Research On The Main Magnet Shimming Of CYCHU-10 Cyclotron

Cyclotron is a complex electromagnetic device which is widely used in nuclear physics basic research, medical diagnosis and treatment, environmental engineering and other areas. Its design, manufacturing and assembly is an interdisciplinary application process. There always exists some deviations between the practical magnetic field and isochronous field when the initial mechanical processing on the cyclotron main magnet is completed. These deviations would lead to loss of particles during acceleration, so the magnetic field measurement and magnet shimming work need to be carried out. This paper aims at the research on main magnet shimming of CYCHU-10 cyclotron. By adopting the method combined with numerical analysis and measurement, the theoretical algorithm and realizing process of the magnet shimming on CYCHU-10 cyclotron will be studied.The article is roughly divided into four parts. The first part introduces the development situation, basic principles and the beam dynamics foundation of isochronous cyclotron. In the second part, based on the finite element magnetic field calculation, the piecewise function shimming method which adopts the multiple linear regression is employed to carry out a shimming experiment on the virtual model, and a good shimming effect is reached. In the third part, magnetic field measurement on CYCHU-10 is implemented. Firstly, the deviation between the practical field and isochronous field is found, so we firstly decrease this deviation by adjusting electric current. Secondly, in the same incentive and geometrical parameters, we find there exists 2.5% error between the measured and computational field. In order to improve the prediction accuracy of FEM model, we make this error no more than 0.1% by adjusting the BH curve of the virtual model, thus a more precise predictor is gained.. In the final part,we compute and assess the shimming quantity according to the measurement result by FEM method, then complete the first time shim work by employing the improved shim tool. It shows a good agreement among the practical shimming result, the predicted effect and the FEM computational result. This means our method is practicable and effective.