NDLI: Measurement of MCG in Unshielded Environment Using a Second-Order SQUID Gradiometer

Content Provider	IEEE Xplore Digital Library
Author	Kang, C.S. Lee, Y.H. Yu, K.K. Kwon, H. Kim, J.M. Kim, K. Lim, H.K. Park, Y.K. Lee, S.G.
Copyright Year	1965
Abstract	In this paper, we fabricated a low-T_C second-order superconducting quantum interference device gradiometer (SQUID) to measure magnetocardiography (MCG) in unshielded environment. The second-order gradiometer consists of the pickup coil and the SQUID. The pickup coil is formed with two single-turn coils and one double-turn coil. The three coils are connected in order of single-, double-, and single-turn coil. The coupling polarity of two single coils is opposite to the double-turn coil. The SQUID is based on double relaxation oscillation SQUID (DROS), which consists of a hysteretic signal SQUID, a reference junction, and shunted a relaxation circuit with a resistor and an inductor. The DROS has ten times larger flux-to-voltage transfer coefficient (~ 1 mV/Phi₀) than that of the conventional SQUID. Therefore, DROS could be operated with a simple flux-locked loop circuit. The pickup coil and the SQUID were fabricated on the independent wafers and connected superconductively using an Nb wire. The overall size of the second-order gradiometer is 94 times 12 mm² with a baseline of 35 mm. The average field noise was about 8 fT /radicHz at 100 Hz with the second-order gradiometer in shielded or unshielded environment. The noise level is low enough to measure MCG signals in the unshielded environment. Finally, we measure the MCG in shielded and unshielded environments by using the second-order gradiometer and compared the signal characteristics measured in both environments.
Sponsorship	IEEE Magnetics Society
Starting Page	2882
Ending Page	2885
Page Count	4
File Size	797150
File Format	PDF
ISSN	00189464
Volume Number	45
Issue Number	6
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2009-06-01
Publisher Place	U.S.A.
Access Restriction	One Nation One Subscription (ONOS)
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	SQUIDs Superconducting coils Magnetic field measurement Superconducting devices Interference Magnetic devices Superconducting magnets Coupling circuits Hysteresis Resistors unshielded environment Magnetocardiography (MCG) second-order gradiometer superconducting quantum interference device (SQUID)
Content Type	Text
Resource Type	Article
Subject	Electronic, Optical and Magnetic Materials Electrical and Electronic Engineering

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1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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