Speaker
Dr
Dmitry Karlovets
(Tomsk polytechnic university)
Description
When moving in a substance or nearby some optical inhomogeneity, a charged particle produces the so-called polarization (or induced) currents, which can be considered as a source for different types of polarization radiation: Cherenkov radiation (ChR), transition radiation (TR), diffraction radiation (DR), Smith-Purcell radiation (SPR), etc. We apply the method of induced currents [1] for a wide class of problems by studying the radiation generated by a particle moving nearby the targets of the complicated shapes and arbitrary permittivity $\varepsilon (\omega) = \varepsilon^{\prime} + i \varepsilon^{\prime \prime}$. In particular, we present solutions for the following problems: DR from a thin rectangular screen, SPR from a thin grating of rectangular strips separated with vacuum gaps, DR from a round hole in a screen, as well as from a rectangular slit in a screen. In all these cases, the solutions obtained have no limitations on the value of the target's permittivity (that means the ChR is automatically included in these solutions) and the particle's energy. In the special cases of ChR in a boundless medium and TR from a slab, our results completely coincide with those by Tamm and Frank, Ginzburg and Frank, Pafomov, Garibyan, et al. We study in detail some interesting examples like SPR from a grating of a finite permittivity and compare the result with the available solutions obtained for the ideally-conducting gratings. The discussion is given on how the method of induced currents is changed when the targets are well-conducting and the skin-effect occurs. We show that the surface current density induced by external field on an ideally-conducting screen must have all three components including the one perpendicular to the screen. This normal component of the surface current is neglected in the existing models for DR or SPR (see review in [2]). However, we demonstrate that it vanishes for ultrarelativistic particles that allows one to indicate the region of applicability for the models with only two tangential components of the surface current. On the other hand, we discuss how one can simplify calculations for the targets of the complicated shapes. It turns out that even for the transparent media all the calculations can be significantly simplified if one neglects from the very beginning the secondary re-reflections of the waves of polarization radiation inside the target. Finally, we show that in the corresponding limiting cases our results coincide with those obtained with the use of some approximate methods applicable when $|\varepsilon (\omega) - 1| \ll 1$ (for example, the eikonal method [3]).
Primary author
Dr
Dmitry Karlovets
(Tomsk polytechnic university)
Co-authors
Prof.
Alexander Potylitsyn
(Tomsk Polytechnic University)
Dr
Alexey Tishchenko
(National Research Nuclear University "MEPhI")
Mr
Konstantin Kruchinin
(Tomsk Polytechnic University)
