Secondary Beam Fragments Produced by 200 and 400MeV/u ¹²C⁶⁺ Ions in Water

Based on the GEANT4 toolkit, we study the transportation of nucleons and nuclei in tissue-like media. The fragmentation of projectile nuclei and secondary interactions of produced nuclear fragments are considered. Livermore data is used to calculate electromagnetic interaction of primary and secondary charged particles. We validate the models using experimental data of 200MeV/u and 400MeV/u carbon ions, interacting with tissue equivalent materials of water. The model can well describe the depth-dose distributions in water and the doses measured for secondary fragments of certain charge and certain mass number. The secondary beam fragments produced by 200MeV/u and 400MeV/u ¹²C⁶⁺ ions in water are investigated using the model. When the primary nuclei are in water, several neutron production mechanisms are involved. The light charged particles (p, d, t, ³He and ⁴He) and fast neutrons contribute to the dose tail behind the Bragg peak. The ¹¹C fragments which may be the most suitable nuclei for monitoring the energy deposition in carbon-ion therapy are also discussed.