Spatial distribution and time evolution of metal-containing plasma of a low-current atmospheric pressure discharge with magnesium cathode

Abstract

The spatial intensity distribution and temporal dynamics of the plasma generated by an atmospheric pressure discharge with magnesium cathode in an argon flow are investigated in a coaxial geometry discharge system. The repetition rate of unipolar pulses was 56 kHz and the pulse duration was 12 μs. The steady-state amplitude of the discharge current was 100 mA at a voltage of about 130 V. Under this operating mode, a local melting of the active cathode surface took place. The evaporated magnesium atoms were captured by the working gas flow and formed a green glow plume around the positive discharge column outside the anode nozzle. The image of the plasma formation was projected onto the entrance slit of the monochromator. The spatial distribution of the radiation intensity and evolution in time of its selected monochromatic components were measured. The radiation spectrum contained groups of ion and magnesium atom lines with wavelengths of 285.21 nm (singlet resonant Mg I); 383.08, 383.36, 383.9 nm (triplet Mg I); 517.3, 517.5, 518.1 nm (triplet Mg I). The results of this work are promising with regard to studying open-type spontaneous radiation sources, as well as the generation of combined gas-metal plasma flows at atmospheric pressure.