Plasma density and depolarization current in mirror-torus-system-1 with divertor magnetic field

Mirror-Torus-System-1 (racetrack form) consists of two straight mirrors connected by U-bend with four divertors in order to obtain the equilibrium plasma. The plasma in a U-bend is detouched from the wall for the divertor configuration and concentrates on the magnetic axis. A depolarization current reducing the electric field by the toroidal drift is experimentally measured. The depolarization current flowing along the azimuthal direction is considered to be composed of two kinds of motions of electrons in a field free area in the divertor. One is the non-adiabatic motion and the other is B x nabla B drift motion. The measured value in U-bend, 8.7 μA/mm2, for the current flowing along the line of force passing the neutral line agrees with the calculated one based on the single particle model. (author)