Thermal transport by ballistic quasiparticles in superfluid He-3-B in the low temperature limit

In the temperature range below 0.2T(c), the gas of thermal excitations from the superfluid He-3-B ground state is in the ultra-dilute ballistic regime. Here we discuss preliminary measurements of the transport properties of this quasiparticle gas in a cell of cylindrical geometry with dimensions much smaller than any mean free path. The vertical cylinder, constructed from epoxy-coated paper, has vibrating wire resonator (VWR) heaters and thermometers at the top and bottom, and a small aperture at the top which provides the only exit for quasiparticles. Using the thermometer VWRs, we measure the difference in quasiparticle density between the top and bottom of the tube when we excite the top or bottom VWR heater. This gives information about the transport of energy along the cylindrical 3 He sample and hence about the scattering behaviour involved when a quasiparticle impinges on the cylinder wall.