3He in 99.5% Porous Aerogel at the Normal-Superfluid Transition

Abstract

We have used a torsional oscillator to measure the superfluid density and dissipation near the superfluid transition of 3 He in aerogel of 99.5% porosity. We used a new cell (constructed at Penn State) for which the aerogel was grown in the pores of a ∼100 μm silver sinter. The cell was tested with 4 He and showed no signs of the second-sound resonances that have interfered with previous torsional oscillator measurements. The measurements with 3 He, presented here, were taken at pressures of 1.34 and 4.13 bars. We observed values of ρ s /ρ in the T→ 0 limit of 0.05 and 0.14 respectively. Our measurements show an increase in the dissipation on warming through T c . This series of measurements is ongoing and temperature sweeps at various pressures are planned.