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 (∼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 1–3×105 ms−1. The post-bifurcation bright-spots persist for up to 40 ns. Analysis of cross-filtered, time integrated, x-ray pinhole images yield bright-spot parameters during the formation phase (diameter ∼80 μm, temperature 250–300 eV, ion number densities ∼2×1026 m−3). With a spatial resolution of 175 μm, the strong temperature and density gradients within the post-bifurcation spots can be resolved in gated x-ray images with 2 ns exposure times. Aft...