A new method to measure the temporal magnetic field instabilities in cryogen-free magnets for magnetic resonance

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. [Display omitted] •Temporal field distortions in cryogen-free magnet systems was studied.•A new experimental method to study the temporal field stability is described.•By application of this method the magnet design was improved.•It was shown that the field temporal instabilities can be suppressed down to sub ppb level.