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Magnetic Field Camera - Superconducting Grid for the Detection of Transient Magnetic Phenomena

IP.com Disclosure Number: IPCOM000042045D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 3 page(s) / 61K

Publishing Venue

IBM

Related People

Chi, CC: AUTHOR [+3]

Abstract

This article relates generally to devices for the detection of magnetic flux and more particularly to a superconducting grid for the detection of transient magnetic phenomena. The magnetic field camera disclosed herein permits the digitization of magnetic flux threading a grid at some instant of time by trapping the flux in it in multiples of do and then reading out the flux at a later period of time. The device or camera 1 shown in Fig. 1 consists of a superconducting grid 2 of holes 3 over a ground plane 4. Ground plane 4 or portions thereof can be driven into the normal state. Gates 5 interconnect holes 3. Gates 5 may also be in either the normal or superconducting state.

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Magnetic Field Camera - Superconducting Grid for the Detection of Transient Magnetic Phenomena

This article relates generally to devices for the detection of magnetic flux and more particularly to a superconducting grid for the detection of transient magnetic phenomena. The magnetic field camera disclosed herein permits the digitization of magnetic flux threading a grid at some instant of time by trapping the flux in it in multiples of do and then reading out the flux at a later period of time. The device or camera 1 shown in Fig. 1 consists of a superconducting grid 2 of holes 3 over a ground plane 4. Ground plane 4 or portions thereof can be driven into the normal state. Gates 5 interconnect holes 3. Gates 5 may also be in either the normal or superconducting state. In operation, device 1 is placed in the external field to be measured with materials from which device 1 is fabricated, all initially in the normal state. Grid 2 is switched into the superconducting state, trapping a pattern, as shown in Fig. 2, of ni flux quanta in the loops surrounding each hole 3 and forming a plurality of cells. The set {ni} contains the basic information about the magnetic field passing through the grid at that instant of time. The external magnetic field may now be removed by turning off the source or interposing a superconducting shield. A mechanical shield or a normal superconducting transition may be used. In device 1 of Fig. 1, grid 2 is read out by shifting the trapped flux surrounding a hole 3 one cell at a time into a readout coil 6 inductively coupled to a SQUID (Superconducting Quantum Interference Device) detector 7, as shown in Figs. 3A-3C. Shifting is accomplished by driving the gates 5 and portions of ground plane 4 underneath particular cells into and out of the superconducting state by means to be more fully described hereinafter. Fig. 3A shows a pair of cells 8, 9 formed from holes 3 in grid 2 interconnected by gates 5. Upper cell 8 has a current, J screening circulating around its associated hole 3 while lower cell 9, which is a readout cell, has no current circulating around its associated hole 3. Readout cell 6 is inductively coupled to lower cell 9 and to SQUID detector 7. The latter may be an RF or DC SQUID. In Fig. 3A, gates 5 are superconducting, cell 9 is empty, ndo threads cell 8, and ground plane 4 is in its normal state. Fig. 3B shows the flux, ndo, bein...