上海科技大学知识管理系统

The technology of optically pumped magnetometers (OPM) operating in the spin exchange relaxation free (SERF) range has rapidly advanced in recent years. To operate in the SERF state, it is crucial to maintain a near zero magnetic field operating condition. Therefore, dynamic compensation of the magnetic field fluctuation is desired. This paper presents a method of suppression the magnetic field fluctuations by utilizing array OPMs that are oriented to different directions. The outputs of the sensors are split into different channels, namely: one channel for the alternating signal measurement and the other one for the closed-loop control to cancel the quasi-static magnetic field with frequency lower than 1.5 Hz. To mitigate the effects of coil non-uniformity and magnetic field inhomogeneity, two coils are employed to generate the compensation field, including the internal Helmholtz coil within the sensor and external tri-axial coils. Experimental results show that this method can suppress the quasi-static magnetic field fluctuations in-situ by over a hundredfold and achieve a magnetic field suppression level of approximately 300 fT/Hz.