To avoid the broadening of Zeeman resonances of the vector atomic magnetometer working in an unshielded environment, the rapid and accurate magnetic compensation is necessary. A three dimensional mini spherical compensating system is presented, which can be used together with a chip-scale atomic magnetometer to realize an ultra-high precision field measurement. Based on the field gradient method, parameters are optimized to obtain a uniformity of 10-3over the region of one half radius with a good tolerance on dimensional variations. A prototype applied in the single laser beam scheme has been built and the experimental results demonstrate the validity of the design.
To avoid the broadening of Zeeman resonances of the vector atomic magnetometer working in an unshielded environment, the rapid and accurate magnetic compensation is necessary. A three dimensional mini spherical compensating system is presented, which can be used together with a chip-scale atomic magnetometer to realize an ultra-high precision field measurement. Based on the field gradient method, parameters are optimized to obtain a uniformity of 10-3over the region of one half radius with a good tolerance on dimensional variations. A prototype applied in the single laser beam scheme has been built and the experimental results demonstrate the validity of the design.
The spin-exchange-relaxation-free(SERF)atomic magnetometer with ultrahigh sensitive becomes the most effective measurement to analyze the component of the planet in space exploration.In order to improve the sensitivity of the SERF atomic magnetometer,we must avoid the influence on the SERF regime disturbed by environment magnetic field.In this paper we design an active compensation system based on in-situ magnetic measurement to compensate the magnetic disturbance.Firstly,we get the three-axis magnetic field information according to the measurement of pop-laser,then control the current of coil to generate a magnetic field which is opposite and equal to the disturbance,to keep the SERF regime.Finally,we validat the method with the atomic magnetometer experimental setup.The result shows that compared with the manual compensation method,the system can track the magnetic compensation point in real time,reduce the signal noise and compensate the magnetic disturbance successfully,validating the efficiency of the active compensation system and establishing the technique foundation of the production.
We propose a novel method, which leverages the atomic signal itself, to achieve rapid in situ magnetic field compensation in an unknown geomagnetic environment for an unshielded spin-exchange relaxation-free atomic magnetometer. This method employs a strong bias magnetic field aligned with the pump beam direction to maximize the strength of the magnetic field resonance signal. The compensation process is divided into three sequential stages, each focusing on one of the x, y, and z axes by adjusting the magnitude of the bias magnetic field. As a result, the zero magnetic field is identified within 11 seconds, with compensation resolution smaller than 3.0 nT, primarily constrained by the laser power stability. This approach not only enhances the applicability of atomic magnetometers in unshielded environment but also proves effective for in situ magnetic field compensation in shielded environment, such as those used in magnetoencephalography, magnetocardiography, and space science.
Magnetic field gradients affect numerous modern sensitive measurements and physics studies using atomic ensemble, resulting in the loss of coherence. In some cases, the presence of small gradients can reduce the performance significantly. In this study, we propose an effectivein situmethod to compensate the triaxial magnetic field gradient for atomic magnetometers, based on multichannel atomic signals in one vapor cell. We design two novel gradient coils by solving closed-form equations to improve the accuracy and efficiency of compensation. We demonstrate the performance of the compensation method in a spin-exchange relaxation-free atomic magnetometer, which reduces the magnetic linewidth by 4.2%–7.6% under the same conditions at a compensation resolution of 50 pT/cm. The proposed coils generate gradients only along two axes and achieve triaxial decoupling, which compensates for the gradient completely without iteration. Our results may aid in suppressing atomic spin relaxations due to magnetic field gradients in several modern measurements and improve their performance, such as the detection of electric dipole moments, ultralow-field nuclear magnetic resonance, and biomagnetism.
We demonstrate a single-beam atomic magnetometer (AM) capable of measuring a three-axis magnetic field with high-sensitivity, achieved by applying a small DC offset field and a high frequency modulation field. To satisfy the miniaturization demand of AMs, an elliptically polarized light detuned by 50 GHz from the resonance transition center is employed. The circularly polarized component is used to polarize the alkali-metal atoms, while the linearly polarized light is used to detect the dynamics of the polarized spin under a magnetic field. Based on theoretical analysis, parameters that significantly affect the performance are optimized, and a sensitivity of 20 fT/Hz 1/2 in x -axis, 25 fT/Hz 1/2 in y -axis, 30 fT/Hz 1/2 in z -axis is achieved with a miniature 4 × 4 × 4 mm 87 Rb vapor cell. Moreover, we also verify that the operation principle of AMs can be used to null background magnetic fields in-situ with isotropic compensation resolution of 6.7 pT, which provides an effectively precise method for zeroing ambient magnetic field. The high-sensitivity operating of an elliptically-polarized-laser-based magnetometer provides prospective futures for constructing a compact, low-cost AM, which is particularly applicable for non-invasive bio-magnetic imaging such as array-based magnetoencephalography (MEG) and magnetocardiography (MCG).
Atomic magnetometer operating in spin-exchange-relaxation-free (SERF) regime has a wide range of applications due to its ultra-high sensitivity. However, the requirement of operating in near-zero magnetic field restricts some of the applications which need the atomic magnetometer to work in the high field environment such as monitoring the magnetic anomalies. A novel scheme of the chip-scale SERF atomic magnetometer operating in geomagnetic field without magnetic shield is demonstrated here. A 18 bits high-precise digital-to-analog converter (DAC) is applied to ensure the stability of the compensated magnetic field. The fluctuation of the compensated magnetic field is less than 8.3nT and a measurement sensitivity of 12.4pT/Hz1/2 is achieved in the laboratory environment without any magnetic shields.
The miniaturization of quantum sensors is a popular trend for the development of quantum technology. One of the key components of these sensors is a coil which is used for spin modulation and manipulation. The bi-planar coils have the advantage of producing three-dimensional magnetic fields with only two planes of current confinement, whereas the traditional Helmholtz coils require three-dimensional current distribution. Thus, the bi-planar coils are compatible with the current micro-fabrication process and are quite suitable for the compact design of the chip-scale atomic devices that require stable or modulated magnetic fields. This paper presents a design of a miniature bi-planar coil. Both the magnetic fields produced by the coils and their inhomogeneities were designed theoretically. The magnetic field gradient is a crucial parameter for the coils, especially for generating magnetic fields in very small areas. We used a NMR (Nuclear Magnetic Resonance) method based on the relaxation of 131Xe nuclear spins to measure the magnetic field gradient in situ. This is the first time that the field inhomogeneities of the field of such small bi-planar coils have been measured. Our results indicate that the designed gradient caused error is 0.08 for the By and the Bx coils, and the measured gradient caused error using the nuclear spin relaxation method is 0.09±0.02, suggesting that our method is suitable for measuring gradients. Due to the poor sensitivity of our magnetometer under a large Bz bias field, we could not measure the Bz magnetic field gradient. Our method also helps to improve the gradients of the miniature bi-planar coil design, which is critical for chip-scale atomic devices.