High symmetry dc SQUID system
First Claim
1. A balanced thin film dc SQUID system comprising:
- a substrate;
a superconductive groundplane layer on said substrate formed with first and second slits forming a mutual intersection intermediate their ends, each said slit having enlarged openings at the end thereof;
thin film Josephson junction means located on diagonally opposite corners of said groundplane at said intersection of said slits, said Josephson junction means being part of a SQUID loop;
means for interconnecting said Josephson junction means across said intersection;
a thin film signal coil in coupling relationship with each said enlarged opening at opposite ends of one of said first and second slits;
an electrically balanced, physically symmetrical pair of thin film modulation coils, each said modulation coil being in coupling relationship with one of said enlarged openings at opposite ends of the other of said first and second slits; and
means for applying bias current to said Josephson junction means so as to not disturb the symmetry created by said modulation coil arrangement.
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Accused Products
Abstract
A thin film dc SQUID and its driving electronic circuitry configured with very high symmetry. The SQUID loop is formed with four holes at the respective ends of crossed slits. Each of these holes forms a single turn secondary for symmetrically arranged pairs of modulation coils and signal coils. The geometrical placement of the modulation coil transformers with respect to the signal coil transformers results in a device which nominally has no mutual inductance between the two groups of coils when the SQUID is biased for normal operation. The external driving circuit is configured to preserve the highly balanced nature of the chip and forces equal magnitudes of current to flow in all four of the bias leads.
79 Citations
49 Claims
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1. A balanced thin film dc SQUID system comprising:
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a substrate; a superconductive groundplane layer on said substrate formed with first and second slits forming a mutual intersection intermediate their ends, each said slit having enlarged openings at the end thereof; thin film Josephson junction means located on diagonally opposite corners of said groundplane at said intersection of said slits, said Josephson junction means being part of a SQUID loop; means for interconnecting said Josephson junction means across said intersection; a thin film signal coil in coupling relationship with each said enlarged opening at opposite ends of one of said first and second slits; an electrically balanced, physically symmetrical pair of thin film modulation coils, each said modulation coil being in coupling relationship with one of said enlarged openings at opposite ends of the other of said first and second slits; and means for applying bias current to said Josephson junction means so as to not disturb the symmetry created by said modulation coil arrangement. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A balanced thin film dc SQUID system comprising:
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a substrate; a superconductive groundplane layer on said substrate formed with first and second slits forming a mutual intersection intermediate their ends, each said slit having enlarged openings at the end thereof; thin film Josephson junction means located on diagonally opposite corners of said groundplane at said intersection of said slits, said Josephson junction means being part of a SQUID loop; means for interconnecting said Josephson junction means across said intersection; a thin film signal coil in coupling relationship with each said enlarged opening at opposite ends of one of said first and second slits; a pair of thin film modulation coils, each said modulation coil being in coupling relationship with one of said enlarged openings at opposite ends of the other of said first and second slits; and means for symmetrically applying bias current to said Josephson junction means. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A balanced thin film dc SQUID system comprising:
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a substrate; a superconductive groundplane layer on said substrate formed with first and second slits forming a mutual intersection intermediate their ends, each said slit having enlarged openings at the end thereof; thin film Josephson junction means located on diagonally opposite corners of said groundplane at said intersection of said slits, said Josephson junction means being part of a SQUID loop; means for interconnecting said Josephson junction means across said intersection; an electrically balanced, physically symmetrical pair of thin film signal coils, each said signal coil being in coupling relationship with one of said enlarged openings at opposite ends of one of said first and second slits; a thin film modulation coil in coupling relationship with each said enlarged opening at opposite ends of the other of said first and second slits; and means for applying bias current to said Josephson junction means so as to not disturb the symmetry created by said signal coil arrangement. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. A balanced thin film dc SQUID system comprising:
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a substrate; a superconductive groundplane layer on said substrate formed with first and second slits forming a mutual intersection intermediate their ends, each said slit having enlarged openings at the end thereof; thin film Josephson junction means located on diagonally opposite corners of said groundplane at said intersection of said slits, said Josephson junction means being part of a SQUID loop; means for interconnecting said Josephson junction means across said intersection; an electrically balanced, physically symmetrical pair of thin film signal coils, each said signal coil being in coupling relationship with one of said enlarged openings at opposite ends of one of said first and second slits; an electrically balanced, physically symmetrical pair of thin film modulation coils, each said modulation coil being in coupling relationship with one of said enlarged openings at opposite ends of the other of said first and second slits, said pair of modulation coils being electrically and physically symmetrical with respect to said signal coils; and means for symmetrically applying bias current to said Josephson junction means so as to enhance the symmetry created by said signal coil and modulation coil arrangement. - View Dependent Claims (41, 42, 43, 44, 45, 46, 47, 48, 49)
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Specification