Modes of Arcing

Abstract

The searches for the ways to increase the efficiency of the plasma generator are leaded, among other things, to the determination of such modes of the arcing, at which the share of the energy transferred to the arc from the power supply is the maximal. This is realized under the condition when the active resistance of the arc repeatedly exceeds the resistance of the discharge circuit and internal resistance of the power supply. As has been repeatedly noted, the characteristic feature of the arcing in the discharge chambers of the coaxial type is the effect of the so-called magnetic blow, i.e., “pulling” the arc and moving of the anode and cathode spots along the surface of the electrodes in the direction of the Lorentz force. The term “magnetic blow” needs to be adjusted, because it unilaterally characterizes the mechanism of the occurrence of this phenomenon. The point is that at the initial stage of the arcing, the gas-kinetic pressure is much higher than the magnetic pressure, and consequently, it determines the mechanism of the arc motion [Lebedev, in I All-union seminar on dynamics of the high-current arc discharge in magnetic field, Novosibirsk, 1990, 1]. Similar conclusions were made in the work [Gurevich et al. in Rep. AS USSR 293, 1102 (1987), 2], where it was stated that in the “plasma focus” at the gas pressure higher than atmospheric, the motion of the current sheath is also due primarily to the gas-kinetic pressure. Thus, partially retaining the terminology of the works [Bianchetta and Sivier, in Second symposium on technic research at hyper sound speeds, Denver, (1962), [3, Rotert and Sivier in National symposium on hypervelocity techniques (1960), 4], it is more correct to call this effect as “gas-magnetic blow”.We have determined the basic principles controlling the arcing regime:

• The interelectrode distance should be such that the final length of the arc is maximal

• There must be guaranteed repeated breakdown/breakdowns of the interelectrode gap, to maximize the transfer of the power supply energy into the arc.