Radiation of charged-particle bunches passing perpendicularly by the edge of a semi-infinite planar wire structure.

The radiation of a charged-particle bunch moving perpendicularly to a semi-infinite plane grid composed of thin parallel wires is analyzed using the method of averaged boundary conditions (the period of the grid is assumed to be much less than the wavelengths under investigation). We perform an analysis of the volume radiation and surface waves generated by a bunch of finite length. It is shown that the patterns of the volume radiation fundamentally differ from those that arise in the case of an infinite grid. The properties of the surface waves are similar to the properties of Cherenkov radiation in a three-dimensional wire metamaterial. These waves propagate along the wires at the speed of light in a vacuum and do not diminish with distance (if absorption is negligible). The structure of the surface waves allows for the determination of the size and form of the particle bunches.

Radiation of charges moving along the boundary of a wire metamaterial.

The electromagnetic fields of charges moving along the boundary of a "wire metamaterial" perpendicularly to the wires are investigated. The metamaterial under consideration represents a volume-periodic structure of thin parallel wires located in a square lattice. This structure is described by an effective permittivity tensor and exhibits both spatial and frequency dispersion. It is shown that the charge generates nondivergent radiation, as in the case of an infinite metamaterial. However, unlike the infinite-metamaterial case, the radiation concentrates near a certain plane (not line) behind the charge, and it is asymmetric with respect to this plane. An algorithm for calculating the wave fields of finite-length bunches is developed, and some typical numerical results are given. They demonstrate that the structure under consideration can be applied to determine the size and form of such bunches. The stopping and deflection forces acting on the charge are also calculated.

Nondivergent Cherenkov radiation in a wire metamaterial.

The electromagnetic radiation of a charge moving in an infinite 3D structure made of parallel wires is considered. The periods of the structure are assumed to be small; therefore, it can be described by an effective permittivity tensor. The charge velocity is perpendicular to the wires. Analytical and numerical investigations are performed, and some unusual properties of the radiation are noted. It is shown that the radiation propagates along the wires and concentrates near certain rays behind the charge. The wave field does not vary with distance from the charge along these rays (if energy loss in the medium is negligible). The prospects for the use of the structure under consideration for diagnostics of bunches are noted.