A study of the superfluid transition of 4He films adsorbed on slip- cast Al2O3 powder will be made, using a torsion oscillator and acoustic techniques. The vortex core size will be obtained as a function of temperature, film thickness and 3He concentration. The dissipation at the transition will be measured over a frequency range from 1 kHz to 30 MHz. It is also proposed to measure the tortuosity of porous ceramics; and to study the dynamics of the lambda transition using a vortex-ring theory. Measurement of the superfluid density in liquid 4He films on a porous substrate can furnish new insight into the quantum behavior of condensed matter at very low temperature.
