Studies of late time behavior of exploding wires using x-ray backlighting
Fine W, Mo, Al, NiCr, Au, Ag, Ti, and other wires, exploded by a 4.5 kA amplitude, 1.4 {micro}s, have been imaged using direct (point-projection) x-ray backlighting as late as 12 {micro}s after the start of the current pulse. The exploded wires, which ranged from 7.5 W to 13.5 {micro}m W, Au, Al and Mo to 25 {micro}m Ti and NiCr, were located about 6 cm away from two Mo X-pinch x-ray backlighter sources. The X-pinches are placed in parallel between the output electrodes of the 450 kA, 100 ns XP pulser at Cornell, each thereby producing a sub-nanosecond x-ray pulse. The source size is small enough to permit micron-scale spatial resolution images of the exploding wires on x-ray film. Changing the relative timing between the 4.5 kA current source and the XP pulser varied the image time. Wires were typically pulsed in pairs, reducing the peak current per wire accordingly. The behavior of the exploded wires on the microsecond time scale depends upon the material. For example, the W wires initially expand slowly (for {approximately} 1 {micro}s), and then quickly develop a fine structure in their interior. A more rapid expansion phase follows for a few {micro}s leading to a few hundred {micro}m diameter exploded wire by the time the current damps away. After that, the remnant wire core appears to break up into droplets. Mo and NiCr wires behave similarly. By contrast, high initial conductivity wires, such as Au and Ag, pass through a highly structured phase very quickly and form a rapidly expanding, radially symmetric vapor/plasma cloud in just a few hundred nanoseconds with a peak current of 2 kA per wire. By 2 {micro}s after current initiation, Au wires have formed a several hundred {micro}m diameter vapor/plasma which is reasonably axially uniform over the length of the wires except near the ends. The implications of these results to experiments on 10--20 MA pulsers and to code validation will be discussed.
- Research Organization:
- Cornell Univ., Ithaca, NY (US)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 20050986
- Resource Relation:
- Conference: 1999 IEEE International Conference on Plasma Science, Monterey, CA (US), 06/20/1999--06/24/1999; Other Information: PBD: 1999; Related Information: In: The 26th IEEE international conference on plasma science, 342 pages.
- Country of Publication:
- United States
- Language:
- English
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