Fundamentals of metastability exchange optical pumping in helium

Batz, Marion; Nacher, Pierre-Jean; Tastevin, Geneviève

doi:10.1088/1742-6596/294/1/012002

Cited by 30 publications

(54 citation statements)

References 29 publications

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“…This preserves the stability of the plasma but does not allow for, e.g., absolute measurements of the absorbed pump and probe light powers at steady-state polarization [24]. Due to strict time constraints (a 4-week period of access time to the 4.7 T MRI magnet granted for the whole study), the experimental runs are planned to include investigations for a combination of three discharge intensities and three pump power conditions, with limited opportunities for tests of reproducibility.…”

Section: Measurement Protocolsmentioning

confidence: 99%

“…5 Equation (2) can be directly extended to the case of strong 2 3 S-2 3 P excitation by replacement of ai with (ai − bj), where nmbj is the number density of 3 He atoms in sublevel Bj [24].…”

Section: Spectral Amplitudesmentioning

confidence: 99%

“…When ME dominates, a Boltzmann-like distribution of angular momenta is established in the 2 3 S state (a i ∝ e βmF ), fully ruled by M and characterized by an effective spin-temperature parameter 1/β given by e β = (1 + M )/(1 − M ) [1,15,24]. The spin-temperature equilibrium populations a i are equal to:…”

Section: Spin-temperature Equilibriummentioning

confidence: 99%

“…Figure 4c displays the corresponding baseline-corrected data (q ). The baselines cannot be reliably computed when OP is performed because of the ill-known population imbalance induced by the intense OP light [5,14,23,24]. Instead, they are corrected for by substraction of linear baselines that are automatically adjusted to the data for the monotonic parts of the alternating frequency sweeps.…”

Section: Impact Of 2 3 S-2 3 P Collisional Broadeningmentioning

confidence: 99%

“…During OP, the pump light drives fast absorption − emission cycles and efficiently transfers atoms out of the pumped sublevels. The imbalanced distribution of populations enforced in the 2 3 S state provides the driving term for the build-up of the nuclear polarization in the ground state [24]. M becomes negative for f − 2 pumping since the OP-induced skew is characterized by a strong depletion in A 5 and A 6 levels and excess populations in A 1 and A 2 , with a 1 ≥ a 2 .…”

Section: Nuclear Polarization Measurementsmentioning

confidence: 99%

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Metastability exchange optical pumping of 3He gas up to hundreds of millibars at 4.7 Tesla

et al. 2013

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Abstract. Metastability exchange optical pumping (MEOP) is experimentally investigated in3 He at 4.7 T, at room temperature and for gas pressures ranging from 1 to 267 mbar. The 2 3 S-2 3 P transition at 1083 nm is used for optical pumping and for detection of the laser-induced orientation of 3 He 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 2 3 S 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 2 3 S state is observed to systematically lead to slower build-up of 3 He orientation in the ground state, as expected. The nuclear polarizations obtained at 4.7 T still decrease at high pressure but in a less dramatic way than observed at 2 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 3 He 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.

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Section: Measurement Protocolsmentioning

confidence: 99%

Section: Spectral Amplitudesmentioning

confidence: 99%