Trofymenko S. Interference effects in the ionization loss, transition and coherent x-ray radiation by relativistic particles

The Doctoral Thesis presents the results of studies of interference effects in various types of electromagnetic radiation and ionization energy loss of relativistic charged particles in amorphous and crystalline media. These effects are associated with large radiation formation lengths and ultrasmall size of charged particle bunches. Simplified analytical expressions describing the spatial evolution of electromagnetic field around the electron after its exit from matter into vacuum in a wide range of distances from the matter within the formation length are obtained. The description of spectral-angular distribution of the transition radiation by a “half-bare” relativistic electron at its oblique incidence on a metal target is generalized for the case of low particle energies. Expressions for the spectral-angular and angular distributions, as well as the integral intensity of coherent x-ray radiation by a “half-bare” electron in ultrathin and thick crystals are obtained. Expressions for the spectral-angular distribution of transition radiation in the near-field zone registered with the use of a parabolic focusing mirror of arbitrary size are derived. Formulas for the spectral distribution of x-ray transition radiation by electrons in multifoil periodic targets for an arbitrary axially symmetric transversal particle distribution in the beam and a limited size of the radiation detector active region are obtained. The conditions for a significant increase in the intensity of such radiation for a sufficiently small detector acceptance angle are derived. The effect of significant increase in the atomic K-shell ionization cross section and intensity of characteristic x-ray radiation by electrons in multifoil periodic targets is predicted. It is shown that the ionization loss of an electron-positron pair in a thin target, which it crosses after escaping from another target, where it is created, is influenced by interference effects on much larger distances from the pair creation point than the pair ionization loss in the same target, where it is created. The interference effect in the ionization loss of an electron-positron pair, similar to the one which occurs in the Fraunhofer diffraction in optics, is predicted. For the pair ionization loss in a thin target, the effect, opposite to the Chudakov effect and being the exceeding by the pair ionization loss of the sum of independent electron and positron losses, is revealed. Classical and quantum expressions for the energy loss due to ionization and excitation of atomic shells of matter by an ultrasmall relativistic electron bunch via its form factors under conditions of manifestation of coherent effects in this loss are obtained. For electron ensembles with periodic density modulation, the resonance effect in the ionization loss is predicted. A new mechanism of radio emission by particles in a pulsar magnetosphere is proposed, which makes it possible to explain the mystery of shifted interpulse for the pulsar in the Crab Nebula. The frequency at which the shifted interpulse should disappear is predicted.