V. G. Baryshevsky

Parametric beam instability of relativistic charged particles in a crystal

Abstract A new mechanism of the instability of an electron (positron) beam under conditions of the parametric X-rays is discovered. Equations, which define the amplitude increment of the instability and the starting current, are obtained. It is shown that a considerable part of the particle energy transforms into coherent X-ray energy due to this parametric instability.

First lasing of a volume FEL (VFEL) at a wavelength range λ∼4–6 mm

First lasing of a volume free electron laser in the millimeter wavelength range is observed.

Volume free electron lasers

Abstract Volume free electron lasers (VFELs) are a new type of radiation sources using volume distributed feedback. The dispersion equation allowing to find the vacuum VFEL gain in the single-mode generation regime is considered. It is shown that a vacuum VFEL provides a more effective lasing process as compared with conventional FELs using one-dimensional distributed feedback (DFB). The VFEL provides the possibility to design compact sources in various spectral ranges. Therefore, it may be interesting for diverse applications in different wavelength ranges, from millimeter to X-ray. A VFEL can be realized on the basis of existing accelerators.

Progress of the volume FEL (VFEL) experiments in millimeter range

Use of non-one-dimensional distributed feedback in Volume Free Electron Laser gives possibility of frequency tuning in wide range. In present work, dependence of lasing process on the angle between resonant diffraction grating grooves and direction of electron beam velocity is discussed.

Theoretical interpretation of parametric X-ray spectra

Abstract The detailed theoretical analysis of the experiments described in refs. [1–3] is considered. It is shown that the intensity, spectral and angular distributions of the radiation observed in [1–3] are completely explained on the basis of the theory of the parametric X-rays in the case of extremely asymmetric diffraction. The threshold behaviour of the parametric X-rays is discussed.

Experimental Study of an Axial Vircator With Resonant Cavity

Multicavity resonators for an axial vircator are developed and experimentally investigated. The frequency and radiation power are analyzed for different cathodes and anode meshes and varied cathode-anode gaps.

2-D Simulation and Experimental Investigation of an Axial Vircator

A method for 2-D simulation of an axial vircator with a resonance cavity is described. It uses a self-consistent solution of relativistic motion equations and Maxwell equations for scalar and vector potentials in the Coulomb gauge. The vector potential is represented as a superposition of resonator eigenmodes, where each eigenmode corresponds to a damping oscillator. Damping enables considering radiative energy losses from the open end of the resonator. Compliance of the simulation results with both published experimental studies and those performed by our team is demonstrated.

Time dependence of the intensity of parametric quasi-Cherenkov radiation produced by relativistic particles passing through electromagnetic (photonic) crystals

Abstract. Examining the temporal evolution of parametric quasi-Cherenkov terahertz radiation (PTR) produced by a relativistic charged particle passing through an electromagnetic crystal, we found that the duration of PTR pulses can be much longer than the particle flight time through the crystal. This enables a thorough experimental investigation of the time structure of parametric quasi-Cherenkov T-ray pulses generated by electron bunches available with modern accelerators. The complicated time structure of parametric radiation can also be observed in natural crystals in the x-ray range.

Dynamical diffraction theory of waves in photonic crystals built from anisotropically scattering elements

Abstract. Analyzing scattering of electromagnetic waves in a two-dimensional photonic crystal from the viewpoint of scattering theory, we come to the conclusion that multiple rescattering of waves by the centers (wires) composing the crystal significantly affects the imaginary part of the crystal refractive index. As a result, it appears that, in the case of crystals, the classical expression relating the refractive index of a random medium to the amplitude of scattering by a single center has limited application, because it does not properly describe the attenuation of waves. We derive an expression that, unlike the classical one, includes the effective amplitude of scattering by a wire in a crystal, instead of the amplitude of scattering by a single wire in vacuum. The same effective amplitude must appear in the equation describing the dynamical diffraction of waves in crystals. We also derive the expression for the effective amplitude in the case when scattering by a single center is anisotropic. Because a most general approach is applied to the description of the scattering process, the results are valid for a wide range of cases without being restricted to either electromagnetic waves or crystals built from wires.

The effect of spin oscillation of relativistic particles passing through substance and the possibility of constituent quark rescattering observation at -hyperon-proton collision

For an -hyperon passing through matter the phenomena of spin rotation and oscillation have been investigated quantitatively. Connections between these phenomena and constituent quark rescattering has been determined. This allows one to investigate quark rescattering directly without a background of single scattering.