Long-Implosion-Time, 12-cm-Diameter Argon-Gas-Puff Experiments at 6 MA

Summary form only given. We wish to maximize the K-shell yield from high-atomic-number Z pinches (photon energy of ~1-8 keV) and to develop Z-pinch-based concepts for sources of higher-photon energy (~8 to 40 keV). To achieve these goals, large-diameter implosions are needed to: (a) produce the high specific energy required to excite K-shell line radiation from high-atomic-number Z pinches, (b) properly match the load to high-current (ges 10 MA) generators, and (c) develop continuum-radiator concepts that require ionizing beyond the optimum He/H-like state for K-shell emission. Large-initial-diameter implosions are also required for efficient coupling between the Z pinch and a generator with a long current rise-time (> 100 ns) and, thus, desirable lower voltage. The expected deleterious effects on final pinch formation associated with the increase in instability growth at larger diameter (e.g., Rayleigh-Taylor) can be mitigated by using an initial mass profile that is strongly peaked on axis. We review recent experiments with, and numerical simulations of, 12-cm initial diameter, argon gas-puff Z-pinch implosions. The experiments were carried out on the Decade Quad at implosion times of 230 to 250 ns and on Saturn at 200 to 215 ns. Both generators provide peak currents of about 6 MA. The argon K-shell yield was 80 kJ on DQ. On Saturn, we obtained 75 kJ of K-shell yield, roughly twice the maximum argon K-shell yield previously obtained there with a several-cm diam. nozzle at < 100 ns implosion times. Numerical simulations are in agreement with the measurements.