[PAST EVENT] Physics Colloquium
Atsushi Fukuyama, Professor Emeritus, Department of Nuclear Engineering, Kyoto University, Kyoto, Japan, Title of Talk: A new approach to kinetic full wave analysis in inhomogeneous plasmas
Various kinds of electromagnetic waves are excited in plasmas, internally as an instability or externally for control purpose. In order to describe the wave structure in bounded plasmas, full wave analysis which solves Maxwell?s equation as a boundary-value problem has been widely utilized. In finite-temperature plasmas, however, it is not straight-forward to include the wave-plasma interaction in the full wave analysis. In a homogeneous plasma, the plasma response to waves, dielectric tensor, is usually expressed as a function of wave number. In an inhomogeneous plasma, however, the wave number is not constant and the thermal particle motion leads to spatial coupling. Therefore, the differential operator approach and the Fourier transform approach have been developed and employed in spite of limitation in applicability. In this talk, a new approach to the kinetic full wave analysis based on the dielectric tensor in the form of integral operator is introduced and three applications are presented. This approach is free from wave number, and the spatial coupling is limited within the range of particle motion. After a brief survey of full wave modeling in plasmas, physics and formulation of the integral operator approach are explained. The first example is the laser-plasma resonant interaction in unmagnetized nonuniform hot plasmas. The incident electromagnetic wave excites the plasma wave at the plasma resonance and the latter is absorbed by collisionless Landau damping. The incident angle dependence of the absorption rate and the deposition profiles are compared with those of conventional collisional damping model. It was found that, with a steep density gradient, stochastic heating occurs even in the case of normal incidence. The second example is the cyclotron damping in the magnetic beach heating. The absorption profile near the cyclotron resonance is obtained. The third example is the finite gyro-radius effects. One-dimensional full wave analysis is applied to the analysis of the O-X-B (ordinary wave, extra-ordinary wave, Bernstein wave) linear mode conversion of electron cyclotron waves in a tokamak plasma con- figuration. Finally, several remaining issues are discussed: two-dimensional kinetic full wave analysis, arbitrary velocity distribution function, and quasi-linear diffusion in the velocity space.