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 In proceeding of: Pulsed Power Conference, 2005 IEEE
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: Interaction of two successive shock waves focused to a common focal point - tandem shocks, has been investigated. The time interval between the two shocks can be varied. We have demonstrated that acoustical inhomogeniety created in water by the first wave strongly modifies propagation of the second wave. In short time intervals between the waves (5–20μs), the second wave, rather surprisingly, arrived the focus as a rarefaction wave producing a large number of cavitations. Amplitude of the second wave gradually decreases with the increasing time delay between the waves. Schlieren photos show very complex pressure field at the focal region for such time delay. For a longer time delay (50–500 μs) the second wave is almost totally damped at the focus. Propagation of the second wave as a pressure wave is renewed only for very long time delays (0,7 - 2 ms) when cavitations produced by the first wave are quenched.

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