(a) Cut-away view of the three-dimensional model representing the experimental radial foil setup, mounted on the anode (A) and cathode (K) of COBRA. The inset shows a larger view of the actual layout. (b) Schematic diagram of currents, magnetic fields, and force distribution. (c) A laser shadowgraph taken 65 ns after the start of the current rise shows the actual setup with the pin cathode at the bottom of the image. The large horizontal dark band in the bottom half of the picture is the shadow of the foil holder. The foil is located above. Foil lift, surface plasma, and miniature Bdot probes are clearly visible.
Schematic diagrams representing the dynamics of a radial foil explosion with pin cathode. Most of the currents run inside the dense plasma, which also carries most of the initial foil mass. A secondary, less dense plasma spreads above the geometrical foil center of the foil and carry secondary currents. Finally the background plasma carries currents necessary to close any electrical circuit.
(a) Generator current with the approximate times corresponding the schematic diagrams a–g of Fig. 2, (b) voltage and current time derivative, (c) the PCDs, and (d) Bdot probe signals for shot no. 1568. The radiation power was scaled onto a 1 m radius sphere to eliminate measurement dependence with photodetector size and location. The vertical dashed line indicates limit between the quiet and energetic regimes.
pin hole XUV quadrant camera pictures with 10 ns between frames (exposure time: ). The first picture (i.e., a) was taken 50 ns into shot no. 1466. We used an artificial color scheme to highlight the different features present in the early dynamics of the foil. The overall intensity is arbitrary. Due to possible pin hole blockage from debris, the absolute correspondence between radiation and color scale may vary in each picture.
Schlieren shadowgraph taken 70 ns after current rise (shot no. 1359) showing the central jet and surface plasma.
Visible light streak camera data for shot no. 1360. The camera looks at the vertical axis of the foil. The height indicates the distance from the foil surface.
Laser shadowgraphs of the different phases in bubble formation for shots (a) no. 1453 taken at , (b) no. 1454 at , (c) no. 1357 at , (d) no. 1358 at , and (e) no. 1356 at .
pin hole XUV quadrant camera pictures showing the bubble explosion and the ejection of the plasma projectile for shot no. 1360 [(a)–(e)]. Due to possible pin hole blockage from debris, the actual color scale in each picture can vary.
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