A dynamic computational model of lower hybrid current drive in the presence of an electric field is described and some results are given. Details of geometry, plasma profiles and circuit equations are treated carefully. Two dimensional velocity space effects are approximated in a one dimensional Fokker-Planck treatment. The model is unable to approximate experimental results in some cases characterized by low density, low current, high aspect ratio and a launched spectrum at high phase velocity relative to the thermal velocity. In other cases, qualitative agreement with measurements is found. A simple formula already in the literature appears to determine whether agreement of model and experiment will be good or poor. Application to an experimental discharge in which q(0) is raised above unity shows an appropriate time-scale. Computation of a planned effort for high /3 suggests potential success.

A common simplifying assumption made in the consideration of radio-frequency heating of tokamaks near the lower hybrid frequency is that the wavelength imposed by the coupling device parallel to the magnetic field is not modified by gradients along the field. In the present calculation, the parallel wavelength is allowed to vary, and important effects are found on wave penetration and damping if the toroidal aspect ratio (Rmajor/rminor) is less than approximately five. The calculation shows that heating at the center of a small aspect ratio torus is inhibited by a decrease in k∥ if waves are launched at the outside, and that it may be possible to change the plasma current via electron Landau damping with a coupler of symmetric power spectrum by placing the coupler at the top (or bottom) of the torus.

Ray tracing simulations based on experimental PBX-M equilibria show a limited range of the parallel wavenumber (n, = R,c/w) along a ray trajectory. The range of nl accessible to the excited wave is shown to have both a lower and an upper bound. The ray's phase volume is projected into (n,, R, Z) space to define a domain of wave accessibility for each toroidal mode number excited by the launcher. A comparison of circular and bean shaped plasmas with a high aspect ratio ( A -5.5) shows that the rays fill a substantially larger portion of the accessible domain in bean shaped plasmas. Furthermore, in the bean shaped case the accessible domain tends to extend to higher n N .