Device for homogenization of the magnetic field at the center of a superconducting coil used in production of a magnetic field in a nuclear magnetic resonance apparatus where the effects of temperature variations are compensated

摘要

Arrangement for homogenization of the magnetic field through the working volume of the main magnet of a magnetic resonance device has a large number of ferromagnetic or permanent magnetic shims arranged around the inner periphery of the main magnet to create an equalizing and homogenizing magnetic field with the field at the center of the work volume being effectively zero. An Independent claim is made in which the number, strength and position of the shims is such that any change in their resultant magnetic field at the center of the main magnet is such that the inductive coupling with the main magnet produces a counter change in the magnetic field through the main coil.