New x-ray backlighting results on small-scale structure formation, including liquid-vapor foam-like appearance, in exploding wire Z-pinches and X-pinches
Exploding wire and wire array experiments have been carried out in Z-pinch and X-pinch geometry using low current (4.5kA amplitude, 1.4 {micro}s period damped sinusoid) and high current (up to 225 kA, 100 ns) drivers, X-ray backlighter images have been obtained using Mg, Al, Ti, Fe, Ni, NiCr, Cu, brass, Mo, Pd, Ag, Ta, W, Pt, Au, and Ni-coated Ti wires with initial diameters ranging from 7.5 {micro}m (W) to 46 {micro}m (Mg). There were typically two Mo X-pinch x-ray backlighters which generated pulses of <0.5 ns duration from sources small enough to allow resolution of {approximately}1 {micro}m scale structure in the resulting images. In the high current experiments, images of dense cores within coronal plasmas are obtained with higher Z materials including Ni, Cu, Mo, Pd, Ta, W, Pt and Au; with lower Z materials, only the dense cores are visible in the backlighter images. In all cases a fine structure in the interior of the dense cores, and/or surface instabilities are observed. some of the dense cores show a shock-wave-like structure and others show gaps that open up more rapidly than the wire cores are expanding. The wire interiors develop a foam-like liquid-vapor mix, with some of the bubbles breaching the surface and spewing vapor out of the dense core. The low current experiments follow the same general behavior but require several {mu}s to complete the process instead of 50--100ns. With W and Al wire explosions, step wedges have been used to permit calibrated density measurements to be made of the core (W and Al) and coronal (W) plasmas. The two X-pinches have also been used to radiograph each other, yielding high resolution images of the on-axis collapsing z-pinch and minidiode formation at the X-pinch cross point very close to the time of x-ray burst emission.
- Research Organization:
- Cornell Univ., Ithaca, NY (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG03-98DP00217; FG02-98ER54496
- OSTI ID:
- 20067642
- 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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