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Optimization of a SQUID vector gradiometer

Authors:
Jukka O. Lekkala at Tampere University
Jukka O. Lekkala
Jaakko Malmivuo at Technische Universität Berlin
Jaakko Malmivuo
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Abstract

A superconducting vector gradiometer for magnetocardiography was designed to maximize sensitivity and minimize errors when determining the magnetic heart vector. This equipment was constructed for clinical research and results are presented for preliminary measurements on a healthy subject.
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... This result echoes the textbook expressions for the classic input coil design for a single washer (71,86), with the exception of the fact that our expression contains variables that represent a single segment in the input coil and a single turn in the fractional washer. Thus, in our case the Josephson junctions will see a much smaller 1), which is beneficial for maintaining a relatively high overall energy sensitivity of the SQUID (meeting the optimization condition for = 1). ...
... Note also, that the energy sensitivity of our design is not better than that of the previous approaches and is still fundamentally limited by the same considerations as in the classic cases (29,50,86), but this design is optimized for the compactness of the pickup loop while maintaining high integrated flux (field) sensitivity without compromising the squid inductance. There is one instructive way to understand our results, that the flux from the pickup loop is effectively squeezed by a factor of about 100 (in our example) into a smaller area while still being effectively coupled to a small inductance SQUID. ...
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  • Mar 2020
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Article
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Book
Full-text available
  • May 1976
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Full-text available
  • Nov 1984
  • J Phys E Sci Instrum
A three-channel SQUID vectormagnetometer for biomagnetic studies is developed. The system is realised by using multiplexing where one of the three SQUIDS is monitored at a time. The system maintains continuously all the SQUIDS in the flux-locking condition. The construction of a gradiometer for recording the magnetic heart vector with the unipositional lead system is described. A low-noise, high-input impedance preamplifier and an RF-switch with nearly ideal properties at low signal levels are constructed and tested. The noise properties of the magnetometer system are estimated and measured. The usefulness of this vectormagnetometer is demonstrated by measuring the magnetic heart vector in real time from several healthy subjects. Two examples of these registrations are presented.
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Article
Full-text available
  • May 1975
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Article
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Article
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Article
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Article
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