Low Temperature Physics: 34, 497 (2008); https://doi.org/10.1063/1.2957000 (6 pages)
Microwave experiments in He II. New peculiarities of persistent superflows
A.S. Rybalko, S.P. Rubets, E.Ya. Rudavskii, V.A. Tikhiy
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Lenin Ave., Kharkov 61103, Ukraine
S.A. Tarapov, R.V. Golovashchenko, and V.N. Derkach
A. Usikov Institute of Radiophysics and Electronics of the National Academy of Sciences of Ukraine 12 Acad. Proskura Str., Kharkov 61085, Ukraine
Received March 11, 2008
Òhe experimental study of stability and oscillating properties of a superfluid ring flow arising around the cylindrical surface of a disk dielectric resonator immersed in liquid helium was carried out. The superflow velocity was controlled with special thermal guns located in He II and generating the counterflows of normal and superfluid components oriented tangentially to the resonator surface. In the experiment, the amplitude of a microwave signal passed through the resonator was measured and the influence of phase and dynamic state of the liquid on the amplitude was studied. It is found that in He II one can observe periodic signal oscillations with each of the periods starting from a very sharp amplitude splash. It is suggested that such a behavior of the signal is connected with a loss of stability of the ring superflow due to a change in the number of circulation quanta of the superfluid velocity in a very short time interval. Other effect consists in observating in the system new recurrent resonance peaks along with the familiar whispering gallery modes. The effect was not observed at temperatures above the l-point. One can suggest that it is connected with hypothetic oscillating modes of the persistent flow. Some possible reasons for the peculiarities observed are analyzed.
PACS: 67.10.Hk Quantum effects on the structure and dynamics of nondegenerate fluids;
Key words: superfluid helium, dielectric resonator, wishpering gallery.