We present a design for a spin-exchange optical pumping system to produce large quantities of highly polarized 129Xe. Low xenon concentrations in the flowing gas mixture allow the laser to maintain high Rb polarization. The large spin-exchange rate between Rb and 129Xe through the long-lived van der Waals molecules at low pressure, combined with a high flow rate, results in large production rates of hyperpolarized xenon. We report a maximum polarization of 64% achieved for a 0.3 l/h Xe flow rate, and maximum magnetization output of 6 l/h at 22% polarization. Our findings regarding the polarization dependence on temperature, nitrogen partial pressure, and gas mixture flow velocity are also reported.
Here we present a $\mathrm{Rb}\text{\ensuremath{-}}^{129}\mathrm{Xe}$ spin-exchange optical pumping polarizer capable of rapid generation of large volumes of highly polarized
129Xe gas. Through modeling and measurements we maximize the
129Xe nuclear spin polarization output to enable the generation of polarized
129Xe gas imaging volumes (
300 cm3) every 5 min within a clinical setting. Our model is verified by experiment to correctly predict the optimum Rb vapor density for maximum
129Xe nuclear polarization for a flux
3.4 W/cm2 of circularly polarized Rb
D1 photons incident on an 80 cm long cylindrical optical cell. We measure a
129Xe magnetization production efficiency of ${\ensuremath{\eta}}_{\mathrm{pr}}=1.8%$, which approaches the photon efficiency limit ${\ensuremath{\eta}}_{\ensuremath{\gamma}}=3.3%$ of this system and enables the polarization of $2.72\ifmmode\times\else\texttimes\fi{}{10}^{22}$
129Xe spins per hour, corresponding to
1013 cm3 of 100% polarized
129Xe at STP. This magnetization production rate is threefold higher than the highest previously published
129Xe magnetization production rate and has enabled routine clinical lung magnetic resonance imaging (MRI) with hyperpolarized
129Xe doses available on demand at run time, as well as high-SNR
129Xe MRI of the human brain and kidneys.
We present a design for a spin-exchange optical pumping system to produce large quantities of highly polarized 129Xe and 131Xe. Low xenon concentrations in the flowing gas mixture which allow the laser to maintain high Cs polarization. The large spin-exchange rate between Cs and Xe through the long-lived van der Waals molecules at low pressure, combined with a high flow rate, results in large production rates of hyperpolarized xenon. The fast rates make it possible to obtain large nuclear polarizations after several minutes of optical pumping with a laser.At high Xe pressures. According to the theory, the longitudinal spin-elaxation rate 1T1 of Xe in a high-pressure sample containing only Xe and Cs vapor has the simple form is the velocity averaged binary spin-exchange cross section, It is the relaxation rate due to wall collisions and perhaps magnetic field inhomogeneities. Our results complement earlier studies performed at 129Xe pressures of about 20 Torr and 131Xe pressures of about 20 Torr and N2 pressures of 600 Torr . This work is useful for predicting spin-exchange rates between polarized Cs atoms and Xe nuclei.
We present a constructed setup for polarizing 129 Xe noble gas. Hyperpolarized 129 Xe has been obtained via spin exchange with an optically pumped rubidium vapor. Optical pumping is based on polarizing the valence electron of rubidium by the resonant absorption of a circularly polarized laser light. The magnetic field of 30 G was used for obtaining 129 Xe polarization. The apparatus for detecting polarization is a nuclear magnetic resonance spectrometer. The highest 129 Xe polarization of 54% has been obtained using 60 W circularly polarized laser light with wavelength of 794.7 nm. The measured longitudinal relaxation time of the hyperpolarized 129 Xe was 72.3 minutes.
Abstract Efficient production of hyperpolarized 129 Xe at clinically relevant output levels remains an important challenge for spin-exchange optical pumping (SEOP). In this work, we report a comparative experimental study of Cs– 129 Xe and Rb– 129 Xe SEOP. The spin-exchange and spin-relaxation rates are measured and separated into binary-collision and van der Waals (vdW) molecular contributions. The resulting parameter set shows that long-lived vdW interactions enhance the intrinsic spin-exchange efficiency within a narrow pressure window, with Cs exhibiting a modest advantage over Rb under comparable conditions. Using these experimentally constrained quantities in a device-level model, we predict that clinically relevant 129 Xe polarization levels and throughput could be achievable at pump powers near 5 W.
Spin-exchange optical pumping (SEOP) enables hyperpolarization of magnetic noble gas nuclei and allows enormously enhanced signal in nuclear magnetic resonance studies in materials, biosciences, and medicine. We model the dynamics of the SEOP process taking place in a $\mathrm{Rb}\ensuremath{-}^{129}\mathrm{Xe}$ gas mixture and shed light on how the different microscopic processes influence the macroscopic polarization transfer. For each Rb-Xe collision taking place in simulated molecular dynamics trajectory, we sample a time series of quantum-chemically preparametrized Hamiltonians. Combined electron and nuclear spin dynamics of each event is propagated by solving the corresponding Liouville--von Neumann equation. The rarely occurring, long-lived van der Waals molecules are seen to give the most significant contribution to polarization transfer under the simulated conditions (
T=300 K,
p=2.4 bar), in agreement with earlier findings. Besides the lifetime of the collision complex, the average and minimum Rb-Xe interatomic distances characterize the efficiency of the polarization transfer events. We obtain insight into magnetization transfer in both individual binary collisions and van der Waals complexes and demonstrate a stepwise buildup of
129Xe spin polarization upon bond-length oscillations in the latter.