中文摘要：

权重窗技术是最常用的降低方差技巧之一，合理运用权重窗技术能大幅提高计算效率。MCNP程序具备基于栅元的伴随权重窗发生器功能，但对一些含重复结构栅元或非对称结构栅元的模型，由于MCNP程序不能计算其中某些栅元体积，伴随权重窗发生器失效。本文在MCNP程序基础上设计了基于M ES H技术的伴随权重窗自动生成方法，该方法不改动真实模型，采用一套虚拟的相空间覆盖真实模型。将新方法应用于重复结构算例，计算效率大幅提升。对光子散射基准实验模拟表明，新方法的计算结果与实验值吻合得非常好，相对偏差仅1.2％，计算效率约为直接模拟的8倍。

英文摘要：

The weight window is one of the most widely used variance reduction tech‐niques . When used judiciously , it can save substantial computer time . Because the MCNP program can not calculate the volume of some special cells ,for example ,repeat‐ed structure cells or asymmetrical cells ,the adjoint weight window generator of MCNP is almost unavailable for a complex geometry model . A mesh‐based adjoint weight window generator was provided in the paper .It utilized an extra virtual mesh model where original model is enclosed ,and no modification was made on the original model . It can be used for almost all models .The new method was successfully used to a repeat‐ed structure model , and the FOM value greatly increased . A satisfactory simulation result of a photon skyshine experiment model was obtained by the new method .Com‐pared with the experiment result ,the relative difference of the new method is 1.2%only .The FOM of the new method is almost eight times as large as that of the direct Monte Carlo simulation .