Design of high gradient quadrupole magnets for SESRI

Abstract The 300MeV proton and heavy ion accelerator is a major radiation source for Space Environment Simulation and Research Infrastructure (SESRI). A high intensity ion linac, as the injection system of the accelerator, includes 27 magnets. There are 4 quadrupole magnets that have high gradient magnetic field and short magnetic length. The bore radius of the high gradient quadrupoles is 24 mm, which gives an equivalent pole tip field of 1.0 T with the magnetic field gradient of 42 T/m. The special material of Fe-Co-V soft magnetic alloy is used to achieve the high gradient magnetic field and improve excitation efficiency. For the design of the magnet, the cross section and end chamfer are used to improve the magnetic field distribution. The field analysis of magnet assembly errors shows these could affect the multipole components of the field. Assessment of the field quality is performed using the rotating-coil measurement system. The high gradient quadrupole magnet can meet the requirements.