Zusammenfassung
Transverse oscillations of a microsphere in liquid helium below 0.3 K are investigated. For small amplitudes we observe ballistic drag by phonons and3He impurities. At a threshold velocity amplitude the drag force increases discontinuously to a value determined by turbulence in the superfluid and varies with the square of the velocity amplitude. The turbulent drag coefficient is determined by the ...
Zusammenfassung
Transverse oscillations of a microsphere in liquid helium below 0.3 K are investigated. For small amplitudes we observe ballistic drag by phonons and3He impurities. At a threshold velocity amplitude the drag force increases discontinuously to a value determined by turbulence in the superfluid and varies with the square of the velocity amplitude. The turbulent drag coefficient is determined by the density of the liquid and the radius of the sphere, similar to the case of uniform motion in a classical liquid. The threshold velocity for the onset of turbulent friction is found to be independent of the temperature.
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