SUPERFLOW AND DISSIPATION IN POROUS GLASSES

The study of superflow of He-4 in porous vycor glass has a long venerable history, dating back to the early days of superfluidity. In this work we wish to address a number of outstanding questions. In doing so we have used a low frequency (250 Hz) Helmholtz oscillator technique which uses filled pores and allows measurements to be made on small samples under a variable pressure gradient and at any temperature - not only below the superfluid transition (a feature also of torsional oscillator1 and acoustic techniques2). An introduction to the resonator has already been published3. The technique has also been used to investigate aerogel porous glass11 but the main emphasis of this report will be on vycor.