Design and Test of Various Adjusting Coils for ${\rm H}^{-}$ Compact Cyclotron

For compact cyclotrons, it is a common practice to avoid using adjusting coils to assist the formation of field distribution. However, it is necessary to employ the adjusting coil system in some special cases, as for CYCIAE-100, a high intensity compact cyclotron under construction at CIAE. To limit the cost for the main magnet, the casting steel is used for the top/bottom and return yokes. The imperfection should not be ignored and the harmonic coils on the return yokes will enable the field to reach the requirements easier during the shimming. During the beam commissioning, centering coils are always needed for this compact machine with ~400 turns' acceleration. When the machine is in operation, the field distribution will be changed by several factors, e.g. the thermal deformation, and the trim coils will probably be used to adjust the isochronism. In this paper, the effects of various adjusting coils, including 2 sets of centering coils on the hills in the central region, 8 sets of trim coils in the valleys and 1 set of trim coils on the hills right outside the centering coils, and 1 set of harmonic coils on the 4 return yokes, have been investigated. Then the detail configuration of the adjusting coils, the mechanical design and installation simulation from the coils to the outlet inside the compact machine, will be introduced in the paper. Some experiments, including those for the conductor inside the high vacuum tank, the insulator for high radiation field, and special feed through for high current and high vacuum, etc., are tested and the results will be given as well.