• T.J. Zhang, C.J. Chu, G.F. Song, S.M. Wei, J.Q. Zhong
  CIAE, Beijing
• J.J. Yang
  TUB, Beijing

To limit the cost for the main magnet of a compact cyclotron CYCIAE-100, the cast steel is used for the top/bottom yoke and return yoke. The imperfection may not be ignored and the harmonic coils on the return yokes will make the fields reaching the requirements easier during the shimming. The centering coils will not only compensate the 1st harmonic fields at the center region, which is usually remain big, but also correct the off-center injection of the beam. The thermal deformation and the vacuum pressure may change the fields distribution during the machine operation and therefore It is necessary to use trim coils to adjust the fields. We arrange the trim coils inside the two opposite valleys of the main magnet. The second harmonics from the trim coils are not big eough to affect the beam dynamics significantly from the beam dynamics study. In this paper, the effects of correction coils of three types are presented. The detail configuration of the correction coils is introduced in the paper as well. One concern is the potential interference of some water cooled coils could have with vacuum. Some experience for the coils inside the high vacuum tank is tested and the results are given.