Measurement and analysis of polarization gradient relaxation in the atomic comagnetometer

In the spin-exchange relaxation-free (SERF) comagnetometer, the transverse nuclear spin relaxation associated with the electron spin polarization gradient restricts the low-frequency magnetic-field suppression ability and self-compensation performance. A three-dimensional model and a measurement method of polarization gradient relaxation rate (PGRR) in the SERF comagnetometer are proposed in this paper. A plateau of PGRR is discovered and well explained by the model. The proposed measurement method confirms that the PGRR accounts for 90%∼98% of the transverse nuclear spin relaxation in the SERF comagnetometer. In addition, the model guides the selection of system parameters to manipulate the polarization distribution, thereby the PGRR is reduced by 14.88 times from 0.02166 1/s to 0.00145 1/s. This research supports improving the long-term stability of the SERF comagnetometer, and the proposed model and method can be extended to other atomic sensors, such as the SERF magnetometer and nuclear magnetic resonance gyroscope.