Research on Achieving High Sensitivity of Overhauser Magnetometer Sensor

As quantum magnetometer with high sensitivity, Overhauser magnetometer is commonly used in geological research, mineral exploration, and so on. Overhauser magnetometer sensor consists of two parts: a resonant cavity and an audio coil. The quality factor (Q-factor) of the resonant cavity and the parameters of the audio coil are the important factors affecting the signal-to-noise ratio (SNR) and thus the sensitivity. The influence of the parameters on the Q-factor and the SNR of the sensor, both the resonant cavity and the audio coil, are investigated, respectively. First, a mathematical model of the resonant cavity is presented. Subsequently, the influence of parameters on the Q-factor is analyzed. By optimizing these parameters, the Q-factor can reach 1470, which is very close to the theoretical value of 1560. Second, a formula is derived to quantify SNR, and a high SNR of 115 for the Larmor signal is observed after multiple optimizations. Finally, the experiment was carried out in the natural magnetic field, and the estimated sensitivity was 0.0099 nT at 3 s by using two synchronized magnetometers. We also estimated the sensitivity in the artificial magnetic field, achieving an estimated sensitivity of 0.0099 nT at 3 s, which is comparable to the results in the natural magnetic field.