On the theory of diffraction radiation

A macroscopic theory of diffraction radiation emerging when a charged point particle moves in the vicinity of a perfectly conducting screen is developed. The integral equations derived for radiation fields form the basis for analyzing the similarity and difference of diffraction of electromagnetic radiation and diffraction radiation from a charged particle. It is shown that in the case considered here, the widely used model in which the radiation field can be represented as the field of surface current has more stringent limits of application as compared to the classical theory of diffraction. This considerably restricts the applicability of the results obtained earlier using the double-layer method to only ultrarelativistic energies and to transit angles of particles close to the direction of the normal to the screen surface. The method developed here is used for analyzing familiar problems of diffraction radiation, such as radiation emerging during normal transit of a particle along the axis of a circular aperture in the screen, radiation emitted during oblique transit near a perfectly conducting half-plane, and radiation emitted during oblique transit of a particle through a rectangular slit in an infinitely large screen. In the latter case, the results obtained after the limiting transition to zero width of the slit completely coincide with the theory of transition radiation for arbitrary energies of the particle and its angle of incidence to the screen.