CHARACTERIZATION AND CONTROL OF THE POWER LOSS AND ITS DISTRIBUTION IN TDEV DURING DIVERTOR PLATE BIASING EXPERIMENTS

Effective control of the particle and power flux distributions between the upper and lower diverters has been demonstrated on TdeV, using biasing of the divertor plates, in ohmic discharges with a double null magnetic configuration. Negative biasing of the divertor plates with respect to the walls significantly increases the pressure and the emitted power from the plasma in the active divertor into which E x B drift is directed, but it has little influence on the opposite divertor. This enhanced power dissipation is the result of improved particle retention in the active divertor. The incident power on the plates in the active divertor also increases with biasing, but at a slower rate. The Franck-Condon and charge exchange neutrals contribute significantly to the power loss in the diverters of TdeV in the present operating mode. Positive biasing of the divertor plates has little influence on the total losses from the divertor regions.