Uniform magnetic fields are widely used in atomic magnetometers, MRI and other fields. The traditional method of solving closed-form equations is usually used to design highly uniform magnetic field coils. In this paper, a new intelligent algorithm, wolf pack algorithm (WPA), is proposed to design the coil structure of a highly uniform magnetic field. This method can replace the traditional method to obtain the coil parameters. We additionally use a discrete optimization method to solve the rounding error. According to the investigation, compared with particle swarm optimization (PSO) algorithm, WPA has stronger global optimization ability, faster convergence speed and multiple optimization strategies. We set appropriate coil constraints (structural and process constraints) and simplify the multi-dimensional solutions to one-dimensional solutions to reduce the difficulty of operation. The distribution of magnetic field intensity of three axes of coils is analyzed by the finite element analysis method, and the 1%, 0.1%, and 0.01% uniform regions are studied. Under the same conditions, the uniform magnetic field regions of the coils designed by the PSO and WPA, as well as a single pair of axial and radial coils are compared. The performance results of multiple pairs of coils are superior to those of a single pair of coils. In general, the uniformity of the axial and radial magnetic field coils designed by the WPA is better than that designed by the PSO. Finally, the experimental value of the magnetic field uniformity is nearly consistent with the theoretical value.

In a spin-exchange-relaxation-free (SERF) atomic magnetometer with ultrahigh sensitivity, the ac-Stark shift generated by circularly polarized light results in the attenuation of the SERF atomic magnetometer response, and the virtual magnetic field gradient induced by the ac-Stark shift can reduce the sensitivity of the SERF atomic magnetometer. In this paper, we use a hybrid optical pumping method to address the ac-Stark shift problem. By switching between left-hand and right-hand circularly polarized lights and compensating the residual magnetic field of the magnetometer, the ac-Stark shift could be reduced and then suppressed effectively.

The alkali-metal density ratio is one of the primary design parameters in hybrid optical pumping magnetometers. Here, experiments were conducted with a hybrid optically-pumped atomic magnetometer using a cell containing potassium and rubidium. Potassium atoms are pumped by a laser and become polarized. Rubidium atoms are polarized via collisions with potassium atoms and can be probed. The light shift was eliminated by adjusting the density ratio of potassium to rubidium atoms and by optimizing the pump laser parameters. The effect of fluctuations in the laser power and frequency were minimized as a result. The optimal density ratio and magnetic field sensitivity were 1:277 and 0.68 fT Hz ^−1/2 , respectively.

Alkali metal atomic cells are crucial components of atomic instruments, such as atomic magnetometers, atomic gyroscopes, and atomic clocks. A highly uniform and stable heating structure can ensure the stability of the alkali metal atom density. The vapor cell of an atomic magnetometer that uses laser heating has no magnetic field interference and ease of miniaturization, making it superior to hot air heating and AC electric heating. However, the current laser heating structure suffers from low heating efficiency and uneven temperature distribution inside the vapor cell. In this paper, we designed a non-magnetic heating structure based on the laser heating principle. We studied the temperature distribution of the heating structure using the finite element method (FEM) and analyzed the conversion and transfer of laser energy. We found that the heat conduction between the vapor cell and the heating chips (colored filters) is poor, resulting in uneven temperature distribution and low heating efficiency in the vapor cell. Therefore, the addition of graphite film to the four surfaces of the vapor cell was an important improvement. This addition helped to balance the temperature distribution and improve the conduction efficiency of the heating structure. It was measured that the power of the heating laser remained unchanged. After the addition of the graphite film, the temperature difference coefficient (CVT) used to evaluate the internal temperature uniformity of the vapor cell was reduced from 0.1308 to 0.0426. This research paper is crucial for improving the heating efficiency of the non-magnetic heating structure and the temperature uniformity of the vapor cell.