Abstract:To meet the scalar magnetic field measurement requirements of vector magnetic field measurement device calibrations in spacecraft, a method for scalar magnetic field measurement of SERF magnetometer based on pump light modulation is proposed. The proposed method realizes the measurement of a scalar magnetic field without introducing an additional magnetic field. By analyzing the transient response of the atomic spin’s free-precession after the pumping light is turned off, the relationship between the free-precession frequency and the magnetic field scalar amplitude is derived. Based on this method, the corresponding pump light modulation-data acquisition timing sequence is designed to realize continuous scalar magnetic field measurements at low magnetic fields. The experimental results show that the measurement results are well fitted to the applied magnetic field, and the linearity is 0.057% in the 0~9nT measurement range. This method is applicable to compact SERF magnetometers and has the ability to achieve interference-free calibration of vector magnetometers.