Abstract: A magnetic field sensing and canceling circuit for use with a cathode ray tube (CRT) has a closed loop system consisting of flux gate sensors to measure external magnetic fields and magnetic field cancellation coils around the perimeter of the faceplate of the CRT to cancel the fields and thus minimize color and positional ac image distortion. The coils are mounted on an enclosure fabricated of a high permeability material and are positioned around the perimeter of the CRT's faceplate. Four of the coils are parallel to the top, bottom, and sides of the enclosure opening and a fifth coil is wound around the enclosure adjacent the CRT faceplate. The magnetic flux gate sensors provide output signals that are functions of the detected fields. These signals control the current in the magetic field cancellation coils and thus control the cancellation fields.

Abstract: The drive modules of a magnetostrictive transducer are fabricated from interleaved permanent magnet disks (samarium cobalt) and high-strain, low-permeability magnetostrictive lanthanide alloy (Terfenol-D) disks to form a stack of such interleaved materials of substantially uniform magnetic field distribution in the stack. Two such stacks in side-by-side relationship provide a series-aiding magnetic circuit completed through high-permeability flux return pole pieces at their ends thereby providing a substantially uniform magnetic field distribution in the stack. Each stack has longitudinally-extending and electrically-insulated planar cuts and each flux return pole piece is a laminate of thin sheets of high-permeability electrically-insulated steel to reduce eddy current losses resulting from the AC field. The steel sheets are constrained by a nonmagnetic end-block into which the steel sheets are inserted and bonded.

Abstract: A transducer which uses paramagnetic magnetostrictive rods or bars, e.g., compositions of the lanthanide series of elements such as Tb.sub.0.3 Dy.sub.0.7 Fe.sub.2, has the bars biased with a lengthwise flux by a permanent magnet, e.g. samarium-colbalt, of high resistance to demagnetization by the alternating field applied to the bars by alternating current in a coil surrounding the bar. The magnet is outside the coil to reduce the ac field to which it is subjected. Uniformity of flux density along the length of the bars is enhanced by having adjacent ends of the bars subjected to like-polarity poles of the permanent magnets associated with each bar.

Abstract: A magnetic materials separator including an axially inclined drum disposed for axial rotation within the curvature of an arcuate magnet structure which extends axially of the drum and is disposed in close-spaced relationship with the outer surface of the drum. The magnet structure comprises an axially extending series of arcuate magnet yokes, each comprising an axially laminated array of arcuate magnet sub-assemblies which are alternately polarized in opposite axial directions. Each of the sub-assemblies comprises an arcuate magnet axially polarized and sandwiched between a arcuate pair of soft magnetic flux concentrators which have respective axial thicknesses between five and twenty percent of one-half the axial thickness of the sandwiched magnet.