Low-noise SQUID
First Claim
1. A high-transition-temperature superconducting device for operation in an ambient magnetic field comprising, a superconducting film wherein the film has a width that is equal to or less than a critical width, the critical width being that width at which magnetic flux vortices are excluded from the superconducting film at a particular ambient magnetic field.
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Accused Products
Abstract
The present invention comprises a high-transition-temperature superconducting device having low-magnitude low-frequency noise-characteristics in magnetic fields comprising superconducting films wherein the films have a width that is less than or equal to a critical width, wC, which depends on an ambient magnetic field. For operation in the Earth'"'"'s magnetic field, the critical width is about 6 micrometers (μm). When made with film widths of about 4 μm an inventive high transition-temperature, superconducting quantum interference device (SQUID) excluded magnetic flux vortices up to a threshold ambient magnetic field of about 100 microTesla (μT). SQUIDs were fabricated having several different film strip patterns. When the film strip width was kept at about 4 μm, the SQUIDs exhibited essentially no increase in low-frequency noise, even when cooled in static magnetic fields of magnitude up to 100 μT. Furthermore, the mutual inductance between the inventive devices and a seven-turn spiral coil was at least 85% of that for inductive coupling to a conventional SQUID.
34 Citations
34 Claims
- 1. A high-transition-temperature superconducting device for operation in an ambient magnetic field comprising, a superconducting film wherein the film has a width that is equal to or less than a critical width, the critical width being that width at which magnetic flux vortices are excluded from the superconducting film at a particular ambient magnetic field.
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10. A high-transition-temperature superconducting quantum interference device (SQUID), for operation in an ambient magnetic field, the SQUID having a body comprising:
- a continuous strip of superconducting film interrupted by at least one Josephson junction, the strip having a width that is less than or equal to a critical width, wherein the critical width is that width at which magnetic flux vortices are excluded from the superconducting film at a particular magnetic field.
- View Dependent Claims (11, 12, 13, 14, 15)
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16. A high-transition-temperature superconducting quantum interference device (SQUID) for operation in an ambient magnetic field, the SQUID having a body comprising:
- at least one continuous strip of superconducting film, interrupted by at least one Josephson junction, the strip having a width that is equal to or less than a critical width, the critical width being that width at which magnetic flux vortices are excluded from the superconducting film at a particular magnetic field.
- View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A high-transition-temperature superconducting magnetometer for operation in a magnetic field, comprising,
a) a SQUID having a body comprising, a plurality superconducting film strips, the film strips having a width that is equal to or less than a critical width, the critical width being that width at which flux noise is excluded from the superconducting film at a particular ambient magnetic field; -
b) a thin dielectric coating over the SQUID; and c) a flux transformer comprising a pickup coil and an input coil deposited on the dielectric coating and inductively coupled to the SQUID. - View Dependent Claims (29, 30, 31, 32)
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33. A directly coupled high-TC superconducting magnetometer for operation in a magnetic field comprising,
a) a SQUID having a body comprising, at least one continuous high-TC superconducting film strip interrupted by at least one Josephson junction, the at least one film strip having a width that is equal to or less than a critical width, the critical width being that width at which flux noise is excluded from the superconducting film at a particular ambient magnetic field; b) a pick up coil having two ends, each end electrically connected to the SQUID body.
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34. A method of measuring magnetic field or flux comprising the steps of,
a) providing a superconducting magnetometer comprising at least one SQUID having a body wherein all film strip widths are less than or equal to a critical width, the critical width being that width at which flux noise is excluded from the superconducting film at a particular ambient magnetic field; -
b) providing the electronics necessary to read out magnetometer signals arising from magnetic field flux; c) cooling the magnetometer to below it'"'"'s superconducting transition temperature; and d) reading out the signals produced by the magnetometer.
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Specification