Spectroscopic measurements of plasma density and temperature in a plasma opening switch

The success of compact pulsed power generators based on inductive storage depends upon the availability of fast reliable opening switches. The short conduction time, {dollar}leq{dollar}100ns, plasma opening switch, POS, has shown itself to be capable of reliable opening in under 10ns into a diode load. However longer conduction time, {dollar}sim{dollar}1ms, POS' have not performed as well, apparently due to processes which are negligible in the short time scale of the original switches, but become important in the longer conduction time switches, such as secondary plasmas from surfaces. The net effect is that the longer conduction time switch opens much more sluggishly and causes more energy loss. Theoretical understanding of the POS has been hampered by the lack of spatial and temporal measurements of plasma density.; The experiment reported here provides measurements of the density and temperature of the carbon plasma in a working, long conduction time POS using spectroscopy. First the carbon plasma sources were characterized and the operation of a planar POS using these sources was investigated. Framing images of the plasma show first a translation of the current channel from the generator end of the injected plasma to the load end and then the development of a gap starting at the anode, as the switch opens. The POS operated independently of any flux arriving during switch conduction. The size of the POS gap was important, however, the smallest gap being dominated by the secondary plasmas from the surfaces, while the largest gap showed bulk motion of the plasma towards the load.; The spectroscopic measurement was made with a photomultiplier at the output of a monochromator measuring the intensity of four different wavelengths of C++ emission. Using a collisional-radiative model of the carbon plasma, the density and temperature of the plasma were inferred from two ratios of these intensities. Good agreement was found in comparing the spatial density and temperature information with the pictures of POS operation obtained through the framing images of the plasma.