The implosion dynamics and emission characteristics of Al liner-on-wire implosions

Previous experiments at 0.1 TW level have shown that stability and X-ray em ission of fast Z-pinch could be significantly improved by imploding an AI v apor jet onto a very thin coaxial wire (Wessel et al., 1992). Here we prese nt the first results of an Al Z-pinch using a similar liner but at mega-amp ere level. The pinch is driven by AMBIORIX facility, a 2 TW, 0.5 Omega, 2 M A, and a 50-ns pulse-line generator. We study the effect of an Al wire and its diameter (20-50 mum) on the implosion dynamics, on X-ray yield, on-axis magnetohydrodynamics (MHD) stability, and on Rayleigh-Taylor instability o f the column at stagnation. Analysis of an Al jet on Al wire shots demonstr ates that X-ray yield due to emission processes in the H- and He-like ioniz ation stages (i.e., the K-shell) is enhanced, relative to the ones with Al jet only. The wire leads also to a better symmetrization of the implosion, and to better reproducibility of the shots. X-ray signals exhibit two simil ar pulses, 10-ns-wide and separated by 15 ns. To discern spectrally the ori gin of each pulse, further experiments have been performed with stainless s teel wire (25 mum in diameter). Results show that liner and wire radiate si multaneously and contribute to both pulses. Full analysis of a typical Al j et on Al wire shot, using detailed collisional-radiative equilibrium (CRE) model is given in this paper. A sketch of the pinch at stagnation, with a c old dense core embedded in a hot low density corona, reproduces well all fe atures of X-ray emission.