Radiative and Electrical Properties of a Center-Post Cathode Magnetron Glow Discharge Device

Abstract

Current-voltage characteristics and spatially resolved atomic emission data are used to describe the basic operation of a magnetron glow discharge plasma device. The low-pressure glow discharge lamp uses a center-post cathode and a concentric ring-shaped anode. A coaxial magnetic field of a few hundred Gauss is used to achieve magnetron operation where plasma electrons are trapped in closed paths which are concentric with the electrode structure. This results in dramatic changes in the radiative and electrical properties of the device. With constant current, lamp operating voltage may be reduced by more than a factor of two when the magnetic field is present. The effects of filler gas pressure and magnetic field strength on the current-voltage characteristics are presented. The presence of the magnetic field results in a radial contraction of the plasma. This contraction increases with increasing field strength and with decreasing pressure. Ion lines from the Ar filler gas are more affected by the field than are neutral-atom lines from the cathode material.