Self-Organized Patterns in Cathode Boundary Layer Discharges

Summary form only given. Direct current glow discharges in cathode boundary layer (CBL) configuration exhibit self-organized patterns in a pressure range of 75 to 760 torr in xenon in the negative glow region. When the discharge current is reduced below a critical value, the abnormal discharge enters a self-organized mode. The plasma patterns, i.e. regularly arranged filaments that are most pronounced at lower pressures (50 to 150 torr), show discrete changes in the number of filaments when the current is decreased by fractions of mA. The number of filaments for xenon discharges at 75 torr decreases to a single filament by reducing the diameter of the opening to 300 mum. For the single filament operation, the UV (172 nm) radiation efficiency increases sharply with decreasing current. This shows promise in an application for a UV flat panel with a thickness of less than 1 mm that would not require a heat sink. The pattern formation can likely be explained by electrostatic interaction of filamentary plasmas in an electrostatic potential which is determined by the electrode geometry. Experimental studies involving side-on observations of the CBL have been also performed to increase understanding of the cathode fall region, and the results will be presented