Ultra-Sensitive Atomic Magnetometers for Studying Spin Precessions of Hyperpolarized Noble Gases Based on System Identification

We reported an efficient approach to analyze spin precessions of different hyperpolarized noble gases with atomic magnetometers based on system identification. Spin evolution of the magnetometer can be robustly approximated as the second order system by referring to the Bloch equation under the negligible self-interaction and its transfer function model can be deduced. We measured the dynamic responses of different atomic pairs, such as cesium magnetometer with a partner of xenon-129, potassium magnetometer with a partner of helium-3, and hybrid of cesium and rubidium magnetometer with a partner of neon-21. By referring to the experimental results, corresponding systematic parameters for the transfer function models have been identified based on least-square method, whose outputs were consistent with experimental results. Based on the models, the system stabilities and their variations with different gains have been analyzed with control theory, both of which are described here. Applying control theory to analyze dynamic responses of spin ensembles plays an important role for the future applications.