Apparatus for determining magnetic properties of materials comprises a portable probe 1, an equipment trolley 2 holding cryogenics and electronics and connecting cables 3.
The probe 1 comprises a drive coil 4 and a correction coil 5, the drive coil 4 being disposed symmetrically with respect to an inner second-order gradiometer sensor coil 8.
Electrical connectors in the form of 2-metre long Belden 1192A microphone cables 3 are used to connect the apparatus on the equipment trolley 2 to the drive coil 4, the correction coil 5 and the sensor coil 8.
The drive coil 4 is driven so as to generate a sinusoidally varying magnetic field.
The electronics comprise a flux-locked loop 9, a SQUID controller 10, a data acquisition module 11, which captures and processes the signals and a computer 12.
A liquid-nitrogen dewar 13 is supported on the equipment trolley 2 and houses a sensitive SQUID detector 14 and a transfer coil 15 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 aluminium and applications in the aeronautics industry.