Radiative properties of high wire number tungsten arrays with implosion times up to 250 ns

High wire number, 25-mm-diameter tungsten wire arrays have been imploded on the 8-MA Saturn generator [R. B. Spielman , AIP Conference Proceeding 195, 3 (American Institute of Physics, Woodbury, NY 1989)], operating in a long -pulse mode. By varying the mass of the arrays from 710 to 6140 mu g/cm, im plosion times of 130-250 ns have been obtained with implosion velocities of 50-25 cm/mu s, respectively. These Z-pinch implosions produced plasmas wit h millimeter diameters that radiated 600-800 kJ of x-rays, with powers of 2 0-49 TW; the corresponding pulsewidths were 19-7.5 ns, with risetimes rangi ng from 6.5 to 4.0 ns. These powers and pulsewidths are similar to those ac hieved with 50-ns implosion times on Saturn. Two-dimensional, radiation-mag netohydrodynamic calculations indicate that the imploding shells in these l ong implosion time experiments are comparable in width to those in the shor t-pulse cases. This can be due to lower initial perturbations. A heuristic wire array model suggests that the reduced perturbations, in the long-pulse cases, may be due to the individual wire merger occurring well before the acceleration of the shell. The experiments and modeling suggest that 150-20 0 ns implosion time Z-pinches could be employed for high-power, x-ray sourc e applications. (C) 1999 American Institute of Physics. [S1070-664X(99)0180 8-X].