Low Temperature Physics: 45, 1053 (2019); https://doi.org/10.1063/1.5125903
Fizika Nizkikh Temperatur: Volume 45, Number 10 (October 2019), p. 1235-1241 ( to contents , go back )
Mutual friction force with oscillations of a quartz tuning fork in superfluid helium
K.A. Mykhailenko, S.S. Sokolov, and G.A. Sheshin
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Nauki Ave., Kharkiv 61103, Ukraine
Received April 26, 2019, published online August 27, 2019
Experimental studies of the vibrational characteristics of a quartz tuning fork at low temperatures have been carried out. It is shown that the results of measurements in vacuum at 1.5 K almost coincide with the data obtained at 0.7 K in the case of a tuning fork covered with a helium film. The dependence of the oscillation velocity of the tuning-fork prongs on the exciting force is determined, and the dependence of the friction force on the oscillation velocity is calculated. The results are analyzed together with the previously obtained data on the nonlinear dependence determined in experiments with the same tuning fork immersed in superfluid helium under conditions of the excitation of turbulent fluid flow. The regions of the oscillation velocities corresponding to the determining influence on the oscillations of the tuning fork from internal friction in the substance of the tuning fork and in helium, are established. The data were analyzed using the nonlinear Duffing equation, which made it possible to determine the temperature dependence of the coefficient of nonlinearity of the tuning fork and the coefficient of mutual friction caused by the turbulent flow of a superfluid.
Key words: quartz tuning fork, internal friction, Duffing equation, nonlinearity coefficient.