High-T/sub c/ SQUID gradiometer for mobile magnetic anomaly detection

Clem, T.R.; Overway, D.; Purpura, J.W.; Bono, J.; Koch, R. H.; Rozen, J. R.; Keefe, George; Willen, Scott; Mohling, Robert A.

doi:10.1109/77.919483

Cited by 24 publications

(11 citation statements)

References 12 publications

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“…This dramatically reduces the dynamic range requirements on the outer SQUIDs by (largely) canceling the earth's field at the sensors. A mobile HTS SQUID gradiometer has been demonstrated that is based on this concept [4]. This system is nonetheless difficult to use as a basis for a tensor gradiometer because the localized feedback coils generate strong gradients that would affect the other gradiometers in the system.…”

Section: Agnetic Anomaly Detection (Mad) Applications Formentioning

confidence: 99%

Actively Shielded, Adaptively Balanced SQUID Gradiometer System for Operation Aboard Moving Platforms

Keene

Humphrey

Horton

2005

IEEE Trans. Appl. Supercond.

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Extremely high dynamic range is required if magnetometer SQUIDs are to be operated while in motion in the earth's field. We have developed an HTS SQUID gradiometer system that uses active shielding and an adaptive signal processing algorithm to achieve the necessary dynamic range. An array of four thin-film SQUIDs with flux transformers is configured to form two orthogonal magnetometers and a single-axis gradiometer with a baseline of 10 cm. External field changes are cancelled by a three-axis Helmholtz coil set, driven by integral feedback from the SQUIDs, which surrounds the array. A real time adaptive balancing algorithm corrects for gradient offset, electronics scaling errors, sensor misalignments and uniformity errors in the Helmholtz coils. For outside use, light RF shielding is provided by thin layers of Al foil.In laboratory tests, intrinsic noise levels of 20 pT m Hz (1 Hz) and 0.3 pT m Hz (white) were measured. In field trials, the Helmholtz coils provided a shielding factor, for uniform fields, of 50-60 dB (0.1-10 Hz) during roll, pitch and yaw rotations of up to 5 . Adaptive balancing reduced gradient noise to the ambient background level of 80 pT m Hz (1 Hz) and 1 pT m Hz (white), whilst in motion.

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Section: Agnetic Anomaly Detection (Mad) Applications Formentioning

confidence: 99%

Actively Shielded, Adaptively Balanced SQUID Gradiometer System for Operation Aboard Moving Platforms

Keene

Humphrey

Horton

2005

IEEE Trans. Appl. Supercond.

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“…A number of tensor gradiometer systems, based on a wide range of different technologies including high temeprature SQUID devices, are under development (e.g., Clem et al 2001;Humphrey et al 2005;Leslie et al 2007;Wiegert et al 2007;Sunderland et al 2009;Keenan et al 2010). We anticipate that over the next decade full gradient tensor systems will be commercialized and be routinely used in next generation magnetic surveys for exploration.…”

Section: Resource Explorationmentioning

confidence: 99%

Mapping and Interpretation of the Lithospheric Magnetic Field

Purucker

Clark

2010

Geomagnetic Observations and Models

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We review some of the controversial and exciting interpretations of the magnetic field of the earth's lithosphere occurring in the four year period ending with the IAGA meeting in Sopron in 2009. This period corresponds to the end of the Decade of Geopotential Research, an international effort to promote and coordinate a continuous monitoring of geopotential field variability in the near-Earth environment. One of the products of this effort has been the World Digital Magnetic Anomaly Map, the first edition of which was released in 2007. A second, improved, edition is planned for 2011. Interpretations of the lithospheric magnetic field that bear on impacts, tectonics, resource exploration, and lower crustal processes are reviewed. Future interpretations of the lithospheric field will be enhanced through a better understanding of the processes that create, destroy, and alter magnetic minerals, and via routine measurements of the magnetic field gradient. IntroductionThe magnetic field originating in the earth's lithosphere is part of the earth's magnetic field complex, a dynamic system (Friis-Christensen et al. 2009) dominated by the interaction of the earth's magnetic field dynamo with that of the sun's. The lithospheric field M.E. Purucker ( ) Raytheon at Planetary Geodynamics Lab, Goddard Space Flight Center, Code 698, Greenbelt, MD 20771, USA e-mail: michael.e.purucker@nasa.gov is dominated by static (on a human time scale) contributions that typically represents less than 1% of the overall magnitude of the magnetic field complex, and originate from rocks in the crust and locally, the uppermost mantle. Interpretation of the lithospheric magnetic field is used in (1) structural geology and geologic mapping, and extrapolation of surface observations of composition and structure, (2) resource exploration and 3) plate tectonic reconstructions and geodynamics.This article is designed as a review describing recent progress in mapping and interpreting the lithospheric magnetic field, and also includes some highlights from the 2009 IAGA meeting in Sopron, Hungary. Since IAGA meets every four years, we have designed this review to highlight progress in the four year period from 2005 through 2009, although references to earlier important works are not neglected, especially in the area of resource exploration. Several reviews bearing on the mapping and interpretation of the lithospheric magnetic field have appeared between 2005 and 2009. Review articles within books and encyclopedias have included those within the Encyclopedia of Geomagnetism and Paleomagnetism (Gubbins and

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“…Magnetometers are widely used in many fields like navigation [1], geology [2], material science [3], magnetic anomaly detection [4], biomedicine [5][6][7], and basic scientific research. Different magnetometers have their own characteristics, which meet the requirements of different applications [8,9].…”

Section: Introductionmentioning

confidence: 99%

Loop-locked coherent population trapping magnetometer based on a fiber electro-optic modulator

Feng

et al. 2014

Appl. Opt.

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We have set up a coherent population trapping (CPT)-based magnetometer prototype with the D1 line of ⁸⁷Rb atoms. The dichromatic light field is derived from a fiber electro-optic modulator (FEOM) connected to an external cavity laser diode. A CPT resonance signal with a 516 Hz linewidth is observed. By feeding back the derivative of the resonance curve to the FEOM with a proportional integral controller, of which the voltage output is directly converted to the measured magnetic field intensity, the resonance peak is locked to the environmental magnetic field. The measurement data we have achieved are well matched with the data measured by a commercial fluxgate magnetometer within 2 nT, and the sensitivity is better than 8 pT/√Hz in a parallel B field.

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High-T/sub c/ SQUID gradiometer for mobile magnetic anomaly detection

Cited by 24 publications

References 12 publications

Actively Shielded, Adaptively Balanced SQUID Gradiometer System for Operation Aboard Moving Platforms

Actively Shielded, Adaptively Balanced SQUID Gradiometer System for Operation Aboard Moving Platforms

Mapping and Interpretation of the Lithospheric Magnetic Field

Loop-locked coherent population trapping magnetometer based on a fiber electro-optic modulator

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