Complete integral suppression of Pfirsch–Schlüter current in a stellarator plasma in Heliotron E

Abstract

The poloidal magnetic field was measured to detect the plasma boundary position. It was found that the pressure-induced plasma shift, an observable characteristic of the Pfirsch–Schlüter current, depends strongly on the initial position of the magnetic axis. When the axis was moved by the vertical field inside the torus, the finite-β shift became smaller. Complete suppression of the finite-β plasma shift was achieved in a deeply inward shifted configuration: 7 cm from the standard position Raxis=2.20 m. This effect is explained by magnetohydrodynamic (MHD) equilibrium theory for stellarator toroidal plasmas with a large magnetic hill and deep inward shift.