Pulsed discharges in a wide density range: Plasma development and media excitation

Modern plasmachemical applications require more selective and efficient excitation of the media. In addition to traditional laser and lamp light sources and microelectronics, plasma assisted flow control, plasma assisted combustion, plasma medicine and biology are considered between the promising areas. The selectivity increase can be achieved by maintaining a predetermined value of the reduced electric field in the discharge. This type of optimization of plasma-chemical processes requires the transition from the quasi-stationary discharges with self-consistent electric field to pulse discharges, capable of supporting a predetermined E/n value at least in the moment of maximal energy input. The Chapter demonstrates the peculiarities of pulsed nonequilibrium plasma generation in different media by nano- and picosecond high-voltage discharges. Fast ionization waves in long tubes at low pressures, streamers and dielectric barrier discharges at moderate and atmospheric pressures, surface dielectric barrier discharges at elevated pressures are considered. Special attention is given to start of picosecond and nanosecond discharges in liquid media. The data used were consciously restricted to ICCD fast imaging of picoseconds and nanosecond discharges to underline the dynamics of pulsed discharge development and the importance of spatial distribution of the discharge energy.Modern technologies of solid state electronics significantly enhance the ability of generating short pulses of high voltage and power. In a wide range of media densities a sharp increase of electric field in the beginning of the discharge increases the homogeneity of resulting plasma and allows a precise control of electrical field in the plasma, electron energy and energy distribution over internal degrees of freedom of the gas. Due to this progress a new field of plasmachemistry - plasmachemistry of nanosecond and picosecond discharges - is actively developed.