INTERLABORATORY COMPARISON OF POSITRON AND POSITRONIUM LIFETIMES IN POLYMERS

A comparison of the results of a series of positron annihilation lifet ime measurements performed in 12 laboratories is presented. The measur ements were conducted on three different polymer samples, all prepared in one laboratory under standard conditions. The objective of the wor k was to gain insight into the variation in derived positron and posit ronium lifetimes and intensities measured in the different laboratorie s on identical specimens. Lifetime data were collected at room tempera ture by each laboratory following their own standard measurement and d ata evaluation procedures. The polymers used were a semi-crystalline l inear polyethylene, an amorphous poly(methyl methacrylate) and an amor phous copolymer of styrene-acrylonitrile. The results show that the or tho-positronium lifetimes and intensities agree fairly well between di fferent laboratories, despite large differences in experimental condit ions, while the lifetimes and intensities of short-lived components sh ow appreciable variations between laboratories. (C) 1998 Elsevier Scie nce B.V. All rights reserved.