Evaluation of Positron Implantation Profiles in Various Materials for 22Na Source

Positron implantation profiles in various materials for Na-22 isotope source are discussed. The spatial distribution of positrons in materials with densities from 1 to 21 g/cm(3) are simulated using GEANT4 code. The results indicate that depth distributions of thermalized positrons in any homogeneous medium can be described by the sum of two exponential functions. Contribution of the short-range exponent is about 11% in the materials. The both absorption coefficients can be well represented as a function of material density and atomic number. Proposed empirical model agrees well with available experimental data.