Transport Rates of the Helium II Film Over Various Surfaces

Liquid helium II film transport over various surfaces has been studied by a new method in which a cylindrical capacitor using liquid helium as the dielectric is employed as a depth gauge. Changes in liquid level resulting from film transport produce changes in capacitance which in turn cause frequency changes in a high frequency circuit. The details of this method are described. The film transport rates, measured to 1.25°K, were found to depend on the substrate; at 1.25°K, the highest rate observed was 51×${10}^{-5\mathrm{}}$ ${\mathrm{cm}}^3$/cm sec for etched copper and the lowest, 7.5×${10}^{-5\mathrm{}}$ ${\mathrm{cm}}^3$/cm sec for glass. The rates were also measured over iron in the magnetized and unmagnetized state and over a superconductor in the superconducting and in the normal state. No differences were noted. In the latter case the thermal conductivity of the container is abruptly changed and the absence of an effect supports the view that heat transfer plays no significant role in determining the transport rate.