Multipulse discharge in the chamber of electric discharge launcher

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.