Closed-loop control of the longitudinal axis compensation point in the K-Rb-²¹Ne comagnetometer

Magnetic field drift is a significant factor that influences the long-term stability of the spin-exchange relaxation-free (SERF) comagnetometer. This work proposes a real-time closed-loop control method for the longitudinal compensation point of the comagnetometer. By developing a model of the transverse (x and y axes) oscillation magnetic field response of the K-Rb-²¹Ne comagnetometer, the relationship between the demodulation phase at a fixed driving frequency and the longitudinal (z-axis) remanence of the comagnetometer are provided in this paper. Based on this equation, a real-time closed-loop control system for the longitudinal axis compensation point is constructed, and the effectiveness of the closed-loop control method is verified by experiments. The experimental results show that the Allan variance at 100 s is reduced by 38.2% and the repeatability of the scale factor is improved by 83.3% in the closed-loop mode relative to the open-loop mode. The research work in this paper is crucial for advancing comagnetometer engineering applications.