Multidimensional Mapping of Spin-Exchange Optical Pumping in Clinical-Scale Batch-Mode ¹²⁹Xe Hyperpolarizers

We present a systematic, multiparameter study of Rb/¹²⁹Xe spin-exchange optical pumping (SEOP) in the regimes of high xenon pressure and photon flux using a 3D-printed, clinical-scale stopped-flow hyperpolarizer. In situ NMR detection was used to study the dynamics of ¹²⁹Xe polarization as a function of SEOP-cell operating temperature, photon flux, and xenon partial pressure to maximize ¹²⁹Xe polarization (<i>P</i>_Xe). <i>P</i>_Xe values of 95 ± 9%, 73 ± 4%, 60 ± 2%, 41 ± 1%, and 31 ± 1% at 275, 515, 1000, 1500, and 2000 Torr Xe partial pressure were achieved. These <i>P</i>_Xe polarization values were separately validated by ejecting the hyperpolarized ¹²⁹Xe gas and performing low-field MRI at 47.5 mT. It is shown that <i>P</i>_Xe in this high-pressure regime can be increased beyond already record levels with higher photon flux and better SEOP thermal management, as well as optimization of the polarization dynamics, pointing the way to further improvements in hyperpolarized ¹²⁹Xe production efficiency