Sensitivity Estimation of JOM-4 Overhauser Magnetometer

Abstract

Overhauser proton magnetometer is a scalar magnetometer measuring the total magnetic field based on dynamic nuclear polarization (DNP) effect. As a critical specification, sensitivity indicates the relative uncertainty of the instrument s repeated measurements on a stable magnetic field. The appropriate sensitivity estimation method can make the sensitivity estimate more accurate. In this paper, the principle of operation is described, the structure of the Overhauser magnetometer is illustrated, and the measurement process is discussed in detail. The experimental results of the RF output and envelope show the quality of the signal. In addition, combined with the synchronization method, the fourth-order difference algorithm is proposed for sensitivity estimation. By calculating the standard deviation of the difference between the two synchronized instruments, the synchronization method can eliminate the environmental interferences and diurnal variation. Moreover, instrument drift is also effectively suppressed due to the high-pass characteristics of the fourth-order difference function. Finally, the experiments are implemented in low EMI environment, and the sensitivity is estimated by utilizing the fourth-order difference algorithm. Experimental results show that the estimation method proposed here suppresses interferences effectively, and the sensitivity estimate is 0.0186 nT@5 s.