First results for an argon z-pinch at currents above 15 MegaAmps

Summary form only given, as follows. We report on the first gas puff z-pinches imploded on the Sandia "Z" accelerator. An 8 cm (outer diameter) argon double-shell load was driven with over 15 MA in 112 ns to produce 274124 kJ of K-shell X-rays. This yield is a factor of >6 times larger than the previously observed maximum for argon and is consistent with the expected current-squared scaling for "efficient" radiation. With this result, we can establish the empirical scaling of argon K-shell yield with current over the range from 2 to 15 MA and test modeling concepts over a wide range of implosion conditions. Final diameter of the K-shell emitting column was under 5 mm but significant axial variations suggest that further improvements in the gas flow geometry could be made. Spectra show that the main argon emission lines have very high opacity. While the peak inferred electron temperatures, approximately 2.0 keV, are a little higher than seen in lower current tests, the most significant difference is in the ion densities which are up to 5 times higher. The selective use of a chlorine tracer in one of the shells on each test indicates that the masses in the two shells do not mix or interpenetrate significantly during the implosion. Data from a variety of diagnostics spectrographs, pinhole cameras, PCDs and XRDs will be presented.