P.G. Rutberg

The review of experimental results of strong current (I=10-10/sup 4/ A) quasi-stationary ac discharges in high pressure (P/spl ges/10/sup 5/ Pa) gases is presented. Structure and properties of alternating current arc in vortex, turbulent flows of air, argon, nitrogen, and hydrogen were investigated. The existence of two arc discharge column regimes, contracted and diffusion, has been established. The processes of heat exchange between the arc and surrounding gas for these regimes were studied. Processes in the discharge volume, mechanisms of charge transition in the electrodes neighbor zone, and electrodes' erosion in the spot and without-spot regimes were investigated in dependence of current quantity, gas pressure, and electrode material. Water-cooled copper electrodes were used as well as high-melting ones (tungsten, molybdenum, and other). Prototypes of powerful (N=10-10/sup 3/ kW) ac plasma generators, intended for usage in different plasma-chemical technologies including toxic wastes destruction and treatment, were designed, developed, and manufactured on the basis of these investigations.

The investigation results of an electric discharge launcher's (EDL) chamber operation at hydrogen initial pressure 20-40 MPa, discharge current 0.5-1.0 MA, current rise rate (0.5-1.0)/spl times/10/sup 10/ A/s and input energy up to 2.2 MJ are presented. The coaxial electrode system consists of cylindrical anode and conic cathode. The discharge is initiated by copper wire in the interelectrode gap of 0.8-2.5 mm. The conditions of multipulse discharge current appearance, at the pulses number 5-15 (in comparison with usual multipulse regime 2-3 pulses), amplitude 0.5-1.0 MA and single pulse duration 50-200 /spl mu/s, are determined. The speeds of arc movement (1.5-3.0 km/s) and arc channel expansion (0.2-0.4 km/s), were measured by means of high-speed camera. The efficiency of energy transfer from the power supply (capacitor storage) to the arc was about 85% and from the arc to gas-90%. Electrodes erosion was found to be 30-40% less compared with usual multipulse regime. Besides the anode and cathode, total erosion was 30-40 mg/C at passed charge up to 800 C. The results estimation of different mechanisms contribution to heat transfer from the arc to surrounding hydrogen are discussed. It was shown that both repeated dissipation of arc plasma internal energy after arc extinction and the shock waves, appearing at the breakdowns of interelectrode gap, increase the efficiency of gas heating. It was proposed that decreasing of electrodes erosion at the multipulse regime is connected both with the growth of electrode spots movement speed and with the decreasing of current amplitude from 1.5-2.0 MA (usual multipulse regime) to 1.0 MA.

The overview summarizes the main electromagnetic activities in Russia since the 12th Electromagnetic Launch Technology Symposium in 2004. This research has been focused on the development and improvement of electro-discharge launchers, railguns, and electrothermal-chemical (ETC) launchers. Research efforts have been directed toward studying the physical phenomena and processes limiting the attainment of high velocities and operational resources of launchers. Considerable attention has been paid to solving problems related to material erosion, the manufacture of new materials and their testing in high-current arc discharges, and the search for new applications of launchers in science and engineering

This paper describes the pulse formation of a programmable multi-stage pulsed power supply for electric railguns. This power supply allows optimal operation of the railgun by maintaining a near constant acceleration force over the launch period. This constant force is gained by matching the voltage of the power supply to the variable inductance and resistance of the launcher. A way to estimate the load inductance is presented in this paper.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The overview summarizes the main electromagnetic activities in Russia since the 13th Electromagnetic Launch Technology Symposium in 2006. This research has been focused on the development and improvement of electric-discharge launchers, railguns, and electrothermal-chemical launchers. Research efforts have been directed toward studying the physical phenomena and processes limiting the attainment of high velocities and life time of launchers. Considerable attention has been paid to solving problems related to material erosion, the manufacture of new materials and their testing in high-current arc discharges and the search for new applications of launchers in science and engineering.