Optically pumped magnetometer with dynamic common mode magnetic field compensation

• DOI: 10.1016/j.sna.2021.113195
• Publication Date: 2021-10-25T20:36:27Z
• Authors: Yang Wang; Yaqiong Niu; Chaofeng Ye
• Keywords: Magnetocardiography; SIGNAL (programming language)

Abstract Optically pumped magnetometer (OPM) working in spin-exchange relaxation-free (SERF) region is extremely sensitive to magnetic field. However, it is desired to operate in zero magnetic field environment. Relative strong common mode magnetic field limits the sensitivity of the sensor and may even make the sensor work outside of SERF range. To reduce the common mode magnetic field in real time, this paper proposes an optically pumped magnetometer with dynamic magnetic feedback. Two similar OPMs work simultaneously with one measuring the target signal and the other one monitoring the common mode magnetic field. With a close loop feedback through a proportional integral derivative (PID) controller, the common mode magnetic field signal is compensated dynamically. Comparative experiments show that the proposed scheme reduces the common mode inference about 30 dB. To validate the feasibility of using the proposed probe for ultra-weak biomagnetism measurement, an artificial magnetocardiography (MCG) signal with peak-to-peak amplitude 60 pT and a 5 pT, 10 Hz sinusoid signal are measured by the prototype sensor. The experiment results show that the signals can be clearly observed after signal processing.