Spectroscopy of a plasma formed in the vicinity of implosion of the shock wave generated by underwater electrical explosion of spherical wire array

Abstract

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.

Converging shock wave focusing and interaction with a target

“…12. However, opposite to earlier research, 12 in the present experiment the plasma in the vicinity of the SW's implosion origin is generated before the SW's convergence. Studying plasma parameters before the SW's convergence, this approach allows one to obtain the evolution of the plasma parameters during the SW's implosion resulting in a better understanding of the SW's convergence uniformity.…”

“…In the present experiment, the plasma was generated by a low-pressure gas (C 3 H 8 ) discharge in a quartz capillary placed in the equatorial plane of the array prior to the SW interaction with the capillary, thus allowing the plasma parameters prior to and during SW interaction to be studied. As in previous experiments, 12 the intense evaporation of the capillary inner wall material allowed the oxygen and silicon spectral lines to be observed. The Stark broadenings of the H a and H b lines were used to determine the plasma density, and NOMAD 13 collisional-radiative (CR) modeling was used to extract the electron temperature of the equilibrium plasma, which has the same ratio of the intensities of different carbon spectral lines as obtained in the experiment.…”

“…In this paper, we present the results of the evolution of the parameters of the plasma under interaction with converging SW generated by the same underwater electrical spherical wire array explosion as that described in Ref. 12. However, opposite to earlier research, 12 in the present experiment the plasma in the vicinity of the SW's implosion origin is generated before the SW's convergence.…”

“…In order to confirm the uniform convergence of the SW, optical emission spectroscopy was applied to study the parameters of the plasma in the vicinity of the SW implosion. 12 In these experiments, a Cu capillary was placed at the equatorial plane of the spherical wire array. The SW approaching the inner surface of the capillary wall leads to intense evaporation of Cu atoms.…”

Uniformity of cylindrical imploding underwater shockwaves at very small radii

“…11,12 Different methods (damage of different targets, spectroscopy of the obtained water plasma created by the convergence of the SSW) were applied to determine the water parameters in the vicinity of implosion. [13][14][15] Also, the SSW's time-of-flight to the axis (cylindrical wire array) or origin (spherical wire array) of implosion leading to intense light emission from compressed and heated water at those locations was used for comparison with the results of one dimensional (1D) and two dimensional (2D) Hydrodynamic (HD) simulations, coupled with the EOS of water and copper. 16 In these simulations, which considered symmetrical SSW convergence, only the energy deposition rate into the wires, calculated using the experimentally obtained resistive voltage and discharge current waveforms, was an input parameter.…”