ISO/TS 23878:2024 PDF

This document describes a method for performing positron annihilation lifetime measurements using a ²²Na positron source that decays with ?⁺ emission. The ?⁺ (positron) lifetime is determined from a measurement of the lifetime of the ortho-positronium which ranges from 1?ns to 10?ns (ascribed to a pore size from approximately 0,3?nm to 1,3?nm in diameter), as observed for polymeric materials in which the positronium atoms mostly annihilate via a two-gamma annihilation process.

This document is not applicable to thin surface layers (that are less than several micrometers).

This document does not apply to measuring:

— non-positronium forming materials;

— positronium-forming materials that induce a spin conversion reaction;

— positronium-forming materials that contain chemicals influencing the annihilation process of ortho-positronium by chemical reactions;

— positronium-forming materials that contain? mesoporous silica gels with a large contribution from the three-gamma annihilation process.