RF ponderomotive forces and electrostatic barriers for scrape-off layer control : phenomenological model

Analytical and numerical models are developed for a new technique of edge plasma control using RF ponderomotive forces. The models are two-fluid for electrons and ions, allowing nonambipolar currents to be calculated. The 1D analytical model neglects plasma drifts and provides a simple expression for how the SOL density decay length and potential may be controlled by the application of RF ponderomotive potentials and biased surfaces. The 2D numerical model solves for the plasma density and potential distribution in the SOL and includes E×B , diamagnetic and ponderomotive drifts. This model also calculates transport from inhomogeneous magnetic fields occurring in toroidal magnetic geometry by retaining gradient terms, when fluid drifts (no curvature or gradient particle drift terms) are substituted into the continuity equation. The numerical model also takes into account the relative contribution of the classical transport and fluctuation driven anomalous transport. Results of the model, as applied to the ponderomotive divertor experiment in PISCES, are presented.