Spectroscopic study of edge poloidal rotation and radial electric fields in the DIII-D tokamak

摘要

Doppler-shift spectroscopy has shown that finite values of poloidal rotation velocity (upsilon)(sub (theta)) and of radial electric field E(sub r) exist at the edge of a tokamak plasma and that dramatic increases occur in these parameters at an L-H transition. E(sub r) is negative in the L-mode and becomes more negative in the H-mode; (upsilon)(sub (theta)) increases in magnitude at the transition. In addition, the radial gradients (shear) of (upsilon)(sub (theta)) and E(sub r) are large and these gradients also increase at the L-H transition. These results are based on measurements of Doppler shifts of light emitted by He II ions, located in a region about 1--3 cm inside the separatrix. These observations have been made with horizontally-viewing and vertically-viewing spectrometer systems on the DIII-D tokamak. The nearly orthogonal views of these systems are used to determine the plasma's flow velocity in terms of the orthogonal sets (upsilon)(sub (theta)) and (upsilon)(sub (phi)) or of (upsilon)(sub (perpendicular)) and (upsilon)(sub (parallel)). Knowledge of (upsilon)(sub (perpendicular)) is used to calculate E(sub r) from the force balance equation for a single ion species. The existing results impose constraints on theories of the L-H transition. More detailed studies of the spatial profiles and temporal evolution of (upsilon)(sub (theta)) and E(sub r) will be made with upgraded instrumentation, which is now coming on-line. 28 refs.