Added mass of the oscillating quartz tuning fork immersed in He II
I.A. Gritsenko, K.O. 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 Nauky Ave., Kharkiv 61103, Ukraine
Received Jule 13 2016
Experimental investigations are carried out of the added mass that accompanies the oscillation of a tuning forks immersed in He II with the resonance frequencies of 6.7, 8.5, 12.1, 25.0, and 33.0 kHz. Added mass coefficient, i.e., the ratio of the added mass to the mass of fluid displaced by a tuning fork, was deter-mined depending on temperature and pressure under measuring the resonance frequency of the tuning forks. The range of temperature under studying was from 2.2 K down to 0.1 K whereas the measurements of the resonance frequency dependences on the pres-sure were performed at the constant temperature of 0.365 K in the pressure range from 1 bar to 24.8 bar. It has been shown that at temperature below 0.7 K where the viscosity of He II is negligible, the resonance frequency of the tuning fork oscillations is specified by the added mass of the fluid. The dependences of resonance frequencies on the pressure are shown to provide the accuracy of the measurements of the added mass coefficient about one order higher than that of the temperature dependences. It is found that the added mass coefficient is frequency dependent decreasing with increasing the frequency.