Increased x-ray power generated from low-mass large-number aluminum-wire-array Z-pinch implosions

A Saturn accelerator study of annular, aluminum-wire-array, Z-pinch implosions in the calculated high-wire-number plasma-shell regime [Phys. Rev. Lett. 77, 5063 (1996)] shows that a factor of 2 decrease in pulse width and an associated doubling of the total radiated x- ray power occurs when the mass of 12 mm radius, 2 cm long array is reduced from above 1.9 mg to below 1.3 mg. The study utilized extensive time- and space-resolved measurements to characterize the implosion over the mass range 0.42-3.4 mg. Eulerian radiation-magnetohydrodynamic-code simulations in the r-z plane agree qualitatively with the measurements. They suggest that the pulse-width decrease with mass is due to the faster implosion velocity of the plasma shell relative to the growth of the shell thickness that arises from a two-stage development of the magnetic Rayleigh-Taylor instability. Over the bulk of the mass-range explored, the variation in K-shell (lines plus free-bound continuum) yield is in qualitative agreement with simple K-shell radiation-scaling models. These models indicate that the doubling of the measured K-shell yield, which also occurs for masses below 1.3 mg relative to masses above 1.9 mg, arises from increased plasma temperature. (C) 1998 American Institute of Physics. [S1070-664X(98)01410-4].