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Content DescriptionThis 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. About ISOISO, the International Organization for Standardization, brings global experts together to agree on the best way of doing things – for anything from making a product to managing a process. As one of the oldest non-governmental international organizations, ISO has enabled trade and cooperation between people and companies all over the world since 1946. The International Standards published by ISO serve to make lives easier, safer and better. |
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