Calculations on dechanneling of protons in Si and W

Abstract

Abstract Dechanneling, i.e. transition of particles from the aligned beam to the random beam, is in a faultless crystal mainly caused by two processes, scattering by thermally vibrating nuclei and by electrons. This leads to an increase in the transverse energy of the channeled particle with penetration depth, while the energy loss of the particle implies a small decrease of the transverse energy. Finally, the transverse energy will reach a certain critical value and the particle will be dechanneled. Starting from Lindhard's(1) description of the scattering of channeled particles, we have calculated the decrease of the channeled fraction as a function of penetration depth for protons in Si and W in the case of incidence parallel with a major axis. Two different expressions for the electronic scattering have been tried. Attempts have been made to take into account the effects of beam divergence, scattering in the surface oxide and the energy dependence of the scattering of the particle during penetration. Comparison is made with experimental results from backscattering measurements.