MEASUREMENTS ON A DYNAMIC A-B PHASE-BOUNDARY IN SUPERFLUID HE-3 AT VERY-LOW TEMPERATURES

We present preliminary measurements of the dynamics of a moving A-B ph ase interface in superfluid He-3 art temperatures below 0.2T(c). We in itially stabilise the interface at lour temperatures with a shaped mag netic field. We can then move the interface in a controlled manner by applying small additional time-dependent fields. The interface is crea ted inside a quasiparticle radiator consisting of a cylindrical chambe r in weal thermal contact with the refrigerant. Vibrating wire resonat ors inside the radiator allow us to monitor the temperature of the sup erfluid and to infer the heat generated by the interface motion. When me oscillate the interface at low frequencies, we measure spectacular oscillatory swings of the liquid temperature arising from the enormous change in the low lying density of states as the volume of the A-phas e superfluid is alternately compressed and expanded. We have also obse rved hysteresis in the transition as a function of magnetic field. In particular, we observe a small history-dependent 'super-magnetisation' of the B-phase prior to A-phase nucleation in the experimental chambe r. When the system is in the metastable super-magnetised state we are abbe to observe a higher nucleation probability of the A-phase when th e cryostat is exposed to neutrons.