Despite the obvious advantages of cryogen-free magnets for NMR such as independence of liquid helium supply and the possibility to use the same magnet at different fields, the practical application of those magnets remains limited because of temporal magnetic field distortions associated with cryogen-free cold head operation. A new experimental method for the simple and reliable detection of the temporal field distortions is described in this paper. The accuracy of the magnetic field measurements by this method is two orders of magnitude higher than by conventional MetroLab Tesla meter. This has enabled us to make improvements in the design of cryogen-free magnets by reducing the amplitude of such field distortions down to sub ppb level. This then results in cryogen-free magnets that are suitable for MRI and MAS NMR applications.

尽管无制冷剂磁体具有明显的NMR优势，例如液氦供应的独立性以及在不同磁场中使用同一磁体的可能性，但由于与无制冷剂的冷态有关的时间磁场畸变，这些磁体的实际应用仍然受到限制。头部操作。本文介绍了一种用于简单，可靠地检测时域畸变的新实验方法。通过这种方法进行的磁场测量的精度比传统的MetroLab Tesla仪表高出两个数量级。这使我们能够通过将这种磁场畸变的幅度降低到低于ppb的水平来改进无制冷剂磁体的设计。然后，这会产生适用于MRI和MAS NMR应用的无致冷剂磁体。