2 research outputs found
Metastability exchange optical pumping of 3He gas up to hundreds of millibars at 4.7 Tesla
Metastability exchange optical pumping of
Metastability exchange optical pumping (MEOP) is experimentally investigated in
3He at 4.7Â T, at room temperature and for gas pressures ranging from 1 to
267Â mbar. The 23S-23P transition at 1083Â nm is used for optical
pumping and for detection of the laser-induced orientation of 3He atoms in the
rf discharge plasma. The collisional broadening rate is measured
(12.0 ± 0.4 MHz mbar-1 FHWM) and taken into account for accurate
absorption-based measurements of both nuclear polarization in the ground state and atom
number density in the metastable 23S state. The results lay the ground for a
comprehensive assessment of the efficiency of MEOP, by comparison with achievements at
lower field (1 mT–2 T) over an extended range of operating conditions. Stronger hyperfine
decoupling in the optically pumped 23S state is observed to systematically lead
to slower build-up of 3He orientation in the ground state, as expected. The
nuclear polarizations obtained at 4.7Â T still decrease at high pressure but in a less
dramatic way than observed at 2Â T in the same sealed glass cells. To date, thanks to the
linear increase in gas density, they correspond to the highest nuclear magnetizations
achieved by MEOP in pure 3He gas. The improved efficiency puts less demanding
requirements for compression stages in polarized gas production systems and makes
high-field MEOP particularly attractive for magnetic resonance imaging of the lungs, for
instance