Formation of a Plasma Ring by a Microwave Discharge in a Narrow Coaxial Cavity beyond the ECR Region

Results are presented from the experimental study of conditions for the formation of a plasma ring by a microwave discharge in a narrow coaxial cavity in an axisymmetric magnetic field the magnitude of which is below the electron-cyclotron resonance value. It is established that the necessary condition for this process is the presence of an electrostatic wave propagating in the azimuthal direction, the circumference of the plasma ring being a multiple of the wave half-length. © 2018, Pleiades Publishing, Ltd.