Calculation of SOL and Divertor Plasma Properties
Stacey, Weston M.
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A complex variety of interacting phenomena determine the properties of the plasma in the scrape-off layer (SOL) and divertor of a tokamak. These phenomena have been modeled in, two-dimensional plasma edge codes, which provide important insights into the physics of the SOL and divertor regions, but which are computationally intensive. In order to provide the means for routine analyses of SOL and divertor plasma properties, a computationally tractable model for the calculation of ion and impurity densities, temperature, currents, particle flows and electric fields along the separatrix in the divertor and scrape-off layer of tokamak plasmas has been developed. This model is described and applied to calculate the effects of particle drifts and the direction of the toroidal magnetic field on these calculated quantities. Several recently observed experimental phenomena—double reversal of the parallel ion velocity in the SOL, enhanced core penetration of argon injected into the divertor when the grad-B ion drift is into rather than away from the divertor—and other interesting phenomena, such as the structure of the parallel current flowing in the SOL and the reversal of the sign of the electrostatic potential in the SOL when the toroidal field direction is reversed, are predicted.