Measurements of plasma density and magnetic field in a 100-ns plasma opening switch (POS)

Summary form only given. Spectroscopic techniques are used to investigate a coaxial POS driven by a 270 kV, 200 kA, 90 ns half-period negative current pulse applied to the inner electrode. The plasma is produced by a flashboard characterized using spectroscopy and biased Faraday cups. The plasma density determined from hydrogen line Stark broadening is 2/spl times/10/sup 14/ cm/sup -3/, an order of magnitude higher than the value obtained by Faraday Cups and Langmuir probes. Thus it is possible that the density in previous POS experiments was higher than inferred from electrical measurements. It was also observed that a similar POS operation is obtained for various flashboard configurations when the same density is reached, regardless of the injection velocity. Thus, previously made scaling considerations may have to be re-examined. The plasma is doped by various elements using laser evaporation techniques to obtain good spatial resolution in the axial direction. All emission lines show fast decrease in the excited level population that is time-correlated with the POS opening. Comparisons of various line intensities and atomic physics calculations show that this sharp decrease results from local evacuation of the electrons. The drop in density propagates from the generator towards the load, and from the cathode to the middle of the POS gap. Local Zeeman splitting measurements of PbII lines are used to determine the magnetic field and current distribution in the plasma. The opening mechanism is investigated by correlating the time dependent data on magnetic field and the local density.