Design And Development Of Radiation Protection System For HIMM

Heavy ion radiotherapy is the most advanced and scientific and the most effective method compared with conventional light particle radiotherapy.Because the heavy ion beam has the advantage in physical characteristics which the heavy ion loss its energy focus at the end of the range in human body,and the relative higher biological effectiveness.In heavy ion beam clinical radiotherapy,heavy ion beam radiation and secondary radiation due to beam loss will bring potential radiation hazards to accelerator workers and the public and to the environment.So in order to protect personnel and their offspring 's health and safety,and to protect the environmental safety,the radiation protect system which including the radiation shielding design,the radiation dose monitor and personal safety interlock system for the Heavy Ion Medical Machine(HIMM)self-developed by Institute of Modern Physics,Chinese Academy of Science was developed.In the runtime operation of Heavy Ion Medical Machine(HIMM),the Carbon ions will interact with the accelerator structural materials,which will bring the instantaneous radiation and residual radiation.The instantaneous radiation includes the primary particle radiation and the secondary neutron and ? radiation caused by the interaction between the carbon ion and the target and accelerator structure materials,all of these determine the HIMM shielding thickness;the residual radiation comes from induced radioactivity including ? and ? rays,which is the major external exposure source of accelerator staff.Based on extensive investigation,the Monte Carlo code FLUKA was used to simulate the accelerator radiation source in the common used energy region and to design and to verify the HIMM radiation shield on the simulation.At the same time the radiation dose distribution of each radiation region of HIMM were given by the simulation in this paper.According to our study,the instantaneous radiation field of HIMM is a mixed and pulsed radiation field,mainly including neutron and photon.On this basis,the radiation dose monitoring system was developed.In this system,wide energy range neutron monitor was developed to improve the high energy neutron response.To prevent accelerator worker entering the beam area and to prevent the beam been delivered to the work location by accident,the personal safety interlock system of HIMM were designed and developed by using the current industrial control technology and information technology on the basis of extensive investigation.In this paper,the radiation protection system of Heavy Ion Medical Machine has been designed developed and test,and the results show that its performance meet the requirements.