Abstract: NMR bias magnet apparatus employing permanent magnets and methods therefor are provided in accordance with the teachings of the present invention. According to the present invention a plurality of insulating sleeves which may be rotated are disposed about the periphery of a structure having a curvilinear cross section such as a cylinder. Each of the plurality of insulating sleeves are filled with stacks of slabs of permanent magnet material forming slugs and having an anisotropic axis of magnetic orientation aligned at an azimuth corresponding to a=2.phi.. The length of slug sections or even of individual slabs within each sleeve may be varied for purposes of introducing desired harmonics, as may the manner in which each sleeve is filled, so long as quadrature symmetry is maintained.

Abstract: Disclosed is a new type of electromagnet which can be used as a gradient coil in NMR imaging systems. The cylindrical electromagnet produces a transverse magnetic field perpendicular to the magnet axis which varies as the displacement along the magnet axis. An NMR imaging system using this new magnet is also disclosed.

Abstract: A segmented permanent ring magnet which is tunable to provide a preselected transverse magnetic field within the magnet interior is disclosed. The permanent magnet is constructed of material which has essentially linear behavior in the second quadrant of the B-H curve. The invention includes a method of tuning a segmented permanent ring magnet and a method of manufacture for the blocks of magnetic material which make up the magnet. The magnets of the present invention are particularly adapted for use as bias magnets in NMR imaging systems.