Accession Number : ADA299436

Title :   Positron Annihilation Studies of Thermoplastic LCP Composites,

Corporate Author : DUKE UNIV DURHAM NC DEPT OF MECHANICAL ENGINEERING AND MATERIALS SCIENCE

Personal Author(s) : Naslund, Robert A. ; Jones, Phillip L.

PDF Url : ADA299436

Report Date : 03 AUG 1995

Pagination or Media Count : 4

Abstract : The time dependent decrease in orthopositronium (o-Ps) intensity detected in polymers during long term positron annihilation lifetime (PALS) experiments has been extensively studies and modeled. This decrease in temperature dependent, polymer specific, source strength dependent and is noted to saturate as a function of source exposure time. Larger decreases and smaller saturation values are exhibited at lower temperatures. Additionally, at sufficiently high temperatures, a negligible decrease is detected. The time dependent decrease is recoverable at elevated temperatures. In contrast, the o-Ps lifetime component remains constant and independent of exposure time. Increasing the exposed sample volume by continuously varying the source-sample orientation dramatically decreases the reduction of o-Ps intensity.

Descriptors :   *POSITRONS, *ANNIHILATION REACTIONS, RECOVERY, TIME DEPENDENCE, EXPOSURE(GENERAL), SATURATION, CONTINUITY, PLASTICS, VISUAL SIGNALS, IONIZATION TRAILS.

Subject Categories : Nuclear Physics & Elementary Particle Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE