Open MRI Magnet With Iron Rings Correcting the Lorentz Force and Field Quality

A magnetic resonance imaging (MRI) superconducting magnet with openness can reduce claustrophobia of a patient. To fabricate an open MRI magnet, a new magnet configuration with iron rings and pole plates balancing the force between the coil and the yoke, and correcting the field homogeneity has been proposed. An MRI magnet with the center field of 0.7 T generated by split-pair coils and yokes is fabricated. The coils are contained in the cryostat with separated vessels connected with two pipes. The coils are separated with a room temperature gap of 480 mm and the diameter spherical volume (DSV) of 300 mm in which the homogeneity is 3 ppm in peak-to-peak. The cryogenic system is cooled by one GM cryo-cooler to realize the zero boiling off liquid helium. In the paper, the detailed design, fabrication, and test will be reported.