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.
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 lm) of an implosion one can expect water pressure of $6 TPa, temperature of $17 eV, and compression of $8. V C 2013 American Institute of Physics.
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 lm in diameter) are reported. In the experiments, a pulsed power generator with current amplitude of $300 kA and rise time of $1.1 ls 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 wave's interaction with matter and the evaporation processes of atoms from a target. V C 2015 AIP Publishing LLC.
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 wire's explosion. In addition, it is shown that in the case of extreme high current densities, a scaling from a single wire to a wire array having the same total cross-sectional area of wires cannot be used to obtain an optimal wire explosion.
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