A target field approach to optimize cylindrical shim coils for superconducting MRI system

Target field method is used to design a specific form of the magnetic field which has been verified in many works of literature. And to restrict the current distribution on a rectangular or cylindrical surface with finite size, the current density is usually expanded by Fourier series with some unknown coefficients, which can be determined by setting the target-field points over the imaging region of interest, and then comparing the calculated field values from the Biot–Savart law and the ideal ones. The stream-function method is adopted to discrete the current density to generate winding patterns. But some design results can't match the predetermined ones. Based on it, this paper proposed a new strategy for cylindrical shim coil design. Finally it can make the final design values meet the ideal fields with limited errors. This method can also be used to design gradient coils for high field superconducting MRI systems.