A method for measuring the equilibrium spin
polarizability of
alkali metal atoms based on the steady-state response of a triaxial
magnetic field is proposed. First, the device is adjusted to its normal operating state. Then, DC magnetic fields are applied in the x, y, and y, z directions, with the magnitude of the
magnetic field in the z direction varied. The ratio of the device outputs in the two applications is fitted with the square of the applied
magnetic field in the z direction to obtain the total
relaxation rate. Next, the pressure broadening of the
alkali metal gas
cell is obtained at low temperature using the
optical depth of the detection light. Then, at the normal
operating temperature, the power of the detection light is varied, and the transfer coefficient is established using the pressure broadening and the fitting slope. Finally, a DC magnetic field is applied along the y-axis with varying magnitude, and the device output is fitted with the B... y‑fit The relationship between these factors, combined with the transfer coefficient, yields the final equilibrium
spin polarization. This method does not disrupt the SERF states required for normal
system operation, is unaffected by temperature, and has small measurement errors. It provides a more accurate measurement method for further optimizing SERF magnetic field measurement devices to improve their sensitivity.