317 research outputs found
Method of functional integration in the problem of line width of parametric X-ray relativistic electron radiation in a crystal
The coherent and non-coherent scattering effects on "backward" parametric
X-ray radiation by relativistic electrons in a crystal on the basis of the
method of functional integration is investigated. A comparison of contributions
of these effects to parametric X-ray radiation line width has been considered.
It is shown that in a number of cases the major contribution to the line width
of parametric X-ray radiation is made by non-coherent multiple scattering.Comment: 7 pages, LaTeX2e forma
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
Transition radiation on semi-infinite plate and Smith-Purcell effect
The Smith-Purcell radiation is usually measured when an electron passes over
the grating of metallic stripes. However, for high frequencies (exceeding the
plasma frequency of the grating material) none material could be treated as a
conductor, but ought to be considered as a dielectric with plasma-like
permittivity. So for describing Smith-Purcell radiation in the range of high
frequencies new theoretical approaches are needed. In the present paper we
apply the simple variant of eikonal approximation developed earlier to the case
of radiation on the set of parallel semi-infinite dielectric plates. The
formulae obtained describe the radiation generated by the particles both
passing through the plates (traditionally referred as "transition radiation")
and moving in vacuum over the grating formed by the edges of the plates
(traditionally referred as "diffraction radiation", and, taking into account
the periodicity of the plates arrangement, as Smith-Purcell radiation).Comment: Submitted to Journal of Physics: Conference Serie
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