Wire detection system

• US 6,215,303 B1
• Filed: 06/14/1999
• Issued: 04/10/2001
• Est. Priority Date: 06/14/1999
• Status: Expired due to Fees

• Current Assignee: Air Force Government of The United States of America As Represented By The Secretary
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Tralshawala, Nilesh, Weinstock, Harold
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US09/332,639
• Time in Patent Office: 666 Days
• Field of Search: 324/263, 324/248, 324/239, 324/240, 505/845, 505/846
• US Class Current: 324/263
• CPC Class Codes: G01N 27/82 for investigating the presence of flaws
• CPC Class Codes: G01N 27/9026 by moving the material
• CPC Class Codes: Y10S 505/846 using superconductive quantum interference device, i.e. squid

Abstract

A SQUID (Superconducting Quantum Interference Device) magnetometer, by far the most sensitive means for detecting small magnetic field variations, is utilized to detect defects inadvertently produced in the manufacture and draw-down of wires. Detection is effected by moving any electrically-conducting wire directly under a shielded SQUID magnetometer with a small aperture to permit the sensing of the magnetic field associated with injected or induced alternating electrical current. Shielding may be provided either by a mu-metal cylinder with a small concentric bottom hole or an open superconducting cylinder strategically placed around the SQUID sensor. Initially, the position of the cryogenic containment vessel (dewar) is oriented to produce a null magnetic signal at the squid sensor location. Any phase-sensitive-detected) signal that appears after wire is spooled under the sensor must be related to non-concentric deviations of the current path in the wire. These deviations can be caused by foreign inclusions, structural anomalies or an irregular geometrical cross section. This technique is especially effective in verifying the integrity of composite wires where it is not possible to visually inspect the embedded wire components, e.g., multifilament superconducting wire encased in a copper matrix. The region of non-uniform current can be localized immediately, and appropriate action can be taken whether to terminate the spooling process or to note the effect for future action.

Claims

1. A system for detecting a defect in a wire comprising:

a means for sending an alternating current signal into the wire and which generates a magnetic field thereby wherein said wire is fed from a supply reel, through a wire guide to a take-up reel, and wherein said sending means comprises;

a power source which produces the current signal; and

a set of pressure contact points which conduct the current signal from the power source to said wires as it flows through the wire guide;

a means for displaying an output signal;

a superconducting magnetic field sensor that produces an output signal when sensing the magnetic field around the wire, said output signal having recognizable characteristics of magnetic anomalies when defects are present in the wire wherein said superconducting magnetic field sensor is enclosed in a dewar which provides an electrical connection between the superconducting magnetic field sensor and a lock-in amplifier which amplifies the output signal of the superconducting magnetic field sensor for the displaying means; and

a superconducting open-ended cylindrical shield that shields the superconducting magnetic field sensor from any undesirable environmental signals that could contaminate readings.