Design And Study Of Compact RFO And DTL For Synchrotron-Based Proton Therapy Facility

Radiation therapy with proton and heavy ions is increasing in popularity because of its distinct physical characteristics in energy deposition,better therapeutic effect,and fewer side effects in many specific tumor treatments than conventional photo radiotherapy.It has significant advantages in killing cancer cells,intraoperative treatment perception,postoperative quality of life,and higher survival rate,which make it to be a focus of current radiation therapy.Proton therapy in China has been under continuous development at the Shanghai Institute of Applied Physics(SINAP)for 10 years.The Advanced Proton Therapy Facility(APTR)was proposed to develop the first homemade proton radiotherapy facility.At present,the whole facility is in the CFDA certification stage.As a key technique of synchrotron-based proton therapy facility,the proton linac injector is mainly composed of a proton source,a low-energy beam transport line(LEBT),and a radio-frequency quadrupole(RFQ),followed by a medium energy beam transport line(MEBT)and a drift tube linac(DTL).In order to accelerate the localization and miniaturization of proton therapy facility,the upgrade of this injector system has been proposed,which will have practical significance to promote the industrialization of the first proton therapy facility in China.Based on the APTRON complex,the preliminary design of the compact linac injector was carried out with the output beam of the LEBT.The main contents include:1)The physical design and corresponding electromagnetic structure design and simulation of RFQ;2)The study on the physical design of the DTL based on KONUS beam dynamics;For RFQ,based on relevant dynamic principles and requirements of stability and compact type,the preliminary design was carried out from parameters selection of physical design.A fast bunching strategy was proposed in the process of optimization.This RFQ,operated at 325 MHz,accelerates proton particles to 3.0 MeV.The phase advance has been taken into consideration,and parametric resonance has been carefully avoided by adjusting the vane parameters.The whole transmission efficiency has been optimized to 98.0%to meet the machining requirements and the emittance growth in horizontal and vertical directions are about 1.2%,3.3%along the entire cavity.Then the MWS-CST program was used to carry out the electro-magnetic design and parameters selections.Finally,the resonance structure was obtained.For DTL,three main stream dynamics principles in low energy range were compared in this paper.In order to improve the acceleration gradient of the linac injector,the KONUS beam dynamics was selected.In order to simplify the machining process and reduce the cost of production,a modified scheme with no magnets inside the cavity was proposed,which combining the feature of APF dynamics and advantages KONUS principle.It is the first time to be employed in proton therapy facility around the world.The LORASR code,which has been verified by many times,was adopted in this physical design and multi-particle simulation.In addition,a preliminary low-power measurement experiment was carried out for a 325 MHz APF IH-DTL cavity.From the construction of measurement platform to actual measurement process,the results of cold-test are in good agreement with the design value.For the field distribution,the difference between two values is within 3%.Through the above research on the optimal design and measurement of RFQ and DTL cavities,it ensures the compact of the linac injector and reduces the processing cost and cycle.It provides and accumulates new design ideas and experiences for the industrial development of linac injector of proton therapy facility in the future.