Shear viscosity measurements of liquid 3He-4He mixtures above 0.5 K

Abstract

Simultaneous measurements of (ρη) and of the molar volume are reported for liquid mixtures of 3He in 4He over the temperature range between 0.5 and 2.5 K. Here η is the shear viscosity and ρ is the mass density. In the superfluid phase, the product of the normal components, ρ n and η n , is measured. The mixtures with 3He molefractions 0.30 < X < 0.80 are studied with emphasis on the region near the superfluid transition T λ and near the phase-separation curve. Along the latter, they are compared with data by Lai and Kitchens. For X > 0.5, the viscosity singularity near T λ becomes a faint peak, which however fades into the temperature-dependent background viscosity as X tends to the tricritical concentration X t. Likewise, no singularity in η is apparent when T t is approached along the phase separation branches Σ− and Σ+. Furthermore, viscosity data are reported for 3He and compared with previous work. Finally, for dilute mixtures with 0.01 ≤ X ≤ 0.05, the results for η are compared with previous data and with predictions.