THERMAL-CONDUCTIVITY STUDY OF THIN HE FILMS ADSORBED IN POROUS GLASSES WITH WELL-CONTROLLED PORE SIZES

Thermal conductivity study of thin He films adsorbed in porous glasses with well controlled pore sizes(\2\) is reported. The measurements ar e performed in a cell where a torsional oscillator monitors the superf luid density change for the same films for comparison. Since the heat flux through the superfluid is proportional to the superfluid velocity , we discuss the possible observation of the intrinsic critical veloci ty v(sl) = h/ml, inherent in superfluid He films in such porous system s with unit pore length l, as discussed by Minoguchi and Nagaoka(\3\), which marks the velocity at which phase slippages start to occur over macroscopic scales.