Radiation properties and implosion dynamics of planar and cylindrical wire arrays, asymmetric and symmetric, uniform and combined X-pinches on the UNR 1-MA zebra generator

Abstract

In the following experiments, we studied implosions of different wire arrays and X-pinches produced on the 1-MA Zebra generator at the University of Nevada, Reno. Diagnostics included both spatially-resolved and time-gated X-ray imaging and spectroscopy, and laser probing. In particular, we compared planar wire arrays, to which little energy could be coupled via the conventional magnetic-to-kinetic conversion mechanism, to cylindrical wire arrays of comparable dimensions and mass. The planar wire arrays were shown to radiate much higher peak power and more energy in subkiloelectronvolt and kiloelectronvolt spectral ranges than cylindrical wire arrays. We tested the theoretical conjecture that enhanced resistivity due to the small-scale inhomogeneity of wire-array plasmas has a major effect on dynamics, energy coupling and radiation performance of wire-array Z-pinches. The study of Al, Alumel, and W cylindrical wire arrays shows a wide variety of characteristic behaviors in plasma implosions discussed hereinafter. Additional experimental results for symmetric and asymmetric, uniform stainless steel, Cu, Mo, combined Al/Mo, Mo/Al, Al/W, W/Al, and Mo/W X-pinches are also presented. New data for the total radiation yield are obtained. The planar structures of X-pinch plasma and the corresponding electron beam was observed for most of X-pinches. The generation of hot spots along original wires positions-cooler than those from the cross-wire region-and arc structures with hot spots between

Wire ablation dynamics model and its application to imploding wire arrays of different geometries

“…(9). If the condition (11) can not be fulfilled, then no filament splitting for nth array wire will be performed after t j−1 , and the ablation of the nth wire will be completed at t = t (n) a , where t j−1 < t (n) a < t j .…”

“…In its turn, the implosion character depends on the planar array geometry. Below in this section we shall consider single planar wire array (SPWA) and double planar wire array (DPWA), built of a single wire row [8,9] and two wire rows [11] respectively. Two Zebra shots No.…”

“…This search has inspired several extensive programs for studying the wire array implosion at 1 MA currents at the university based laboratories, first at the Imperial College in UK [6,7] and later at the University of Nevada, Reno (UNR) [8][9][10][11] and Cornell University (see, for example, Ref. [12]) in the United States.…”

“…Since that time numerous experiments have demonstrated that among all the other low-wirenumber loads the planar wire arrays yield the highest x-ray radiation energies and powers [9][10][11]. Two years later, the single planar array loads have been successfully tested at 3 − 5 MA currents on Saturn generator at SNL [5,13,14].…”

The importance of EBIT data for Z-pinch plasma diagnostics

“…Currently, x-ray spectra of X-pinches are collected and studied at dif ferent pulsed power machines, for exam ple, at the university-scale 1 MA Zebra device at University of Nevada, Reno [8][9][10][11][12] and Cobr a f acility a t Cornell University (CU ) [11][12], as well as at smaller devices such as at a 450 kA pulsed power device at C U [13]. It was shown that X-pinch plasm a can r each tem peratures of 2-3 keV and densities up to 10 23 cm -3 .…”