Electric and magnetic structure of an edge plasma in a tokamak with a helical magnetic limiter

Abstract
A strong modification of plasma potential was observed at the plasma surface with the application of a helical field produced by a set of local helical coils. The structure of magnetic field lines was computed by a field line tracing code for a tokamak plasma. Such a field structure was examined in the experiment using electron beam probing. The potential formation and the magnetic structure are discussed referring to the scheme of an ergodic magnetic limiter.