Overview of Recent Large-Diameter, Gas-Puff Z-Pinch Research

Summary form only given. Large radius implosions of gas-puff Z-pinches are the subject of intense investigation. Such implosions are needed to achieve the high specific energy required to excite K-line radiation from high-atomic-number (e.g. Z>26) radiators, for proper matching with high-current (~10 MA and higher) generators, for continuum radiator concepts that require heating beyond the optimum He/H-like state for K-shell emission, and to utilize more efficiently long-current-rise-time (>100 ns) generators. The key physics issues involve R-T instability mitigation and energy coupling to the radiating plasma by the choice of the initial radial and axial mass profiles. In this talk, recent experimental and theoretical progress in this work are reviewed, including achieving 20-kJ of argon K-shell radiation from a 12-cm-diam. nozzle at 3.5 MA and 200-ns implosion time. The primary experimental testbeds are double-EAGLE (long-pulse mode, 3.5 MA, 210 ns) at TPSD and the Decade Quad (6 MA, 300 ns) at Arnold Engineering Development Center. Supporting experiments on Hawk (0.6 MA, 300 ns) at NRL are also reviewed. Besides the usual soft X-ray and electrical diagnostics, we have developed methods for measuring: the initial gas profile, the L-shell emitting region, the UV and continuum, the initial current flow paths, and the 2-D evolution of the pinch. Recent developments in 2-D radiation-hydrodynamic simulations are also reviewed