Figure 1

Double resonance torsional oscillator. It contains two masses and BeCu torsion rods (a) (2 mm outer diameter). The upper mass includes a BeCu disc (b) with movable detector and generator electrode fins (c). The lower mass is made of a Stycast 1266 epoxy block (e) containing a hollow cylindrical solid ${}^4\mathrm{He}$ sample space (10.2 mm in diameter and 7.6 mm in height). A second movable detector electrode (f) attached to the bottom side of the lower mass is used to calibrate the upper electrode detector motion. ${}^4\mathrm{He}$ is filled through a central 0.8 mm diameter hole (d) drilled in the torsion rods and the upper mass. Fixed electrodes placed facing the movable electrodes are not shown.Reuse & Permissions

Figure 2

Temperature dependence of nonclassical rotational inertia fraction and change of dissipation (see text) at $f_1$ (○) and $f_2$ (▵). Pressure of the solid is 37 bar. Rim velocities are $8.5\sim 13.5\mu \mathrm{m}/\sec $ at $f_1$ and $7.2\sim 16.0\mu \mathrm{m}/\sec $ at $f_2$.Reuse & Permissions

Figure 3

Rim velocity dependence of nonclassical rotational inertia fraction for two frequencies at the temperature of 19 mK. Measurements are taken as the drive is decreased (+) [increased (○)] in sequence from the maximum (minimum) value shown for $f_1$. Similarly, measurements are taken as the drive is decreased (▵) [increased (⋄)] in sequence from the maximum (minimum) value shown for $f_2$. Arrows indicate the direction of the rim velocity changes.Reuse & Permissions

Figure 4

Rim velocity dependence of nonclassical rotational inertia fraction for two frequencies at 63 mK. Symbols refer to the same processes as in Fig. 3.Reuse & Permissions