Resonance cone interaction with a self-consistent radio-frequency sheath.

We study the propagation of lower-hybrid-type resonance cones in a tenuous magnetized plasma, and, in particular, their interaction with, and reflection from, the plasma sheath near a conducting wall. The sheath is modeled as a vacuum gap whose width is given by the Child-Langmuir law. The application of interest is when the resonance cones are launched (parasitically) by an ion-cyclotron radio-frequency antenna in a typical rf-heated tokamak fusion experiment.

Blob dynamics in 3D BOUT simulations of tokamak edge turbulence.

Propagating filaments of enhanced plasma density, or blobs, observed in 3D numerical simulations of a diverted, neutral-fueled tokamak are studied. Fluctuations of vorticity, electrical potential phi, temperature Te, and current density J parallel associated with the blobs have a dipole structure perpendicular to the magnetic field and propagate radially with large E x B drift velocities (>1 km/s). The simulation results are consistent with a 3D blob dynamics model that incorporates increased parallel plasma resistivity (from neutral cooling of the X-point region), blob disconnection from the divertor sheath, X-point closure of the current loops, and collisional physics to sustain the phi, Te, J parallel dipoles.

Sheared poloidal flow driven by mode conversion in tokamak plasmas.

A two-dimensional integral full-wave model is used to calculate poloidal forces driven by mode conversion in tokamak plasmas. In the presence of a poloidal magnetic field, mode conversion near the ion-ion hybrid resonance is dominated by a transition from the fast magnetosonic wave to the slow ion cyclotron wave. The poloidal field generates strong variations in the parallel wave spectrum that cause wave damping in a narrow layer near the mode conversion surface.