Interlaboratory comparison of positron and positronium lifetimes in polymers

A comparison of the results of a series of positron annihilation lifetime measurements performed in 12 laboratories is presented. The measurements were conducted on three different polymer samples, all prepared in one laboratory under standard conditions. The objective of the work was to gain insight into the variation in derived positron and positronium lifetimes and intensities measured in the different laboratories on identical specimens. Lifetime data were collected at room temperature by each laboratory following their own standard measurement and data evaluation procedures. The polymers used were a semi-crystalline linear polyethylene, an amorphous poly(methyl methacrylate) and an amorphous copolymer of styrene-acrylonitrile. The results show that the ortho-positronium lifetimes and intensities agree fairly well between different laboratories, despite large differences in experimental conditions, while the lifetimes and intensities of short-lived components show appreciable variations between laboratories. (C) 1998 Elsevier Science B.V. All rights reserved.