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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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