Studies on Helium Liquids by Vibrating Wires and Quartz Tuning Forks

Integrated electronic transport and thermometry at milliKelvin temperatures and in strong magnetic fields

“…The motion of the quartz tuning fork in pure He-3 is described by the Stokes hydrodynamic model [16][17][18] which has recently been verified to be valid in the 5-100 mK range by a cross-calibration against He-3 melting curve thermometers. 16,18 According to this model the quality factor of the oscillator Q is inversely proportional to the square root of the viscosity.…”

“…15 We measure the viscosity of He-3 with an oscillating quartz tuning fork which is fastened to the main heat exchanger of our immersion cell. Quartz tuning fork thermometers have recently been used in studies of quantum liquids [16][17][18] and have a number of advantages. In our setup the quartz viscometer is in close vicinity of the sample and measures the in situ temperature of the He-3 bath in real time.…”

Decoupling of first sound from second sound in dilute He3–superfluidHe4 mixtures

“…The velocity of second sound ranges approximately between 0 and 40 m/s in the temperature and concentration range of our experiment. Largest values are obtained at low temperatures and at high concentrations, while near T λ it tends to zero, as second sound ceases to exist [9,[24][25][26][27]. Since the second sound velocity has a significant temperature and concentration dependence, there exist numerous possible standing sound wave modes that can be observed with a quartz tuning fork [28].…”

“…We also had another fork with a different resonance frequency and larger physical size installed, but it behaved erratically, and it then could not be used to produce any meaningful experimental data. We measured the fork in so-called tracking mode [9], in which a computer program determines the resonance frequency and the width of the resonance from a single measurement point close to the actual resonance frequency, assuming that the shape of the resonance is Lorentzian. The tracking mode enables us to repeat the measurement every few seconds instead of minutes, as it would take if we were to record entire resonance spectra with sufficient precision.…”

“…These kind of anomalies in the quartz tuning fork response, or second sound resonances, have been observed before [9][10][11], but the detailed mechanism producing the anomalies has not been thoroughly investigated. Calculations of the coupling factors between first and second sound in helium mixtures have been presented by Brusov et al [12], but, as first noted by Rysti [13], they made a sign error in their calculations, which washed out the decoupling behavior.…”