Abstract: Proton energy in the range of 70-250 MeV are used for tumor therapy. The neutron spectrum, which has wide energy range and large angle distribution difference, generated in target object bombarded by protons which may escape or expected to be stopped in the target is the main source term for the shielding design of proton therapy system. In this paper, the point kernel model is adopted to estimate the ambient neutron dose equivalent rate outside the Probeam proton therapy system tunnel. Estimation results are compared with the measured results to verify the effectiveness of the shielding construction.

Key words: medical proton accelerator, estimation, monitoring, ambient neutron dose equivalent