摘要:
在放射源能谱测量过程中，PIPS-谱仪探测效率的影响因素有几何因子、空气层吸收、死层吸收、本征探测效率等，为了更精确地计算放射源的活度，分析母体核素种类和浓度，探究各因素对探测效率的影响具有重要意义。使用蒙特卡罗软件模拟不同探源距、真空度下的放射源的能谱测量；使用SRIM模拟5 MeV 粒子在空气和死层中的射程及分布；使用PIPS-谱仪测量241Am，238Pu，239Pu三种标准源的实际能谱；根据实验与模拟的结果对各个因素对探测效率的影响进行分析，并计算得到谱仪对不同放射源的本征探测效率。结果表明：在PIPS-谱仪的能谱测量过程中，影响谱仪探测效率的主要因素是几何因子和本征探测效率，空气层和死层对粒子的吸收可以忽略不计；谱仪对241Am，238Pu，239Pu三种标准源的本征探测效率分别为64.84%，49.95%，51.55%。
Abstract:
In the process of -source spectrum measurement, influence factors of the detector efficiency of the PIPS- spectrometer are the geometric factor, air layer absorption, dead layer absorption, the intrinsic detection efficiency, and so on. In order to calculate the activity of sources more accurately, to analyse the type and concentration of the parent nuclide, it is of great significance to explore the influence of these factors on the detection efficiency. Monte Carlo software was used to simulate the energy spectrum measurement of different source-detector distance and vacuum degree, SRIM was used to simulate the range and distribution of alpha particles in the air and dead layer with 5 MeV alpha particles, and PIPS- spectrometer was used to measure the actual spectra of three standard radioactive sources 241Am, 238Pu，239Pu. According to the results of experiments and simulation, the influence of various factors on the detection efficiency was analyzed, the intrinsic detection efficiency of spectrum of different -sources was calculated. The results show that: in the PIPS- spectrometer measurement process, the main factors affecting the detection efficiency of the spectrometer is geometric factor and intrinsic detection efficiency; the absorption of alpha particles by air and dead layer is negligible; the intrinsic detection efficiencies of the spectrometer for 241Am, 238Pu, 239Pu standard sources are 64.84%, 49.95%, 51.55% respectively.
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