Study Of The Electronics Of Beam Monitors For The Beam Delivery System In Proton Therapy

In proton therapy,the beam delivery system,used to transfer of the extraction beam from the accelerator into the beam for treatment,guarantees the irradiation dose and dose distribution with sufficient accuracy defined by treatment planning system.The key of the beam delivery system is the measurement of the dose and the position of proton beam accurately.The free air parallel plate ionization chambers are adopted as the dose monitors and the position monitors in Shanghai Advanced Proton Therapy Facility.The electronics of these monitors are the important device in the beam delivery system.The accuracy of irradiation dose and dose distribution directly depends on the performance of these electronics.In the paper,the requirements of the electronics for these beam monitors are described,according to the specification of the beam delivery system,the beam parameters in slow extraction and the specification of the ionization chambers.Based on the requirements,the technical schemes of the two different electronics were designed for the dose monitor and the position monitor.In the system,the scheme of I/V+ADC was implemented for dose monitors,and the scheme of capacitor integration was implemented for the position monitors.The test platform is built in the laboratory for both two electronics.The test results of dose monitor electronics show that the integral nonlinearity is less than ±0.04 n A in full scale and the resolution is about ±0.6n A(2 sigma).The test results for position monitor electronic shows that the resolution is about 0.1n A(rms).The study in the thesis will be a valuable reference for the development of the electronics of the beam monitors in Shanghai Advanced Proton Therapy facility.