Apparatus and Method for Determining Magnetic Properties of Materials

Abstract

Apparatus for determining magnetic properties of materials comprises a portable probe, an equipment trolley holding cryogenics and electronics and connecting cables. The probe comprises a drive coil and a correction coil, the drive coil being disposed symmetrically with respect to an inner second-order gradiometer sensor coil. Electrical connectors in the form of 2-metre long Belden (1192A) microphone cables are used to connect the apparatus on the equipment trolley to the drive coil, the correction coil and the sensor coil. The drive coil is driven so as to generate a sinusoidally varying magnetic field. The electronics comprise a flux-locked loop, a SQUID controller, a data acquisition module, which captures and processes the signals and computer. A liquid-nitrogen dewar is supported on the equipment trolley and houses a sensitive SQUID detector and a transfer coil made from copper. Possible applications of the apparatus include an intra-operative tool for sentinel lymph node detection in the treatment of breast cancer, and a non-destructive evaluation tool for detecting voids and defects in aluminum and applications in the aeronautics industry.

1 - 53 . (canceled) 
     
     
         54 . An apparatus for determining magnetic properties of materials, comprising:
 a superconducting quantum interference device (SQUID) located within a cryostat;   a probe having a longitudinal axis and comprising:
 means for applying an alternating magnetic field to a sensing region containing a material; 
 means for sensing a change in a magnetic parameter of the material resulting from the applied alternating magnetic field and for generating a sensor output signal in response thereto; 
 means for conveying the sensor output signal to the SQUID which is located remotely from the means for sensing a change in a magnetic parameter of the material; and 
 means for receiving an output signal from the SQUID indicative of the sensed magnetisation, 
   wherein the means for applying the field and the means for sensing a change in a magnetic parameter are arranged symmetrically about the longitudinal axis of the probe,   wherein the means for sensing a change in a magnetic parameter of the material is operable at non-cryogenic temperatures, and   wherein the magnetic field generated by the means for applying a magnetic field is non-zero in at least one location external to the probe and along the probe longitudinal axis.   
     
     
         55 . A probe for detecting magnetic properties of materials, including:
 a rod having a longitudinal axis and an exterior surface about the longitudinal axis;   a sensor coil wound circumferentially on the rod about its longitudinal axis; and   a drive coil comprising at least one set of windings wound circumferentially about the longitudinal axis of the rod and being symmetrically arranged about the longitudinal axis of the rod and arranged symmetrically about a plane oriented perpendicular to the longitudinal axis of the rod,   wherein the sensor coil is arranged symmetrically about the plane oriented perpendicular to the longitudinal axis of the rod, and   wherein, when in use, the drive coil produces an alternating magnetic field that is non-zero in at least one location along the longitudinal axis of the rod and external to the rod.