A 230 MeV superconducting cyclotron CYCIAE-230 is being constructed by the China Institute of Atomic Energy. The technology of magnetic field measurement and amending processing is the primary task to realize the isochronous acceleration of cyclotron. The CYCIAE-230 has higher magnetic field, higher field gradient and dense rotation orbits. Therefore, the isochronous field and resonance crossing amended simultaneously. The first harmonics is also shimmed at the same process to achieve about 80% of the extraction efficiency by using resonance and precession extraction. The precision of field measurement, amending and processing is much higher and the algorithm is much more difficult. In addition, the compact structure of the magnet has very narrow installation space, which makes mapper design more difficult. In this paper, we will introduce:
1.The asymmetric field amending method for spiral sectors of SC cyclotron based on 45 degree chamfering on the pole edge is proposed and implemented for the first time. This method can effectively shim the isochronous field and first harmonics, reduce the magnetic saturation surround the pole edge, and facilitate the installation of main components such as central region and RF cavity.
2.During the processing, the asymmetric amending on both sides of the spiral sectors is creatively introduced to adjust the local tune value, so as to avoid the beam staying near harmful resonance and realize the effective control of the beam quality in the cyclotron.
3.A automated magnetic field measurement device, with both searching coil and hall probe has been developed. A series of optimum design and implementation of mechanical parts and EMC have effectively improved the positioning accuracy, greatly reduced the interference signal, and achieved the relative field measurement accuracy of 5×10-5.
After four times of field measurements, amending and processing, the results show that the phase shift, tune value and first harmonics have achieved excellent results. Detailed process will also be given in this paper. Such results will benefit greatly the overall performance of CYCIAE-230.