Dechanneling of Positrons in Disordered Lattices – Effect of Anharmonic Potential

Dechanneling of positrons due to lattice disorder has been investigated for two stable configurations of the disordered face-centered cubic(fcc) lattices. Dumbbell configuration (DBC) and Body-centered interstitial (BCI) for channeled positrons with incident energy (10-200) MeV in Cu single crystal in the planar direction (100). The effects of anharmonic terms in the channeling potential have been considered in the calculations. The calculations covered the transition channeling probability, dechanneling probability. transmission and dechanneling coefficients. It has been found that the transition-channeling probability from the normal into the disordered region occurs only for the transitions n (normal) -> n (disordered). Also the dependence of the transmission and dechanneling coefficients on the incident beam position has been studied by using a planar potential function based on shell structure model and compared with the results of a planar potential based on Lindhard's model.