Energy efficient iron based electronic field cycling magnet

A new concept for an energy efficient electromagnet for fast field cycling NMR applications as well as its construction and first test results are presented. The magnet, which provides a rectangular sample space of 17 × 25 mm, has an iron yoke and pole pieces optimised with respect to the B₀ homogeneity. The maximum field is 0.66 T at a current of 320 A; its field inhomogeneity for a cylindrical sample (length 7 mm, diameter 6 mm) is about 50 ppm. The power dissipation during polarisation at 0.55 T is as low as 1.4 kW. The magnet is powered by a commercially available power supply and can be rapidly switched with a slew rate of 0.55 T/ms. The system has shown a stability of 50 ppm/h.