129 Xe-Rb spin-exchange optical pumping with high photon efficiency

Here we present a Rb−129Xe 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 ηpr=1.8%, which approaches the photon efficiency limit ηγ=3.3% of this system and enables the polarization of 2.72×1022 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.