Andrews L L, Schery S D, Wilkening M H
Health Phys. 1984 Apr;46(4):801-8. doi: 10.1097/00004032-198404000-00006.
An system has been developed to measure airborne radioactivity using electrostatic precipitation for collection and alpha-particle spectroscopy for detection. Features include good energy resolution (e.g. 170 and 300 KeV for full-width half maximum and full-width tenth maximum for 7.7-MeV alpha particles using a 7-cm2 area detector; and 52- and 122-KeV, respectively, using 1.2-cm2 area detector) and versatile computer control for collection, counting and data reduction. Aerosols bearing the radioactive atoms are deposited on a foil tape by electrostatic precipitation for a predetermined time after which the foil is moved under a solid-state detector to count the alpha-particle emissions. Activities are determined at the same frequency as samples are collected. Helium gas can be introduced at the detector to reduce energy loss and improve resolution. Although in principle certain aerosol sizes could be difficult to collect, in practice no difficulties were observed for typical environmental conditions, provided sufficiently low air-sampling rates were used. One important application is the measurement of 222Rn daughters. The sensitivity is such that detection of individual daughter concentrations less than 0.1 pCi/l. with only a 10% counting error is possible.
已经开发出一种系统，该系统利用静电沉淀进行收集并使用α粒子光谱法进行检测来测量空气中的放射性。其特点包括良好的能量分辨率（例如，对于使用7平方厘米面积探测器的7.7兆电子伏α粒子，半高宽和十分之一高宽分别为170和300千电子伏；对于使用1.2平方厘米面积探测器的情况，分别为52和122千电子伏）以及用于收集、计数和数据处理的通用计算机控制。携带放射性原子的气溶胶通过静电沉淀在箔带上沉积预定时间，之后箔带在固态探测器下方移动以对α粒子发射进行计数。在收集样品的相同频率下确定活度。可以在探测器处引入氦气以减少能量损失并提高分辨率。虽然原则上某些气溶胶尺寸可能难以收集，但在实践中，对于典型的环境条件，只要使用足够低的空气采样率，就不会观察到困难。一个重要的应用是测量222Rn子体。其灵敏度使得能够检测到浓度低于0.1皮居里/升的单个子体，且计数误差仅为10%。
