Goodwin Matthew A, Regan Patrick H, Bell Steven J, Britton Richard, Davies Ashley V
Atomic Weapons Establishment (AWE), Aldermaston, Reading, Berkshire, RG7 4PR, United Kingdom; Department of Physics, University of Surrey, Stag Hill, Guildford, GU2 7XH, United Kingdom.
Department of Physics, University of Surrey, Stag Hill, Guildford, GU2 7XH, United Kingdom; National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, United Kingdom.
J Environ Radioact. 2022 Sep;250:106915. doi: 10.1016/j.jenvrad.2022.106915. Epub 2022 May 30.
A high-resolution β - γ coincidence spectrometry system has been set-up and calibrated at the UK CTBT Radionuclide Laboratory (known as GBL15) at AWE. The system has been configured specifically to measure the signatures of radioxenon isotopes that can be indicative of a nuclear explosion. The high purity germanium (HPGe) and PIPSBox detectors have been placed in an ultra-low-background lead shield to reduce the background count-rate and new software allows the combination of signals from four detectors (two HPGe detectors and two silicon-based detectors) to cover a larger solid angle. Measurements of samples of radioxenon isotopes are used to realise an improved detection efficiency and background acquisitions have demonstrated the achievable detection limits to reach 1.3 mBq for Xe and ≤0.3 mBq for the metastable isomers Xe and Xe. Due to the improved energy resolution in both photon and electron detectors, the detection sensitivity remains high in the presence of interfering signals from other radioxenon isotopes, such as those that may be present due to the significant levels of atmospheric radioxenon in parts of the world. This paper summarises the detector setup, efficiency calibration measurements and determination of the limits of detection. This work demonstrates the benefits of high-resolution coincidence detector systems for re-measurement of samples from the CTBT International Monitoring System (IMS) - improved detectability of metastable isomers Xe and Xe in the presence of Xe, compared to the current laboratory system.
一个高分辨率β-γ符合光谱系统已在英国原子武器研究机构的英国全面禁止核试验条约放射性核素实验室（称为GBL15）搭建并校准。该系统经过专门配置，用于测量可指示核爆炸的放射性氙同位素特征。高纯度锗（HPGe）探测器和PIPSBox探测器被放置在超低本底铅屏蔽中，以降低本底计数率，新软件允许组合来自四个探测器（两个HPGe探测器和两个硅基探测器）的信号，以覆盖更大的立体角。对放射性氙同位素样品的测量用于实现更高的探测效率，本底采集结果表明，对于Xe，可达到的探测限为1.3 mBq，对于亚稳态异构体Xe和Xe，探测限≤0.3 mBq。由于光子探测器和电子探测器的能量分辨率都有所提高，在存在来自其他放射性氙同位素的干扰信号（例如世界部分地区大气中大量放射性氙可能导致的干扰信号）的情况下，探测灵敏度仍然很高。本文总结了探测器设置、效率校准测量以及探测限的确定。这项工作展示了高分辨率符合探测器系统对全面禁止核试验条约国际监测系统（IMS）样品进行重新测量的优势——与当前实验室系统相比，在存在Xe的情况下，对亚稳态异构体Xe和Xe具有更高的可探测性。
