Plasma properties of high-pressure microhollow cathode discharges in argon

Summary form only given, as follows. Stable d.c. microhollow cathode discharges have been operated in argon up to atmospheric pressure by reducing the diameter of the electrodes and the cathode opening to values on the order of 100 /spl mu/m. The discharges have been operated in a wide current range up to 15 mA at forward voltages around 200 V. Current densities up to 100 A/cm/sup 2/ have been estimated. These microdischarges have proven to be an efficient source of UV- and excimer radiation in noble gases and noble gas halogen mixtures, revealing the presence of a reasonable large number of electrons with energies >10 eV at high gas pressure. Optical diagnostic methods have been used in order to get more information on the plasma properties of the microhollow cathode discharge. In the visible range and the near infrared the plasma light emission is dominated by excited Ar I states, the precursors of the excimer. Light emission from ionized argon species (Ar II) was investigated to get more information on the electron energy in the plasma. Interference filters were used to get information on the spatial distribution of the light emission.