| 摘要 |
A magnet assembly has a field shaping device (P1) that is cylindrically symmetric with respect to the z-axis and made of magnetic material. At least parts of the field shaping device have a radial distance from the z-axis of less than 80 millimeters and compensate for at least one of the inhomogeneous field parts An0·zn of the magnet coil system. The field shaping device has one or more non cylindrically symmetric recesses, which are constituted such that at least a coefficient Anm or Bnm in the magnetic field expansion of the magnet assembly according to the spherical harmonic functions is reduced by at least 50%. In this way, the field homogeneity of the working volume can be substantially increased in a simple manner and without increasing the volume of the magnet assembly, wherein only a few iterations are required to optimize the magnet assembly. |
