SUPERFLUID-HELIUM IN POROUS-MEDIA

The superfluid properties of He-4 absorbed in porous media are discussed. Emphasis is given to the nature of the super fluid transition for helium contained in a variety of different porous structures. Recent heat capacity and superfluid measurements for helium in Vycor glass and other porous media are presented in some detail The onset of superfluidity as a function of adsorbed helium coverage at zero temperature, or "boson localization," is touched on briefly. The problem of dissipation of superflow in porous media, especially in the vicinity of the superfluid transition, is discussed.