Factors affecting the exploding characteristics of tungsten wires with negative-polarity current

Abstract

This paper presents the experimental results of electrical explosion of tungsten (W) wires in a vacuum using a negative-polarity current pulse with a magnitude of 1–2 kA. Uniform wire explosions with deposited energy sufficient for full vaporization are achieved for 0.5 cm-long W wires with the help of dielectric coating and soldering. Experimental results show that the dielectric coating can give 2–3 times more energy deposition by delaying the voltage breakdown. In order to improve the electrical contact, the metallic oxide on the surface of the electrodes is removed with sandpaper, and then the W wire is soldered to the electrodes. It is found that the improved electrical contact does not have an obvious influence on increasing the energy deposition. However, from the optical images, it can be seen that the uniformity of the wire explosion is greatly improved, especially for the W wire with 2 μm polyimide coating. Therefore, the dielectric coating and good electrical contact are the two key factors to uniformly transform the W wire into a gaseous state. With this method, the uniform wire explosions for longer tungsten wires (1 and 2 cm) are also realized under the same experimental conditions.

Wire Explosion in Vacuum

“…It follows that the current rate for a wire of length 0.5 cm will be considerably higher than that for a wire of length 3 cm. Therefore, in the experiments [19], [188], [189], ε dep should be maximum for wires of length 0.5 cm, as was just observed.…”

“…In the experiments of Sinars et al [151], the driver impedance, estimated from short-circuit waveforms, was close to 100 , that is, it was significantly greater than the wire resistance under Joule heating (about 8-15 ). However, in the experiments of Shi et al [19], [188], [189], the driver impedance was about 10-15 , which is comparable to the resistance of a wire under Joule heating. As a result, in the experiments [19], [188], [189], the current decreased with increasing wire length.…”

“…However, in the experiments of Shi et al [19], [188], [189], the driver impedance was about 10-15 , which is comparable to the resistance of a wire under Joule heating. As a result, in the experiments [19], [188], [189], the current decreased with increasing wire length. It follows that the current rate for a wire of length 0.5 cm will be considerably higher than that for a wire of length 3 cm.…”

“…It turned out that the electric field along the wire at the time of voltage collapse, E coll , and the energy deposited in the wire per unit length, ε dep , were nearly invariant with wire length (see [152,Table II]). At the same time, the experiments performed by Shi et al [19], [188], [189] for bare Al and Cu wires of different lengths: 0.5, 1, and 2 cm, showed that both E coll and ε dep decreased with increasing wire length. The contradiction between these two results is related to the different impedances of the drivers that were used for the WE experiments described in [151] and in [19], [188], and [189].…”

“…At the same time, the experiments performed by Shi et al [19], [188], [189] for bare Al and Cu wires of different lengths: 0.5, 1, and 2 cm, showed that both E coll and ε dep decreased with increasing wire length. The contradiction between these two results is related to the different impedances of the drivers that were used for the WE experiments described in [151] and in [19], [188], and [189]. In the experiments of Sinars et al [151], the driver impedance, estimated from short-circuit waveforms, was close to 100 , that is, it was significantly greater than the wire resistance under Joule heating (about 8-15 ).…”