Radiation of a bunch in a waveguide with a semibounded anisotropic dielectric

Abstract

We analyze the electromagnetic field (EMF) of a small bunch that moves uniformly in a circular metal waveguide and crosses the boundary between two areas: a vacuum area and an area loaded with an anisotropic homogeneous nondispersive dielectric characterized by a diagonal permittivity tensor. Two cases are studied in detail: the bunch flies from a vacuum into the dielectric and, inversely, from the dielectric into a vacuum. In the second case, so-called Cherenkov-transition radiation (CTR) can be generated in the vacuum area of the waveguide. Exact expressions for the EMF components are obtained and investigated. A comparison between the present problems and the analogous problems in the case of an isotropic dielectric is performed. We discuss some benefits occurring from using the anisotropic dielectric. For example, anisotropic dielectric allows more efficient generation of radiation compared to the isotropic dielectric for the same bunch and geometry parameters.

Reversed Cherenkov-transition radiation in a waveguide partly filled with a left-handed medium

“…Here we give only expression for the magnetic component of the forced field in the form of decomposition on normal modes [19]: The second summands in (2.2) which are the 'free' field components [18] connected with the influence of the boundary. The magnetic component is written in the form [20]  …”

“…where The second summands in (2.2) which are the 'free' field components [18] connected with the influence of the boundary. The magnetic component is written in the form [20]  …”

“…Asymptotic expressions for the free field components of each mode (2.5) are obtained with the steepest descent technique [24]. Note that the procedure used for the vacuum area ( 0 z  ) is similar to the procedure that was developed for different situations in our previous studies [10,11,13,17,20,22,23]. So, we only pay attention to the main points.…”

“…is the Heaviside step function and the CR amplitude is This expression is obtained traditionally with the residue theorem, as in the paper[20]. Note that  0n is real value because of the symmetry of the bunch under consideration.The behavior of the CR frequency (3.2) and amplitude (3.4) for the first mode of the wakefield for different values of  and the anisotropy parameter a x are presented inFigure 1.…”

Focusing of Drive and Test Bunches in a Dielectric Waveguide Filled with Inhomogeneous Plasma

“…Cherenkov radiation generated by charged particles bunches in dielectric structures can be used to develop high-gradient wake accelerators of the high-energy range [1][2][3][4][5] and to obtain intense coherent radiation for industrial purposes, environment monitoring and medicine [6][7][8][9][10][11][12][13][14]. However, there is severe shortcoming of dielectric wakefield accelerators (DWA) namely the susceptibility of bunches to the beam breakup (BBU) instability [15,16] peculiar to electron linear accelerators [17].…”