A novel system for studies of dc discharge in cylindrical magnetron

Abstract

In a cylindrical magnetron, the electric field is applied in the radial direction and the magnetic field in the axial direction. In this paper, we present a description of a novel construction of cylindrical magnetron developed in the University of Greifswald, FRG. The system has been designed for experimental and computer-modelling studies of the DC discharge in crossed electric and magnetic fields in cylindrical geometry. In order to approach conditions close to an infinitely long system, and hence, to enable a more precise comparison with 1-D simulations, the ratio of the vessel length to the distance between the cathode and the anode has been chosen equal to 20. Six evenly distributed coils create the axial magnetic field. The homogeneity of the magnetic field ±0.2% has been achieved over the whole discharge vessel length 300 mm. The system is equipped with a rotable planar Langmuir probe movable in the radial direction. Measurements of the axial dependencies of plasma parameters are enabled by positioning the Langmuir probe in one of the 5 probe ports located between each couple of coils. We present the results of preliminary measurements of the radial and axial profiles of the plasma density and the mean electron energy.