Radiation shielding calculations and design for a novel multi-room carbon therapy facility (SIMM)

The Second generation heavy Ion Medical Machine (SIMM) can deliver carbon ion beams with a maximum energy of 400 MeV/u and maximum current intensity of 5 × 10⁸ pps for cancer treatment. Radiation shielding is the most effective protection measure against the prompt radiation generated by accelerators. The FLUKA program was used to perform the radiation shielding calculations and design for SIMM. Firstly, the prompt radiation field was simulated, which indicates that the secondary neutrons are the determining factor for shielding thickness. Then, the shielding effects of different combinations were compared, and the combination of iron and concrete is selected for local shielding. Finally, the radiation shielding design was completed according to the layout of the building, the beam loss parameters and the related design standards, as well as the radiation dose rates at 58 points of interest outside the shielding met the prescribed safety criteria. The radiation shielding scheme given in this study can provide a reliable guarantee of radiation safety for SIMM.