Analysis and Correction of Beam Misalignment in the In Situ Magnetometer for Rotation Sensing

Due to their significant potential for ultrahigh sensitivity, in situ magnetometers have emerged as an essential part of Xe isotope-based nuclear magnetic resonance (NMR) gyros for inertial measurements. However, installation errors can deviate beam propagation from ideal paths, thereby degrading the measurement accuracy. In this work, a comprehensive response model is established to reveal alignment effects on in situ magnetometers and NMR gyros. To address this, a dual-beam alignment method is proposed to align pump and probe beams sequentially. The core advancement lies in the exploitation of the direct correlation between beams’ misalignment and the phase error, which is obtained by canceling the reference-frequency signal component via a closed-loop structure. This ensures continuous and rapid alignment. For verification, a series of alignment experiments is conducted in two stages: pump beam alignment and probe beam alignment. The results demonstrate that after dual-beam alignment, the sensitivity of the in situ magnetometer can be improved by approximately 35% relative to the existence of small misalignment angles. Correspondingly, the white phase noise of the NMR gyro can be suppressed by about 26%, enhancing its dynamic response capability.