Initial results for tandem puff X-ray loads on ACE 4

Summary form only given, as follows. Thompson et al. (1989) reported on a new Z-pinch load termed a "tandem puff". In this geometry, current from a Marx bank is initially carried by an annular plasma column. Magneto-hydrodynamic forces push the current sheath axially. At the end of the conduction region, the current is transferred onto an annular gas puff without an intervening vacuum power flow volume. The puff then implodes much like a standard Z-pinch. The advantages of this geometry are (1) it uses a simple, compact and relatively inexpensive Marx bank, (2) a separate plasma opening switch (POS) is not needed between the source and the load, and (3) Z-pinch parameters like mass loading and radius need not be tuned to match the Marx bank\´s current time history. We present here initial tests of this tandem puff configuration using the 4 MJ ACE 4 inductive energy storage (IES) machine. Neon and a few krypton puffs from an 11 centimeter diameter fast gas valve gave significant (>10 kJ) soft X-ray (/spl sim/1 keV) yields. Load currents exceeded 3 megamps, a level 3 times higher than our earlier experiments. We observed implosion times of over 400 nanoseconds. Our diagnostics included calorimeters, time-resolved sensors (PCDs, XRDs, and silicon PIN diodes), and time-integrated images (pinhole and KAP spectra). Only a limited number of shots were made, hence this configuration is far from optimized. However, our results suggest that the tandem puff geometry is very promising as a long implosion time X-ray source.