Inverse polarity effect for electrical explosion of fine metal wires in vacuum

It has been experimentally demonstrated that the geometry of a high-voltage electrode strongly affects the magnitude and structure of energy deposition into a thin metal wire before breakdown in vacuum. Additionally, two-dimensional electrostatic simulations provide evidence that the direction and magnitude of the radial electric field on a wire surface are dependent on the geometry of the electrodes. Increasing the size of the ground electrode leads to an increase in the radial electric field, but does not affect the direction of this field. However, modifications of the high-voltage electrode geometry alter the direction and magnitude of radial electric fields on the wire surface. Thus, the hot and homogeneous electrical explosion of a thin metal wire in vacuum can be realized with proper design of the wire's holding electrodes and independent from the polarity of the high-voltage electrode.

Figure 1

Vacuum chamber with coaxial target unit.

Figure 2

Shadowgrams for Ti, W, W-polyimide coated, Mo, Pt, Pd, Al, Au, Cu, and Ni wires 1 cm long for normal (a), ground-cup enhanced (b), and high-voltage-cup enhanced (c) electrode geometry.

Figure 3

Current-voltage waveforms for exploding W wire 13 μm in diameter and 1 cm long for normal (a), ground-cup enhanced (b), and high-voltage-cup enhanced (c) geometry of electrodes.

Figure 4

Distribution of electric field for normal (a), ground side with cup $\mathrm{ID}=10\mathrm{mm}$ (b), and high-voltage side with cup $\mathrm{ID}=10\mathrm{mm}$ (c) geometry of electrodes. Wire diameter is 12 μm and length is 1 cm.

Figure 5

Radial electric field profiles along the wire surface for ten different electrodes.

Figure 6

Axial and radial electric field distributions for two wires with different diameters (a); radial electric field on different distances from wire surface (b).

Figure 7

Wire-array holders: standard (a) and alternative design with radial field inverter (b).