害,为避免有害辐射,需准确测量环境空气中的氡浓度。氡及其子体衰变放出的α粒子能将空气分子电离,据此研发了一套基于离子脉冲电离室的探测器系统,实现对单个辐射粒子的信息记录和空气中的浓度准确测量。该探测器通过双屏蔽结构来有效抑制噪声,并采用离子脉冲收集方式,通过示波器波形采样来获取数据。探测器的工作电压区间为-400~-1 200 V,对241Am衰变产生的α粒子的能量分辨半峰全宽(Full Width at Half Maximum,FWHM)达到了17%,并在不同地点对空气中的氡含量进行了测量,得到有效信号和计数。测量结果表明:该地点符合GB/T 50325-2020对室内氡浓度的规定。

[Background]Radon and its daughters are seriously harmful to human respiratory organs.[Purpose]This study aims to accurately measure the concentration of radon in ambient air by ion pulse ionization chamber for online measurements.[Methods]Based on the principle that alpha rays emitted by radon and its daughters ionize air molecules,a detection system based on ion pulse ionization chamber was developed to record the information of single radioactive particles and accurately measure the concentration in the air.Double shielding structure to adopted to suppress the noise effectively for the detector,and ionized data was obtained by ion pulse collection and oscilloscope waveform sampling.The radon content in the air was measured in different locations,and the effective signals and counts were obtained.[Results&Conclusions]The measurement results show that the full width at half maximum(FWHM)of the 241Am alpha particle energy resolution is 17%under the detector's working voltage range of−400 to−1200 V.The radon concentrations in the air measured at two campus sites in Lanzhou city are(22.05±0.86)Bq·m^(−3)and(20.31±0.84)Bq·m^(−3),respectively,that conform to the provisions of GB/T 50325‒2020 on indoor radon concentration.