γ能谱测量中死时间与最佳峰计数率相关性研究

Study of the Correlation of Relative Dead Time and Optimum Peak Count Rate in Gamma Ray Spectrum Measurement

探讨了在有限测量时间内更准确测量高放样品的最佳峰计数率条件。基于标准不确定度评价原理,获得了给定统计不确定度条件下,峰下本底占比和峰面积临界值之间应满足的函数关系。结果表明,要达到给定不确定度,峰下本底占比越大,要求累计的峰面积临界值越大。基于泊松分布研究了相对死时间、峰计数率和输入计数率之间的函数关系,在相对死时间为(1-1/e)≈63.2%时,各能峰的计数率达到最大值。采用两种商用谱仪对上述结论进行了实验验证。

The condition of optimum peak count rate for more accurate measurement of high level radioactive samples within limited time was discussed in this paper.According to the standard uncertainty evaluation principle,the function of the critical full-peak area vs.ratio of peak-background and full-peak area was obtained.The results indicate that in order to achieve a given uncertainty,the larger the ratio,the greater the critical value of full-peak area required.The function of the relative dead time,peak count rate and input count rate was studied based on Poisson distribution.The result shows that the output count rate can reach the maximum value when the relative dead time equals to(1-1/e),that is 63.2%.Two commercial-ray spectrometers were used to verify above results.