Research On Magnetic Field Shimming Of Isochronous Cyclotrons

Isochronous cyclotrons are widely used in fundamental researches in national defense, isotopes production, medical diagnosis and therapy due to the compactness and low power consumption compared with other type of accelerators.The isochronous acceleration of beams in cyclotrons requires accurate magnetic field distribution, but the machining and alignment process of the main magnet often introduces field error inevitably, which will destroy the isochronism of the magnetic field and generates unwanted harmonics. Thus the magnetic field shimming of the isochronous cyclotron is very important.This paper discussed relative methods of magnetic field shimming, including the magnetic properties, the beam dynamic analysis in cyclotrons, methods of magnetic field shimming for isochronous field and first harmonic field etc.CYCCEO program was developed with Visual C++, and it can be used to calculate the equilibrium orbits and its main parameters by the analytical method. This paper introduces the function and the user interface of the program. Using this program the equilibrium orbit and its main parameters of a 10MeV PET cyclotron CYCHU-10 has been calculated, and the result is compared with the numerical result which is calculated from the program CYCCAE. Good agreement is found between the two programs.An algorithm of the first harmonic shimming based on the hard edge model was deduced. This thesis presents the detailed derivation of this algorithm, which is validated with MATLAB code. The same model is calculated by the algorithm used in China Institute of Atomic Energy (CIAE). The two results are compared.