A new design of compact zero-field atomic gradiometer was proposed and integrated using alkali vapor cell and customized optical components. This gradiometer used two parallel elliptically polarized lights, whose output intensity was measured to perform gradient magnetic field detection, respectively. To improve the gradiometer’s sensitivity of the magnetic field detection, the gradiometer was operated in the spin-exchange relaxation-free (SERF) regime. For the sensitivity study, the gradiometer was placed in a person-sized four-layer μ-metal magnetic shielding. With the magnetic shield closed up, the sensitivity of each channel was near 34 fT/ √ Hz, and the corresponding gradient sensitivity could reach 14 fT/√ Hz/cm on a 1cm baseline. When the cover of magnetic shielding was removed, the magnetometer sensitivity of single channel was about 90 fT/√ Hz, and the corresponding gradient sensitivity could reach 34 fT/√ Hz/cm. The experimental results implied that in a poor magnetic shielding environment, the performance of magnetometer was limited due to the fluctuations of the environmental magnetic field, while the gradiometer could work well.
Recent developments in the exploration of atomic spin instrumentation have enabled the atomic magnetometer to become the most effective detector of magnetic fields. The stability of temperature in alkali vapor cells is an important factor for ensuring the measurement accuracy of atomic magnetometers. The alkali vapor cell is usually heated to 80°C ∼ 190°C. During the heating process, although the heating system reaches a steady state, the temperature inside the alkali metal cell will still fluctuate, which will affect the accuracy of the device measurement. In this paper, K cells were simulated and analyzed by using the theory of atomic absorption spectroscopy theory. By the mathematical relationship models, the simulation analysis of the cell containing alkali vapor found that, within a small temperature fluctuation range (±1°C), the temperature fluctuation of the alkali vapor cell filled with buffer gas and the broadening parameter of the atomic absorption spectrum, as well as the frequency shift parameter all show a linear relationship. In order to facilitate the actual measurement, the relationship between the detection light intensity transmitted through the alkali metal cell and the temperature fluctuation inside the cell was also analyzed in this paper. Through simulation analysis, it is found that, within a small temperature fluctuation range (±1°C), the linear relationship between the detected light intensity transmitted through the alkali vapor cell and the temperature fluctuation inside the cell also exists.
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