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

Simulation of the electron coherent radiation process in a crystalline undulator

When a high-energy electrons move in a crystal along one of the crystallographic planes the phenomenon of planar channeling is possible, in which the particles move in channels formed by the continuous potential of crystalline planes. Such particle motion in a crystal is conserved for most particles even for weak bending of crystalline planes of atoms. In [1-3] the process of channeled electrons radiation in such a device was considered. It was shown that the radiation spectrum of particles in the crystal in this case contains maxima associated with the period of oscillation of the channeled particles in the channel and with the period of the crystal planes bending. In [4] the radiation process in a crystalline undulator with large bending amplitude of the crystal planes was considered. In this case the trajectories of particles that are crossing the crystal planes are close to rectilinear. This allowed consider the radiation process in the first approximation in the interaction of particles with the crystal field analytically. In that paper the possibility of manifesting coherent and interference effects in radiation leading to high radiation intensity was demonstrated. Taking into account the incoherent effects in the particle scattering leads to particle mutual transitions from the sub-barrier to the above-barrier states and vice versa. Analysis of the radiation process in this case can be carried out on the basis of numerical simulation method for this process. In this paper such method is developed on the basis of the proposed in [5] method of the radiation process simulation in a direct crystal. We present some results of simulation of 1 and 10 GeV electron radiation in crystalline undulator at different values of the plane bending amplitudes. The calculations are performed in the dipole approximation of radiation theory with taking into account the recoil effect in radiation.Comment: 6 pages, 5 figures, conference RREPS-1

Contribution of incoherent effects to the orientation dependence of bremsstrahlung from rapid electrons in crystal

The bremsstrahlung cross section for relativistic electrons in a crystal is split into the sum of coherent and incoherent parts (the last is due to a thermal motion of atoms in the crystal). Although the spectrum of incoherent radiation in crystal is similar to one in amorphous medium, the incoherent radiation intensity could demonstrate substantial dependence on the crystal orientation due to the electrons' flux redistribution in the crystal. In the present paper we apply our method of the incoherent bremsstrahlung simulation developed earlier to interpretation of some recent experimental results obtained at the Mainz Microtron MAMI.Comment: VIII International Symposium "Radiation from Relativistic Electrons in Periodic Structures" (RREPS-09) Zvenigorod, Russia, September 7-11, 200