A. Fedotov

Nanosecond time scale, high power electrical wire explosion in water

Experimental and magnetohydrodynamic simulation results of nanosecond time scale underwater electrical explosions of Al, Cu, and W wires are presented. A water forming line generator with current amplitude up to 100kA was used. The maximum current rise rate and maximum Joule heating power achieved during wire explosions were dI∕dt⩽500A∕ns and 6GW, respectively. Extremely high energy deposition of up to 60 times the atomization enthalpy was registered compared to the best reported result of 20 times the atomization enthalpy for energy deposition with a vacuum wire explosion. Discharge channel evolution and surface temperature were analyzed by streak shadow imaging and by a fast photodiode with a set of interference filters, respectively. A 1D magnetohydrodynamic simulation demonstrated good agreement with experimental parameters such as discharge channel current, voltage, radius, and temperature. Material conductivity was calculated to produce the best correlation between the simulated and experimentally o...

Addressing the efficiency of the energy transfer to the water flow by underwater electrical wire explosion

Experimental and hydrodynamic simulation results of submicrosecond time scale underwater electrical explosions of planar Cu and Al wire arrays are presented. A pulsed low-inductance generator having a current amplitude of up to 380 kA was used. The maximum current rise rate and maximum power achieved during wire array explosions were dI/dt≤830 A/ns and ∼10 GW, respectively. Interaction of the water flow generated during wire array explosion with the target was used to estimate the efficiency of the transfer of the energy initially stored in the generator energy to the water flow. It was shown that efficiency is in the range of 18%–24%. In addition, it was revealed that electrical explosion of the Al wire array allows almost double the energy to be transferred to the water flow due to efficient combustion of the Al wires. The latter allows one to expect a significant increase in the pressure at the front of converging strong shock waves in the case of cylindrical Al wire array underwater explosion.

Characterization of converging shock waves generated by underwater electrical wire array explosion

Results of ∼200 kbar pressure generation at 50 μm distance from the implosion axis of the converging shock wave produced by an underwater electrical explosion of a cylindrical wire array are reported. The array was exploded using a submicrosecond high-current generator (stored energy of ∼4.2 kJ, current amplitude of ∼325 kA, rise time of ∼1 μs). Multiframe shadow imaging of the shock wave was used to determine its time of flight. These data were applied for calculating the pressure at the vicinity of the implosion axis using one dimensional hydrodynamic calculations and the Whitham approach. However, it was found that in the case of wire array radius ≤5 mm, multiframe imaging cannot be used at the final stage of the shock wave implosion because of possible changes in the optical properties of the water. Optical and spectroscopic methods based on either the change in the refraction index of the optical fiber or spectroscopy of the plasma formed inside the capillary placed at the implosion axes were used fo...

Spectroscopic research of underwater electrical wire explosion

Results of spectroscopic research in the visible range of light of the radiation generated by underwater electrical wire explosions (UEWE) are presented. A pulsed generator with an output voltage of ∼110kV, current of ∼70kA, and rise time of ∼60ns was used for electrical explosion of Cu wires 0.1mm in diameter and 50mm in length. It was shown that UEWE is not governed by the “polarity” effect, which plays an important role in electrical wire explosions in vacuum. The results of detailed space- and time-resolved spectroscopic measurements show that the radiation spectrum differs significantly of the spectrum expected from the exploding wire. A model is suggested based on the formation of a few μm “water” plasma layer in the vicinity of the exploding wire plasma which efficiently absorbs the radiation of the exploding wire.

Generation of cylindrically symmetric converging shock waves by underwater electrical explosion of wire array

It is shown that the originally corrugated shock wave generated in the process of an underwater electrical explosion of a cylindrical wire array is self-aligned into a cylindrically symmetric converging front. It was found that by increasing the number of the wires in the array this self-alignment process occurs faster. It is also demonstrated that in the case of a large wire number (>20), one-dimensional calculations can be successfully employed for theoretical analysis.

Underwater electrical wire explosion

The results of the investigation of the underwater electrical wire explosions using a high power sub-ns generator are reported. The spectroscopic analysis of the emitted radiation has unveiled no evidence for the formation of shunting plasma channel. The latter appears in vacuum and gas wire explosions and causes to the seizure of energy deposition into an exploding wire material. The combination of mechanism for the suppression of formation of shunting channel together with the increased energy deposition rate allows busting the efficiency of the energy deposition into the exploding wire. Estimated energy deposition into Cu and Al wire of up to 200 eV/atom was reported.

Underwater Electrical Wire Explosion

Electrical explosion of wires in a water medium is a promising method for generation of strong shock waves (SSW) and non-ideal plasma. Here we report on underwater electrical wire explosions (UEWE) that were investigated experimentally and using computer modeling. Micro- and nano-second time scale generators for UEWE of Cu wire and Cu wire cylindrical arrays were employed. A microsecond time scale (6 kJ stored energy, current of 300 kA, rise time of 1.2 mus) and nanosecond time scale (400 J stored energy, current of 80 kA and current rise time of 80 ns) were used in mus and ns time scale experiments, respectively. Different configurations of the single UEWE were tested to obtain maximal maximal amplitude of the generated SWW. Results of a detailed research of the radiation from the plasma formed as a result of UEWE are presented as well. It was shown also that application of underwater explosion of Cu wire arrays allows one generation of converging SSW which produces of several hundreds kbar at the axis of the SSW implosion.

Micro- and nanosecond time scale, high power electrical wire explosion in water

Summary form only given. Experimental and magneto-hydro-dynamic simulation results of micro- and nanosecond time scale underwater electrical Al, Cu and W wire explosions are presented. A capacitor bank with stored energy up to 6 kJ (discharge current up to 80 kA with 2.5 mus quarter period) was used in microsecond time scale experiments and water forming line generator with current amplitude up to 100 kA and pulse duration of 100 ns were used in nanosecond time scale experiments. Extremely high energy deposition of up to 60 times the atomization enthalpy was registered in nanosecond time scale explosions. A discharge channel evolution and surface temperature were analyzed by streak shadow imaging and using fast photo-diode with a set of interference filters, respectively. Microsecond time scale electrical explosion of cylindrical wire array showed extremely high pressure of converging shock waves at the axis, up to 0.2 Mbar. A 1D and 2D magneto-hydro-dynamic simulation demonstrated good agreement with such experimental parameters as discharge channel current, voltage, radius, and temperature