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Geometrical optics method in the theory of channeling of high energy particles in crystals
The process of scattering of fast charged particles in thin crystals is
considered in the transitional range of thicknesses, between those at which the
channeling phenomenon is not developed and those at which it is realized. The
possibility is shown of application of the methods of geometrical optics for
description of the scattering process. The dependence is studied of the total
scattering cross-section of ultrarelativistic positrons on target thickness in
this range of crystal thicknesses. In the case of ultrarelativistic particles
channeling the possibility is shown of the existence of an effect analogical to
the Ramsauer-Townsend effect of conversion into zero of the total scattering
cross-section at some values of crystal thickness. The important role is
outlined of the Morse-Maslov index that enters into the wave function
expression in the geometrical optics method.Comment: 6 pages, 2 figure
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