Survey of Features in Radiative Power Loss Profiles in the Tokamak Fusion Test Reactor

Although the total radiated power in the Tokamak Fusion Test Reactor is often as high as 70% of the heating power, most of the radiation is concentrated near the surface of the plasma, and the interior loss is almost negligible. Fractional radiation loss declines during neutral beam heating. Under most interesting plasma conditions, the radiation profiles are dominated by asymmetrical peaks, which indicate locally intense edge radiation. As the high-density limit is approached, under most conditions, a bright band of radiation (a “marfe”) appears on the inner side of the plasma column. Marfe location is affected by toroidal field direction, neutral beam direction, and nearness to the high-density limit. Marfes have been observed to drift under the plasma column to the lower outside plasma edge. Marfes naturally develop into detached plasmas. In enhanced confinement discharges (“super-shots”), an unexplained peculiar bright band, distinct from a marfe, appears in the lower outside part of the vacuum vessel, outside of the limiter radius. In high-density pellet-fueled discharges, there is a central peak that shows evidence for inward impurity convection.