中文摘要：

介绍了一种测量低浓度220 Rn的方法---时间间隔分析方法。220 Rn原子发生衰变发射α粒子并产生216 Po时，在很短时间内，216 Po衰变（半衰期0.145 s）又发射α粒子。多时间分析方法就是对2个连续发射的α粒子的时间间隔进行分析，使220 Rn从222 Rn中分辨出来。本实验通过卢卡斯氡探测器（FD125）对10 Bq的220 Rn标准源进行流气式测量。当222 Rn活度小于10倍左右220 Rn活度时，计数率控制在60 min-1以内，时间分辨率设置为1 ms ，测量时间为10 h ，测量结果的相对偏差在7％内。

英文摘要：

T his paper introduced a measurement method of low concentration 220 Rn-time interval analysis （TIA） method .In the short time after the alpha particle emitted at the decay of a 220 Rn atom an alpha particle from the decay of 216 Po （half life 0.145 ） follows .The multi-time analysis method is based on the analysis of the emitting time interval between the two successive alpha particles ,which can be used to discriminate the 220 Rn from 222 Rn .A flow through Lucas cell （FD125） was used to measure 10 Bq standard 220 Rn source .When the 222 Rn activity is less than 10 times the 220 Rn activity , count rate is controlled within 60 min-1 ,the time resolution is set to 1 ms and the meas-uring time is 10 h ,and the relative deviation of the results is within 7% .