Generation of Two Successive Shock Waves Focused to a Common Focal Point

Inst. of Plasma Phys., Acad. of Sci. of the Czech Republic, Prague
IEEE Transactions on Plasma Science (Impact Factor: 0.87). 09/2006; DOI: 10.1109/TPS.2006.878435
Source: IEEE Xplore

ABSTRACT A generator of two successive shock waves focused on a common focal point has been developed. Cylindrical pressure waves created by multichannel electrical discharges on two cylindrical composite anodes are focused by a metallic parabolic reflector-cathode. Near the common focus, the waves are transformed into strong shock waves. The anodes are energized from separate power supplies. This allows us to vary the time interval between the discharges and stagger the waves' arrival to the focal point. Schlieren photographs of the focal region show that mutual interaction of the two waves results in generation of a large number of secondary short wavelength shocks. Measurements of the shock waveforms at the focus demonstrate that the second (i.e., later arriving) wave is strongly attenuate due to the medium inhomogeneity produced by the first wave. Localized injury of a rabbit's liver induced by the shock waves has been demonstrated by the method of magnetic resonance imaging. Histological examination of the liver samples taken from the injured region revealed a very sharp boundary between the injured and healthy tissues

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    ABSTRACT: A generation of focused shock waves by underwater multichannel pulsed electrical discharge on a porous-ceramic-coated electrode in saline water is studied. This work describes the effect of solution conductivity of saline water on the pressure of shock waves. It was found that the amplitude of shock waves has a nonlinear dependence on water conductivity: The amplitude increases with the increase of water conductivity up to 18-20 mS/cm and then decreases again. In this paper, we show that two effects take place. First, the electrical energy dissipated in the discharge depends on the impedance of the electrode system being affected by water conductivity. Second, the velocity of streamer growth strongly depends on energy deposition time into the discharge. The two mentioned effects result in “hill-like” shape of the curve presenting the dependence of the maximum amplitude of the shock wave on water conductivity.
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