| 摘要 |
A background field magnet for image transmitting devices of nuclear spin tomography is designed for the generation of a magnetic background field of predetermined first field strength and contains on a tubular coil support, and six super-conductive single coils which are arranged in pairs symmetrically with respect to a plane of symmetry at predetermined median distances from the plane. The coil support is also suitable for the generation of a second field strength which is smaller than the first field. According to the invention, it is provided that on the coil support (25) the coils (11, 12, 14) are applied with the same median distances (z1, z2. z4) with respect to the plane of symmetry (S), however, with reduced winding numbers N1', N2', N2'), that additionally a pair (P3) of serially switched auxiliary coils (13) is provided which each is placed in the vicinity of the outer single coils (14) on the coil former (25) and that with given reduced winding number (N4') of the outer single coils ( 14) under consideration of their original outer radius (R4) and a change of the conductor cross section (from q4 to q4') as well as with the median distance (z3) and the center radius (R3) of the auxiliary coils (13) given, the further winding numbers (N1', N2', N3') of the corresponding coils (11 to 13) by using the winding number (N1, N2, N4) resulting for the first field strength have to be determined according to given mathematical relations.
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