Spherical wire arrays electrical explosion in water and glycerol

Abstract

The results of experiments and one-dimensional (1D) hydrodynamic (HD) simulations of electrical explosions of spherical Cu wire arrays in water and glycerol for various stored energy of the pulse generator and sphere diameters are presented and discussed. It was found that the convergence of the shock wave generated by an exploding spherical wire array in glycerol is significantly faster than in water. The resulting pressure in the vicinity of the implosion center is several times larger in glycerol than in water. Increasing the initially stored energy from 3.6 to 6.1 kJ (for identical array diameters) or decreasing the sphere diameter from 30 to 20 mm (for identical stored energy) leads to an increase in the pressure, temperature, and density in the vicinity of the implosion center. The pressure in a spherical volume of ∼0.2 mm in diameter at the origin of the sphere is estimated by 1D HD simulations to be in excess of 1012 Pa.

Comparison of electrical explosions of spherical wire arrays in water and glycerol on different timescales

“…These energies are close to those used in our ls-timescale research. 12 The differential waveforms of the current and voltage were measured using B-dot and D-dot probes, respectively, placed near the load. The power was calculated as PðtÞ ¼ ½/ðtÞ À LðdI=dtÞIðtÞ, where /ðtÞ is the voltage, IðtÞ is the current, and L ¼ 14 nH is the inductance of the SWA and the current path between the Ddot probe and the SWA.…”

“…To measure the TOF of the SSW, a 1 mm optical fiber was placed in an opaque tube at the equatorial plane of the SWA. 12 One end of the fiber was attached to a Hamamatsu photomultiplier tube (PMT) connected to a Tektronix TDS-640S oscilloscope. The converging SSW's interaction with the fiber close to the implosion origin leads to intense light emission which was used for measurements of SSW TOF which was in the range 2.8-5.6 ls depending on the array radius, stored energy, and medium.…”

“…As described in Ref. 12, here too, generator shots were repeated for each sphere diameter until, for two to three shots, reliable light emission from the fiber was obtained. The difference in the TOF for the same experimental conditions, but different shots of the generator, was 660 ns.…”

“…Recently, 12 we studied electrical explosions using different diameters of SWA's on the microsecond (ls) timescale in water and glycerol for various energies stored in the pulse generator. It was found that the convergence of the SSW in glycerol is faster than in water resulting, according to 1D HD simulations, in several times larger pressures near the implosion origin in glycerol than in water.…”

Use of synchrotron-based radiography to diagnose pulsed power driven wire explosion experiments

“…6 Such experiments are often used to perform equation of state studies, and more recently, the shock waves generated in water by exploding wires have become of interest for efficiently producing high pressure conditions at the meeting point of multiple shocks waves generated by arrays of wires in a cylindrical or spherical geometry. 7,8 Wire explosions in water, rather than gas or vacuum, are often preferred as high breakdown voltage prevents the formation of plasma on the wire's surface, and as the low compressibility of water slows the expansion of the wire and ensures high energy density deposition in the wire material.…”