Interlaboratry comparison of psotitron annihilation lifetime measurement

Ito, Kenji*; Oka, Toshitaka*   ; Kobayashi, Yoshinori*; Shirai, Yasuharu*; Wada, Kenichiro*; Matsumoto, Masataka*; Fujinami, Masanori*; Hirade, Tetsuya  ; Honda, Yoshihide*; Hosomi, Hiroyuki*; Nagai, Yasuyoshi*; Inoue, Koji*; Saito, Haruo*; Sakaki, Koji*; Sato, Kiminori*; Shimazu, Akira*; Uedono, Akira*

So far no standard procedure for the positron annihilation lifetime (PAL) technique has been established. A lack of the standards has led to difficulty in ensuring equivalency and reliability of data from different laboratories. Recently, as a first step toward the standardization of the PAL technique, we conducted an interlaboratory comparison of PAL measurements for fused silica, polycarbonate and metal with agreed procedures for data recording and analysis. Based on the results of the reported lifetimes, possible sources of the uncertainties in the PAL measurements is probably caused by the backscattered -rays by other detectors. We succeeded to show that inserting shields between detectors can reduce the uncertainty.