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SQUID Multiplexing Method

IP.com Disclosure Number: IPCOM000062346D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Tesche, CD: AUTHOR

Abstract

This article relates generally to superconducting quantum interference devices (SQUIDs) and, more particularly, to the multiplexing of such devices. A plurality of magnetometer pick-up coils arranged in parallel can be sequentially sensed by a single SQUID in determining a magnetic field pattern. In the figure, identical pick-up coils L1 and L2, each sensing respective flux fields d1 and d2, are connected in parallel with an inductor L3 whose field is, in turn, sensed by SQUID 4. An output voltage change is detected at terminal V. The current through inductor L3 is the resultant of that due to the effective flux divided by the total effective inductance of all coils. If a portion of the loop containing L1 is driven to the normal or resistive state, the current in that loop becomes zero.

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SQUID Multiplexing Method

This article relates generally to superconducting quantum interference devices (SQUIDs) and, more particularly, to the multiplexing of such devices. A plurality of magnetometer pick-up coils arranged in parallel can be sequentially sensed by a single SQUID in determining a magnetic field pattern. In the figure, identical pick-up coils L1 and L2, each sensing respective flux fields d1 and d2, are connected in parallel with an inductor L3 whose field is, in turn, sensed by SQUID 4. An output voltage change is detected at terminal V. The current through inductor L3 is the resultant of that due to the effective flux divided by the total effective inductance of all coils. If a portion of the loop containing L1 is driven to the normal or resistive state, the current in that loop becomes zero. When L2 is much larger than L3, the change in current at L3 is approximately equal to the flux d1 divided by the inductance of L1 and L2 and represents the flux stored in L1. Subsequently, coil L2 can be driven to the resistive state, and the resulting change in current represents the flux d2 stored at L2. In the general case, L1 and L2 are not necessarily large compared to L3, but the current changes are linearly related to the unknown fluxes and can be simply determined. The number of pick-up coils can be increased and is limited by the intrinsic SQUID noise, accuracy and maximum input inductance to the SQUID. Normal state resistance should limit the cu...