First Experimental Observation Of The Ignition Of A ''Superdense Glow'' Before The Glow-To-Arc Transition In A Pseudospark Discharge

The presented results are the first experimental indication for the existence of a homogeneous superdense glow in the bore hole of the cathode in a pseudospark discharge. The start of this mechanism is leading to the low-impedance high-current phase and starts before the glow-to-are transition in the pseudospark discharge. It is assumed that the high-current density is carried mainly by metal ions which originate from a self-sustained self-sputtering mechanism, or by a large number of, on a macroscopic scale, homogeneously distributed Schottky emitters. It is shown that the geometric features of the bore hole cause an enhancement of this effect. These results and the theoretical assumptions can also explain very effectively the current quenching of the pseudospark discharge. Current quenching is only occurring during the superdense glow when no cathode spots are ignited. (C) 1996 American Institute of Physics.