GB1360606A - Magnetic systems - Google Patents

Abstract

1360606 Magnets; electromagnets L K PARKER 5 Aug 1971 [7 Aug 1970] 38206/70 Heading H1P In a magnet system, e.g. for measurement of nuclear magnetic resonance, a source of MMF, e.g. a permanent or electromagnet produces a high density field between like poles separated by an air gap or non-magnetic laminate and mounted on the ends of an armature stack (Fig. 1, not shown). To obtain uniform field distribution in the gap the poles comprise a frustoconical central high permeability pole 4 (Fig. 2) encircled by a gap filled with non-magnetic material, e.g. resin and a magnetic guard ring of lower permeability; the pole and ring being separated from the armature by a further gap 8. A threaded magnetic ring 6A encircles the outer edge of the guard ring, and the combined effect is to reduce non-uniformity and leakage of flux. The ring 6A is adjustable by rotation to modify the field therein and obtain minor correction of the interpolar flux distribution. In modifications (Fig. 3, not shown) the combined pole profile may be shaped and (Fig. 4, not shown), a rotatable portion of the guard ring may be adjustably threaded to the base circumference of the ring body. In a further modification, the adjustable ring may be threaded to the outer circumference of the end of the magnetic armature (Fig. 5, not shown) and the main body of the guard ring may have a cylindrical surface encircled by an extension of the adjustable ring. The magnetic guard ring may comprise one or more windings carrying electric current and the central pole or the guard ring or both may comprise transverse highly permeable magnetic laminae separated by alternate laminae of non-magnetic material. The latter may be elastic and the assembly may be compressible for adjustment.