Direct measurement of the speed of sound in a complex plasma under microgravity conditions

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Published 10 November 2011 Europhysics Letters Association
, , Citation M. Schwabe et al 2011 EPL 96 55001 DOI 10.1209/0295-5075/96/55001

0295-5075/96/5/55001

Abstract

We present a direct measurement of the speed of sound in a three-dimensional complex plasma —a room-temperature plasma that contains micrometer-sized particles as fourth component. In order to obtain an undisturbed system, the setup was placed under microgravity conditions on board the International Space Station. The speed of sound was measured with the help of Mach cones excited by a supersonic probe particle moving through the extended particle cloud at Mach numbers M≲3. We use the Mach cone relation to infer the particle charge and compare with that predicted by standard theories. In addition, we compare our results with a numerical simulation. In both experiment and simulation, we observe a double Mach cone structure.

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10.1209/0295-5075/96/55001