Transmission of helium atoms through a helium-II slab

We describe a measurement of the transmission probability of 4He atoms through a freely suspended slab of superfluid 4He at low temperatures. This geometry was treated in a recent theoretical calculation (J. Low Temp. Phys. 113 (1998) 519). In our experiment the slab is realised by using an array of parallel cylindrical holes of diameter 50 μm in a glass disc of thickness 200 μm. By controlling the chemical potential, the holes can be made to fill or empty with liquid, and the surface curvature varied. We have measured the transmission of atom beams, generated by a thin-film heater and detected with a sensitive bolometer, through this structure