Development Of High-gradient S-band Accelerating Structure For Compact Proton Therapy Facility

Proton therapy and its facilities are currently a hot spot in the field of medical physics.Due to its excellent protection to normal tissues and its biological effects near the Bragg peak,proton therapy has been recognized by more and more doctors and favored by patients.Is currently one of the most cutting-edge radiotherapy methods in the world.However,advanced proton therapy facility is huge and expensive.To solve this problem,the miniaturization of proton therapy facility must be achieved.Since then,compact proton therapy facilities have emerged,and the development of high-gradient radio frequency technology has helped to achieve a more compact and more efficient proton therapy facility.According to the new requirements of single-room facility,proton CT and FLASH therapy,the development of compact and efficient proton therapy accelerator has attracted everyone's attention.In order to satisfy the technical requirements of a compact,miniaturized and rapidly adjustable energy proton therapy facility,critical technologies such as the high-field problem of the accelerating structure,the high-gradient standing wave accelerating structure,and permanent magnet quadrupoles(PMQs)focusing need to be solved.By investigating internationally proposed proton therapy facilities,and combining with our country's demand for proton therapy facilities,the design of the S-band standing wave accelerating structure has been determined.Compared with synchrotron radiation accelerators and cyclotrons,linear accelerators have continuous and rapid energy adjustment;the output beam size and emittance are small;the control system is relatively simple;the beam quality is high.Proton therapy facility based on linacs can exert better performance.The thesis first introduced the general situation of proton therapy technology,the theoretical knowledge of accelerator,and then systematically discussed the design and research work of 50 MV/m high gradient S-band standing wave accelerating structure.The simulation calculation software MWS-CST and Superfish are used to complete the simulation work of the accelerating structure,and the dimensional parameters of the accelerating structure are optimized by the method of polynomial fitting.The first domestic prototype for the main accelerating structure of a compact proton therapy linear accelerator was completed through advanced manufacturing technology.After the prototype was processed,a complete measurement platform was established in the measurement room,and the microwave parameters were measured using the pull-bead method(perturbation method).After the tuning process,the conditions for high-power testing are reached.Subsequently,high-power experiments were completed on the Shanghai soft X-ray Free Electron Laser facility(Shanghai soft X-ray Free Electron Laser facility,referred to as SXFEL)platform.From the design of the experimental platform to the construction and the analysis of the final experimental results,the final measured effective acceleration gradient value reached 46 MV/m,indicating that the test results of the prototype reached the expected design goal.So far,the feasibility study of the high-gradient S-band standing wave acceleration structure has been completed.Finally,the prospect of this subject is to carry out beam experiments on the successfully developed high-gradient,compact S-band standing wave accelerating structure to further verify the effectiveness of the high-gradient.