Optimisation design of cylindrical containers for improving the detection efficiency of a high-purity germanium detector
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Optimisation design of cylindrical containers for improving the detection efficiency of a high-purity germanium detector using the LabSOCS Baolu Yang • Yiming Ha • An Li • Hongjie Zhou Feng Wang • Weiming Li
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Received: 18 March 2013 Ó Akade´miai Kiado´, Budapest, Hungary 2013
Abstract The LabSOCS software was used to optimise the geometric dimensions of cylindrical containers and improve the detection efficiency of a high-purity germanium detector for the measurement of environmental radioactivity samples. The optimum ratio of diameter and height for different sample volumes were determined. In addition, the degrees of influence of the sample volume and density when the amount of sample was fixed were compared. Results show that the effect of sample volume on detection efficiency was significantly greater than that of sample density for a given sample amount. Keywords Cylindrical containers Detector efficiency HPGe LabSOCS
Introduction High-purity germanium (HPGe) detector have been widely used for radioactivity measurements, especially for lowlevel activity materials, for its major advantages such as high energy resolution and sensitivity. Detection efficiency is among the most important parameters for determining the operating characteristics of a spectrometer for radioactivity measurement. In a case where the same accuracy is
B. Yang Y. Ha (&) A. Li H. Zhou F. Wang W. Li Institute of Agro-products Processing Science and Technology, Chinese Academy of Agricultural Science, Beijing 100193, China e-mail: [email protected] B. Yang Y. Ha A. Li H. Zhou F. Wang W. Li Key Opening Laboratory of Agricultural Products Processing and Quality Control, Ministry of Agriculture, Beijing 100193, China
achieved, higher detection efficiency can reduce measurement time, thereby improving the utilisation of the spectrometer. However, HPGe detectors often have lower full energy peak efficiency compared with other detectors, including NaI(TI). Therefore, improving the detection efficiency of HPGe is important. The detection efficiency curve depends not only on a detection system but also on the sample shape [1–4]. Thus, investigating the optimum geometric parameters of different sample shapes is necessary to maximise the detection efficiency of the HPGe detector. In general, to avoid polluting the detector in actual measurement, the detector is often covered with a hood-shaped protection cap. Therefore, in order to be consistent with the actual measurement situation, the influence of sample-to-detector distance on detection efficiency should be considered in optimizing geometric parameters of different sample shapes. Efficiency calibration can be performed theoretically by using Monte Carlo computation techniques or a semiempirical analytical method [5]. Simulating the calibration procedure is a useful tool for environmental radioactivity laboratories because simulation not only can obtain accurate experimental results but also can avoid the need to make standards of different shapes and sizes
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