Liquid and Solid Helium at Very Low Temperatures

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They propose to study the following phenomena at very low temperatures: 1) The transmission probability of quasiparticles striking the interface between normal or superfluid liquid 3He and a saturated solution of 3He in liquid 4He. The probability will be obtained by measuring the transmission of spin waves across the interface. 2) The damping of a vibrating wire in superfluid 3He-A at extremely low temperatures. This experiment will reveal whether the superfluid energy gap varies with the direction of the quasiparticle momentum according to the sin0 dependence predicted by theory. 3) The Kapitza thermal conductance of the interface between the superfluid A and B phases in 3He. 4) The reflection probability of rotons at the free surface of liquid 4He and at smooth solid surfaces. 5) The reflection probability of 3He atoms at the surface of liquid 3He.