Probing Liquid $$^4$$ 4 He with Quartz Tuning Forks Using a Novel Multifrequency Lock-in Technique

• DOI: 10.1007/s10909-016-1634-5
• Publication Date: 2016-06-15T15:46:29Z
• Authors: D. I. Bradley; R. P. Haley; S. Kafanov; M. T. Noble; G. R. Pickett; V. Tsepelin; J. Vonka; T. Wilcox
• Keywords: Lock (firearm); Tuning fork

We report on a novel technique to measure quartz tuning forks, and possibly other vibrating objects, in quantum fluid using multifrequency lock-in amplifier. The allows the resonance curve of object much faster than conventional single frequency amplifier technique. Forks with frequencies 12 kHz 16 were excited measured electro-mechanically either at or up 40 different simultaneously around same mechanical mode. response each fork was identical for both methods validates use probe properties liquid helium low velocities. Using we drag two 25- $$\upmu $$ m-wide forks immersed $$^4$$ He temperature range from 4.2 K 1.5 saturated vapour pressure. damping shift experienced by velocities are well described hydrodynamic contributions framework two-fluid model. sensitivity is larger compared similar 75- combination could be used improve thermometry He. also studies onset non-linear phenomena such as turbulence cavitation superfluids.