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An acoustic "Tokamak"


On October 13, 2023

Tomamak Acoustique

Thanks to 3D-printed cages, we've shown that bubbles can be stabilized in water in any shape: cubes, spheres, even rings. Here, we're printing a large number of 2cm ring bubbles, arranged on a large circle to create an acoustic tokamak.

Indeed, its geometry resembles that of the Tokamak used to magnetically confine hot plasmas for nuclear fusion experiments. 
When this bubble tokamak is excited by sound, the bubbles oscillate strongly. A first collective resonance of the 24 ring bubbles occurs, at around 500 Hz, twice as low as the resonance frequency of a single bubble, as the bubbles interact collectively in phase. At higher frequencies, other modes appear where the bubbles are not in phase.
An original feature of the acoustic field within the resonant Tokamak is its homogeneity, whereas acoustic fields usually vary greatly when moving close to a source, making it a unique acoustic object.


Acoustic Tokamak with strongly coupled toroidal bubbles, A. Caumont, O. Stephan, E. Bossy, B. Dollet, C. Quilliet, and P. Marmottant, Physical Review E 108,  045105


On October 13, 2023


Philippe MARMOTTANT (philippe[dot]marmottant[at]univ-grenoble-alpes[dot]fr)

Submitted on February 13, 2024

Updated on February 13, 2024