O. Antonov

Generation of converging strong shock wave formed by microsecond timescale underwater electrical explosion of spherical wire array

A study of generation of converging strong shock wave using microsecond underwater electrical explosion of spherical Cu-wire array is presented. Hydrodynamic simulations coupled with the equation of state for Cu and water, deposited energy, and the magnetic pressure were used to calculate the water parameters in the vicinity of the implosion origin. The results of simulations agree with the shock wave time-of-flight and energy delivered to the water flow and show that in the vicinity (diameter of ∼12 μm) of an implosion one can expect water pressure of ∼6 TPa, temperature of ∼17 eV, and compression of ∼8.

Underwater Electrical Explosion of Wires and Wire Arrays and Generation of Converging Shock Waves

A brief review of the results obtained in recent research of underwater electrical explosions of wires and wire arrays using microsecond-, submicrosecond-, and nanosecond-timescale high-current generators is presented. In a microsecond-timescale wire explosion, good agreement was attained between the results of experiments and the results of magnetohydrodynamic calculations coupled with equations of state (EOS) and modern conductivity models. Conversely, in a nanosecond-timescale wire explosion, the wire resistance and the EOS were modified in order to fit experimental data. In experiments with cylindrical and spherical wire arrays, generation of a converging shock wave (SW) was demonstrated allowing formation of an extreme state of water in the vicinity of either the axis or the origin of the SWs implosion. In addition, it is shown that SW convergence in superspherical geometry allows one to achieve larger values of pressure, density, and temperature of water in the vicinity of the axis of convergence than in the case of a spherical implosion. The results of experiments and numerical analysis showed that a cylindrical SW keeps its symmetry along the main path of its convergence. In addition, it is shown that underwater electrical explosion of an X-pinch wire configuration and a cone wire array allows one to generate fast jets of metal and water, respectively, without using chemical explosions.

Generation of extreme state of water by spherical wire array underwater electrical explosion

The results of the first experiments on the underwater electrical explosion of a spherical wire array generating a converging strong shock wave are reported. Using a moderate pulse power generator with a stored energy of ≤6 kJ and discharge current of ≤500 kA with a rise-time of ∼300 ns, explosions of Cu and Al wire arrays of different diameters and with a different number and diameter of wires were tested. Electrical, optical, and destruction diagnostics were used to determine the energy deposited into the array, the time-of-flight of the shock wave to the origin of the implosion, and the parameters of water at that location. The experimental and numerical simulation results indicate that the convergence of the shock wave leads to the formation of an extreme state of water in the vicinity of the implosion origin that is characterized by pressure, temperature, and compression factors of (2 ± 0.2) × 1012 Pa, 8 ± 0.5 eV, and 7 ± 0.5, respectively.

Modified wire array underwater electrical explosion

The results of experiments involving underwater electrical explosion of different wire arrays using an outer metallic cylinder as a shock reflector are presented. A pulse generator with a stored energy of about 6 kJ, current amplitude ≤500 kA, and rise time of 350 ns was used for the wire array explosion. The results of the experiments and of hydrodynamic simulations showed that in the case of a Cu wire array explosion, the addition of the reflector increases the pressure and temperature of the water in the vicinity of the implosion axis about 1.38 and about 1.33 times, respectively. Also, it was shown that in the case of an Al wire array explosion with stainless steel reflector, Al combustion results, and, accordingly, additional energy is delivered to the converging water flow generating about 540 GPa pressure in the vicinity of the explosion axis. Finally, it was found that microsecond time scale light emission that appears with microsecond time scale delay with respect to the nanosecond time scale self-light emission of the compressed water in the vicinity of the implosion axis is related to water bubbles formation which scattered light of exploded wires.

Diagnostics of a converging strong shock wave generated by underwater explosion of spherical wire array

The results of experimental studies of the convergence of shock waves (SWs) generated by the underwater electrical explosion of a spherical wire array supplied by a current pulse with an amplitude ∼300 kA and rise time ∼1.1 μs are reported. In the experiments, the power and spectrum of the light emission from an optical fiber, the explosion of a copper tube, and the time-dependent resistance of a resistor placed in the equatorial plane of the spherical wire array were measured. A comparison of the experimental data with the results of numerical simulations of SW convergence shows that the SW keeps its uniformity along the major part of the convergence towards the implosion origin.

