0000000000076793
AUTHOR
Andreas Maul
Nuclear hyperpolarization of 3He by magnetized plasmas
International audience; We describe a method, referred to as PAMP (polarization of atoms in a magnetized plasma), that allowshyperpolarization of 3He nuclear spins at high magnetic field solely by excitation of a rf gas discharge.A magnetized plasma is obtained when the mean free path of the free electrons is much larger than theirgyration radius in the rf gas discharge. Investigations of PAMP are carried out in the 1–15-mbar pressure rangewith rf excitation around 100 MHz. Quantitative NMR measurements at 4.7 T and room temperature showthat, for different cell sizes and gas densities, 3He nuclear polarizations in the 1 to 9% range are achieved(i.e., larger than the Boltzmann equilibrium sp…
Spherical fused silica cells filled with pure helium for nuclear magnetic resonance-magnetometry.
High magnetic fields (> 1 T) are measured by NMR magnetometers with un-rivaled precision if the precessing spin sample provides long coherence times. The longest coherence times are found in diluted ${}^{3}$He samples, which can be hyperpolarized for sufficient signal strength. In order to have minimal influence on the homogeneity and value of the measured magnetic field the optimal container for the ${}^{3}$He should be a perfect sphere. A fused silica sphere with an inner diameter of 8 mm and an outer diameter of 12 mm was made from two hemispheres by diffusion bonding leaving only a small hole for cleaning and evacuation. This hole was closed in vacuum by a CO${}_{2}$ laser and the inner…