An Accurate Passive Shimming Method

Passive shimming optimizations usually contain constrain condition about the maximum number of shim-piece on the position where the shim-pieces may be placed at, but the papers do not involve how to set the maximum number of shim-piece. In traditional optimization method, the maximum number of shim-piece is set into a same constant. But, in this paper, the maximum number of shim-piece is determined according to its position and the requirement of magnetic field uniformity. By the comparison of these two methods, this method can obtain the better optimization result which has smaller error with the accurate calculation of the magnetic field uniformity. The numerical simulation of the open 1.5T permanent nuclear magnetic resonance(NMR) also verified this point. However, this method is not only suitable for conventional NMR magnet, but also, it can be applied to any other magnets.