环境样品装样量对低能γ射线放射性核素活度测量的影响

摘要

为提高用HPGeγ谱仪测量环境样品中发射低能γ射线核素活度的准确性,研究了装样量对测量结果的影响.首先用蒙特卡罗方法模拟计算了不同能量γ射线探测效率与装样量(装样高度)之间的关系,由此得到了不同能量γ射线的全能峰计数与装样高度的关系,由此关系可以确定不同能量γ射线的最佳装样量.然后以土壤样品中的238U为例,分别模拟计算其92.6 keV标识γ射线在不同装样高度时的单能能谱和存在高能γ射线康普顿散射时的叠加能谱.结果表明:合适的装样高度可以在不明显减少全能峰净计数的情况下,有效降低由高能γ射线康普顿散射引起的本底误差.%In the experiment of using HPGe γ spectrum instrument to measure the activity of low-energy γradionuclide in environmental sample,in order to improve the accuracy of the result,this paper studied the influence of sample quantities on the accuracy of the result.Monte-Carlo method was firstly used to obtain the simulative results of the relationship between the detection efficiency of different energy γ-rays and different sample quantity(i.e.sample height)and thus the relationship between counts of the full-energy peak of different energy γ-rays and different sample height was obtained,then the optimal quantities corresponding to different energy γ-rays were determined.Secondly,taking 238 U of soil sample for example,energy spectrums of a single energy and energy spectrum mixed with Compton scattering from high-energy γ-rays of different sample quantities were simulated.It turned out that appropriate sample quantity can effectively reduce the background error caused by Compton scattering.Meanwhile,the net counts of full-energy peak isnt significantly reduced.