Positron lifetime measurements have been made on a series of polycrystalline metals with atomic numbers varying from 13 to 82, using positron sources deposited on Ni, Al, and Kapton support foils. Bulk positron lifetimes for Al, Ni, Zr, In, and Pb are reported. The results support previous assignments of monovacancy lifetimes for Ag, Ta, and Pb. A method for obtaining the extrinsic positron lifetime components due to the radionuclide source is developed, and the experimentally determined source lifetime components are studied as a function of the sample atomic number. The Z dependence of the source foil component intensities were fitted using known expressions for positron backscatter and multiple scattering within the source sample geometry, neglecting backscatter from the foil. The foil material positron absorption coefficients were obtained and found to be comparable with the results of previous transmission experiments.
- Positron absorption
- Polycrystalline metals