Mass Flow through Solid 4H

We continue our solid He-4 flow experiments in which we grow solid helium samples at constant temperature in the hcp region of the phase diagram. We exploit the properties of liquid helium in a confined geometry (porous Vycor glass), and induce a mass flow through the solid at pressures higher than the bulk melting pressure. We previously observed flow, but our temperature was limited to Ta parts per thousand yen350 mK. At Ta parts per thousand 400 mK it was found that the flow ceased at Pa parts per thousand 27 bar, and no flow was observed for T > 550 mK. We have begun to extend our measurements to lower temperatures, and our data show that at lower temperatures we observe flow at higher pressures.