Development of an Electromagnetic Microscope for Eddy Current Evaluation of Materials
Abstract
Superconductive quantum interference devices (SQUIDs) offer new technology for locating material flaws electromagnetically that promises to increase sensitivity and depth of field as well as to enhance resolution and imaging. The ultrahigh sensitivity of SQUIDs to magnetic flux allows use of microscopic pickup loops in a gradiometer configuration to give high resolution. To realize the advantages of SQUID technology for Air Force requirements in evaluating the integrity of airframes, SQM Technology, Inc. is developing an electromagnetic microscope that uses an array of microscopic pickup loops for imaging micro flaws in aluminum. The prototype comprises a triangular array of microscopic gradiometers that are coupled to SQUID sensors through a flexible, cryogenic umbilical, which enables convenient scanning. Development to date shows three main accomplishments: (1) a planar, azimuthal gradiometer configuration enables suppressing source interference, (2) instrument noise at drive currents of 1 A or so at frequencies below a few kilohertz is of the order of SQUID noise, and (3) a cryogenic umbilical can provide adequate cooling over a four to six foot length.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1991
- Accession Number
- ADA242007
Entities
People
- Walter N. Podney