Surface microwave discharge in a multipolar magnetic confinement system

Results of an experimental study of a steady-state microwave discharge (2.45 GHz, 5 kW) in the multipolar confinement system PN-I (with a volume of 70 1) at a gas pressure of < 10(-3) mmHg are presented. The excitation of a wave in a plasma waveguide formed by the plasma surface and the chamber wall is observed; this wave causes the strong collisionless heating of electrons at the plasma periphery. The necessity of revising the role of electron cyclotron resonance in microwave discharges in a multipolar magnetic field at high plasma densities is noted. The results obtained in the PN-1 device confirm the validity of the concepts of a neutralizer designed for the ITER injector and provide a basis for the design of a larger device with a plasma volume of 1000 1.