Design and Construction of the Main Magnet for a 230-MeV Superconducting Cyclotron

For the applications of proton therapy and proton irradiation, and based on the RD then, the construction progress and the B–H curve measurement results of the warm iron over the magnetic saturation region are outlined; the R&D of the superconducting coils system and the design of the field mapping system are also briefly introduced.