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Title: Magnetic microscopic imaging with an optically pumped magnetometer and flux guides

Abstract

Here, by combining an optically pumped magnetometer (OPM) with flux guides (FGs) and by installing a sample platform on automated translation stages, we have implemented an ultra-sensitive FG-OPM scanning magnetic imaging system that is capable of detecting magnetic fields of ~20 pT with spatial resolution better than 300 μm (expected to reach ~10 pT sensitivity and ~100 μm spatial resolution with optimized FGs). As a demonstration of one possible application of the FG-OPM device, we conducted magnetic imaging of micron-size magnetic particles. Magnetic imaging of such particles, including nano-particles and clusters, is very important for many fields, especially for medical cancer diagnostics and biophysics applications. For rapid, precise magnetic imaging, we constructed an automatic scanning system, which holds and moves a target sample containing magnetic particles at a given stand-off distance from the FG tips. We show that the device was able to produce clear microscopic magnetic images of 10 μm-size magnetic particles. In addition, we also numerically investigated how the magnetic flux from a target sample at a given stand-off distance is transmitted to the OPM vapor cell.

Authors:
ORCiD logo [1]; ORCiD logo [1];  [2]; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); National Tsing Hua Univ., Hsinchu (Taiwan)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1344366
Report Number(s):
LA-UR-16-28672
Journal ID: ISSN 0003-6951; TRN: US1700944
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 110; Journal Issue: 4; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; Atomic and Nuclear Physics

Citation Formats

Kim, Young Jin, Savukov, Igor Mykhaylovich, Huang, Jen -Huang, and Nath, Pulak. Magnetic microscopic imaging with an optically pumped magnetometer and flux guides. United States: N. p., 2017. Web. doi:10.1063/1.4975069.
Kim, Young Jin, Savukov, Igor Mykhaylovich, Huang, Jen -Huang, & Nath, Pulak. Magnetic microscopic imaging with an optically pumped magnetometer and flux guides. United States. doi:10.1063/1.4975069.
Kim, Young Jin, Savukov, Igor Mykhaylovich, Huang, Jen -Huang, and Nath, Pulak. Mon . "Magnetic microscopic imaging with an optically pumped magnetometer and flux guides". United States. doi:10.1063/1.4975069. https://www.osti.gov/servlets/purl/1344366.
@article{osti_1344366,
title = {Magnetic microscopic imaging with an optically pumped magnetometer and flux guides},
author = {Kim, Young Jin and Savukov, Igor Mykhaylovich and Huang, Jen -Huang and Nath, Pulak},
abstractNote = {Here, by combining an optically pumped magnetometer (OPM) with flux guides (FGs) and by installing a sample platform on automated translation stages, we have implemented an ultra-sensitive FG-OPM scanning magnetic imaging system that is capable of detecting magnetic fields of ~20 pT with spatial resolution better than 300 μm (expected to reach ~10 pT sensitivity and ~100 μm spatial resolution with optimized FGs). As a demonstration of one possible application of the FG-OPM device, we conducted magnetic imaging of micron-size magnetic particles. Magnetic imaging of such particles, including nano-particles and clusters, is very important for many fields, especially for medical cancer diagnostics and biophysics applications. For rapid, precise magnetic imaging, we constructed an automatic scanning system, which holds and moves a target sample containing magnetic particles at a given stand-off distance from the FG tips. We show that the device was able to produce clear microscopic magnetic images of 10 μm-size magnetic particles. In addition, we also numerically investigated how the magnetic flux from a target sample at a given stand-off distance is transmitted to the OPM vapor cell.},
doi = {10.1063/1.4975069},
journal = {Applied Physics Letters},
number = 4,
volume = 110,
place = {United States},
year = {Mon Jan 23 00:00:00 EST 2017},
month = {Mon Jan 23 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
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  • 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
  • A continuous recording total earth's field magnetometer is demonstrated that utilizes optical pumping in He/sup 3/ and the resultant polarization of the nuclear spins. The device operates as a self-oscillator at the Larmor frequency of the ground state atoms. The osciliator has a Q of 10/sup 4/ in a 0.5-G field. The sensitivity of the instrument to fluctuations in the magnetic field is presently several microgauss. The characteristics and operating principles of the instrument are described. The application of the device to the measurement of the absolute value of the total external magnetic field is discussed. (auth)
  • We demonstrate a way of operating an optically pumped magnetometer with miniaturized cesium cell using the light-narrowing effect. The magnetometer setup shows improvement of shot-noise-limited sensitivity (42 fT/{radical}(Hz) in a cell of only 9.3 mm{sup 3} volume) due to the suppression of spin-exchange relaxation to a large extent and the use of a strikingly increased fraction of alkali-metal atoms for signal generation, working even in {mu}T magnetic fields, by using only a single high-intensity laser beam both for pumping and probing of atomic spins.
  • 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
  • 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.