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Title: Four-channel optically pumped atomic magnetometer for magnetoencephalography

Abstract

We have developed a four-channel optically pumped atomic magnetometer for magnetoencephalography (MEG) that incorporates a passive diffractive optical element (DOE). The DOE allows us to achieve a long, 18-mm gradiometer baseline in a compact footprint on the head. Using gradiometry, the sensitivities of the channels are < 5 fT/Hz 1/2, and the 3-dB bandwidths are approximately 90 Hz, which are both sufficient to perform MEG. Additionally, the channels are highly uniform, which offers the possibility of employing standard MEG post-processing techniques. As a result, this module will serve as a building block of an array for magnetic source localization.

Authors:
 [1];  [1];  [1];  [1];  [2];  [1];  [1]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Charles Stark Draper Lab., Cambridge, MA (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
National Institutes of Health (NIH); USDOE
OSTI Identifier:
1325716
Report Number(s):
SAND-2016-5979J
Journal ID: ISSN 1094-4087; OPEXFF; 642490
Grant/Contract Number:
AC04-94AL85000
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Optics Express
Additional Journal Information:
Journal Volume: 24; Journal Issue: 14; Journal ID: ISSN 1094-4087
Publisher:
Optical Society of America (OSA)
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION; coherent optical effects; diffractive optics; polarimetry; Faraday effect; magneto-optic systems; biological sensing and sensors

Citation Formats

Colombo, Anthony P., Carter, Tony R., Borna, Amir, Jau, Yuan -Yu, Johnson, Cort N., Dagel, Amber L., and Schwindt, Peter D. D. Four-channel optically pumped atomic magnetometer for magnetoencephalography. United States: N. p., 2016. Web. doi:10.1364/OE.24.015403.
Colombo, Anthony P., Carter, Tony R., Borna, Amir, Jau, Yuan -Yu, Johnson, Cort N., Dagel, Amber L., & Schwindt, Peter D. D. Four-channel optically pumped atomic magnetometer for magnetoencephalography. United States. doi:10.1364/OE.24.015403.
Colombo, Anthony P., Carter, Tony R., Borna, Amir, Jau, Yuan -Yu, Johnson, Cort N., Dagel, Amber L., and Schwindt, Peter D. D. 2016. "Four-channel optically pumped atomic magnetometer for magnetoencephalography". United States. doi:10.1364/OE.24.015403. https://www.osti.gov/servlets/purl/1325716.
@article{osti_1325716,
title = {Four-channel optically pumped atomic magnetometer for magnetoencephalography},
author = {Colombo, Anthony P. and Carter, Tony R. and Borna, Amir and Jau, Yuan -Yu and Johnson, Cort N. and Dagel, Amber L. and Schwindt, Peter D. D.},
abstractNote = {We have developed a four-channel optically pumped atomic magnetometer for magnetoencephalography (MEG) that incorporates a passive diffractive optical element (DOE). The DOE allows us to achieve a long, 18-mm gradiometer baseline in a compact footprint on the head. Using gradiometry, the sensitivities of the channels are < 5 fT/Hz1/2, and the 3-dB bandwidths are approximately 90 Hz, which are both sufficient to perform MEG. Additionally, the channels are highly uniform, which offers the possibility of employing standard MEG post-processing techniques. As a result, this module will serve as a building block of an array for magnetic source localization.},
doi = {10.1364/OE.24.015403},
journal = {Optics Express},
number = 14,
volume = 24,
place = {United States},
year = 2016,
month = 6
}

Journal Article:
Free Publicly Available Full Text
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Citation Metrics:
Cited by: 4works
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  • Abstract not provided.
  • In a compact optically pumped atomic magnetometer (OPAM), there is a plateau in the sensitivity where the dependence of the sensitivity on pumping power is small compared with that predicted by the uniform polarization model. The mechanism that generates this plateau was explained by numerical analysis. The distribution of spin polarization in the alkali metal cell of an OPAM was modeled using the Bloch equation incorporating a diffusion term and an equation for the attenuation of the pump beam. The model was well-fitted to the experimental results for a module with a cubic cell with 20 mm sides and pumpmore » and probe beams with 8 mm diameter. On the plateau, strong magnetic response was generated at the regions that were not illuminated directly by the intense pump beam, while at the same time spin polarization as large as 0.5 was maintained due to diffusion of the spin-polarized atoms. Thus, the sensitivity of the magnetometer monitored with a probe beam decreases only slightly with increasing pump beam intensity because the spin polarization under an intense pump beam is saturated. This plateau, which is characteristic of this type of magnetometer using a narrow pump and probe beams, can be used in arrays of magnetometers because it enables stable operation with little sensitivity fluctuation from changes in pump beam power.« less
  • Abstract not provided.
  • Optically pumped magnetometers (OPMs) based on lasers and alkali-metal vapor cells are currently the most sensitive non-cryogenic magnetic field sensors. Many applications in neuroscience and other fields require high-resolution, high-sensitivity magnetic microscopic measurements. In order to meet this demand we combined a cm-size spin-exchange relaxation-free (SERF) OPM and flux guides (FGs) to realize an ultra-sensitive FG-OPM magnetic microscope. The FGs serve to transmit the target magnetic flux to the OPM thus improving both the resolution and sensitivity to small magnetic objects. We investigated the performance of the FG-OPM device using experimental and numerical methods, and demonstrated that an optimized devicemore » can achieve a unique combination of high resolution (80 μm) and high sensitivity (8.1 pT/). Additionally, we also performed numerical calculations of the magnetic field distribution in the FGs to estimate the magnetic noise originating from the domain fluctuations in the material of the FGs. We anticipate many applications of the FG-OPM device such as the detection of micro-biological magnetic fields; the detection of magnetic nano-particles; and non-destructive testing. From our theoretical estimate, an FG-OPM could detect the magnetic field of a single neuron, which would be an important milestone in neuroscience.« less
  • Here, optically pumped magnetometers (OPM) can be used in various applications, from magnetoencephalography to magnetic resonance imaging and nuclear quadrupole resonance (NQR). OPMs provide high sensitivity and have the significant advantage of non-cryogenic operation. To date, many magnetometers have been demonstrated with sensitivity close to 1 fT, but most devices are not commercialized. Most recently, QuSpin developed a model of OPM that is low cost, high sensitivity, and convenient for users, which operates in a single-beam configuration. Here we developed a theory of single-beam (or parallel two-beam) magnetometers and showed that it is possible to achieve good sensitivity beyond theirmore » usual frequency range by tuning the magnetic field. Experimentally we have tested and optimized a QuSpin OPM for operation in the frequency range from DC to 1.7 kHz, and found that the performance was only slightly inferior despite the expected decrease due to deviation from the spin-exchange relaxation-free regime.« less