|Ph.D Student||Fedotov Gefen Alexander|
|Subject||Underwater Electrical Wire Explosion and Shock Wave|
Generation in Water
|Department||Department of Physics||Supervisors||Professor Yakov Krasik|
|Professor Emeritus Joshua Felsteiner|
|Full Thesis text|
The present thesis is devoted to research of underwater wire electrical explosion (UEWE) and generation of converging shock wave by explosion of a cylindrical wire array. The process of UEWE is accompanied by rapid phase transitions (solid-liquid-gas-plasma) of the wire material, intense light emission and generation of a strong shock wave (SSW). The plasma formed as a result of UEWE is strongly coupled and can be concerned as warm dense matter characterized by relatively low temperature of several eV and large density (>1020 cm-3) and pressure >109 Pa.
The experiments were carried out using three pulsed current generators having stored energies and current rise time of 500 J and 60 ns, 4 kJ and 1000 ns, 9.7 kJ and 350 ns, respectively. The maximum rate of energy deposition achieved in the experiments was 25 GW. In the experiments three types of diagnostics were applied, namely, electrical (current and voltage measurements), optical (shadow imaging, visible and UV spectroscopy) and laser based diagnostics (schlieren, Faraday rotation and Kerr effect).
Investigation of single UEWE in nanosecond time scale showed that the emitted plankian spectrum in visible range with characteristic temperature <1.5 eV do not resemble the spectrum of exploding wire radiation predicted by EOS and MHD simulations that predict temperature >6 eV. Also it was found that there are no current leaks from the wire and electrode surfaces and electric fields sufficient to cause electrical breakdown in the vicinity of the exploding wire.
Experiments of SSW generation by planar wire arrays showed that ~24% of the energy deposited into the exploding wires is transferred to the water flow. Investigation of the self-alignment of an initially corrugated front of a cylindrical converging SSW showed that the propagation of the SSW can be simulated by a 1D hydrodynamic code when using wire arrays consisting of more than 20 wires. In the experiments carried out using the pulsed current generator with stored energy of 8 kJ, pressure, density and temperature of the water of up to 400 GPa, 4.3 g/cm3 and 2.2 eV, respectively, were generated. Those values were inferred from the hydrodynamic 1D simulation coupled to the experimental data of SSW time-of-flight and water EOS. Also, the dependences of the maximum generated pressure on the wire array radius and deposited energy per unit array length were obtained.