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对于小尺寸探测器处于大块介质的情形,在探测器的校正因子的Monte Carlo模拟中,存在两个难题:一是由于探测器尺寸很小粒子难以到达探测器并发生碰撞;二是两个随机变量比值难以达到要求精度．本文使用经过改进的粒子碰撞自动重要抽样方法,再结合相关抽样方法,解决了这两个难题,并在MCNP-4C程序平台上加以实现．除了粒子碰撞自动重要抽样以外,还选用了其他3种方法:直接模拟、区域分裂、强迫碰撞+Dxtran球分别与相关抽样方法结合,对一个简化的探测器校正因子计算模型进行了计算．实际计算结果表明,相关抽样方法无论与哪种方法结合,都起到了提高相关量计算效率的作用;而它与粒子碰撞自动重要抽样结合,比其他方法具有明显的优越性．
In the case of small size detectors in bulk media, there are two problems in the Monte Carlo simulation of detector calibration factors: one is that the detector is difficult to reach the detector due to the small size of the detector and the collision occurs; and the other two are two Random variable ratio difficult to achieve the required accuracy. In this paper, we use improved particle collision automatic important sampling method, combined with the relevant sampling method to solve these two problems, and MCNP-4C program platform to be achieved. In addition to the auto-important sampling of particle collisions, three other methods were selected: direct simulation, zone splitting, forced collision + Dxtran sphere, respectively, in combination with the relevant sampling method, to calculate a simplified detector calibration factor calculation model. The actual calculation results show that the correlation sampling method plays an important role in improving the computational efficiency of correlation quantity, no matter which method is combined with it. And it combines with the automatic important sampling of particle collisions, which has obvious advantages over other methods.