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Electrical explosion of wires (EEW) can be utilized as an efficient method to prepare nanopowders of metal, metal oxide, metal alloy, and so on, and the behavior of exploding wires varies greatly with different load and circuit parameters. In this paper, the relationship between discharge modes of EEW and load parameters (length and diameter) was studied during the preparation of Al nanopowders via EEW in argon gas. The experimental results showed that with fixed wire length and increasing diameter, the EEW will successively show the feature of current pause, current dwell, current pause again, and finally “being matched”; and for fixed wire diameter, there is a “critical length” of wire which divides the current-dwell mode and the current-pause mode. The critical length as a function of wire diameter peaks between 0.2 and 0.3 mm for the charging voltage of 11.5–20 kV (2.6- $\mu \text{F}$ capacitor); and the specific heat (deposited energy divided by sublimation energy) of wires was approximately 1 at the peaks. [ABSTRACT FROM AUTHOR]

The discharge plasma channel (DPC) evolution process is observed by taking time-series self-emission intensified charge-coupled device (iCCD) photos and simultaneous shadow images. By adding neutral density filters before iCCD, the subtle structure of the DPC self-emission is observed. It is interesting that a treelike structure is observed soon after the voltage breakdown. Long exposure time photos demonstrate that this structure existed for hundreds of nanoseconds. An inner homogeneously luminous column arises latterly, forming a two-layer self-emission structure. Then, this column gradually occupies the whole DPC. Shadow images show that the expanding DPC maintains good axial uniformity, manifesting the long-standing uneven treelike structure only has limited impact on the energy distribution and the expansion process. The calculated expansion rate reaches its maximum value (4.75 km/s) not at the power peak, but 0.24 $\mu \text{s}$ after that. Then, the expansion rate undergoes fast drop and slow decline. In addition, it seems that the distributions of related plasma parameters experience an evolution from nonuniform to uniform. [ABSTRACT FROM AUTHOR]

Based on electrical and optical diagnostics and electrostatic calculations, the relationship between distribution of radial electric field and energy deposition of electrically exploded wires in vacuum was investigated. Copper plates with different diameters were used to modify the distribution of radial electric field along wire surface in the experiments. The calculated radial electric field showed good consistency with the wire core outline in optical images, and there is a saturated positive correlation between maximum specific energy (Esm) and averaged radial field strength over the wire length. It can be concluded that the direction and amplitude of radial electric field significantly affects Esm and dominates the structure of energy deposition. [ABSTRACT FROM AUTHOR]

The evolution of single- and dual-wire Z-pinch of 8- \(\mu \) m W was investigated by X-ray backlighting using an X-pinch X-ray source. The experiments were carried out on the pulsed-power generator PPG-I (400 kA/500 kV/100 ns), which was designed and constructed by the Department of Electrical Engineering of Tsinghua University. To scale the mass density distributions at different explosion time, a mass step wedge including eight tungsten layers was fabricated and inserted between the object Z-pinch and the X-ray film. By a large number of imaging experiments, the physical images of coronal plasma formation and interwire plasma merging were obtained. Based on the X-ray photos of 8- \(\mu \) m W and mass step wedge, the mass density distributions at different explosion time were drawn, and the conductance curve of time dependence of 8- \(\mu \) m W was also calculated using waveform of voltage and current. [ABSTRACT FROM PUBLISHER]

X-ray point source generated by X-pinches on the compact pulsed power device PPG-2 of Tsinghua University is well suited for phase-contrast imaging of weakly X-ray absorbing organism. Using six sets of photoconducting devices each covered by a filter of specific transmittance curve, the X-ray radiation energy spectra from Mo-wire and W-wire X-pinches were experimentally studied. It was found that X-ray with photon energy less than 2 keV takes the main part, about 70% of the total radiation, and the energy spectrum obeys exponential distribution; the bumps in the intervals of 2–3 keV for Mo and 4–6 keV for W may be attributed to the existence of line spectra such as L-shell of Mo and M-shell of W. Compared with the results of other groups, our measured X-ray energy yield were several times higher. The reasons may be attributed to differences in load current rising rate or different responses of X-ray detectors. [ABSTRACT FROM PUBLISHER]

Wire explosion is the initial stage of the development of wire array Z-pinch load driven by high pulsed current. Based on the pulsed power generator PPG-1 (400 kA/100 ns), the process of 10- \(\mu \) m-W wire explosion at tens of kiloamperes was investigated. The time sequence images of wire explosion were obtained by X-ray backlighting with X-pinch X-ray point source, and the mass density distribution of the exploding wire at a certain time was calibrated by method of grayscale contrast based on a particular step wedge filter. By image processing of the time sequence images of wire explosion, the evolution of mass density distribution of wire explosion was presented. [ABSTRACT FROM PUBLISHER]