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Low Resonance SQUID Structure

IP.com Disclosure Number: IPCOM000038447D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Teschel, CD: AUTHOR

Abstract

This article relates generally to magnetometers employing DC superconducting quantum interference devices (SQUIDs) and, more particularly, to a technique for reducing the high frequency coupling between the SQUID and associated input circuitry. A reduction of the high frequency coupling between the SQUID loop and the input coil to the SQUID is accomplished by coupling the major part of the distributed capacitance of the input coil to a ground plane which is in turn coupled only weakly to the body of the SQUID.

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Low Resonance SQUID Structure

This article relates generally to magnetometers employing DC superconducting quantum interference devices (SQUIDs) and, more particularly, to a technique for reducing the high frequency coupling between the SQUID and associated input circuitry. A reduction of the high frequency coupling between the SQUID loop and the input coil to the SQUID is accomplished by coupling the major part of the distributed capacitance of the input coil to a ground plane which is in turn coupled only weakly to the body of the SQUID. Since the resonant frequency of the effective SQUID inductance and capacitance is proportional to the inverse of the square root of the inductance times capacitance, a reduction of the effective capacitance in the SQUID structure results in a corresponding reduction of the effects of resonances at the characteristic frequencies of the SQUID. The presence of these resonances degrades the performance of the device. Thus, reducing the effective SQUID capacitance improves performance, particularly for SQUIDs with large input coil inductances. Referring to the figure, input coil 1 and SQUID loop 2 are both wound over ground plane 3. The SQUID loop is reduced from the usual broad washer to a single narrow turn of wire. Ground plane 3 is washer-shaped, having opening 4 and slot 5, and insures that coil 1 and loop 2 are tightly coupled in the sense of their mutual inductance. Magnetic flux from both the coil and SQUID loop is forced th...