THE EFFECTS OF FIELD REVERSAL ON THE ALCATOR C-MOD DIVERTOR

Imbalances between the inboard and outboard legs of the single null di vertor in tokamak Alcator C-Mod are observed to reverse when the direc tion of the toroidal field is reversed. These imbalances are measured by embedded probes in the target plates, tomographic reconstructions o f bolometry and line radiation, and visible imaging. Density imbalance s of about a factor of ten at the targets are observed at moderate den sity, decreasing as the density is raised until they are almost balanc ed. The data indicate that the electron pressure is not imbalanced, th us arguing against momentum imbalance as the cause of these drift-indu ced effects. Instead, power flux imbalance caused by E(r) boolean AND B convection, and enhanced by radiation, is suggested as the underlyin g cause.