Bump Magnets for Injection System in SESRI

The Space Environment Simulation and Research Infrastructure (SESRI), located at the Harbin Institute of Technology (HIT) in China, is a new infrastructure project proposed by the Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS), and completed in 2022. As a critical part of SESRI, the compact synchrotron was designed with a circumference of less than 44 m and compact magnets. In order to achieve compact injection and improve injection efficiency, four fast-ramping bump magnets based on ferrite yokes were used. All four bump magnets have a fast falling time from 20-100 mu s, a maximum magnetic field of 0.0797 T, and a gap of 60 mm. To reduce the magnetic eddy current effect and coil inductance during fast excitation, ferrite core structures with single copper bar saddle windings are used. Further, window-frame structures are used to facilitate the ferrite-core machining process. After the prototype bump magnet was fabricated and the pulsed magnetic field measured, it was found that the integrated magnetic field curve did not align with the output current curve of the power supply. This was found to be caused by eddy currents from the copper gaskets between ferrite cores. Through the simulation and secondary testing of the gasket-induced eddy currents using different materials, the eddy current has been significantly reduced. In this study, the magnetic field optimization, structural design, eddy current calculation, and magnetic field measurement of the fast-ramping bump magnets are analyzed.