QFS 2016 Book of Abstracts

Abstracts

P2.13 The damping and drag coefficient of quartz tuning fork in superfluid solutions 3 He - 4 He Bakhvalova V. A., Chagovets V.K., Gritsenko I.A. and Sheshin G.A. ILTPE - B.Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine. Prospekt Nauky 47, Kharkiv 61103 , UKRAINE The influence of 3 He impurity on the damping and drag coefficient of the oscillating tuning fork in superfluid solutions 5 and 15% of 3 He are presented. The measurements were performed at temperature range 0.5 - 4 K and the exciting voltage from 1 mVpp to 500 Vpp. The carried measurements allowed constructing the temperature dependences of the damping coefficient for measured 3 He concentrations, which have agreement with similar measurements for vibrating sphere. The calculation of the contributions of the viscosity, first and second sounds of the temperature dependence of the dissipation of the vibrations of the tuning fork has been performed. P2.14 Coupling between first sound and second sound in dilute 3 He – superfluid 4 He mixtures Riekki Tapio(1), Manninen Matti(2), Tuoriniemi Juha(3) 1,2,3) Aalto University, Department of Applied Physics, Low Temperature Laboratory, P.O. BOX 15100 FI-00076 AALTO Bulk superfluid helium supports two sound modes: first sound is an ordinary pressure wave, while second sound is a temperature wave, unique to superfluid systems. The sound modes do not usually exist independently, but pressure variations are accompanied by variations in temperature, and vice versa. We studied the coupling between first and second sound in dilute 3 He - superfluid 4 He mixtures, around 2 K, at saturated vapor pressure, using a quartz tuning fork oscillator. Second sound coupled to first sound creates anomalies in the resonance response of the fork, which disappear only at very specific temperatures and concentrations, where two factors governing the coupling cancel each other.

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