In order to decrease the edge effect of the field, the designed magnetic field distribution in a large-scale FFAG magnet is realized by both the trim coil and the shape of the magnet pole-face.

• 摘要为减小边缘场效应，大型固定磁场交变梯度(FFAG)磁铁的磁场分布由修整线圈和磁极形状两者共同来实现。