Recent results from the 60 GHz inside launch ECH system on the DIII-D tokamak

Electron cyclotron heating (ECH) is a useful tool in global transport and local confinement studies. Operational experience with the inside launch ECH system on DIII-D shows that reliable operations are possible with power densities up to 0.7 GW/m2 in vacuum waveguide. Global confinement is roughly predicted by the Rebut-Lallia or ITER-89P scaling law, but direct analysis indicates a nearly linear scaling with toroidal field not found in these scaling laws. Local transport studies with off-axis heating clearly show inward transport in the electron fluid. This implies that diffusive and critical gradient models cannot completely describe plasma transport. (orig.)