Plasma Confinement by Surface Magnetic Field

Abstract

The mechanism of plasma confinement by a surface magnetic field configuration (surmac) is studied in a linear device. The end losses are reduced by bending the surmac coil so as to have a small aperture at the both ends. The penetrating length of a plasma into the magnetic wall is much shorter than the local ion gyroradius. A sharp potential dip was observed at the position of the density drop, and it is confirmed that the formation of the dip is essential for the plasma confinement. The particle loss across the magnetic wall is due to classical ambipolar diffusion, and the saturation at high magnetic field operation is explained by the end loss.