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For the atomic gyroscope (AG) operated in spin-exchange relaxation-free (SERF) regime, the sensitivity to external magnetic fields has been suppressed while the ability to sense inertial rotations has been kept. Here, a theoretical relationship between the magnetic fields and the AG response is given, and the influence of field fluctuations on the systematic stability is also shown. The spin-exchange rate of the electron spins R se en and the relaxation rate of the nuclear spins R tot n aggravate the influence of the field component B x . Experimental results indicate that the contributions of long-term fluctuations in the fields, approximately 2.4 pT/h for B x and 0.9 pT/h for B y , to the bias stability are 2.19 × 10 −2 deg/h and 5.29 × 10 −4 deg/h. This work is not only valuable for understanding the field-suppression effect in SERF AG, but also provides a useful tool for identifying the influence of fields on the systematic stability. [ABSTRACT FROM AUTHOR]

In the spin-exchange relaxation-free (SERF) comagnetometer, the atomic polarization gradient caused by light absorption can cause significant but unexpected nuclear spin transverse relaxation, which affects the system's accuracy and sensitivity. This paper proposes the SERF comagnetometer configuration based on optical compensation to suppress polarization gradient in the vapor cell. The influence of polarization gradient on the system's magnetic field suppression ability is analyzed by the state-space method. In addition, the atomic polarization distribution simulation and the performance testing between the traditional SERF comagnetometer and the proposed configuration are conducted. Compared to traditional configuration, the polarization gradient relaxation of the proposed configuration is effectively suppressed by 62%, the magnetic field suppression ability of the system is improved by 51%, and the rotation sensitivity is increased by 25.4%. This work investigates the influence of polarization gradient on system characteristics and proposes a comagnetometer configuration to suppress polarization gradient, enhancing the system's magnetic field suppression ability and improving sensitivity. The demonstration of the polarization gradient suppression method is of significance for improving the performance of other inertial measurement devices such as nuclear magnetic resonance gyroscopes. [Display omitted] • A uniform atomic comagnetometer based on optical compensation is proposed. • The influence of polarization gradient on the system is analyzed. • The atomic spatial distribution model of the proposed configuration is established. • The polarization gradient relaxation is suppressed by 62%. • A rapid polarization confirmation method is proposed for performance comparison. [ABSTRACT FROM AUTHOR]

Spin Exchange Relaxation-Free Co-Magnetometer (SERFCM) possesses ultra-sensitive rotation measurement capabilities, offering broad application prospects in inertial navigation and fundamental physics research. Precision of SERFCM in rotation measurements is directly influenced by its ability to suppress magnetic noise. In this study, a state-space method is used to establish a SERFCM response model, considering the effect of pump light wavelength. An analysis is conducted to assess the effect of pump light wavelength detuning on the ability to suppress magnetic noise of SERFCM. Theoretical results indicate that detuned pump light wavelength can effectively reduce the magnetic field gradient generated by atomic polarization, thereby improving overall system performance. Experimental validation demonstrates that a slight detuning of the pump light wavelength results in a 21% improvement in the ability to suppress low-frequency magnetic fields. [Display omitted] • Establish a SERFCM response model considering the effect of pump light wavelength. • Effect of pump light wavelength on magnetic field gradient is analyzed and proved. • The low-frequency magnetic field suppression ability improves by 21%. [ABSTRACT FROM AUTHOR]

