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US 5,293,119 AGranted
Electromagnetic microscope for evaluation of electrically conductive and magnetic materials
AssigneeSQM Technology, Inc.
InventorWalter N. Podney
Life of this patent
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AssigneeSQM Technology, Inc.
InventorWalter N. Podney
Estimating the term…
An instrument for non destructive evaluation (NDE) is called an electromagnetic microscope, formed by superconductive microprobes arrayed in parallel rows. When moved over a test piece, the array generates a scanned image of flaws, stress variations or changes in composition. Each microprobe has a drive coil a few mm in radius that encircles pickup loops forming a concentric, coplanar gradiometer 1 mm or less in diameter, coupled to a superconducting quantum interference device (SQUID). Drive coils transmit an oscillating magnetic field that induces eddy or magnetization currents in conductive or ferromagnetic materials, respectively. The gradiometer senses distortions in paths of induced currents. The sensitivity of SQUIDs increases sensitivity, penetration depth, and spatial resolution of flaws.
An electromagnetic flaw detecting apparatus, comprising an array of probes, each probe having a pickup loop forming a gradiometer and a drive coil, and a superconducting quantum interference device (SQUID) connected to the pickup loops, wherein plural SQUIDS are mounted in a liquid helium bath within a vacuum jacket and plural probes are connected to the SQUIDS by a flexible cryogenic umbilical cord, which includes electrical connectors for supplying current to the drive coils and for communicating sensed currents from the pickup loops to the SQUIDS, and thermal conductors for cooling the plural probes.
An electromagnetic microscope instrument for sensing flaws in a conductive or magnetic material, comprising a moveable cryostat, a flexible umbilical cord having distal and proximal ends, the proximal end of the cord being attached to the cryostat, a movable eye connected to the distal end of the cord for moving on the material, a window mounted on the eye for contacting the material, microprobes mounted in the eye within the window, the microprobes having pickup loops forming gradiometers, drive coils, and sensors connected to the pickup loops.
The method of detecting flaws, comprising positioning a probe on a material to be tested, creating changing magnetic fields with an array of drive coils in the probe, sensing currents in an array of pickup loops in the probe, communicating the sensed currents through electrical connectors in a thermally insulated, flexible umbilical cord to SQUIDS within a liquid helium bath, cooling the pickup loops from the bath via the umbilical cord, moving the probe on the material, sensing changes in the currents in the electrical connectors with the SQUIDS, and thereby sensing flaws in the material.
Dependencies are inferred from the claim text.