Target field method for superconducting MRI cylindrical gradient coil design

This paper presented a set of gradient coils design for a superconducting magnetic resonance imaging (MRI) system via target field method. The gradient coils were fixed on a cylinder of radius 0.8 m and length 3 m, and the target field with radius 0.2 m was located in the center of the cylinder. The design gradient was 40 mT/m. In this method, the current density was expanded into a summation of trigonometric series in the cylindrical coordinate system. The undetermined coefficients of these trigonometric series were got by solving linear equations, which were obtained by a Tikhonov regulation approach based on target field method. Finally, the current density distribution was transformed to the winding pattern of gradients using stream function method. The magnetic field deviation was also analyzed, and the results showed that the deviation was far less than the general requirement 5%. In addition, the above method can also be used to design active shim coils.