RECENT RESULTS ON HYPERPOLARIZED HE-3-HE-4 LIQUID-MIXTURES

Laser optical pumping in law magnetic field provides very high nuclear polarizations in gaseous helium mixtures, and is used to prepare pola rized liquid. Wall relaxation in glass cells is efficiently reduced us ing cesium coatings, and bulk longitudinal relaxation times are measur ed. In highly magnetized samples, dipolar fields control the spin dyna mics in anisotropic volumes and weak external magnetic field inhomogen eities. Long lived magnetostatic modes are observed by pulsed NMR. Det ailed analysis of their frequency and damping gives information on mag netization density and spin diffusion coefficient in polarized mixture s. Experiments are performed above 0.2 K on mixtures with He-3 concent rations of order a few percents or larger. When phase separation occur s, the He-3-rich phase retains a high polarization.