Biasing and improved divertor performance on the TdeV tokamak

Abstract

Summary form only given. Electrical biasing of the plasma is used on the TdeV tokamak to improve the divertor impurity confinement and exhaust pumping capability two important issues for fusion research. Plasma biasing, applied through the divertor neutralization plates, strongly affects the plasma properties in the scrape off layer (SOL), modifying the plasma potential, the edge density profile, and ion flow in the SOL. The ExB flow, associated with the radial electric field established near the separatrix, increases impurity transport into the divertor. Biasing greatly increases the efficiency of the divertor. There is a linear dependence of divertor pressure on the bias voltage, negative biasing having the strongest dependence. For negative biasing, divertor pressure is a nonlinear function of plasma density. Negative biasing also increases impurity retention in the divertor.