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Courtade, Emmanuel; Marion, François; Nacher, Pierre-Jean; Tastevin, Geneviève; Dohnalik, T.; Kiersnowski, K.

doi:10.1023/a:1012673902661

Cited by 20 publications

(40 citation statements)

References 4 publications

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“…In practice, the LHCP/RHCP fraction can not be zero due to, for example, a slight miss-alignment of the optical components, and perfect polarization is not obtainable, and hence the optimum OP radiation density should be determined to acquire the highest He + polarization. It is noted that the pumping rate obtained from the fitting in the present study is much larger than that derived by Courtade et al, 12 although a precise comparison is difficult because the linewidth of the OP radiation is unknown in the range 1 -2 GHz in the present setup. A possible explanation for this discrepancy may be radiation trapping.…”

Section: Resultscontrasting

confidence: 67%

Development of Spin-Polarized Ion Scattering Spectroscopy

Suzuki

Yamauchi

2008

ANAL. SCI.

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Spin-polarized ion scattering spectroscopy using an electron-spin-polarized 4 He + ion beam was developed as a novel analytical method of the element selective spin state at outermost surfaces. Spin-polarized He + ions were generated from the Penning ionization of metastable He 2 3 S1 atoms (He*), which were spin-polarized by optical pumping (OP). The spin polarization of He* (PHe*) was observed to be the highest with an OP radiation density of about 0.05 W cm -2 , and a further increase of the OP radiation density reduced PHe*. This decrease of PHe* is attributed to imperfect polarization of the OP radiation, hence optimization of the OP radiation density is essential to obtain He + ions with high spin polarization. As a result of this optimization, we successfully observed the spin dependence of the scattered He + ion yield on an Fe(100) surface exposed to an oxygen atmosphere.

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Section: Resultscontrasting

confidence: 67%

Development of Spin-Polarized Ion Scattering Spectroscopy

Suzuki

Yamauchi

2008

ANAL. SCI.

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“…1. More details and numbers can be found in [18] and references therein. The atomic resonance lines are distributed over nearly 70 GHz, with line widths originating from various processes.…”

Section: Metastability Exchange Optical Pumping and Laser Requirementsmentioning

confidence: 99%

“…This parameter is mainly determined by the laser line width and mode structure. Collisional redistribution between velocity classes also plays a role [18], but it is only crudely taken into account for the numerical simulations [10]. Attempts to accurately reproduce saturation profiles measured for narrowband laser sources bring to light the need to improve such input parameters, and maybe also to include other effects like radiative broadening of resonance lines (at high laser powers) [24].…”

Section: Metastability Exchange Optical Pumping and Laser Requirementsmentioning

confidence: 99%

“…Power densities well below a few mW/cm 2 are needed to avoid saturation (see next subsection). When circularly polarized light is used, a strong local field inhomogeneity must be imposed in the He cell to prevent nuclear polarization build-up, which would significantly alter the line profiles [18]. At high laser intensities finite orientation can still be produced in the metastable state despite strong nuclear relaxation in the ground state (over-polarization of the 2 3 S atoms [10]) and the best way to avoid OP effects is to use linearly polarized light.…”

Section: Line Width Measurementsmentioning

confidence: 99%

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A broadband ytterbium-doped tunable fiber laser for 3He optical pumping at 1083�nm

Tastevin

Grot

Courtade

et al. 2004

Applied Physics B: Lasers and Optics

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Large amounts of hyperpolarized 3 He gas with high nuclear polarization rates are required for use in neutron spin filters or nuclear magnetic resonance imaging of human lung. Very high efficiency can be obtained by metastability exchange optical pumping using multimode lasers to excite the 2 3 S-2 3 P transition at 1083 nm. Broadband Ytterbium-doped tunable fiber lasers have been designed for that particular application. Different options for the architecture of the fiber oscillator are presented and compared. Emphasis is given to a linear cavity configuration that includes a high reflectivity fiber mirror and a low reflectivity tunable fiber Bragg grating. Optical measurements are performed to finely characterize the spectral behavior of the lasers. Atomic response is also quantitatively probed to assess the optimal design of the oscillator for optical pumping. Multimode operation matching the 2 GHz Doppler-broadened helium resonance line and tunability over more than 200 GHz are demonstrated. Boosting the output of this fiber laser with a Yb-doped fiber power amplifier, allfiber devices are built to provide robust, high power turn-key sources at 1083 nm for improved production of laser polarized 3 He. 42.55.Wd; 32.80.Bx PACS

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“…It was achieved by operating OP in a higher magnetic field (0.1 T) than is commonly used. High field OP in 3 He had been previously reported at 0.1 T [14] and 0.6 T [15], but the worthwhile use of high fields for OP at high pressures (tens of mbar) had not been reported until recently [16].…”

Section: Introductionmentioning

confidence: 99%

Magnetic field effects on the 1 083 nm atomic line of helium

Courtade¹,

Marion²,

Nacher³

et al. 2002

The European Physical Journal D - Atomic, Molecular and Optical

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Abstract. The structure of the excited 2 3 S and 2 3 P triplet states of 3 He and 4 He in an applied magnetic field B is studied using different approximations of the atomic Hamiltonian. All optical transitions (line positions and intensities) of the 1083 nm 2 3 S-2 3 P transition are computed as a function of B. The effect of metastability exchange collisions between atoms in the ground state and in the 2 3 S metastable state is studied, and rate equations are derived, for the populations these states in the general case of an isotopic mixture in an arbitrary field B. It is shown that the usual spin-temperature description remains valid. A simple optical pumping model based on these rate equations is used to study the B-dependence of the population couplings which result from the exchange collisions. Simple spectroscopy measurements are performed using a single-frequency laser diode on the 1083 nm transition. The accuracy of frequency scans and of measurements of transition intensities is studied. Systematic experimental verifications are made for B=0 to 1.5 T. Optical pumping effects resulting from hyperfine decoupling in high field are observed to be in good agreement with the predictions of the simple model. Based on adequately chosen absorption measurements at 1083 nm, a general optical method to measure the nuclear polarisation of the atoms in the ground state in an arbitrary field is described. It is demonstrated at B ∼0

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Untitled

Cited by 20 publications

References 4 publications

Development of Spin-Polarized Ion Scattering Spectroscopy

Development of Spin-Polarized Ion Scattering Spectroscopy

A broadband ytterbium-doped tunable fiber laser for 3He optical pumping at 1083�nm

Magnetic field effects on the 1 083 nm atomic line of helium

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