氡子体α能谱真空测量RaB的反冲损失率

氡子体α能谱法测量时的真空度使RaB发生反冲损失，这会对氡子体测量精度产生影响并造成测量腔室的污染。本实验选用0.8 μm孔径的Millipore AA型滤膜，在流率为6.3、12.3和15.6 L/min下，使用ELPI粒径分析仪、α测量仪和α谱仪分别对氡室气溶胶粒径分布、滤膜自吸收系数及反冲损失率进行测量。结果显示：氡室内气溶胶浓度呈单峰分布；相应流率下的自吸收系数为0.978、0.980、0.989，反冲损失率为0.362 8、0.368 4和0.362 9；所得反冲损失率并未表现出较大的差异，但滤膜样品上由RaA衰变产生的RaB原子却有较大的反冲损失。

RaB’s Recoil Loss Rate of α Spectrometric Measurement for Radon Progeny Under Vacuum

The α spectrometric measurement for radon progeny under vacuum results in the recoil loss of RaB. The recoil loss impacts on the measuring accuracy of radon progeny and causes contamination of the measuring chamber. Millipore AA type membranes (about 0.8 μm pore size) were selected and three different sampling flow rates were 6.3, 12.3, and 15.6 L/min respectively. ELPI particle size analyser, α measurer and α spectrometer were used for measuring aerosol size distribution of radon chamber, self-absorption coefficient of filter membrane and recoil loss rate respectively. The results show that the aerosol spectrum in radon chamber presents a single peak distribution; under the corresponding flow rates as mentioned above, the self-absorption coefficients are 0.978, 0.980 and 0.989 respectively, and the recoil loss rates are 0.362 8, 0.368 4 and 0.362 9 respectively. It shows no significant difference, but the RaB produced by the decay of RaA on the filter membrance samples has large recoil loss.