Initial Results for a 20 cm Diameter, Structured Argon Z-pinch on the Sphinx Machine

Summary form only given. The Sphinx generator uses LTD technology to produce >4 MA pulsed power to drive large diameter (>14 cm), long implosion time (>600 ns) aluminum wire array Z-pinch implosions. Recently, an argon gas puff load was developed for use on Sphinx. Specifically, we prepared a triple plenum, triple valve system that drives (1) a central 1 cm diameter gas column, (2) a wide "shell" flow between diameters of 1 and 9 cm, and (3) an outer wide "shell" over the diameter range 9 to 20 cm. A large initial diameter is needed to get a long implosion time. Then one can take advantage of the current drive of the generator while still achieving a high enough implosion velocity to excite argon. 0D modeling shows that the optimum implosion time will be about 500 ns, more than a factor of two larger than previous experience with argon at many megamp currents. Initial, limited testing on Sphinx produced remarkably tight pinches (~2 mm in the K-shell) with <= 8 ns overall pulse widths. Corrected for zipper, the intrinsic K-shell pulse width was under 4 ns. As seen in optical framing images, the implosions were not hopelessly unstable. However, there clearly remains a need for additional refinements to the gas puff system to make it easier to operate and to optimize for implosion time (less than 540 ns) and radial gas distribution (more on-and near-axis mass). The un-optimized system produced ~3 kJ of argon K emission.