Magnetic Properties of Superfluid and Normal Helium -3, and a Search for Superconductivity in Gold.
Abstract
This dissertation describes measurements of the nuclear susceptibility of ('3)He in the normal, A and B phases of the liquid, and an experiment designed to look for superconductivity in gold. The ('3)He work covers the pressure range from 0 to 32.65 bars in seven steps. The susceptibility was measured by cw NMR in fields up to 4.78kG and in the temperature range from 0.35 to 10mK. The susceptibility of the B phase was found to be field dependent and has been fit to a theory of Tewordt and Schopohl (1979). Through a comparison of normal liquid data (Alvesalo et al., 1980) and the results of the fits to theory, the data can be extrapolated to the weak coupling limit (T(,c)/T(,F) = 0). This extrapolation determines the absolute temperature near 1mK. The value for T(,c) at zero pressure is found to be 1.005 (+OR-) 0.015 mK. Spin waves were detected on the cw NMR lineshapes in the normal liquid at pressures below 9 bars and temperatures less than 5mK. The spins are in a collisionless regime with (omega)(tau) >> 1, where (omega) is the spin frequency and (tau) is the spin diffusion relaxation time. The spin waves have been correlated with the theory of Platzman and Wolff (1967). Spin waves were also observed in the A and B phases of ('3)He near T(,c) below a pressure of 9 bars. In the experiment on gold we searched for superconductivity down to 0.22mK and did not see a transition. The experimental procedure is described as well as some of the difficulties involved in low temperature superconductivity experiments, such as the effects of impurities, residual magnetic fields, and the problem of detection of the transition.
- Publication:
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Ph.D. Thesis
- Pub Date:
- 1981
- Bibcode:
- 1981PhDT.......213S
- Keywords:
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- Physics: Fluid and Plasma