Eur. Phys. J. Special Topics 144, 255-263 (2007)
https://doi.org/10.1140/epjst/e2007-00138-3

Metastability exchange optical pumping of ³He at high pressure and high magnetic field for medical applications

¹ M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland
² Department of Physics, Agricultural University, Al. Mickiewicza 21, 31-120 Kraków, Poland
³ Faculté des Sciences, Université Saint Joseph, BP. 11-514 Riad el Solh, 1107 2050 Beirut, Lebanon
⁴ Laboratoire Kastler Brossel, École Normale Supérieure, 24 rue Lhomond, 75005 Paris, France
⁵ Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, 31-342 Kraków, Poland

Abstract

Systematic studies of the metastability exchange optical pumping (MEOP) process in ³He gas at high magnetic fields (0.45, 0.9, 1.5, and 2 T) and pressures (32 and 64 mbar) are performed. The impact of experimental parameters such as laser power, beam profile, and shape of the pumping cell is evaluated. By varying the discharge intensity in the cell, the density of metastable state atoms and the plasma-induced nuclear relaxation rate are also controlled, and their effect on the MEOP efficiency can be investigated. Very accurate experimental results are obtained, opening the way to quantitative tests of a recently proposed model of the MEOP process at high magnetic field. We report selected MEOP results with nuclear polarizations exceeding 50 % at 64 mbar and 2 T, which represents a dramatic improvement in performances over MEOP at low magnetic field. The present findings suggest that still higher polarizations can be achieved in higher magnetic fields, and motivate investigations at higher gas pressures. New ways of producing hyperpolarized ³He for magnetic resonance imaging and medical applications can be envisaged, as most clinical whole-body scanners operate at 1.5 T.