Peculiarities of the ordinary to extraordinary wave conversion in the electron cyclotron frequency range near the cut-off surfaces in magnetized plasmas are analysed in a two-dimensionally inhomogeneous simplified tokamak-like geometry. It is demonstrated that the mode conversion may be of essentially two-dimensional nature even neglecting the curvature of the cut-off surfaces; for the latter case a set of reduced wave equations in the transformation region is derived and solved analytically. Transformation coefficients for quasi-optical beams with a finite transverse distribution of rf field are obtained as well as a recipe for synthesis of the optimal (perfectly converted) beam. Applicability limits of a conventional one-dimensional theory are finally discussed.

No abstract

Possible nonlinear effects in electron-cyclotron plasma production and heating by microwave radiation are analyzed. They include nonlinear regimes of electron acceleration in strong microwave fields under cyclotron resonance conditions, nonstationary regimes of microwave beam self-focusing, and some parametric processes. Presented results may be of importance for predictions of plasma response to electron-cyclotron resonance (ECR) heating or preionization by powerful radiation.

Collective scattering of gyrouon radiation and its potennal for plasma diapostics was investigated using the WFAS stellamor. The ion temperature was determined from thermal spectra in neuwd-beom-heated plasmas. The excitation of a n m w band plasma wave by a non.thermd ion component w a observed and the wave characteristics wece investigated experimentally. The results constitute an important step toward a-pmicle diagnostic via scattering of powerful microwave radiation.

No abstract

Absorption of microwave energy at electron-cyclotron frequency is a promising method of heating plasma to thermonuclear temperatures in large toroidal devices in which the energy confinement time exceeds the characteristic time of energy exchange between the electron and ion components of the plasma. The smallness of the wavelength compared with the dimensions of the system makes it possible to use quasioptical waveguides which are easy to match with the plasma. The microwave power, injected in the form of an ordinary wave from the outer part of the torus in the direction of increase of the toroidal component of the magnetic field, is efficiently absorbed if the dimensions of the tokamak are greater than or of the order of those of the T-10 device and the initial temperature of the plasma is greater than 1 keV. In the quasi-continuous heating regime and with reasonable microwave beam cross-sections non-linear effects have no appreciable effect on the cyclotron heating efficiency.

No abstract

Results of experimental and theoretical investigations on generation of terahertz radiation at the interaction of femtosecond laser pulses with a metal surface are presented. Investigations are performed with the laser pulse intensities higher compared with that used in papers [Opt. Lett.29, 2674 (2004); Opt. Lett.30, 1402 (2005)]. The most effective generation is observed for p-polarized optical pulses with incidence angles in the range 5°-10° (from the surface), depending on the kind of metal. For the copper, the exponential growth of terahertz pulse energy with the increase of optical pulse energy was registered. Theoretical interpretation for some of the experimental results is proposed based on the model of free electrons in metal.