Arrangement for producing a base magnetic field in a nuclear magnetic resonance instrument has a shim device with a set of spherical objects of varying magnetic saturation arranged to provide a more homogenous base field

摘要

Arrangement for producing a base magnetic field in a nuclear magnetic resonance instrument has a shim device with a magnetic field induction arrangement for coupling the magnetic field into the observation area. The field coupling device comprises a number of ferromagnetic objects (A-F), preferably spheres that have different magnetic properties, especially different magnetic saturation. Independent claims are made for a set of ferromagnetic objects (63) with varying ferromagnetic properties and a method for improving the homogeneity of the base field of an NMR instrument using the inventive ferromagnetic objects.