Boson Jonas, Lidström Kenneth, Nylén Torbjörn, Agren Göran, Johansson Lennart
Swedish Defence Research Agency, FOI NBC-skydd, SE 901 82 Umeå, Sweden.
Radiat Prot Dosimetry. 2006;121(3):310-6. doi: 10.1093/rpd/ncl041. Epub 2006 Apr 21.
In situ gamma spectrometry using high-purity germanium (HPGe) detectors is a frequently used method for the determination of radionuclide ground deposition levels. Such measurements do, however, require an efficiency calibration based on detector sensitivity and parameters such as soil density and vertical activity distribution. In this work, a novel expression is used for the detector efficiency, incorporating both the influence of photon energy and incidence angle. Detector-specific efficiency data are determined empirically. For the theoretical calculation of the photon fluence at the detector, a three-layer model of finite thickness is developed for the description of soil density and vertical activity distribution. In order to facilitate the calibration of in situ measurements, a PC program has been developed to enable rapid, on-site calculations of radionuclide ground deposition levels. The semi empirical calibration method was tested on in situ measurements with two different detectors, and the results show good agreement with results obtained from traditional soil sampling.
使用高纯锗（HPGe）探测器的原位伽马能谱法是测定放射性核素地面沉积水平的常用方法。然而，此类测量确实需要基于探测器灵敏度以及诸如土壤密度和垂直活度分布等参数进行效率校准。在这项工作中，采用了一种新颖的探测器效率表达式，该表达式纳入了光子能量和入射角的影响。通过实验确定特定于探测器的效率数据。为了对探测器处的光子注量进行理论计算，开发了一个有限厚度的三层模型来描述土壤密度和垂直活度分布。为便于原位测量的校准，已开发了一个PC程序，以实现对放射性核素地面沉积水平的快速现场计算。对半经验校准方法在使用两种不同探测器的原位测量中进行了测试，结果与传统土壤采样获得的结果显示出良好的一致性。
