Diffraction Radiation Generated by a Density-Modulated Electron Beam Flying Over the Periodic Boundary of the Medium Section. Iii. Anomalous and Resonant Phenomena

Abstract

The paper is focused on the reliable analysis of the phenomena associated with the resonant and anomalous transformation of the field of a plane, density modulated electron beam, flying over the periodically rough boundary of a natural or artificial medium, in the field of bulk outgoing waves. The physical results presented here have been obtained as the result of numerical implementation of the rigorous mathematical models described in the two first papers of this series. The corresponding analytical constructions have been associated with the correct formulation of model problems and their algorithmization, with the provision of the possibility of a correct physical interpretation of the results of their numerical solution.

Diffraction Radiation Generated by a Density-Modulated Electron Beam Flying Over the Periodic Boundary of the Medium Section. Iv. Structures of Finite Thickness

“…As we wrote in the first of three papers [1][2][3] of this series, Vavilov-Cherenkov radiation (VChR) [4] and Smith-Purcell radiation (SPR) [5] are among the most significant physical phenomena discovered in the 20th century. Classic works [6][7][8][9] are devoted to the theory of these phenomena and questions of their practical use.…”

“…It is not enough to simply record such results, and they also need to be convincingly explained in order to make them interesting, to disclose their potential for prospective consumers working in the field of diffraction electronics, diagnostics of charged particle beams, and monitoring of natural or artificial materials and environments of practical interest. The works [1][2][3] are just devoted to this problem, and there are the main components that are solved: (i) a mathematical model has been constructed and implemented in software that allows obtaining reliable numerical data on all the features of the processes of coherent diffraction radiation during the flight of a plane density-modulated electron beam over a periodic boundary of a half-space occupied by a dispersion medium [1]; (ii) the conditions for the excitation of the so-called eigen modes of the corresponding periodic structure were studied, and those of them which could provoke the effects with an anomalously high level of VChR and SPR were determined [2]; (iii) problem-oriented computational experiments confirming the conclusions based on an analytical consideration of model problems were carried out; they once again demonstrated the possibility of implementing regimes of spatial-frequency transformations of the electron beam field having undoubted practical interest [3].…”

“…All the results of works [1][2][3] concerned the system 'flat density-modulated electron beam -the periodic boundary of the half-space occupied by the dispersion medium'. Obviously, with necessity they had to be 'extended' to more realistic systems in which the dispersion half-space would give way to periodic structures with the same material parameters, but limited in thickness, or the geometric variety of multilayer structures arising due to their wide application in various areas of science and technology.…”

“…Consequently, the secondary fields arising as a result of such excitation also coincide. This allowed us, while solving numerically the problem (1) for artificial plasma-like medium in lower half-space y < f(z), to investigate anomalous and resonant phenomena, accompanying the excitation of Vavilov-Cherenkov or Smith-Purcell radiation, and unambiguously relate these phenomena to the excitation of 'unusual true eigen waves' of the periodic boundary Σ ε,μ [2,3]. In this paper, we continue our analysis, extending it to the structures with similar materials and geometric parameters, but limited in thickness (see, for example, Fig.…”

“…Same as in [1][2][3], the time dependence t for harmonic processes considered in this work is defined by the factor exp(−iωt) omitted everywhere, and ω is a circular frequency. The dimensions of the SI system of all mentioned physical quantities are also omitted.…”