Ionizing Radiation Influence On Key Electrical Equipment And Shielding Optimization Design For HUST-PTF

As the number of cancers in China continues to rise,new technologies,new methods,and new equipment for cancer treatment have also received great attention.The global medical community unanimously recognizes proton therapy as the most superior cancer treatment at present.Huazhong University of Science and Technology,with the support of the Ministry of Science and Technology,is launching the ‘Huazhong University of Science and Technology Proton Therapy Facility,HUST-PTF’ research and development project.There is unavoidable beam loss during the formation,acceleration,extraction,and transport of the proton beam.The resulting secondary particle fields expose the electrical equipment in the device to a complex high-intensity radiation environment.Radiation damage to electrical equipment will cause abnormal operation of HUST-PTF and even medical accidents.Therefore,it is necessary to analyze the radiation field in HUST-PTF,evaluate its impact on the electrical equipment in the system,and optimize the shielding system.Firstly,this paper analyzes and calculates the generation and distribution of ionizing radiation in HUST-PTF and its influence on structural materials.When the high-energy protons in HUST-PTF interact with components,various secondary particles will be produced.Among them,the higher energy neutrons and photons affect the radiation dose.Fluka was used to obtain the distribution of radiation field in HUST-PTF,and it was found that the radiation from the energy reducer and cyclotron was the most serious.The radiation field distribution and the particle generation at the beam loss point are analyzed.The simulation results show that the dose rate at the beam loss point is much higher than that at the other parts,and most of the secondary particles produced at the beam loss point have a larger proportion of neutrons,which is about twice that of photons.The electronic devices in HUST-PTF are most vulnerable to damage,and the radiation dose threshold is much smaller than that of metal materials and polymer materials.A method based on PSpice is then used to analyze the total dose effects of electronic devices in HUST-PTF.The damage to electronic equipment caused by ionizing radiation is essentially due to the degradation of electrical parameters of electronic devices caused by ionizing radiation,which leads to a series of chain effects that make electronic equipment deviate from the normal working state.Therefore,this article first determines the electrical equipment that is vulnerable to radiation.Then,the relationship between the total dose and the electrical parameters can be obtained by simulation or existing literature.Finally,import the relationships into the circuit model of the electronic device in PSpice,and use the parameter scan mode to analyze the operation of the electronic device at different total doses.Then,taking Kicker magnet’s excitation power supply as an example.Firstly,the total dose effect of FF600R06ME3 IGBT’s threshold voltage and conductive factor are constructed.And the service life is estimated to be 8.5 years.Finally,after radiation hardening of the circuit,its total dose threshold was increased by 25%.Finally,in view of HUST-PTF compact structure,the characteristics of the complex radiation field and electrical equipment,on the basis of shielding system of limited space,considering the various electrical equipment under the condition of the dose rate,under various working conditions of neutron and photon energy distribution,as well as photon and neutron shielding priority,based on the genetic algorithm and FLUKA,Optimal design method for shielding system of electrical equipment in HUST-PTF.The shielding system of the stepper motor in energy reducer system is taken as an example to explain in detail.