EFFECT OF TOROIDAL FLOW ON THE STABILITY OF A DIFFUSE HIGH-BETA TOKAMAK

The effect of toroidal flow on the stability of a diffuse current model tokamak to external kink modes is examined. For a high-beta tokamak it is shown that, to leading order in the inverse aspect ratio, the effect of toroidal flow is simply to modify the kinetic pressure by adding to it the flow pressure. Then the limit on the plasma beta in the presence of toroidal flow can be obtained from the results for a static plasma. It is shown that, for a given safety factor profile and shape of the plasma boundary, the maximum plasma beta for stability to external kink modes is always lower in the presence of flow compared to a static configuration. This is true for any arbitrary profile of the toroidal flow velocity.