Suppression method of the thermally induced Rb-Xe coupling error in NMR sensor

As a novel category of atom sensor, the nuclear magnetic resonance (NMR) sensor is capable of delivering high-precision inertial measurement within a compact volume. However, the Rb-Xe coupling error induced by temperature fluctuations within the vapor cell has emerged as a critical factor limiting the stability of the NMR sensor. Variations in the cell temperature can lead to changes in the magnetic field experienced by the Rb atom, which shifts the Rb atom spin frequency and consequently causes the Rb-Xe coupling error in the measurement signal. To address this issue, unlike conventional methods that rely on static parameter optimization, we propose a dynamic suppression method for the thermally induced Rb-Xe coupling error. By introducing a non-resonant reference magnetic field to the measurement axis, the demodulation frequency is locked in real time. This novel closed-loop approach continuously tracks and isolates the temperature-induced frequency shift without disturbing the main resonance signal. Results from sinusoidal temperature excitation experiments (500 mK amplitude, 200 s period) verify that the proposed method effectively reduces the maximum variation of the ¹²⁹Xe and ¹³¹Xe spin frequencies by approximately 19.3% and 22.2%, respectively. Furthermore, continuous static measurement experiments over 3 h demonstrate that this approach reduces the range of the Xe isotope frequency ratios by approximately 44.4% and the standard deviation by about 39.1%. These results confirm that the proposed method significantly enhances the measurement stability of the NMR sensor under normal operating conditions.