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

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We have used a torsional oscillator to measure the superfluid density and dissipation near the superfluid transition of 3He 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 4He and showed no signs of the second-sound resonances that have interfered with previous torsional oscillator measurements. The measurements with 3He, presented here, were taken at pressures of 1.34 and 4.13 bars. We observed values of ρs/ρ in the T→ 0 limit of 0.05 and 0.14 respectively. Our measurements show an increase in the dissipation on warming through Tc. This series of measurements is ongoing and temperature sweeps at various pressures are planned.

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