Recent "tandem puff-on-wire" experiments on ACE 4

Summary form only given, as follows. The "tandem-puff" configuration is a variant on a plasma opening switch Z-pinch, driven by a microsecond timescale Marx bank. Current flows in an annular-plasma column for about a microsecond and is then commutated to a central, annular-gas puff. The gas puff subsequently implodes near maximum generator current. The ACE 4 facility is a 4 MJ, 2 microsecond risetime, inductive-energy storage (IES) generator equipped with the following diagnostics: calorimeters, time-resolved sensors (PCDs, XRDs, and silicon PIN diodes), and time-integrated images (pinhole and KAP spectra). Previously reported tandem puff experiments were configured with a single, co-axial, 25-50 micron diameter copper wire on the pinch axis. The data showed enhanced yield in the soft X-ray energy range of /spl sim/1 keV which included significant Cu L-shell thermal emission. This paper will present recent results using neon gas injected by a fast valve and 11-centimeter diameter annular nozzle, imploded onto one or more central aluminum wires using load currents of over 2 megamps and implosion times in the range of 300-400 nanoseconds. The radiated spectrum is predominantly thermal K-shell radiation from both atomic species. We will attempt to characterize the energy transfer mechanisms relative to existing data.