Electron Bernstein Wave Studies: Emission and Absorption with Nonthermal Distributions; Current Drive; Delta-F Particle in Cell Simulations

Electron Bernstein waves (EBW) are suitable for heating, current drive, and radiation temperature measurements of overdense plasma, ωpe>>ωce , in spherical torus devices. In NSTX, design of a multi-megawatt EBW current drive system is supported by experimental measurements and computations of obliquely viewing, dual-polarization EBW emission (EBE) radiometry. Efficient EBW coupling, 80±20% at 16.5 GHz, is demonstrated, in agreement with calculations. Ohkawa EBWCD is calculated with Fokker-Planck and ray tracing codes to generate 40-50 kA/MW of off-axis current. Calculations for the Pegasus experiment are also presented. BXO emission from rf quasilinear modified nonthermal distributions calculated due to 1 MW of injected EBW power gives intermediate temperature between the thermal and tail nonthermal temperature. First results of slabmodel simulation of EBW by a delta-f PIC code are given. Delta-f enables low-noise simulations of the linear mode-conversion of injected X-mode radiation to EBWs in the edge region of an overdense plasma, in good agreement with analytic analysis. At higher input power, harmonics of the fundamental EBW are nonlinearly generated, as well as decay into two EBWs at higher frequencies.