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Theses

Etude thermodynamique et de R.M.N. des mélanges liquides d'hélium 3 polarisé dans l'hélium 4

Abstract : Laser optical pumping in low magnetic field provides very high nuclear polarizations in gaseous helium mixtures. The transfer of polarized helium 3 atoms to a cold, liquid sample operates in steady states thanks to an efficient thermal technique which drives a circulation of helium 3. Wall relaxation in glass cells is efficiently reduced by using cesium coatings. In highly magnetized samples, dipolar fields control the spin dynamics in anisotropic volumes and weak external magnetic field inhomogeneities. Long-lived magnetostatic modes are observed by pulsed NMR. Detailed analysis of their frequency and damping gives information on magnetization density and spin diffusion coefficient in polarized mixtures. Experiments are performed above 0.2K on mixtures with helium 3 concentrations of the order of a few percent or larger. When phase separation occurs, the helium 3 rich phase retains a high polarization. Preliminary results concerning the observation of the phase separation as well as the measurement of the chemical potential of helium 4 are also reported in this thesis.
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  • HAL Id : tel-00011910, version 1

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Eric Stoltz. Etude thermodynamique et de R.M.N. des mélanges liquides d'hélium 3 polarisé dans l'hélium 4. Matière Condensée [cond-mat]. Université Pierre et Marie Curie - Paris VI, 1996. Français. ⟨tel-00011910⟩

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