Physical And Experimental Research Of IH DTL For The Medical Proton Linac Injector

In recent years,the morbidity of cancer has increased year by year,and the increasing demand of the cancer treatments has promoted the technology development of medical proton and heavy ion accelerator facilities.Synchrotron is a main accelerator scheme for the medical facilities,one of its main development is the optimization of the linear injector.The main purpose of the linear injector optimization is to shorten the injector length,improve RF efficiency,reduce the manufacturing cost and improve the stability and reliability in the operation,while satisfying the injection requirements of medical synchrontron.The advantages of IH DTL are the high shunt impedance,high acceleration gradient and small radius of the cavity,which can shorten the accelerator length,improve RF efficiency and reduce manufacturing cost respectively.The difficulties and cost of manufacturing of the DTL is reduced effectivelty if the IH DTL is applied in the medical proton injectors,which is of promising application prospect and important research value.According to the typical design requirements of the current medical proton injectors,an IH DTL test cavity is designed and the design requirements are the input particle energy 3 Me V,the output particle energy 7 Me V,the peak beam current 15 m A,and the RF frequency 325 MHz.A modified KONUS beam dynamics is proposed,which divides IH DTL into three sections in the longitudinal direction:-80° bunching section,0° acceleration section and the 10° debunching section.This beam dynamics design needs no focusing magnets inside the accelerator cavity,simplifes mechanical design and reduces the difficulty of machining and alignment.The modified KONUS beam dynamics also enlarges the phase width and energy spread of the output beam at the exit of the IH DTL,and shortens the distance between the IH DTL and the downstream debuncher.The design of the IH DTL is divided into three parts: Cell-array design,multi-particle tracking simulation and RF calculation.The dynamic design,dynamic calibration and RF field distribution simulation of the IH DTL are done in three parts respectively,and the design process is closed-loop and iterated to make sure the design results satify the requirements.In the first part,TG-KONUS is developed for the design of KONUS beam dynamics,which is based on the Thin gap model.The latter two parts are done by mature commercial or public softwares.The mechanical design,manufacturing,cold measurement and tuning,high power test and beam commissioning of an IH DTL test cavity are completed.The difference between the measured and designed values of the electric field distribution is less than ±3.0%,and the unloaded Q factor is 7800.The preliminary experimental results of the IH DTL test cavity are: the central energy of the bunch is 6.96±0.17 Me V,the energy spread is-0.6?0.3 Me V,the transmission efficiency is 94%.The results of the simulation are in good agreement with the measured results.The design method and software of IH DTL is presented in this paper,while the design,fabrication,tuning,high power test and beam commissioning of the IH DTL test cavity is completed,which is the first 325 MHz proton IH DTL accelerator in the world.The application of IH DTL in medical proton synchrotron injector is promoted by this thesis.