滤膜对放射性气溶胶α能谱测量拖尾影响

Impact of different filters for measuring α radioactive aerosol energy spectrum

滤膜是放射性气溶胶测量系统中重要组成部分,由于滤膜本身的特性造成天然放射性气溶胶α能谱拖尾会干扰人工放射性气溶胶测量结果,甚至会造成测量结果错误。通过实验分别测试相同滤膜(混合纤维)不同孔径和相同孔径不同滤膜对α能谱测量拖尾的影响。实验表明,用小流量(5 L·min-1)系统采集天然放射性气溶胶时,选用和天然放射性气溶胶最大粒径(0.5μm)相当大小孔径的混合纤维滤膜(0.45μm)时,α能谱拖尾最小,加大抽气流量(20 L·min^(-1)),α能谱拖尾最小的混合纤维滤膜孔径略有减小(0.3μm);相同孔径下(0.45μm),混合纤维滤膜相比聚四氟乙烯滤膜和聚醚砜滤膜,对α能谱测量拖尾影响最小。本文为减小天然放射性气溶胶测量时α能谱拖尾选取合适滤膜提供了重要依据。

Background： Filters are important parts of α radioactive aerosol measurement system. The characters of different filters causing energy peak tailing will interfere the result of artificial radioactive aerosol measurement, or might even make results failure. Purpose： The work aims to test peak tailing of different filters in measuring α radioactive aerosol energy spectrum. Methods： The research collects α radioactive aerosol on different filters by aerosol sampling device and uses tt spectrometer to measure peak tailing of ^214Po （7.68 MeV）. Results： The results show that the peak tailing is minimized when hybrid filters with pore size of 0.45μm was adopted. When high-flow system is applied, the filters＇ pore size are expected to be reduced to 0.3 μm. Hybrid fibers are better than PTFE （Polytetrafluoroethylene） and PES （Polyethersulfone） filters in reducing peak tailing with the same pore size （0.45 μm）. Conclusion： The research provides important basis on how to select filters to reduce peak tailing in measuring α radioactive aerosol energy spectrum.