What is EPR polarimetry?
EPR measurement is an alternative way to measure the polarization of polarized 3He target. It can be used either as a direct on-line monitoring of target polarization, or as a calibration for NMR measurement, in addition to the water calibration. • What is the principle of EPR measurement? EPR polarimetry measures the frequency shift of Rb Zeeman resonance caused by polarized 3He inside pumping chamber. The absolute frequency of Rb Zeeman resonance is determined by both the holding field (25 Gauss) and a small field caused by the polarization of 3He (about 0.1 Gauss). Because the holding field fluctuates at a level of 10E-3, it is necessary to reverse the direction of 3He polarization (usually this is done by AFP). By measuring the frequency difference between these two polarization directions, the instability of holding field is cancelled so one is able to extract 3He polarization. • How do we measure Rb Zeeman resonance frequency? To detect the EPR resonance, we rely on the fact that
