Research and development of the high precision low field dipole magnet for CEPC Booster

In the Conceptual Design Report (CDR) stage of the Circular Electron and Positron Collider (CEPC), the injection energy of the Booster is 10 GeV and minimal working field of the dipole magnets is only 29 G, the magnets with iron cores could not meet the requirement of the field precision due to the remnant field. In the CEPC Technical Design Report (TDR) stage, the injection energy of the Booster is increased to 30 GeV and the minimal working field of the dipole magnets is raised to 95 G so that the influence of the remnant field becomes relatively small, the iron core dipole magnets can be used for the Booster. In this paper, the technical design of the CEPC Booster dipole magnets is described, the development and test of a full scale prototype pure dipole magnet are presented.