Interlaboratory comparison of positron annihilation lifetime measurements

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 the equivalency and reliability of data from different laboratories. As a first, we conducted an interlaboratory comparison of PAL measurements for metal, polymer and silica glass with agreed procedures for data recording and analysis. The PAL data recorded at different laboratories were analyzed with a single lifetime component for the metal sample and with three components for the others, respectively. Based on the results of the reported positron and ortho-positronium lifetimes, the possible sources of the uncertainties in the PAL measurements are discussed. To reduce the effect of scattered rays, a lead shield was placed between the detectors. The uncertainty was significantly decreased, signifying that placing lead shields between the detectors effectively reduced the false signals due to the scattered rays.