Measurement of rubidium and xenon absolute polarization at high temperatures as a means of improved production of hyperpolarized (129)Xe

We report on a rubidium-xenon (Rb-Xe) polarization unit for the continuous production of large quantities of hyperpolarized (129)Xe. The unit includes two diagnostic systems which enable the absolute measurement of both the (85)Rb and (129)Xe polarization in situ and at high temperatures. The Rb diagnostic system allows the measurement of one- or two-dimensional images of the absolute Rb polarization and thus enables the experimental study of light penetration into the optical pumping cell. The equilibrium Xe polarization measured in the optical pumping cell and in the freezing unit is typically approximately 20%, under optimal flowing conditions, and this is much lower than the volume-averaged rubidium polarization.