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Large current profile modifications (−0.4

Current drive experiments have been performed on TdeV over a wide range of parameters. It is found that the current drive efficiency {eta} does not scale with {ital N}{sub {parallel}} as expected from simple theory. Simulations with the ACCOME code suggest that the reduced efficiency at low {ital N}{sub {parallel}} values is mostly due to a large toroidal upshift in the LH wave spectrum. The loss of suprathermal electrons to the divertor plates was monitored during CD experiments. The power loss increases with decreasing {ital N}{sub {parallel}} values and can be reach up to 15{percent} of the injected rf power in low density plasmas. {copyright} {ital 1996 American Institute of Physics.}

In this review paper the effects of an electric field are addressed. The focus is on open field lines in a tokamak. Electrically biasing the divertor plates of TdeV with respect to the vacuum vessel sets up a radial electric field and a radial current between the separatrix and the wall. It has been demonstrated that the resulting E×B flow and the j×B force produce fundamental phenomena, affecting confinement on closed field lines, parameters of the SOL and the performance of a divertor.