90Sr/90Y放射源及外推电离室蒙特卡罗模型建立与实验验证

针对β射线次级标准装置(BSS2)中的⁹⁰Sr/⁹⁰Y放射源以及PTW23392型外推电离室进行蒙特卡罗(MC)建模。使用BEAMnrc计算⁹⁰Sr/⁹⁰Y放射源在不同校准位置处产生的组织深度剂量曲线，并与实验结果进行比较。根据模拟结果与实验结果的差异，修正放射源MC模型。此外，对外推电离室的外推曲线、校准位置处的组织透射因子和组织吸收剂量率进行模拟计算。在距离放射源30 cm和使用展平过滤的条件下，外推曲线的计算结果和实验结果基本吻合。组织透射因子和组织吸收剂量率的模拟结果与校准证书值相差分别在1.43%和2.11%之内。最终建立了较为准确的⁹⁰Sr/⁹⁰Y放射源和外推电离室的MC模型，研究结果可以为计算β参考辐射场中的注量谱、剂量转换系数和外推电离室相关的修正因子等提供参考。

The Monte Carlo Modeling and Experimental Verification of the 90Sr/90Y Source and the Extrapolation Chamber

The Monte-Carlo (MC) model of the 90Sr/90Y source used in the BSS2 β-ray secondary standard and the PTW 23392 extrapolation chamber was constructed. The depth-dose curves produced by the 90Sr/90Y source at the calibrated distance were calculated using BEAMnrc and compared with the experimental results. According to the difference between the simulation results and the experimental results, the MC model of the 90Sr/90Y source was revised. In addition, the extrapolation curve of the extrapolation chamber, the tissue transmission factor and the tissue absorbed dose rate at the calibration position were simulated. Under the condition of 30cm away from the source and using the beam flattening filter, the calculated extrapolation curves are in good agreement with the experimental results. The differences between the simulated results of the transmission factor and the absorbed dose rate in tissue and the calibration certificate values are within 1.43%and 2.11%, respectively. The mentioned study constructed a more accurate MC model of the 90Sr/90Y source and extrapolation chamber. The results can provide a reference for the calculation of the β fluence spectrum, dose conversion factor and correction factors of the extrapolation chamber in β reference radiation field.