TEMPERATURE DEPENDENCE OF PLANAR CHANNELING IN TRANSMISSION EXPERIMENTS

Preliminary measurements on temperature and energy dependence of planar channeling in Si thin crystals are reported. Backscattering and transmission of MeV H+ have been used to obtain information on the half-thickness x 1 2 for escape on the critical angle and on the energy loss of channeled particles. The x 1 2 values extracted from the backscattering data are smaller than those obtained by transmission measurements in crystals of thicknesses comparable with x 1 2 values. A change of about 15–20% has been measured in x 1 2 on going from 80 K to 300 K for both backscattering and transmission techniques. An increase at 80 K of about 20% has also been measured in the full-width at half-maximum of the transmitted angular distributions for particles impinging around the {110} plane. A comparison of these results with theoretical predictions suggest a value of the screening distance lower than the Thomas-Fermi radius. A small but systematic decrease with temperature has been also found in the energy losses of the well channeled particles.