The search for electrical discharges from single- and multi-bubble sonoluminescence

Abstract

Previous research supported the notion that electrical discharges resulted from the collapse of bubbles in cavitation fields [G. Giminez and F. Goby, in Cavitation and Inhomogeneities in Underwater Acoustics, edited by W. Lauterborn (Springer-Verlag, New York, 1980), pp. 101–107]. Further research was performed in a cavitation field, as well as with a single cavitating bubble. The cavitation field was generated in a standing wave-field using gassy water, resulting in a small confined region of cavitation. Single-bubble cavitation was also performed in this system, but with degassed water. Two methods were used to detect electrical pulses. In one case a small probe consisting of two fine wires coupled to a low-current differential amplifier was placed near the cavitation bubble(s). Signals were only observed when the probe was in contact with the cavitation field (no signals were observed in the single-bubble system). The second method utilized a coiled loop of wire surrounding the levitation cell, connected to a high-bandwidth lock-in amplifier. In this case, the reference frequency was scanned from about 25 kHz to more than 20 MHz. Signals were observed at harmonics of the drive frequency. [This research supported by DOE-EM.]