IMPURITY POLOIDAL ROTATION VELOCITY IN TOKAMAKS

The impurity poloidal flow velocity, upsilon(thetaz), was measured for Ohmic discharges in banana, plateau, and Pfirsch-Schluter regimes in the Texas Experimental Tokamak (TEXT) [K. W. Gentle, Nucl. Tech./Fusion 1, 479 (1981)]. The velocities were measured spectroscopically using the Doppler shift of a C+4 emission line, and then compared with neoclassical predictions that were evaluated with sets of measured plasma profiles that included the radial electric field. Specifically, neoclassical theory was used to relate upsilon(thetaz) to measured radial profiles, but it was not used to predict any profiles other than upsilon(thetaz)(r). On that basis, neoclassical theory adequately describes upsilon(thetaz). The prediction is dominated by the impurity and ion density scale lengths. Contributions proportional to the parallel viscosity ratio do not contribute significantly to the prediction in this experiment, and thus' are not tested. Similarly, though charge exchange momentum loss may significantly retard the toroidal flow velocity and introduces an unusual electric field dependence into the poloidal flow velocity, the charge exchange contribution to upsilon(thetaz) is too small to be detected.