# US 4,393,349 A · Asymmetrical SQUID

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- Number: US 4,393,349 A
- Document ID: US4393349A
- Status: Granted
- Kind: A
- Application number: 06/151,815
- Filed: 1980-05-21
- Granted: 1983-07-12
- Earliest claimed: 1979-07-26
- Assignees: Her Majesty the Queen in right of Canada, as represented by the Minister of National Defence
- Inventors: Max B. Burbank; Randy K. Lomnes; Jiri Vrba; Alistair A. Fife
- Web page: https://patentgrep.com/patent/US4393349A

## CPC

- H10N 60/12: Josephson-effect devices
- G01R 33/0358: {coupling the flux to the SQUID (gradiometer coils G01R33/022; coils with superconductive winding H01F6/06)}
- Y10S 505/846: using superconductive quantum interference device, i.e. squid
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

The present invention relates to a SQUID device for magnetic field measurement. The device is comprised of a body of superconducting material. First and second holes are located therein. A slot is provided joining the first and second holes. A contact unit is provided which is located in the slot thereby forming a weak link across the slot. The dimensions of the first and second holes produce first and second inductances respectively. These inductances have unequal magnitude.

## Claims

### Claim 1

A SQUID device for magnetic field measurements comprising a tubular body of superconducting material, said body being truncated longitudinally to provide a flat surface; a hole having a longitudinal axis which is coaxial with the longitudinal axis of said body; a slot having a longitudinal axis parallel with said longitudinal axis of said body and joining said hole and said flat surface; a coil of superconducting wire having ends centrally affixed to said flat surface and directly adjacent said slot, wherein the inductance of said coil is different than the inductance of said hole; and wherein a weak link is located in said slot adjacent said flat surface.

### Claim 2

A SQUID device for magnetic field measurements comprising a body of superconducting material; a toroidal cavity located within said body, a planar circular slot circumferentially joining the interior wall of said toroidal cavity; said slot having a weak link located therein; first and second holes located centrally in said body having longitudinal axes which are perpendicular to the plane of said planar slot; a coil of superconducting wire having ends which are connected through said first and second holes respectively, and affixed to the opening faces of said planar slot; wherein the inductance of said coil is different than the inductance of said toroidal cavity.

### Claim 3 (depends on 1, 2)

The device according to claims 1 or 2 wherein said superconducting material is niobium.

### Claim 4

A SQUID device for magnetic field measurements comprising a body of superconducting material, said superconducting material being niobium; first and second holes located therein; a slot joining said first and second holes; a weak link located within said slot; the dimensions of said first and second holes creating first and second inductances respectively which are of unequal magnitudes; said body being divided into a first and a second region, said first region containing said first hole being tubular and being truncated longitudinally to form a flat surface, said second region extending centrally and perpendicularly from said flat surface and containing said second hole; and said slot being oriented longitudinally with respect to said first region.