Transforming dielectric coated tungsten and platinum wires to gaseous state using negative nanosecond-pulsed-current in vacuum

Wu, Jian; Li, Xingwen; Wang, Kun; Li, Zhenghong; Yang, Zefeng; Shi, Zongqian; Jia, Shenli; Qiu, Aici

doi:10.1063/1.4902364

Cited by 24 publications

(14 citation statements)

References 18 publications

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“…In the WE experiments reported in [4], [81], [82], [123], [125], [126], [150], [151], and [163]- [171], I max was in the 3-5 kA range and the quarter period of the (sinusoidal) current pulse was in the 300-500 ns range; hence, the LC pulser provided (d I/dt) av that ranged between 10 and 70 A/ns. The use of LC pulsers with low-inductance, low-capacitance (0.2-1 nF) capacitors made it possible to increase (d I/dt) av to 100-170 A/ns [19], [172]- [175]. However, in these cases, the intrinsic impedance of the driver became comparable to the resistance of the exploded wire, and the actual rate of the wire current is decreased.…”

Section: Experimental Arrangements For Studying the We In Vacuummentioning

confidence: 99%

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Wire Explosion in Vacuum

Oreshkin

Baksht

2020

IEEE Trans. Plasma Sci.

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This article presents a review of experimental and theoretical studies devoted to the processes that occur during explosions of wires in vacuum when the current densities in the wire are of the order of 10 8 A/cm 2 and the current density rise rates are no less than 10 15 A/(cm 2 • s). The theoretical background is focused on the transformation of the wire metal into ionized plasma. In particular, the basic physical notions used to describe wire explosions (WEs; state diagram, current action integral, and metal conductivity changes in phase transitions) are given; magnetohydrodynamic equations are described which are used to simulate WEs, and the simulation predictions are discussed together with their reliability. Extensive experimental data on WEs in vacuum are presented which made it possible to describe the corona and core formation and the development of electrothermal instabilities in the core. The data on the energy deposited in a wire exploding in vacuum reported by different authors are compared. In conclusion, problems are discussed that require additional experimental investigations, namely, the role of metastable states in a WE and the mechanism by which the core is shunted.

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Section: Experimental Arrangements For Studying the We In Vacuummentioning

confidence: 99%

“…This type of voltage divider was proposed by Fletcher [183]. Voltage dividers of this type were used in the WE experiments reported in [19], [174], [175], and [184]. For a capacitive voltage probe, the response to a unit pulse can be described approximately as…”

Section: Experimental Arrangements For Studying the We In Vacuummentioning

confidence: 99%

Wire Explosion in Vacuum

Oreshkin

Baksht

2020

IEEE Trans. Plasma Sci.

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“…Tungsten wires with a diameter of 15 lm and a 2 lm thickness polyimide coating were used here based on our previous studies. 10 These wires had a length of 1 cm and a gap distance of 1 mm, the same configuration of the aluminum wires described above. The mass of the polyimide coating was less than 2% of the tungsten, which could be negligible.…”

Section: Polyimide Coated Tungsten Wiresmentioning

confidence: 99%

“…10 Here, two parallel wires with a half-length (1 cm) were tested, keeping the total mass unchanged. Special care had been taken to ensure that both wires had a similar electrical contact with the electrodes.…”

Section: Experimental Setupsmentioning

confidence: 99%

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Atomization and merging of two Al and W wires driven by a 1 kA, 10 ns current pulse

et al. 2016

Physics of Plasmas

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Possibility of preconditioning of wires in wire array Z-pinch loads by an auxiliary low-level current pulse was investigated in experiments with two aluminum or two polyimide-coated tungsten wires. It was found that the application of a 1 kA, 10 ns current pulse could convert all the length of the Al wires (1 cm long, 15 μm diameter) and ∼70% of length of the W wires (1 cm long, 15 μm diameter, 2 μm polyimide coating) into a gaseous state via ohmic heating. The expansion and merging of the wires, positioned at separations of 1–3 mm, were investigated with two-wavelength (532 nm and 1064 nm) laser interferometry. The gasified wire expanded freely in a vacuum and its density distribution at different times could be well described using an analytic model for the expansion of the gas into vacuum. Under an energy deposition around its atomization enthalpy of the wire material, the aluminum vapor column had an expansion velocity of 5–7 km/s, larger than the value of ∼4 km/s from tungsten wires. The dynamic atomic polarizabilities of tungsten for 532 nm and 1064 nm were also estimated.

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Effects of load voltage on voltage breakdown modes of electrical exploding aluminum wires in air

Yang

et al. 2015

Physics of Plasmas

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The effects of the load voltage on the breakdown modes are investigated in exploding aluminum wires driven by a 1 kA, 0.1 kA/ns pulsed current in air. From laser probing images taken by laser shadowgraphy, schlieren imaging, and interferometry, the position of the shockwave front, the plasma channel, and the wire core edge of the exploding product can be determined. The breakdown mode makes a transition from the internal mode, which involves breakdown inside the wire core, to the shunting mode, which involves breakdown in the compressed air, with decreasing charging voltage. The breakdown electrical field for a gaseous aluminum wire core of nearly solid density is estimated to be more than 20 kV/cm, while the value for gaseous aluminum of approximately 0.2% solid density decreases to 15–20 kV/cm. The breakdown field in shunting mode is less than 20 kV/cm and is strongly affected by the vaporized aluminum, the desorbed gas, and the electrons emitted from the wire core during the current pause. Ohmic heating during voltage collapses will induce further energy deposition in the current channel and thus will result in different expansion speeds for both the wire core and the shockwave front in the different modes.

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Transforming dielectric coated tungsten and platinum wires to gaseous state using negative nanosecond-pulsed-current in vacuum

Cited by 24 publications

References 18 publications

Wire Explosion in Vacuum

Wire Explosion in Vacuum

Atomization and merging of two Al and W wires driven by a 1 kA, 10 ns current pulse

Effects of load voltage on voltage breakdown modes of electrical exploding aluminum wires in air

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