Theoretical studies of the positron implantation profiles in the layered samples are presented. Simulations performed using a GEANT4 tool kit revealed accumulation of positrons in denser layer embedded by less dens environment. This effect is significant for implantation profiles of slow positrons formed in a beam. Nevertheless, it is also present in conventional experiments, where positrons are emitted from radioactive nuclei. In some cases the diffusion process, which follows the implantation and thermalization processes, can smear this effect. However, defects on the interfaces or differences in the positron affinity can sustain it.
We calculated theoretically the mass absorption coefficients for positrons emitted from the commonly used sources 22Na and 68Ge/68Ga in numerous materials. For this purpose, we used the tool kit GEANT4 which allows to generate the implantation profile. An excellent agreement between the experimental profile and the calculated one was achieved. The calculated values of the mass absorption coefficients coincide well with the experimental values determined by the DSIP method.
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