Magnetic field gradients affect the signal-to-noise ratio of the spin-exchange relaxation-free gyroscopes (SERFG), thereby affecting sensitivity and long-term stability. A novel method to in situ measure, decouple and suppress the effect of magnetic field gradient on relaxation rate of SERFG is studied. The total magnetic field gradient is in situ measured by fitting the relationship between magnetic field gradient (applied by magnetic field coil) and relaxation rate method, and the effects of magnetic field gradients generated by electron spin polarization and those generated by inhomogeneous distribution of the residual magnetic field on the relaxation rate of SERFG are separated by turning the pump light on and off. The experimental study demonstrates that the magnetic field gradient in the atomic vapor cell is compensated by a self-developed magnetic field gradient coil to reduce the effect on the nucleon spin relaxation rate, and that the sensitivity and bias instability of SERFG are improved due to the in situ measurement, decoupling and compensation of the magnetic field gradient. This study lays the path for effectively improving the performance index and practical application potential of SERFG. [Display omitted] • The experimental demonstrates that the magnetic field gradient is compensated by coils to reduce the effect on the nucleon spin relaxation rate • Our experiments show that the shorter the time to pump the laser through the atomic vapor cell, the closer the measured T 2 is to T 1 • The measurement, decoupling and suppression methods have the potential to be applied to other atomic sensors. [ABSTRACT FROM AUTHOR]

Alkali-metal-noble-gas comagnetometers have broad applications in fundamental physics research and inertial navigation. Micro-vibration, as one of the main disturbances of the system, significantly limits the sensitivity of the comagnetometer. However, there are no researches to systematically test and quantify the effect of micro-vibration on comagnetometer, and suppressing this effect remains a challenge. In this paper, the response characteristics of the comagnetometer to angular and linear vibration are analyzed and tested based on the designed experimental setup for the first time. And then, we analyze the response characteristics of comagnetometer with passive vibration isolation platform to the ground vibration noise and the effect of height of center of mass on vibration transfer. Based on the established model and test results, we optimized the structure, the center of mass, and the direction of the sensitive axis of the comagnetometer, and the vibration equivalent sensitivity of comagnetometer is suppressed by about 20 times in the range of 1–4.75 Hz. [Display omitted] • The comagnetometer's response to angular and linear vibration is tested for the first time. • The transfer function model between vibration noise and comagnetometer output is established. • The structure of the comagnetometer is optimized to reduce the influence of vibration noise. • The vibration equivalent sensitivity of the comagnetometer is significantly suppressed. [ABSTRACT FROM AUTHOR]

Spin-exchange free-relaxation (SERF) co-magnetometer has promising applications in the field of inertial navigation and fundamental physics experiments since its coupled spin ensemble is capable of measuring rotation with ultra-high sensitivity. Electron spin polarization determines the performance of the SERF co-magnetometer directly. In this paper, it is found that there is a non-negligible coupling between the probe light frequency and electron spin polarization. A model of the polarization in relation to the probe light frequency for a hybrid pumping cell is established. This paper discovers the existence of a theoretical optimum frequency that enables a more stable polarization in the model, and an experimental verification is carried out. Experiments results show that when the SERF co-magnetometer operates at this optimization frequency, its short- and long-term stability is significantly enhanced. Further, based on this model, the detuned frequency stabilization technique is proposed. The long-term stability of the probe light frequency is also improved by 43.85% after closing the loop. [Display omitted] • In this paper, it is found that there is a non-negligible coupling between the probe light frequency and electron spin polarization. A model of the relationship between them is established. • It is finds that there is an optimal frequency which can significantly reduce the disturbance of probe system to the SERF co-magnetometer in the response model. • The detuned frequency stabilization technique is proposed based on the model and the long-term stability of frequency is improved by 43.85% after stabilization. [ABSTRACT FROM AUTHOR]

