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滤膜是气球测氡仪的重要组成部分,选择过滤效率高、自吸收小的滤膜,不仅可以提高取样速度,更可有效减小测量误差。根据氡及其子体在滤膜上收集的物理过程,能够推导出空气滤膜上氡子体的收集和衰变随时间的变化规律。通过实验,在标准氡室中对不同材料的三种微孔滤膜过滤效率和自吸收因子关键指标进行了测试。实验表明,在同等厚度条件下,聚四氟乙烯滤膜和尼龙滤膜的过滤效率比常用玻璃纤维滤膜高,其自吸收情况也较玻璃纤维膜小;从气阻情况分析,聚四氟乙烯滤膜气阻最低,尼龙滤膜气阻最大;对常用玻璃纤维滤膜,通过增加膜厚度能够有效改善其性能指标。不仅为气球法测氡仪滤膜的选择提供了重要依据,也适用于其他滤膜测氡装置。
The filter is an important part of the balloon radon detector. The filter with high efficiency and low self-absorption can not only improve the sampling speed but also reduce the measurement error effectively. According to the physical process of radon and its daughters collecting on the membrane, the variation of radon population collection and decay over time can be deduced. Through the experiment, three kinds of microporous membrane filtration efficiency and the key indexes of self-absorption factor of different materials were tested in the standard radon chamber. Experiments show that under the same thickness conditions, PTFE filter and nylon filter efficiency than the commonly used glass fiber filter, its self-absorption is also smaller than the glass fiber membrane; gas resistance from the situation analysis, PTFE The lowest gas barrier of ethylene membrane, the largest gas barrier of nylon membrane; the common glass fiber membrane can effectively improve its performance by increasing the membrane thickness. It not only provides an important basis for the selection of radon filter by the balloon method, but also applies to other radon filters.