光子传输过程中g因子的计算

Calculation of g Factor in Photon Transmission

在电离辐射空气比释动能基准量值复现过程中,g因子作为关键组成部分之一参与量值复现和不确定度计算,其量值的确定需要通过光子的质能传输系数和质能吸收系数计算得到。采用不同的软件,在不同参数设置条件下模拟计算并对结果进行比较。结果显示采用EGSnrc计算结果更为合理,而且对于低能光子,尽管g因子相对较小,但在不同的参数设置条件下所得到的数值差异较大。因此对于涉及到低能光子的质能传输系数和质能吸收系数的计算和使用过程中,需对有关相互作用的物理机制予以重视。

In the process of realization of the air kerma primary standards,the g factor is one of the key components involves in the value realization and uncertainty calculation.The determination of the value of g factor requires the calculation of mass energy transfer and mass energy absorption coefficient of the photon.Different software is used to simulate the calculation,and results are compared under different parameters.It is shown that the calculation results from EGSnrc are more reasonable comparing to other methods.Furthermore,although the g factor is relatively small,we found that the values obtained under different parameter settings are quite different,especially for low-energy photons.Therefore,attention should be paid to the physical mechanism of the relevant interactions while calculating and using the mass energy transmission and the mass energy absorption coefficient for low-energy photons.