An ultrasonic study of liquid helium filled porous ceramics.

摘要

The velocity and attenuation of transverse sound was measured in a variety of liquid helium filled, porous ceramics. These measurements were made both above and below the superfluid transition temperature (2.17 K in bulk helium) between the frequencies of 4 and 31 MHz using a pulsed, phase sensitive technique. An attenuation due to motion of the viscous normal fluid component in the pores was observed and compared to the predictions of Biot. Overall, the observed frequency and temperature dependence of the attenuation was in good agreement with the theoretical predictions over an extended range in pore size.