DETECTION SENSITIVITY OF TIME-INTERVAL ANALYSIS FOR THE DETERMINATIONOF ALPHA-RADIONUCLIDES WITH MILLISECOND ORDER LIFETIMES

A selective extraction of the correlated events due to three kinds of short-lived alpha-decay events, Po-216 (145 ms), At-217 (32.3 ms) and Po-215 (1.78 ms), from other random background events were examined by using a time interval analysis (TIA) from the viewpoint of detection sensitivity. In the theoretical treatment based on the probability and statistics, it was clarified that the detection sensitivity proportio nally increased with shortening half-lives in the following order Po-2 15 > At-217 > Po-216. In the experiments, pulses from a liquid scintil lator owing to alpha-decay events were analyzed using a multiple TIA t echnique and resulted in the highest sensitivity of Rn-219 - Po-215 pa irs in the actinium series. Thus, the multiple TIA method was applied to the practical determination of Rn-219 - Po-215 pairs in natural sam ples.