Modelling of the toroidal asymmetry of poloidal halo currents in conducting structures

摘要

During plasma disruptions, substantial toridal and poloidal eddy currents are gener- ated in the vacuum vessel and other plasma facing conducting structures. Eddy currents that conduct charge through paths which close through the plasma periphery are called halo currents, and these can be of substantial magnitude. Of particular concern for tokamak design and operation is the observed toroidal asymmetry of the halo current distribution: such an symmetric distribution leads to prob- lematic non-uniform forces on the conducting structures. The premise is adopted that the source of toroidal asymmetry is the plasma deformation resulting from the non-linear external kink instability that develops during the current quench phase of a disruption.