We describe a dual-axis atomic spin gyroscope based on an alkali metal-noble gas comagnetometer. Alkali metal vapor is optically pumped, and then the noble gas is hyperpolarized along the z axis. When sensing a transverse rotation, the polarized noble gas will be induced to precess and produce an effective magnetic field in the x – y plane for alkali metals to precess under. Operating in the spin-exchange relaxation-free regime, alkali atoms are modulated by the z axis magnetic field and serve as an integrated in-situ dual-axis magnetometer to detect the gyroscopic precession in the x and y axes simultaneously, using a single probe beam. By using the parametric modulation technique, the low frequency drift is effectively suppressed and a bias instability of less than 0.05 deg/h has been achieved in our dual-axis atomic spin gyroscope.

Spin-exchange relaxation-free gyroscope (SERFG) is a promising rotation sensor, and the bias error is one of its most important characteristics. It is identified that rotation measurement noise induced by thermal magnetization fluctuations inherent in the ferrite shield in a SERFG limits its bias stability. The root cause of this error lies in the low-frequency magnetic field sensitivity dominated by the nuclear spin relaxation rate. In this paper, the steady state response model of a SERFG is modified considering the non-negligible nuclear relaxation rate and the pressure-dependent magnetic field sensitivity is experimentally studied. Our results show that reducing nuclear spin relaxation is an effective method to suppress the bias error induced by thermal magnetization fluctuations. Finally, in case of Pneon=1 atm, it is estimated that a bias stability limit of 5×10-4 deg/h is set by the lowest thermal magnetization noise of 4.4f-1/2 fT ever reported in a ferrite shield.

A new design method is proposed for a triaxial magnetic field gradient compensation system based on ferromagnetic boundary for atomic sensors. The target field method and the whale optimization algorithm are combined to design magnetic field coils thus transforming the complex analytical solution process into an intelligent optimization problem, while the boundary mirror method is introduced to decouple the coil from the magnetic shield. Magnetic field gradient coils are designed according to the coil design method and combined with the divergence and rotation theorems to form the triaxial gradients compensation system to suppress the magnetic field inhomogeneity in nine directions. The simulation and experimental results are compared with the results before and after compensation by using the box line diagram representing the statistics of the magnetic field deviation, in which the median value is reduced by 65.87% and 85.16%, the minimum by 99.66% and 77.76%, the 25 th quantile by 97.89% and 79.94%, and the 75th quantile by 91.52% and 85.17%, respectively.

We propose a novel method for measuring relaxation rates and Fermi-contact fields of the electron and nuclear spin ensembles rapidly and synchronously in spin-exchange relaxation-free (SERF) atomic comagnetometers based on the transient response. The transient response model of the comagnetometer is established by solving a set of Bloch equations. The decay rates and oscillation frequencies of the transient response as functions of the longitudinal magnetic field are investigated theoretically and experimentally. The total relaxation rate of the nuclear spin ensemble is obtained from its decay rate. A linear model is presented with a detailed mathematical derivation based on the decay rates and oscillation frequencies of the spin ensembles. The Fermi-contact fields of the spin ensembles and the slowing-down factor are extracted from the slope and intercept of the linear model. The total relaxation rate of the electron spins is obtained from the decay rates of the spin ensembles and the measured slowing-down factor. The validity of this method is further checked by the magnetic resonance (MR) method from a perspective of the electron resonance linewidth. Identification of these systematic parameters paves the way for operating the comagnetometers efficiently as well as the practical applications of the comagnetometers.

This study presents the development of a SERF atomic co-magnetometer with a magnetic shielding system. The shielding system includes multiple cylindrical passive magnetic shield and active magnetic compensation coils. The multilayer shield, which adopts a structural style comprising a barrel body and end cover, is applied to attenuate the external magnetic field to less than 10 nT or ideally close to zero. For the purpose of degaussing, pumping, and probing light paths, several openings must be made on the magnetic shield. A hybrid approach combining theoretical calculations and the finite element method is proposed to analyze the shielding properties, considering the influence of openings. To evaluate the shielding properties of the magnetic shield, two different simplified finite element models are established and analyzed. The simulation results are compared with theoretical and experimental data, and the results are in good agreement. The modeled results show that the openings bear a considerable influence on the shielding performance, and thus, their effect cannot be ignored. The axial magnetic shielding factor with several openings is roughly 4.4×104, which is about two orders of magnitude lower than that without openings. Further, a rotation sensitivity of 5.86×10–7rad·s–1·Hz–1/2 is obtained with the open-hole magnetic shield. This sensitivity corresponds to a magnetic sensitivity of 27.8 fT/Hz1/2. Based on the results, possible improvements are suggested for future designs.