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Underwater pulsed spark discharge has been widely used in industrial fields as a source of shock waves or acoustic waves, and numerical modeling of the discharge and pressure wave characteristics is necessary to improve the application performance. In this paper, a numerical model is proposed that couples the circuit equation, the mass and energy conservation equations, and a momentum conservation equation based on the Rankine–Hugoniot conditions. A tabulated wide range equation of state and conductivity data of water are used, and various physical processes during the plasma channel expansion are considered, including the energy flow and mass exchange between the channel and the surrounding water due to thermal radiation, evaporation, and condensation. The model self-consistently solves the circuit current and voltage, the plasma channel parameters including composition, temperature, conductivity, pressure, etc., and the pressure profile at a certain distance from the discharge channel. The calculated results show good consistency with the experimental measurements, and three sets of experimental results from other literature are tested to further verify the applicability and effectiveness of the model. [ABSTRACT FROM AUTHOR]

The x-ray spectrum of a flash radiography source based on wire-shorted rod-pinch diode (RPD) is measured by an absorption spectrometer and calculated by the Geant4 Monte-Carlo code. The RPD is driven by a two-stage linear transformer driver (charging voltage ±45 kV per stage), which delivers ∼300 kA current within ∼200 ns on a short-circuit inductive load (∼30 nH). The spectrometer consists of LiF thermoluminescence dosimeters and metal filters of different materials and thicknesses, and the spectrum is reconstructed based on the Geant4 simulated dosimeter responses to various photon energies through different filters. The measured spectrum reaches an endpoint photon energy of ∼130 keV. The radiation characteristics of the RPD in the experiment are also modeled in Geant4 using measured voltage and current waveforms, and the results show an overestimation in photon number and endpoint energy (∼147 keV) compared to the measured spectrum, which indicates that during the bremsstrahlung process, the effective electron current is ∼27% of the total current, and the effective voltage is ∼12% lower than the directly reconstructed resistive voltage. A rough agreement is found between the spectra results and the non-relativistic Bethe–Heitler model with Sommerfeld correction; therefore, the analytic result can serve as an initial guess for spectrum reconstruction methods such as the perturbation method. [ABSTRACT FROM AUTHOR]

Measurement of plasma parameters during the ablation phase in the Z-pinch is crucial for investigating the dynamic behaviors. In this study, optical Thomson scattering was employed to measure the temperature and velocity of the ablation plasma in a double-wire Z-pinch. The scattering spectra profiles were fitted using a model that considered the velocity distribution. The experimental results revealed the energy evolution of ablation plasma, the establishment of the global magnetic field and the development of axial non-uniformities. The precursor plasma was found to play a key role in strengthening the global magnetic field. A resistive layer near the wire core with a size of 1.5 mm was observed in the ablation plasma after the precursor plasma column formed. The plasma underwent rapid heating in this layer, the electron temperature rises from 17 eV to 22 eV. Upon leaving this layer, electron the temperature is stable at around 22 eV. The radial distribution of the ablation rate increases and decreases, indicating the axial motion of the ablation plasma, which could be caused by the tilt motion of the stream and the secondary modulation of the natural wavelength. [ABSTRACT FROM AUTHOR]

In this paper, Fe10Co25Ni34Cu23Al8 high-entropy-alloy nanoparticles have been synthesized by the in situ instantaneous electrical wire explosion method. Based on the thermodynamic parameters of the face-centered cubic phase of high-entropy-alloy, the parameters of the five kinds of wires were calculated and controlled, and the stable face-centered cubic structure with good crystallinity was synthesized in one step. The influence of the energy deposition during the electrical explosion on the nanoparticles and their electromagnetic absorption performance was explored. The results show that the face-centered cubic structure high-entropy-alloy with high crystallinity has better electromagnetic wave absorption performance when the energy deposition of the wires is increased. The minimum reflection loss can reach −39.37 dB at 15.34 GHz when the thickness is 1.9 mm and the effective absorption bandwidth is 6.63 GHz. It can provide a strategy for the microstructure and morphology design of high-entropy-alloy nanoparticles in electromagnetic wave absorption and magnetism in the electronics industry. [ABSTRACT FROM AUTHOR]

Underwater electrical wire explosion is usually used as a source of underwater shock waves, and the generated shock wave intensity can be regulated by adopting a wire array. In this paper, the dynamics of the electrical explosion of two wires with different diameters connected in parallel were studied. The current flowing through each wire was measured to study the current distribution, and the self-emission image and laser backlight shadow image was obtained to observe the evolution of the wires. A numerical model was built to make explanations and predictions. The results showed that due to the presence of wire inductance and contact resistance between the wire and electrode, the wires are with different current densities and undergo asynchronous heating from the beginning of the discharge. Furthermore, the variation of current distribution among the wires was divided into six stages according to the moment the wire melted and exploded, and analyzed stage by stage. The unbalanced energy deposition results in obvious differences in thermal dynamic parameters, which explains the gradual "extinguishment" of the thinner wire in the self-emission image. [ABSTRACT FROM AUTHOR]

Underwater electrical wire explosion (UEWE) is an efficient source of underwater shock waves (SWs). In order to efficiently simulate the interaction between the UEWE SW and structures, a coupled model that includes the electric circuit, the exploding wire and the surrounding water is established based on user-subroutines provided by the commercial explicit dynamics software ANSYS AUTODYN. The modeling starts from room temperature by using the tabular wide-range metal equation of state (EOS) and conductivity data. Experimental validation is performed with copper wires exploded by a μ s-timescale pulsed discharge. The numerical results show satisfactory consistency with experiments in terms of the current and voltage waveforms, the wire expansion trajectory, the evolution of SW front, the interaction between SW and electrodes and the SW pressure profiles. The main discrepancy lies in the SW amplitude that is ∼20% higher in the calculation and the possible reasons are discussed in detail. Based on this approach and with proper modifications to the metal EOS and conductivity data, the interaction between UEWE SWs and structures can be efficiently modeled in 2D and 3D for practical applications. [ABSTRACT FROM AUTHOR]