Comparisons of neon implosions driven by 0.1 to 0.1-μs rise-time currents

Neon plasmas created by Z-pinch implosions driven by different rise-time currents are studied. A plasma opening switch (P0S) is used to adjust the current rise time. Neon radiations in the soft x-ray, extreme ultraviolet (XUV), and near ultraviolet (UV) are measured and compared with atomic theory to determine the ionization state, density and temperature the plasma. The dependence of these quantities on current rise time, as well as on current magnitude and neon mass, are investigated. The neon plasma is formed by imploding a 4-cm long cylindrical gas puff, ejected from a 1-cm diam nozzle, with a currents of up to 300-kA and 900-ns quarter period. With a P0S, the current rise time can be reduced to 50 - 200 ns. Qualitative features of the imploded plasma are determined from pinhole-camera and filtered x-ray diode measurements. Without the P0S, K-shell x-ray (1 keV) images indicate emission from localized spots, while open-shutter (UV and visible) pictures show axial non-uniformities. Also, successive inductive drops in the current coincident with peaks in the K-shell and XUV emissions indicate that the first implosion is followed by a second implosion. With the P0S, the K-shell emission is reduced an order of magnitude, and open-shutter pictures indicate more uniform axial emission. Time-resolved structure in the XUV emission is observed but does not appear to be directly correlated with temporal variations in the current.