Noise Modeling of the Overhauser Magnetometer

The Overhauser magnetometer (OVM) is an electron resonance-enhanced nuclear magnetic resonance (NMR) magnetometer, which significantly enhances the Larmor signal, hence the signal-to-noise ratio (SNR) and sensitivity compared to traditional proton magnetometers (PM). In this paper, we intended to improve SNR and sensitivity only by reducing system noise. For this purpose, an equivalent circuit model of noise is established, and the contributions of sensor and transmission characteristics of the circuit are calculated quantitatively. By sensor parameter optimization, matching resistance, and preamplifier selection to reduce the noise of the system, the root mean square (rms) of system noise is 26.7 mV, which is consistent with the theoretical 23.9 mV. By reducing the noise of the system, the SNR of the Larmor signal can reach 39 dB. The measured results in the natural environment show that the sensitivity of the OVM is 0.0079 nT at 3 s cycling time.