A5049266195- Quantum, superfluid, helium dynamics
- Atomic and Subatomic Physics Research
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced NMR Techniques and Applications
- NMR spectroscopy and applications
- Advanced MRI Techniques and Applications
- Gas Dynamics and Kinetic Theory
- Advanced Thermodynamics and Statistical Mechanics
- Spectroscopy and Laser Applications
- High-pressure geophysics and materials
- Spacecraft and Cryogenic Technologies
- Methane Hydrates and Related Phenomena
- Physics of Superconductivity and Magnetism
- Nuclear Physics and Applications
- Quantum optics and atomic interactions
- Superconducting Materials and Applications
- Aerogels and thermal insulation
- Advanced Frequency and Time Standards
- Phase Equilibria and Thermodynamics
- Quantum Mechanics and Applications
- Catalytic Processes in Materials Science
- Rheology and Fluid Dynamics Studies
- Optical properties and cooling technologies in crystalline materials
- Laser Design and Applications
- Geophysics and Sensor Technology
Laboratoire Kastler Brossel
2005-2024
Centre National de la Recherche Scientifique
1990-2013
Laboratoire de Physique de l'ENS
1986-2013
Sorbonne Université
1990-2013
École Normale Supérieure - PSL
1988-2007
École Normale Supérieure
2005-2007
École Normale Supérieure d'Abidjan
2007
Centre National pour la Recherche Scientifique et Technique (CNRST)
2005
2014 Il est possible de produire l'hélium trois liquide polarisé par liquefaction d'un gaz prealablement orienté pompage optique.Nous avons cette façon obtenu des polarisations nucléaires plus 40 % dans un à ~ 400 mK et pression presque nulle.Le temps relaxation nucléaire quelques minutes, comparable au en volume le liquide.Les signaux RMN que donne sont fortement déplacés fréquence, ce qui fournit une précise commode mesurer la polarisation nucléaire, également suivre mouvement coule long...
2014 Les gaz polarisés comme H~ ou 3He~ possèdent des modes oscillants et amortis basse température, les ondes de spin, dont l'origine est l'effet rotation spins identiques se produisant lors collisions entre particules indiscernables.Cette lettre décrit l'observation ces effets dans le domaine température 2 T 6 K, mesures préliminaires du coefficient 03BC qui donne la surtension ondes.Ces sont en accord avec calculs numériques C. Lhuillier.Abstract.2014 Spin polarized gases such as or can...
Although it is a dilute nondegenerate system, gas of 3He ↑ (spin-polarized 3He) can exhibit interesting quantum effects due to particle indistinguishability. One these variation the heat conduction coefficient as function nuclear polarization. An experiment described where this change has been observed and measured. The polarization obtained by optical pumping at wave-length λ = 1.08 μm with LNA crystal laser. experimental results are in reasonable agreement theoretical predictions, but...
Abstract This work reports the use of single‐shot spin echo sequences to achieve in vivo diffusion gas measurements and ultrafast imaging human lungs, vivo, with hyperpolarized 3 He at 0.1 T. The observed transverse relaxation time lasted up 10 s, which made it possible long Carr‐Purcell‐Meiboom‐Gill trains. Preliminary NMR studies showed that resolution lung images acquired is limited about 6 mm because applied field gradients. Ultrafast lungs normal subjects, achieved less than 0.4 s...
Advances in metastability exchange optical pumping (MEOP) at high laser powers, but also gas pressures and magnetic field strengths, has provided strong motivation for revisiting the understanding of limitations this powerful technique. A comprehensive model been developed improved description combined effects OP, ME, relaxation, detailed MEOP features observed over broad range operating conditions. brief is provided, with illustrative comparisons computed experimental results. This tool...
Metastability exchange optical pumping (MEOP) is experimentally investigated in 3He at 4.7 T, room temperature and for gas pressures ranging from 1 to 267 mbar. The 23S-23P transition 1083 nm used detection of the laser-induced orientation atoms rf discharge plasma. collisional broadening rate measured (12.0 ± 0.4 MHz mbar−1 FHWM) taken into account accurate absorption-based measurements both nuclear polarization ground state atom number density metastable 23S state. results lay a...
To study how highly magnetized liquids behave in NMR experiments, we have performed low-field on laser-polarized liquid ${}^{129}\mathrm{Xe},$ with nuclear polarization of up to 6%. Contrary conventional results, find that instabilities develop after a large pulse, leading an unexpectedly abrupt decay the signal. In contrast, spectrum small pulse collapses series unusually sharp lines (spectral clustering), whose widths correspond precession lifetimes longer than half minute. We discuss key...
A combination of a narrow linewidth, tunable DBR diode laser and high power ytterbium fibre amplifier in master oscillator (MOPFA) configuration is demonstrated for efficient optical pumping helium. compact pumped prototype system shown to compare favourably with alternative sources production hyperpolarised 3He using direct medical application MRI.
2014 Dans un gaz de 3He polarisé, la diffusion spin prend à basse température caractère oscillant et engendre des ondes spin; ces ondes, amorties, ont une surtension 03BCM, où M est le taux polarisation nucléaire 03BC coefficient caractéristique l'importance relative effets d'échange lors collisions binaires.Nous décrivons ici technique RMN modes oscillants sont direc- tement excités détectés par deux paires bobines, chaque paire étant formée enroule- ments en opposition afin créer ou...
We perform metastability exchange optical pumping of helium-3 in a strong magnetic field 1.5 T. The achieved nuclear polarization, from 80% at 1.33 mbar to 25% 67 mbar, shows substantial improvement high pressures with respect standard low-field pumping. specific mechanisms are investigated, advantages and intrinsic limitations discussed. From practical point view, our results open the way alternative technological solutions for polarized applications particular resonance imaging human lungs.
We demonstrate time reversal of nuclear spin dynamics in highly magnetized dilute liquid (3)He-(4)He mixtures through effective inversion long-range dipolar interactions. These experiments, which involve using magic sandwich NMR pulse sequences to generate echoes, probe the spatiotemporal development turbulent and promise serve as a versatile tool for study control dynamic magnetization instabilities. also show that repeated sequence can be used dynamically stabilize modes precession are...
Hyperpolarized 3He is used to non-destructively probe by NMR the structure of custom-made and commercial silica aerogels (97% 98.5% porous). Large spin-echo signals are obtained at room temperature very low magnetic field (2 mT) even with small amounts gas. Attenuation induced applied gradients results from combined effects gas diffusion confinement porous medium on atomic motion. Nitrogen as a buffer reach equivalent pressures ranging 5 mbars 3.5 bars. The observed pressure dependence...