Wire array Z-pinch insights for enhanced x-ray production

Comparisons of measured total radiated x-ray power from annular wire-array z-pinches with a variety of models as a function of wire number, array mass , and load radius are reviewed. The data, which are comprehensive, have pro vided important insights into the features of wire-array dynamics that are critical for high x-ray power generation. Collectively, the comparisons of the data with the model calculations suggest that a number of underlying dy namical mechanisms involving cylindrical asymmetries and plasma instabiliti es contribute to the measured characteristics. For example, under the gener al assumption that the measured risetime of the total-radiated-power pulse is related to the thickness of the plasma shell formed on axis, the Heurist ic Model [IEEE Trans. Plasma Sci. 26, 1275 (1998)] agrees with the measured risetime under a number of specific assumptions about the way the breakdow n of the wires, the wire-plasma expansion, and the Rayleigh-Taylor instabil ity in the r-z plane, develop. Likewise, in the high wire-number regime (wh ere the wires are calculated to form a plasma shell prior to significant ra dial motion of the shell) the comparisons show that the variation in the po wer of the radiation generated as a function of load mass and array radius can be simulated by the two-dimensional Eulerian-radiation-magnetohydrodyna mics code (E-RMHC) [Phys. Plasmas 3, 368 (1996)], using a single random-den sity perturbation that seeds the Rayleigh-Taylor instability in the r-z pla ne. For a given pulse-power generator, the comparisons suggest that (1) the smallest interwire gaps compatible with practical load construction and (2 ) the minimum implosion time consistent with the optimum required energy co upling of the generator to the load should produce the highest total-radiat ed-power levels. (C) 1999 American Institute of Physics. [S1070-664X(99)915 05-7].