A Highly Sensitive In Situ Magnetic Field Fluctuation Measurement Method Based on Nuclear-Spin Depolarization in an Atomic Comagnetometer

In this article, a highly sensitive in situ magnetic field fluctuation measurement method is proposed based on nuclear-spin depolarization in a spin-exchange relaxation-free (SERF) atomic comagnetometer (ACM). The steady-state model of the hybrid atomic spin ensemble is systematically studied. According to the theoretical model, two different states of nuclear-spin polarization and unpolarization lead to different sensitivities of the system to rotation and magnetic fields. The gradient magnetic field (GMF) is employed to change the state of nuclear-spin polarization of the noble gas, transforming the ACM into an atomic magnetometer (AM). The polarization and relaxation rates of the electron spin and nuclear spin under the two measurement modes are measured and compared by the magnetic resonance method and transient response method. At the same time, the performances in the ACM and AM are tested. Detailed experiments verify that the AM can achieve sensitivity for the magnetic field measurement with an average value of 53.6 fT/Hz(1/2) in the frequency range of 10 similar to 30 Hz. The Allan variance method is adopted to evaluate the x- and y-axis magnetic field stabilities of the ACM, and the magnitudes are 61.6 and 55.9 fT at 100 s, contributing about 4.9 x 10(-3) degrees/h and 2.6 x 10(-4) degrees/h to the long-term stability of the ACM. This method can not only realize the high-sensitivity in situ measurement of the close-to-zero magnetic field and its fluctuation but also realize the switching of the two measurement modes of rotation and magnetic field measurements, which is essential for the evaluation of magnetic field error.

Automated summary

A highly sensitive in situ magnetic field fluctuation measurement method based on SERF atomic comagnetometer is proposed. Experimental results demonstrate that this method can achieve high-precision measurement of magnetic field fluctuations.