α-particle discrimination in the measurement of α/β decaying chains by the use of ultra-thin plastic scintillation sheets

We found that problems of α/β pulse-height overlapping can be solved by use of ultra-thin plastic scintillator sheets. In order to determine individual α-counting efficiencies for nuclides in the 223Ra decay-chain, the 4πα−γ anti-coincidence spectrometry technique was employed with a 4πα-γ detector configuration composed of a source sandwiched between ultra-thin plastic scintillator sheets and a Ge detector. This technique was applied to the activity measurements of 223Ra. This type of sandwich source is useful to prevent possible leakage of 219Rn gas. •Selective α-rays detection can be performed with very thin plastic scintillator.•Individual α-efficiencies can be determined by anti-coincidence spectrometry.•α-efficiency does not depend on energies when ultra thin scintillator was used.•The leakage of 219Rn can be avoided by source sandwiched with scintillators.