SQUID detector with flux feedback coil sized and located to produce uniform feedback flux
AssigneesThe Broken Hill Proprietary Company Limited, Commonwealth Scientific and Industrial Research Organisation
InventorsGraeme J. Sloggett, David L. Dart
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Abstract
A high temperature T.sub.c SQUID chip magnetometer has a flux-locked loop circuit including an independent feedback coil having an internal diameter greater than the maximum SQUID chip dimension. The feedback coil is mounted in close co-axial proximity to the SQUID chip to produce a substantially uniform feedback field over the entire area of the SQUID chip to cancel applied fields which penetrate the superconducting material.
Claims43
A high critical temperature (high-T.sub.C), superconducting quantum interference device (SQUID) magnetometer for measuring a subject magnetic field in which the SQUID magnetometer is positioned, the magnetometer including:
- a SQUID chip having a non-super conducting region threaded by a first magnetic flux produced by the subject magnetic field and energized by an excitation circuit,
- a separate feedback coil positioned adjacent to the SQUID chip, and
- a flux-locked loop for producing a feedback signal to energize the feedback coil,
- the flux-locked loop driving the feedback coil to produce a feedback magnetic flux which adds to, or subtracts from, the first magnetic flux to produce a resultant total magnetic flux threading the SQUID chip, and
- the feedback coil having a size relative to the SQUID chip to cause the resultant total magnetic flux to be substantially uniform over the SQUID chip, the feedback signal thereby being indicative of the magnitude of the first magnetic flux and the subject magnetic field which produces it.
A high critical temperature (high-T.sub.C) radio frequency superconducting quantum interference device rf (SQUID) magnetometer for measuring a subject magnetic field in which the SQUID magnetometer is positioned, the magnetometer including:
- a SQUID chip having a single weak link and a non-superconducting region threaded by a first magnetic flux produced by the subject magnetic field and energized by a radio frequency excitation circuit having a radio frequency tuned circuit including a radio frequency coil,
- a separate feedback coil positioned adjacent to the SQUID chip,
- a flux-locked loop for producing a feedback signal to energize the feedback coil, and
- a single interconnecting cable and a cross over network for connecting the rf coil and the feedback coil to the flux-locked loop,
- the flux-locked loop driving the feedback coil to produce a feedback magnetic flux which adds to, or subtracts from, the first magnetic flux to produce a resultant total magnetic flux threading the SQUID chip,
- the feedback coil having a size relative to the SQUID chip to cause the resultant total magnetic flux to be substantially uniform over the SQUID chip, the feedback signal thereby being indicative of the magnitude of the first magnetic flux and the subject magnetic field which produces it.
A high-T.sub.C SQUID magnetometer for TEM comprising:
- a SQUID chip having an RF excitation field coil disposed thereon;
- and
- a feedback electromagnetic coil dimensioned and disposed to provide a substantially uniform magnetic flux over the entire SQUID chip when electrical current is passed through the feedback coil.
Dependencies are inferred from the claim text.