The thermal boundary resistance of the superfluid He-3 A-B phase interface in the low temperature limit.

We have constructed a vertical cylindrical cell in which we cool superfluid He-3 to the low temperature limit. At the top and bottom of this cylinder are pairs of vibrating wire resonators (VWRs), one to act as a heater and the other as a thermometer. Quasiparticle excitations are created by driving the heater VWRs. These excitations can only leave the cylinder via a small hole at the top. Using a shaped magnetic field, we can produce a layer of A phase across the tube, while maintaining low field B phase in the vicinity of the VWRs for reliable thermometry. Preliminary results show that the two A-B interfaces lead to a measurable extra resistance for quasiparticles between the top and bottom of the cylinder