A novel strategy for designing uniform magnetic field and gradient magnetic field coils considering the boundary effect of magnetic shielding is proposed in this study. This strategy uses intelligent optimization algorithm to skillfully transform the complex coil design problem into the spatial optimization problem of individual population. The mirror method is combined with Green's function to accurately calculate the magnetic field, and the target field method (TFM) is combined with the whale optimization algorithm to optimize the stream functions using adaptive ridge regression. The minimum fitness function is defined as the real-time magnetic field relative error, and the optimal ridge coefficient is continuously obtained by determining the current density coefficient. The proposed method significantly reduces the magnetic field deviation in the target area compared to the conventional TFM, with reductions ranging from 12.2 % to 0.11 % (B x coil), 0.3 % to 0.02 % (B z coil), 20 % to 10 % (d B x / d z coil) and 2.9 % to 2.4 % (d B z / d z coil). The strategy has been effectively validated by analytical simulations and experimental results, and is expected to be applied to the design of uniform field coils and gradient coils for ultra-high precision atomic sensors. [Display omitted] • The coupling problem between the magnetic shielding system and the designed magnetic field coil is greatly reduced. • This method determines the fitness evaluation function according to the real-time actual current density. • The magnetic field coil designed by the hybrid optimization method proposed in this paper reduces the magnetic field deviation by nearly one to two orders of magnitude compared to the conventional TFM. • The proposed method significantly reduces the magnetic field deviation in the target area compared to the conventional TFM. [ABSTRACT FROM AUTHOR]

The magnetic field performance of the uniform coils will be affected by magnetic shields and produce errors in the atomic magnetometer. It is necessary to analyze the influencing factors and guide the coil design. Aiming at the above shortcomings, this paper analyzes the coupling effect of magnetic shield and coil and proposed a Lee-Whiting coil design method based on the linearly decreasing inertia weight particle swarm optimization (LDW-PSO) algorithm. Firstly, the magnetic field model under the ferromagnetic boundary is established, and the effects of the size, thickness and permeability of the magnetic shield on the magnitude and uniformity of the Lee-Whiting coil magnetic field are analyzed. The results show that the coupling coefficient of the coil changes monotonically with the change of the size of the magnetic shield, while the uniformity error has a minimum value with the change of the size of the shield. In addition, an improved Lee-Whiting coil is designed by combining the LDW-PSO algorithm, which improves the uniformity of the coil. Compared with the original coil, the measured uniformity error of the improved coil is reduced from 8. 39 × 1 0 − 4 to 2. 81 × 1 0 − 4 . The accuracy of the theoretical analysis is verified by experiments. This paper is of great significance to study the coupling and optimization design of the coil based on the magnetic shields in atomic magnetometers. [Display omitted] • The influence of magnetic shield parameters on coil uniformity is analyzed. • The optimal coil size for the uniformity in magnetic shield is given by analysis and testing. • The improved Lee-Whiting coil is designed by intelligent optimization algorithm. • Improved Lee-Whiting coil overcomes the coupling effect between coil and magnetic shield. • The correctness of the analysis and the effectiveness of the design are proved by experiments. [ABSTRACT FROM AUTHOR]

Spin-exchange relaxation-free (SERF) co-magnetometer presents promising applications in both inertial navigation and basic physical experiments because of its ultrahigh rotation measurement sensitivity and magnetic field disturbance cancellation capacity. Magnetic shielding system is an essential part of the co-magnetometer, and the intrinsic magnetic noise of shielding material is one of the main factors limiting the sensitivity of co-magnetometer. This paper presents a low-noise nanocrystalline magnetic shield for SERF co-magnetometer. The transfer function model of SERF co-magnetometer to transverse magnetic noise was established based on Bloch equation. The amplitude and frequency band of the co-magnetometer signal noise caused by transverse magnetic noise were quantitatively obtained, and the magnetic noise characteristics of nanocrystalline and other shielding materials were analyzed by theoretical calculation and experimental measurement in the obtained frequency band. The superiority of nanocrystalline in low magnetic noise was verified. Experimental results show that the signal noise and bias instability of the SERF co-magnetometer can be considerably decreased by using the nanocrystalline shield as the inner shield. [Display omitted] • A low-noise nanocrystalline shield for atomic co-magnetometer is proposed. • The transfer function model of the co-magnetometer to biaxial magnetic noise is established based on Bloch equation. • The advantages of nanocrystalline shield in magnetic noise characteristics are confirmed. • The signal noise and bias instability of the co-magnetometer are significantly reduced. [ABSTRACT FROM AUTHOR]