Ultrasound studies of superfluid 3He-B in a magnetic field

An ultrasonic pulse-time-of-flight experiments were performed to investigate the squashing mode of the superfluid 3He-B in a magnetic field. All five of the expected Zeeman sublevels for this J = 2- mode were observed. The investigation was done at a very low temperature (T/Tc < 0.35) to reduce the quasi-particle broadening that tends to smear the collective modes and makes resolution of the individual sublevels impossible. Variation of the pressure was used to sweep the collective mode frequencies through the operating frequency, 137.6 MHz of the resonant sound transducers. Both group velocity spectroscopy and pulse-shape analysis were used for identification of different sublevels. Performing experiments at different orientations of the sound propagation with respect to magnetic field direction (parallel, perpendicular, 55 and 13 degrees) was the key to observation of all 5 modes and their identification. The Lande g factor was obtained from the linear dependence of the Jz = +2 mode on magnetic field and compared to theory. In the second part of this dissertation I describe the ultrasound pulse transmission experiments that were performed to investigate the pair breaking edge for superfluid 3He-B in a magnetic field. These experiments were performed at 3 He temperatures below .4 Tc, pressures between 6 and 29.3 bars, and ultrasound frequencies of 168.33 MHz, 137.6 MHz and 107 MHz. Both depressurization and demagnetization techniques were used to measure the linear and quadratic magnetic field dependence of the pair breaking edge frequency. The values for a the Fermi Liquid interaction parameter F2α are obtained from the coefficient of the linear term. The quadratic term is due to the energy gap distortion and its value is consistent with calculations of Schopohl and Tewordt