The dynamics of bifurcating bright-spots in fiber Z-pinch plasmas

Results are presented from the diagnosis of the optical and x-ray emission from ''bright-spots'' in carbon fiber Z-pinch experiments using the MAGPIE (Mega-Ampere Generator for Plasma Implosion Experiments) generator [I. H. Mitchell et al., Rev. Sci. Instrum. 67, 1533 (1996)]. Inhomogeneities evolve very rapidly within the plasma with bright-spots becoming detectable after 15-20 ns. After a short (similar to 4 ns) duration formation phase, these bright-spots exhibit highly dynamic behavior. Bifurcation of the bright-spots is observed giving rise to rapid axial motion at 1-3 x 10(5) ms(-1). The post-bifurcation bright-spots persist for up to 49 ns. Analysis of cross-filtered, time integrated, x-ray pinhole images yield bright-spot parameters during the formation phase (diameter similar to 80 mu m, temperature 250-300 eV, ion number densities similar to 2 x 10(26) m(-3)). With a Spatial resolution of 175 mu m, the strong temperature and density gradients within the post-bifurcation spots can be resolved in gated x-ray images with 2 ns exposure times. After the dynamic phase of bright-spot evolution, the pinch enters a quiescent phase where the time scale for evolution is much longer. (C) 1997 American Institute of Physics.