ABSTRACT

In this work, we discuss two results from GEANT4 simulations of the broad-energy germanium (BEGe) lung counting system used by the Carlsbad Environmental Monitoring and Research Center (CEMRC) internal dosimetry laboratory. The first component of the presented research consists of the integration of the cosmic muon background into the environmental background spectra and updated calculations of the minimum-detectable activities (MDAs) that were previously published by the authors. This is followed by an investigation of methods to increase the detection sensitivity to low-energy $\gamma$ rays produced by the trans-uranic radioisotopes of interest by reducing the number of background counts observed in the region-of-interest (ROI) of the measured $\gamma$ ray spectra measured by the CEMRC in vivo counting system. Two methods were investigated for improving the MDAs: (1) a reduction in the thickness of the germanium detector crystals, and (2) the addition of a Compton-suppression detection system surrounding the germanium detectors, acting as a anti-coincidence veto counter.

摘要

在这项工作中，我们讨论了卡尔斯巴德环境监测与研究中心（CEMRC）内部剂量测定实验室使用的宽能锗（BEGe）肺计数系统的GEANT4模拟的两个结果。本研究的第一部分包括将宇宙μ子背景整合到环境背景光谱中，以及作者先前已发布的最小可探测活动（MDA）的更新计算。接下来是对提高低能量检测灵敏度的方法的研究$\gamma$ 通过减少在测量的目标区域（ROI）中观察到的背景计数的数量，由目标跨铀放射性同位素产生的射线 $\gamma$CEMRC体内计数系统测量的射线光谱。研究了两种改善MDA的方法：（1）降低锗探测器晶体的厚度，以及（2）在锗探测器周围增加一个康普顿抑制探测系统，用作反符合否决权计数器。