IMPROVED LARGE-DIAMETER WIRE ARRAY IMPLOSIONS FROM INCREASED WIRE ARRAY SYMMETRY AND ON-AXIS MASS PARTICIPATION

Aluminum wire array, Z-pinch experiments have been performed on an 8 M A generator using arrays consisting of 24, 30, and 42 wires. These exp eriments were designed to scan through a region of (array mass, implos ion velocity) space in which greater than 30% conversion of the implos ion kinetic energy into K-shell x rays was predicted to occur [Thornhi ll et al., Phys. Plasmas 1, 321 (1994)]. Array masses between 120 and 2050 mu g/cm were used in these experiments. An analysis of the x-ray data taken using 24 wire arrays, shows a one-to-one correspondence bet ween the observed kilo-electron-volt yields (5-64 kJ) and the fraction of initial array mass (0.3%-60%) that is radiating from the K shell. The 30 and 42 wire experiments demonstrated that tighter pinches with increased radiated powers were achieved with these larger wire number, improved symmetry arrays. In addition, increases in the implosion mas s and array diameter in the 30 and 42 wire number cases resulted in in creases in the radiated yield over the corresponding 24 wire shots, up to 88 kJ, which can be interpreted as due to improved coupling and th ermalization of the kinetic energy. Moreover, spectroscopic analyses o f the 30 and 42 wire experiments have shown that the increased wire nu mbers also resulted in K-shell radiating mass fractions of greater tha n 50%. (C) 1998 American Institute of Physics. [S1070-664X(98)03606-4]