Dynamics of micropinches in exploding wire and vacuum spark plasmas

A vacuum spark develops in the metallic vapor emitted by the electrodes. The plasma thus created experiences contractions that originate plasma points or micropinches. We report here an investigation into the dynamics of these both in the vacuum spark and the exploding wire. A fast, 2 kJ generator was used for the experiments. The diagnostics employed include optical frame and streak photography, time-resolved filtered X-ray detection and pinhole X-ray photography. The results obtained indicate that there is a substantial amount of pinching, some of it producing X-radiation. The energy of the X-rays tend to be rather soft and no characteristic lines were detected, even when swapping electrodes, which are made of dissimilar material. This demonstrates that radiative collapse is not attained at this type of energy and that for this type of experiments it is irrelevant what metallic vapors initiate the vacuum arc.