Noise Analysis in Pre-Amplifier Circuits Associated to Highly Sensitive Optically-Pumped Magnetometers for Geomagnetic Applications

Liu, Leisong; Lu, Yunxiang; Zhuang, Xin; Zhang, Qunying; Fang, Guangyou

doi:10.3390/app10207172

Cited by 10 publications

(5 citation statements)

References 29 publications

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“…The results of the MEG data recorded from an empty room without participants indicated that the OPMs do produce intrinsic noise. An OPM is constructed using a laser, vapor cell, photodiode, photocurrent, electrical circuit, and other components, which may generate magnetic noise that is inherently related to the physical sensor [ 37 , 38 ]. We consider magnetic signals originating from the OPM components as intrinsic noise.…”

Section: Discussionmentioning

confidence: 99%

Improved Biomagnetic Signal-To-Noise Ratio and Source Localization Using Optically Pumped Magnetometers with Synthetic Gradiometers

Xiang

Bonnette

et al. 2023

Brain Sciences

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Optically pumped magnetometers (OPMs) can capture brain activity but are susceptible to magnetic noise. The objective of this study was to evaluate a novel methodology used to reduce magnetic noise in OPM measurements. A portable magnetoencephalography (MEG) prototype was developed with OPMs. The OPMs were divided into primary sensors and reference sensors. For each primary sensor, a synthetic gradiometer (SG) was constructed by computing a secondary sensor that simulated noise with signals from the reference sensors. MEG data from a phantom with known source signals and six human participants were used to assess the efficacy of the SGs. Magnetic noise in the OPM data appeared predominantly in a low frequency range (<4 Hz) and varied among OPMs. The SGs significantly reduced magnetic noise (p < 0.01), enhanced the signal-to-noise ratio (SNR) (p < 0.001) and improved the accuracy of source localization (p < 0.02). The SGs precisely revealed movement-evoked magnetic fields in MEG data recorded from human participants. SGs provided an effective method to enhance SNR and improve the accuracy of source localization by suppressing noise. Software-simulated SGs may provide new opportunities regarding the use of OPM measurements in various clinical and research applications, especially those in which movement is relevant.

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Section: Discussionmentioning

confidence: 99%

Improved Biomagnetic Signal-To-Noise Ratio and Source Localization Using Optically Pumped Magnetometers with Synthetic Gradiometers

Xiang

Bonnette

et al. 2023

Brain Sciences

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show abstract

“…An OPM is constructed with laser, vapor cell, heater, photodiode, photocurrent, electrical circuit, and other components that are used to heat the vapors. These components may generate magnetic artifacts that are related to the physical sensor [ 29 , 30 ]. We consider magnetic artifacts from the OPM itself (e.g., laser, vapor, and heater) to be intrinsic artifacts.…”

Section: Discussionmentioning

confidence: 99%

Spatial and Frequency Specific Artifact Reduction in Optically Pumped Magnetometer Recordings

Xiang¹,

Han²,

Jiang³

et al. 2022

J. Integr. Neurosci.

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Background: Magnetoencephalography (MEG) based on optically pumped magnetometers (OPMs) opens up new opportunities for brain research. However, OPM recordings are associated with artifacts. We describe a new artifact reduction method, frequency specific signal space classification (FSSSC), to improve the signal-to-noise ratio of OPM recordings. Methods: FSSSC was based on time-frequency analysis and signal space classification (SSC). SSC was accomplished by computing the orthogonality of the brain signal and artifact. A dipole phantom was used to determine if the method could remove artifacts and improve accuracy of source localization. Auditory evoked magnetic fields (AEFs) from human subjects were used to assess the usefulness of artifact reduction in the study of brain function because bilateral AEFs have proven a good benchmark for testing new methods. OPM data from empty room recordings were used to estimate magnetic artifacts. The effectiveness of FSSSC was assessed in waveforms, spectrograms, and covariance domains. Results: MEG recordings from phantom tests show that FSSSC can remove artifacts, normalize waveforms, and significantly improve source localization accuracy. MEG signals from human subjects show that FSSC can reveal auditory evoked magnetic responses overshadowed and distorted by artifacts. The present study demonstrates FSSSC is effective at removing artifacts in OPM recordings. This can facilitate the analyses of waveforms, spectrograms, and covariance. The accuracy of source localization of OPM recordings can be significantly improved by FSSSC. Conclusions: Brain responses distorted by artifacts can be restored. The results of the present study strongly support that artifact reduction is very important in order for OPMs to become a viable alternative to conventional MEG.

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“…The testing results indicate that the magnetometric sensitivity approaches 140 fT/ √ Hz at 1 Hz, a factor of ~1.5 above the photon-shot noise limit, confirming the technological advancement and applicability of this sensor for magnetic anomaly detection applications. Compared to the published work [12,14], the cesium atomic magnetometer could have a wider operating temperature range and a higher sensitivity.…”

Section: Introductionmentioning

confidence: 91%

“…It achieved a sensitivity of approximately 1 pT/ √ Hz and a power consumption below 3 W [13]. In 2020, a cesium atomic magnetometer with a sensitivity of 0.6 pT/ √ Hz was also reported by Liu et al [14]. The G-824A and QTFM represent two technological directions in the current development of atomic magnetometers for geomagnetic applications.…”

Section: Introductionmentioning

confidence: 99%

A High-Sensitivity Cesium Atomic Magnetometer Based on A Cesium Spectral Lamp

Liu

Shi

et al. 2023

Applied Sciences

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Based on a low-noise cesium spectral lamp, a high-sensitivity self-oscillating cesium atomic magnetometer with a wide operating temperature range has been developed, solving problems with existing sensors such as a limited operating temperature range and difficult startup at low temperatures. The temperature feedback mechanism is used to make adjustments to any fluctuations in the cesium lamp’s excitation source in real time, improving the magnetometer’s stability and operating temperature range. Herein, the design and optimization of the cesium atomic magnetometer are presented, and a prototype of the magnetometer is described. The quantum limit sensitivity of the cesium atomic magnetometer is estimated by evaluating the intrinsic relaxation rate in the geomagnetic field. A test demonstrates that the cesium atomic magnetometer’s sensitivity in the geomagnetic background is around 140 fT/Hz at 1 Hz at room temperature, and the operating temperature range is from −50 °C to 70 °C, surpassing most of the commercial products of its kind in terms of sensitivity and operating temperature range.

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Noise Analysis in Pre-Amplifier Circuits Associated to Highly Sensitive Optically-Pumped Magnetometers for Geomagnetic Applications

Cited by 10 publications

References 29 publications

Improved Biomagnetic Signal-To-Noise Ratio and Source Localization Using Optically Pumped Magnetometers with Synthetic Gradiometers

Improved Biomagnetic Signal-To-Noise Ratio and Source Localization Using Optically Pumped Magnetometers with Synthetic Gradiometers

Spatial and Frequency Specific Artifact Reduction in Optically Pumped Magnetometer Recordings

A High-Sensitivity Cesium Atomic Magnetometer Based on A Cesium Spectral Lamp

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