铟活化诊断氘氘中子产额不确定度分析

Evaluation of uncertainty in DD neutron yield diagnosis by indium activation

介绍了铟活化诊断氘氘中子产额的测量原理,分析了中子产额测量不确定度的来源及评定方法。中子产额测量不确定度主要由灵敏度标定不确定度、活化射线净计数不确定度、立体角测量不确定度及测量系统的随机误差等构成。评估了灵敏度标定过程中加速器中子与聚变中子能量差异、大厅散射中子本底等因素对灵敏度标定的影响,并评估了宇宙射线本底对活化射线净计数测量的影响。分析了中子产额处于不同量级时起主要作用的不确定度分量,提出了减小灵敏度标定不确定度的方法。以实验数据为基础,对具体的实验数据进行了分析计算。结果表明:利用伴随粒子法在加速器中子源上标定出铟活化测量系统灵敏度的相对标准不确定度为4.3%。中子产额低于1010时,产额测量不确定度大于7%,活化射线净计数误差是产额测量误差的主要来源;产额大于1010时,测量不确定度好于7%,中子产额测量不确定度主要由灵敏度标定不确定度引起。

The measurement principle of DD neutron yield diagnosis by indium activation is introduced,and the uncertainty sources of neutron yield diagnosis are analyzed.The measurement uncertainty of DD neutron yield consists of the sensitivity calibrating uncertainty,the net-count uncertainty of radioactive rays,the measurement uncertainty of the solid angle and the random error of the activation system.The calibrating uncertainties of activation sensitivity are determined by such causes including the neutron energy variety in the accelerator neutron source and the measurement error of background neutron of accelerator room. The influence of cosmic rays on the net-count measurement of radioactive rays is analyzed.The main uncertainty source of neutron yield diagnosis in different magnitude range is given,and the improved method of the calibrated activation sensitivity is introduced.The uncertainty of neutron yield diagnosis is calculated based on the experimental data.The result shows that the relative standard uncertainty of the activation system which is calibrated on the accelerator using the associated particle method is 4.3%. When the neutron yield is below 1010,the measurement uncertainty is higher than 7%,and it is mainly caused by the net-count error of radioactive rays.The measurement uncertainty is lower than 7% when the neutron yield is higher than 1010,and it is mainly caused by the uncertainty of calibrated sensitivity.