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 are performed in a cell where a torsional oscillator monitors the superfluid 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 velocity v_sl = h/ml, inherent in superfluid He films in such porous systems 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.on leave from: Inst. Physics near Prahaon leave from: Lukin's Research Inst. Phys. Problems, Zelnograd, Moscow.