Study of the effects of the prefilled plasma parameters on the operation of a short-conduction plasma opening switch

Spectroscopic methods are used to determine the density, the temperature, t he composition, the injection velocity, and the azimuthal uniformity of the flashboard-produced prefilled plasma in an 85-ns, 200-kA plasma opening sw itch (POS), The electron density is found to be an order of magnitude highe r than that obtained by charge collectors, which are commonly used to deter mine the density in such POS's, suggesting that the density in short conduc tion POS's is significantly higher than is usually assumed. We also find th at the plasma is mainly composed of protons; The spectroscopically measured plasma parameters are used here to calculate the conduction currents at th e time of the opening predicted by various theoretical models for the POS o peration, Comparison of these calculated currents to the measured currents indicates that the plasma behavior during conduction is governed either by plasma pushing or by magnetic-field penetration and less by sheath widening near the cathode, as described by existing models. Also, the conduction cu rrent mainly depends on the prefilled electron density and less on the plas ma flux, which is inconsistent with the predictions of the erosion (four-ph ase) model for the switch operation. Another finding is that a better azimu thal uniformity of the prefilled plasma density shortens the load-current r ise time.