Observation of Second Sound in SuperfluidHe3-B

The speed and attenuation of second sound in the $B$ phase of superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ near the transition temperature were measured at pressures of 18.2, 21.3, and 24.4 bars under zero applied magnetic field. The second sound was detected by use of a resonance method (frequency ∼ 1 Hz) and Peshkov transducers. The measured speed of second sound is in good agreement with the expected value. The measured quality factor is compared with a recent theory on the second viscosity coefficient.