Commissioning of the PRIOR proton microscope

Recently, a new high energy proton microscopy facility PRIOR (Proton Microscope for FAIR Facility for Anti-proton and Ion Research) has been designed, constructed, and successfully commissioned at GSI Helmholtzzentrum für Schwerionenforschung (Darmstadt, Germany). As a result of the experiments with 3.5-4.5 GeV proton beams delivered by the heavy ion synchrotron SIS-18 of GSI, 30 μm spatial and 10 ns temporal resolutions of the proton microscope have been demonstrated. A new pulsed power setup for studying properties of matter under extremes has been developed for the dynamic commissioning of the PRIOR facility. This paper describes the PRIOR setup as well as the results of the first static and dynamic proton radiography experiments performed at GSI.

Spectroscopy of a plasma formed in the vicinity of implosion of the shock wave generated by underwater electrical explosion of spherical wire array

The results of visible spectroscopy of the plasma formed inside a copper capillary placed at the equatorial plane of an underwater electrically exploded spherical wire array (30 mm in diameter; 40 wires, each of 100 μm in diameter) are reported. In the experiments, a pulsed power generator with current amplitude of ∼300 kA and rise time of ∼1.1 μs was used to produce wire array explosion accompanied by the formation of a converging strong shock wave. The data obtained support the assumption of uniformity of the shock wave along the main path of its convergence. The spectroscopic measurements show that this rather simple method of formation of a converging strong shock wave can be used successfully for studying the shock waves interaction with matter and the evaporation processes of atoms from a target.

Converging shock wave focusing and interaction with a target

Converging shock waves in liquids can be used efficiently in the research of the extreme state of matter and in various applications. In this paper, the recent results related to the interaction of a shock wave with plasma preliminarily formed in the vicinity of the shock wave convergence are presented. The shock wave is produced by the underwater electrical explosion of a spherical wire array. The plasma is generated prior to the shock waves arrival by a low-pressure gas discharge inside a quartz capillary placed at the equatorial plane of the array. Analysis of the Stark broadening of Hα and Hβ spectral lines and line-to-continuum ratio, combined with the ratio of the relative intensities of carbon C III/C II and silicon Si III/Si II lines, were used to determine the plasma density and temperature evolution. It was found that during the first ∼200 ns with respect to the beginning of the plasma compression by the shock wave and when the spectral lines are resolved, the plasma density increases from 2 × ...

Addressing optimal underwater electrical explosion of a wire

The underwater electrical explosion of a wire in the timescale 10−7–10−6 s is characterized by different phase transitions at extreme values of deposited energy density, allowing one to obtain warm dense matter using rather moderate pulse power generators. In order to achieve maximal energy density deposition, the parameters of the wire and the pulse generator should be optimized to realize an overdamped explosion where most of the initially stored energy is delivered to the exploding wire during a time comparable with the quarter of the discharge period. In this paper, the results of 1D magneto-hydrodynamic modeling, coupled with the copper and water equations of state, of the underwater electrical explosion of Cu wires having an identical length and average current density but different discharge current rise time are analyzed and compared with those of a simplified model of a conductivity wave, the propagation velocity of which determines the mode of the wires explosion. In addition, it is shown that ...

Convergence of shock waves between conical and parabolic boundaries

Convergence of shock waves, generated by underwater electrical explosions of cylindrical wire arrays, between either parabolic or conical bounding walls is investigated. A high-current pulse with a peak of ∼550 kA and rise time of ∼300 ns was applied for the wire array explosion. Strong self-emission from an optical fiber placed at the origin of the implosion was used for estimating the time of flight of the shock wave. 2D hydrodynamic simulations coupled with the equations of state of water and copper showed that the pressure obtained in the vicinity of the implosion is ∼7 times higher in the case of parabolic walls. However, comparison with a spherical wire array explosion showed that the pressure in the implosion vicinity in that case is higher than the pressure in the current experiment with parabolic bounding walls because of strong shock wave reflections from the walls. It is shown that this drawback of the bounding walls can be significantly minimized by optimization of the wire array geometry.