Analysis for halo current induced during plasma quench

The expression for the halo current induced during the plasma quench phase is analytically obtained. The numerical calculation shows that the highest value of the halo current in the present large tokamaks is approximately 20% of the plasma current. For the reduction of the halo current, the edge cooling due to the active impurity generation or emission from the wall is adequate, in addition to the enhancement of the wall resistance in the halo current loop by the use of insulators. (author)