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The intensities of several optical emission lines of C 11, CIII and C IV were measured on the Hawk plasma opening switch (POS) in order to determine the role of contamination from plasma-surface interactions during the conduction phase. To operate the switch, the inverse pinch (IP) plasma source was used with hydrogen gas.2 This source injects a pure hydrogen plasma from inside the inner conductor (cathode) into the POS gap. Therefore, detection of carbon is direct evidence that impurities from material surfaces have been incorporated in to the switch plasma. In fact, previous experimental results with the IP suggested that impurities dominate the conduction scaling.* A visible and UV range monochromator was used simultaneously to monitor sets of lines from carbon in each spectral range. Both monochromators were set to view the switch plasma using an axial line-of-sight at the same radial position, but at different azimuths. Data was taken at three radial positions, near the anode, near the cathode, and in the radial center of the switch. Each system was calibrated for absolute intensity using two traceable standards: a tungsten filament spectral radiance lamp and an UV deuterium spectral irradiance lamp. Initial analysis showed that the impurity emission was significantly higher near the anode, which is reasonable, because the anode is solid and the cathode semitransparent using the IP source. The data analysis is being performed with input from a time-dependent collisionalradiative model. The absolute intensities together with electron temperatures from line ratios (and from the time-histories), will be used to quantitatively determine impurity concentrations. Results from this analysis will be presented and the significance of these results to the future of POS development will be discussed. 1. Work supported by DTRA. 2. Moschella et al., in Proc. 12" Inter.We study the operation of a planar microsecond plasma opening switch (POS) in which a current of 140 kA is conducted by the plasma for a duration of 400 ns before opening into an inductive load within 90 ns. Spectroscopic measurements, local in 3D, are made by doping the plasma with various species and observing the characteristic emission of the doped particles. The electron density and temperature and the plasma composition of the prefilled flashboard plasma are studied spectroscopically. The electron density and temperature are found to be (5+2)x10L4 cm" and 6H.5 eV, respectively. The plasma is found to consist mainly of protons with a significant fraction of CIV and CV ions only near the anode. During the POS operation, measurements of the magnetic field evolution from Zeeman splitting, the electron density and temperature from line intensities and collisionalradiative calculations, and the ion velocities from Doppler shifts are made. The magnetic field is seen to penetrate into the POS region in the form of a broad current channel (>1.5 cm) at an average velocity of 3.5~10' c d s . The electron density at each location is found to rise by 2040% at the ...

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acted to reduce the effect of zippering. W preionization of the Kr was used for all of these shots. The pinch length was 2 cm. Current in the z pinch was measured with both B-dot current monitors and piezoelectric pressure transducers.

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