靶室散射对ICF中子产额用铅活化法测量准确性的影响

 通过用MCNP4B程序计算在铅样品中的来源于靶室散射中子的注量和来源于未经靶室散射的源中子注量，结合由ENDF/B-Vi评价数据库给出的中子铅活化核反应截面，得到了在铅样品周围存在不同屏蔽材料时，神光Ⅱ靶室散射对聚变中子产额用铅活化法测量准确性影响小于1‰的结果。

Effect of target chamber scattered neutrons on ICF neutron yield measurement accuracy by Pb activation

Measuring ICF neutron yield by Pb activation is performed in the target chamber, but calibrating the Pb detect system using an accelerator neutron source is not performed in the target chamber. The difference between the measuring environment and the calibrating environment will affect the measurement accuracy, for the neutrons scattered by the target chamber will contribute to the production of radionuclide~(207m)Pb which emits detectable γ radiations.In this paper, by Monte Carlo method, the effect on the measurement accuracy has been calculated and the result is less than 1‰.This effect is defined as the ratio of the number of ~(207m)Pb(N_s) generated from the target chamber-scattered neutron activation to the number of~(207m)Pb(N) generated without target chamber existing. The target chamber used in the calculation is the Shengguang Ⅱ chamber in China. The calculated result shows that the effect is very small and negligible.