ENERGY-BALANCE DURING DISRUPTION ASSOCIATED WITH VERTICAL DISPLACEMENT EVENTS

The presence of an extended region of open flux surfaces (halo), during the current quench phase of the disruption of elongated plasmas, is supported by measurements of halo currents and by numerical simulations. The halo, in addition to providing a poloidal current path between the plasma and the first-wall components, allows rapid conduction and convection of energy along field lines, and therefore a mechanism for the localized deposition of energy onto the wall. The heat load to the region of the plasma-first-wall interaction is higher than in the scenario in which the magnetic energy is mostly dissipated by radiative processes.