Mass flux through solid 4He induced by chemical potential differences

The thermo-mechanical effect and also direct mass injection have been used to create chemical potential differences between two reservoirs of superfluid 4He connected to each other through superfluid-filled Vycor rods in series with solid hcp 4He. An increasing DC flux of atoms takes place through the solid-filled cell with decreasing temperature below asymp 600 mK That flux falls abruptly in the vicinity of 75–80 mK, but increases again at lower temperatures. These experiments, done in collaboration with M Ray, will be briefly reviewed as will our studies of the growth of solid 4He where it is seen that it is impossible to add density to a solid freshly made at 60 mK and samples freshly made near 60 mK do not allow mass flux, even when raised in temperature to 200 mK Solids created above asymp 300 mK and cooled to 60 mK accept added density and demonstrate finite mass flux. Relationships to theoretical work and other solid helium work will be briefly discussed.