About an electromagnetic magnet system of an NMR tomography apparatus there is arranged a second electromagnetic magnet system which is capable of generating a magnetic field such that the external stray field of the first magnet system is compensated for. When use is made of superconducting magnet coils, the reduction of the measurement field which is caused by the compensation magnet can be readily cancelled. Using a construction where the surface O2 of the cross-section of the second magnet system amounts to twice the surface O1 of the cross-section of the first system, the field at the area of the windings of the first system is also compensated for in the case of energizing where O1 x H1 = O2 x H2, with the result that substantially larger persistent currents are permissible.
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机译：关于NMR层析成像设备的电磁系统，布置有第二电磁系统，该第二电磁系统能够产生磁场，从而补偿第一磁体系统的外部杂散场。当使用超导磁体线圈时，可以容易地消除由补偿磁体引起的测量场的减小。使用第二磁体系统的横截面的表面O2等于第一系统的横截面的表面O1的两倍的结构，还可以补偿第一系统的绕组区域的磁场。在通电情况下，O1 x H1 = O2 x H2，结果是允许更大的持续电流。
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