In an arrangement for adjusting the spatial dependence of a magnetic field in
a working volume of a main field magnet (19) by means of ferromagnetic field
shaping elements (16), the field shaping elements (16) are formed
from foils (1, 5, 7, 8) and/or sheet metals (10) having openings
(2, 3) whose shape, position and size are selected such that the shape and
the amount of the remaining ferromagnetic material produces a desired spatial dependence
of the magnetic field in the working volume of the main field magnet for appropriate
positioning of the foils (1, 5, 7, 8) and/or sheet metals (10) relative
to the working volume of the main field magnet.
