Alexey E. Ter-Oganesyan

Analysis of the discharge channel structure upon nanosecond electrical explosion of wires

The structure of the discharge channel during nanosecond wire explosions has been studied using laser probing. Wires of 25μm diameter and 12mm length were exploded in air and vacuum by 10kA current pulse having a 50A∕ns rate of rise. Upon electrical explosion of thin wires in the air, the development of shock waves was observed. The propagation of shock waves was analyzed, and it was possible to draw conclusions on the location of the flow of most of the current in the volume of the discharge channel. This permitted distinguishing between two scenarios (shunting and internal) of the interelectrode gap breakdown development. The scenario depends to a large extent on the properties of the exploding wire material. The same two scenarios are valid upon electrical explosion of wire in vacuum. Moreover, if secondary breakdown develops in the internal scenario, the value of the energy deposition in the wire material during explosion in vacuum may be comparable with that found during explosion in air.

Nanosecond electric explosion of a tungsten wire in different media

The effect of surrounding media of different densities and electric strengths on the heating dynamics of a micron wire during its nanosecond electric explosion is investigated. Tungsten wires with diameters of d = 25–50 μm were exploded in air and water at a current rise time of (dI/dt) ∼ 1010 A/s. The diagnostic complex is described.

Electric explosion of fine wires: Three groups of materials

Experimental data demonstrating differences in the structures of channels formed during nanosecond discharges through fine wires made of different materials are presented. In addition to the traditional two classes of metals and alloys (the copper and tungsten groups), a new class is proposed to which materials of the nickel type belong. Their properties combine the characteristic properties of the two traditional groups, due to which they occupy an intermediate position between the latter. This manifests itself in the unstable character of explosion, the type of which can change drastically when changing the ambient medium or other conditions. Most of the reported results were obtained at a small setup with maximum values of the current and voltage of 10 kA and 20 kV, respectively, the current rise time being about 300 ns. An attempt is made to construct a scenario of the development of a nanosecond explosion that would make it possible to qualitatively describe the formation of the discharge channel structure. The analysis is based on the recent experimental results indicating that the cores formed in the course of the discharge have a tubular structure.

Maximum Energy Deposition During Resistive Stage and Overvoltage at Current Driven Nanosecond Wire Explosion

A wire explosion in a gaseous and condensed media extends possibilities of studying of phase transition of the wire material. The copper and tungsten wires of the diameter of d=25 mum were exploded in vacuum, air, and water by current pulse with the rate increase of ~ 50 A/ns. Energy deposited into the wires at different stages of explosion in the media and maximum voltage reached during wire explosion was estimated from the experiments. Laser probing measurements were performed with the second harmonic of a YAG:Nd+3 laser (lambda=0.53 mum; Deltat=10 ns). Shadow images of the expanding wire materials and shock waves leading the explosion were obtained at different times during the discharge

Overvoltage pulse development upon electrical explosion of thin wires

Experimental data are presented on the electrical explosion of wires of micrometre diameters with a 10 kA current having a rise time rate of up to 50 An s −1 . The influence of circuit and wire parameters and properties of the wire material on the process of possible rupture of current in the circuit and resulting overvoltage at the discharge gap is evaluated. A large amount of experimental data on electrical explosion of wire in various media and in vacuum in the micro- and nanosecond range is analysed. The data are compared with theoretical estimations.

Laser Imaging of Secondary Breakdown Upon Nanosecond Electrical Explosion of Wire

Copper wires of diameter d = 25 mum were exploded in air by a current pulse with a rise rate of ~25 A/ns. Laser probing measurements were performed with the second harmonic of a YAG:Nd3+ laser (lambda = 0.53 mum and Deltat = 10 ns). For the first time, laser images of the current channels were obtained upon electrical explosion of copper wires in air.

Current‐Driven Explosion of Micron Size Wires in Different External Media

A wire explosion in gaseous and condensed media extends possibilities of study of phase transitions of the wire material. In the present work we studied the influence of the external media on the explosion of micron‐size wires by a nanosecond discharge. The 25 μm diameter copper, nickel and tungsten wires were exploded in vacuum, air, water and glycerine by current pulse with a rate increase of 50 A/ns. Energy deposited in the wires during the resistive phase of heating in the different media was estimated from the experiments.

Development of a Discharge Channel upon Electric Explosion of a Wire in Interrupted‐ and Uninterrupted‐Current Regimes

Experimental results on the electrical explosion of thin W, Cu and Ni wires with a current density of ∼1012 A/m2, a current rise rate (dI/dt) ∼40 A/ns and a current pulse with amplitude 9 kA are presented. The structures of the discharge channels developed in single wire explosions in air and vacuum using laser shadow and schlieren imaging have been studied under the condition that the current in the circuit was interrupted. A difference in the shock wave propagation in air and the expansion of the exploded wire dense core in interrupted‐ and uninterrupted‐current regimes has been observed. Analysis of the optical images has been performed in a shunting breakdown scenario.

Distribution of Dense and Current‐Conducting Matter in the Discharge Channel upon Electrical Explosion of Wires in Vacuum

Distribution of dense and current‐conducting matter upon electrical wire explosion using electrical, optical, and UV diagnostics was studied. Wires of 25 μm diameter and 12 mm length were exploded in vacuum by 10 kA current pulse having a 50 A/ns rate of current rise.

Laser Probing of Nanosecond Wire Explosions

Copper and tungsten wires of 25 μm diameter were exploded in open air and vacuum using a pulse generator with a rate of rise of current of 1010–1011 A/s. Laser probing measurements were performed with the second harmonic of the YAG:Nd+3 (λ=0,53 μm; τ=10 ns). Shadow images of the expanding wire material and shock waves leading the expansion were obtained at different times during the discharge. Expansion rates and shock wave speeds have been measured.