Shim Coil Set for NMR Using a Novel Target Field Method Based on Trigonometric Series

Abstract

Target field (TF) method is very important for design of shim and gradient coils. Many works based on TF have been proposed. To restrict the current distribution on a cylinder with a given finite length, the current density is expanded by trigonometric series and the unknown coefficients are estimated based on the standard least square (LS) with L2 norm regularization (LS-L2). Then the winding pattern of the coils can be obtained by the stream function method. In this paper, the proposed method was employed to design a room temperature (RT) shim coil set for a 400 MHz nuclear magnet resonance spectrometer (NMR). The length of the main magnet used in this system is 400 mm, and the diameter of which is only 54 mm. The simulation results demonstrate that the proposed method is practical, and the magnet field homogeneity after shimming increases significantly.