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RESEARCH PRODUCT

Nuclear hyperpolarization of 3He by magnetized plasmas

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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 spin polarization of the free electrons). A description involvingalignment-to-orientation conversion in the excited 23P state is proposed. The PAMP method appears as a veryattractive alternative to established laser polarization techniques (spin exchange or metastability exchange opticalpumping). Application to 3He nuclear magnetometry with a relative precision of 10^(−12) is demonstrated.