Research at Tsinghua University on electrical explosions of wires

Abstract

Electrical explosion of a wire (EEW) has been investigated for more than ten years at Tsinghua University, and the main results are reviewed in this paper. Based on EEW in vacuum, an X-pinch was used as an x-ray source for phase-contrast imaging of small insects such as mosquitoes and ants in which it was possible to observe clearly their detailed internal structures, which can never be seen with conventional x-ray radiography. Electrical explosion of a wire array (EEWA) in vacuum is the initial stage in the formation of a wire-array Z-pinch. The evolution of EEWA was observed with x-ray backlighting using two X-pinches as x-ray sources. It was found that each wire in an EEWA exhibits a core–corona structure instead of forming a fully vaporized metallic vapor. This structure is detrimental to the plasma implosion of a Z-pinch. By inserting an insulator as a flashover switch into the cathode, formation of a core–corona structure was suppressed and core-free EEWA was realized. EEW in gases was used for nanopowder production. Three parameters (vaporization rate, gas pressure, and energy deposited in the exploding plasma) were found to influence the nanoparticle size. EEW in water was used for shock-wave generation. The shock wave generated by melting could be recorded with a piezoelectric gauge only in underheat EEW. For EEW with a given stored energy but different energy-storage capacitor banks, the small capacitor bank produced a rapidly rising current that deposited more energy into the wire and generated a stronger shock wave.

Electrical wire explosion as a source of underwater shock waves

“…where ρ, u, T, p, ε are respectively the density, radial velocity, temperature, pressure and the specific internal energy; W R is the radiation flux; B θ is the azimuthal component of the magnetic field strength; E z is the axial component of the electric field strength; j z is the axial component of the current density; κ and σ are respectively the thermal and electrical conductivity; µ 0 is the permeability of a vacuum. Equations ( 4)-( 6) are the conservation equations in HDs; equation ( 7) are the Maxwell equations, from which the magnetic diffusion equation can be obtained; equation (8) are the EOS and transport coefficients needed to close the equation set, usually written as functions of density and temperature.…”

“…summarized in Exploding Wires I-IV [2][3][4][5]. Over the last few decades, progress on Z-pinch radiation sources, inertial confinement fusion and potential industrial applications, including nanoparticle synthesis, electrohydraulic forming, food processing, and stratum stimulation have restored interest in the EWE phenomenon [6][7][8][9][10][11][12][13][14].…”

Prediction of γ-ray shielding performance and study of Bi/PU coated fabric

“…When the incident energy of γ-rays is 122 keV and 184 keV, the maximum value of energy deposition in the sample increases with the increase of Bi content, and the range of energy deposition also gradually increases, indicating that the absorption and scattering of γ-rays by the material are enhanced. This is because, with the increase of incident energy, the probability of the Compton effect 41 of photons in materials increases. On the other hand, with the increase of the content of Bi, the number of radiation-absorbing atoms per unit area increases, and the probability of the photoelectric effect and Compton scattering between photons and materials increases.…”

Experiments on plasma dynamics of electrical wire explosion in air

“…It is already known that in most cases, increasing the initial stored energy could boost the energy deposition rate during the ohmic heating phase, resulting in a more intense explosion and stronger shock waves [15]. Additionally, a higher charging voltage may cause a larger overvoltage factor, promoting the development of breakdown and shortening or even vanishing the current pause [36,37].…”