Experimental investigation on the energy deposition and expansion rate under the electrical explosion of aluminum wire in vacuum

Abstract

Experimental investigations on the electrical explosion of aluminum wire using negative polarity current in vacuum are presented. Current pulses with rise rates of 40 A/ns, 80 A/ns, and 120 A/ns are generated for investigating the influence of current rise rate on energy deposition. Experimental results show a significant increase of energy deposition into the wire before the voltage breakdown with the increase of current rise rate. The influence of wire dimension on energy deposition is investigated as well. Decreasing the wire length allows more energy to be deposited into the wire. The energy deposition of a 0.5 cm-long wire explosion is ∼2.5 times higher than the energy deposition of a 2 cm-long wire explosion. The dependence of the energy deposition on wire diameter demonstrates a maximum energy deposition of 2.7 eV/atom with a diameter of ∼18 μm. Substantial increase in energy deposition is observed in the electrical explosion of aluminum wire with polyimide coating. A laser probe is applied to construct the shadowgraphy, schlieren, and interferometry diagnostics. The morphology and expansion trajectory of exploding products are analyzed based on the shadowgram. The interference phase shift is reconstructed from the interferogram. Parallel dual wires are exploded to estimate the expansion velocity of the plasma shell.

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 ).…”