The National Institute of Standards and Technology (NIST) has developed a table-top positron annihilation lifetime spectrometer for analyzing material defects and voids at the sub-nanometer scale. The device uses a ²²Na source to inject positrons between Kapton foils, with a time resolution of approximately 270 picoseconds. It can detect voids in polymers, metals, and semiconductors smaller than a nanometer, but lacks depth-resolving capabilities. Recommended sample dimensions are 25 mm x 25 mm, with measurements taking 5-10 days per sample set. The spectrometer primarily studies polymeric materials and fiber-reinforced composites by analyzing positronium annihilation processes, correlating free volume with material aging and mechanical properties.
Source: https://www.nist.gov/laboratories/tools-instruments/positron-annihilation-lifetime-spectrometer
Keywords: positron, annihilation, lifetime
