[en] The authors report progress on a measurement of the specific heat of ⁴He-filled Vycor glass near 2K. It has been suggested that due to the reduced superfluid density in the ⁴He-Vycor system, the heat capacity signature will be diminished by a factor of 10⁴ over the bulk value and will occur at the superflow onset temperature of T_c = 1.955 K. This is supported by observations of thin films of ⁴He in Vycor which show reduced heat capacity peaks coincident with superflow onset. The adiabetic heat capacity technique the authors are currently implementing should have resolution of 1 part in 10⁶ and is expected to determine the presence of the predicted peak in C_v

No abstract available

[en] The authors report heat capacity measurements of ⁴He films in Vycor near the critical coverage. The goal of these studies is to determine whether the low temperature phase at coverages below the onset of superfluidity is a glass or an insulator with a gap. The data cover a temperature range of 5 mK to 600 mK. At the lowest temperatures, a CMN DC-SQUID thermometer is used. This thermometer contains 3 mg of CMN to minimize its heat capacity. The sensitivity at 10 mK is better than 500 pK/√Hz. The CMN powder is mixed with a Ag sinter to improve thermal conductivity. The resistance thermometers mounted on the cell are found to be reliable down to 14 mK

[en] The superfluidity of the A phase of ³He is established by the propagation of fourth sound. The measured velocity is consistent with a two-fluid model. The superfluid density agrees well with other measurements. 2 figures

No abstract available

[en] The authors have completed a systematic study of the superfluid density of ⁴He films adsorbed in 91% porosity aerogel glass. They have concentrated on the low-coverage regime (T_c < 200 mK) in an attempt to address recent theoretical work on the onset of superfluidity in dirty boson systems. Their data are not in agreement with the predictions of a scaling theory of the onset transition developed by Fisher et al. They discuss the extent of this disagreement and the limitations of other models of the onset transition. 8 refs., 3 figs

No abstract available

[en] The superfluid response of helium films with transition temperatures ranging from 70 mK to 0.5 K has been studied using a torsional oscillator technique. A detailed analysis of the background indicates that the initial nonsuperfluid layer has an unexpected temperature-dependent period shift and dissipation. The superfluid response obeys a general scaling law which can be derived from the Kosterlitz-Thouless theory. Comparisons with the dynamic theory reveal nonuniversal behavior as a function of coverage

[en] We have measured the moment of inertia of hcp ⁴He crystals from 25 mK to 2 K. With a precision of five parts in 10⁶ we find no evidence for a nonclassical rotational inertia. This indicates that if a supersolid exists, it has a rho/sub s//rho of less than 5 x 10^-6, a transition temperature of less than 25 mK, or a critical velocity of less than 5 μm/sec

[en] In this paper, the measurements of the hydrodynamic quantities, superfluid density and viscosity in liquid ³He are described. At Cornell, the technique developed by Andronikashvili was adapted for the measurement of the superfluid density in liquid ⁴He. Liquid helium is contained in a cell formed by parallel circular plates of radius R. The spacing, h, between the plates and the frequency of oscillation are chosen so that the viscous penetration depth is greater than the spacing between the plates. The data produced by the Andronikashivli experiment consist of the period, P, of the oscillator, the drive voltage, D, required to maintain a constant amplitude of oscillation and the susceptibility of either NMR or CMN thermometers. Temperatures are obtained from the susceptibility data in the conventional manner by assuming Curie law behavior for temperatures down to the transition. An expression for torque, L, produced by the fluid in the Andronikashvili cell during torsional oscillation is obtained. In the Fermi liquid region above the transition, the viscosity is expected to be proportional to 1/T² on the basis of theory and previous measurement. Measurement of normal fluid density, anisotropy of the superfluid density, B phase superfluid density, and B phase normal fluid viscosity were carried out. The main accomplishments of the measurement to date have been the clear demonstration of the anisotropy of A-phase superfluid density and the high resolution measurement of B-phase normal fluid shear viscosity in the immediate neighborhood of the transition. (Kato, T