MAGNETOHYDRODYNAMIC EQUILIBRIA OF ATTACHED PLASMAS AFTER LOSS OF VERTICAL STABILITY IN ELONGATED TOKAMAKS

Magnetohydrodynamic equilibria in elongated tokamaks after the loss of vertical stability are studied using externally measured magnetic data from the DIII-D device. The experimentally reconstructed equilibria are found to be generally of the type that has currents flowing along the magnetic field lines in the scrape-off region between the plasma and the vessel and hence involves both poloidal and toroidal currents in the surrounding vacuum vessel wall. Vertical forces on the vacuum vessel due to the induced toroidal and poloidal currents are evaluated. It is shown that the part of the vessel forces associated with the poloidal vessel current can be substantially larger than the part associated with the toroidal vessel current.