Investigating Rb vapor density and temperature distributions in a high throughput 129Xe-Rb polarizer

Accurate knowledge of the Rb vapor density, [Rb], is essential for optimizing 129Xe polarization (PXe) and production rates in clinical-scale 129Xe-Rb SEOP hyperpolarizers, used for hyperpolarized 129Xe MRI. We used atomic absorption spectroscopy to measure [Rb] for multiple Rb transitions to assess [Rb] measurement accuracy and extend [Rb] measurement range sensitivity. It was shown that [Rb] is significantly lower than saturation [Rb] and that [Rb] homogeneity was improved by implementing a larger Rb source distribution or a presaturator. The 129Xe-Rb spin-exchange cross section, $γ^$, was determined to be $$γ^$= (1.2± 0.1) ×10−21m3s−1 for our operating conditions.