Figure 1

(a) Photograph of a 20 mm diameter, 300-wire array before installation. (b) Diagram of the $Z$ facility, showing the energy storage section, intermediate storage capacitors, pulse forming lines, and magnetically insulated transmission lines used to deliver current to the wire array. (c) Vertical slice through the load region hardware. The array is surrounded by a return-current canister with nine slots in the horizontal plane for diagnostic access. (d) Conceptual diagram of the spherical crystal x-ray backlighting diagnostic. The crystal acts as an x-ray mirror with a $\le 0.5\mathrm{e}\mathrm{V}$ spectral bandpass. The detector is placed at the focal point of the object (the array center in these tests). (e) A horizontal slice through the center of the array showing the field of view of the arrays allowed by the return-current canister slots.Reuse & Permissions

Figure 2

Data for 20 mm diameter tungsten wire arrays with 300 $7.4\mu \mathrm{m}$ W wires. The machine and load currents are plotted as red and green curves, respectively, along with the normalized x-ray power from a typical test (z1049), shown in blue. The trajectory for a thin shell with the same total mass (2.5 mg) is overlaid. Also plotted are bars corresponding to the radially outermost and innermost positions of the outer edge of the imploding mass as seen via radiography (green) and optical shadowgraphy (blue).Reuse & Permissions

Figure 3

(a)–(f) Expanded 1.865 keV radiographs showing portions of the edge of 2.5 mg arrays at 45, 70, 81, 89, 95, and 115 ns, respectively. Parts (a)–(c) include artificial radiographs of baseline (STD) and modified ($\sigma /10$) ALEGRA simulations at those times. The modified simulations artificially reduced the electrical conductivities in the cores by a factor of 10 as a method for reducing the wire mass ablation rate as discussed in the text. Axial perturbations, faintly visible as early as frame (b), develop and begin to correlate azimuthally while the array is “wirelike” and seed instability growth later, resulting in trailing mass as in (f). The color scale shown is linear in units of transmission. The arrays in (a) and (b) were slightly twisted. (g)–(j) 1.865 keV radiographs from assorted 20 mm diameter, 300-wire arrays, all taken when the load current was 8.5–8.8 MA. Initial wires were (g) $7.4\mu \mathrm{m}$ W, (h) $11.5\mu \mathrm{m}$ W, (i) $36\mu \mathrm{m}$ Al, and (j) $20\mu \mathrm{m}$ Cu. In each case the vertical wavelength was within 20% of the wire core diameter at the time of the image [cores nearly merged in (i)]. A linear black-to-white (0%–100%) scale with transmission was used.Reuse & Permissions

Figure 4

1.865 keV radiographs of the 2.5 mg array from Fig. 2. (Top) pretest radiograph from test z1055 illustrating the field of view. (Middle) complete radiograph image test z1050 showing the outer edge of the imploding mass in addition to the expanded region shown in Fig. 3f. (Bottom) radiograph from test z1054 taken at 121 ns illustrating the highly unstable trailing mass. In the z1050 and z1054 radiographs, the image regions blocked by slots are marked in green and the position of a 0D thin shell at each time is marked in red.Reuse & Permissions

Figure 5

(a)–(e) Sequence of optical shadowgraphy images from a 20 mm diameter, 300 $11.5\mu \mathrm{m}$ W wire-array test (z1176) illustrating the growth of instabilities in the low-density trailing mass. (f) Plots of the vertical wavelength and horizontal perturbation amplitudes for five of the six frames from this test. All times shown are relative to peak x rays. Other tests show that this view is empty at the time of peak x rays.Reuse & Permissions

Figure 6

(a) 6.151 keV radiograph at 123 ns. The white spots are from time-integrated self-emission at 6.151 keV. (b) Streaked self-emission (400–450 eV) from the same test showing the spatial distribution of the self-emission. (c) Spatially integrated line out of the x-ray streak camera (XRSC) data plotted alongside a comparable x-ray diode (XRD) signal.Reuse & Permissions