Research On The Key Technology Of Magnetic Alloy Loaded Cavity Deceleration RF System

The High Intensity Heavy-Ion Accelerator Facility(HIAF)is one of the major science and technology infrastructure projects during the 12^th Five-Year Plan period undertaken by the Institute of Modern Physics,Chinese Academy of Sciences.As one of the core components of HIAF,the high-precision Ring Spectrometer(SRing)is an important equipment to obtain high-quality radioactive secondary beams and to be used in nuclear physics experiments.In order to obtain high-charged,low-energy and high-quality heavy ion beam,a deceleration radio frequency(RF)system with peak voltage of 50 KV and operating frequency of 1.0?0.5 MHz is needed in the internal target mode of SRing.The key technologies of the RF system will be studied in depth.First of all,we analyze the longitudinal motion process of the HIAF SRing deceleration process by using the beam dynamics analysis method.The variable-harmonic deceleration method was adopted under the combination of the physical experiment requirements and characteristics of the MA cavity.The heavy ion U⁹²⁺with the energy of 800Me V/u is reduced to 120Me V/u,and then the heavy ion beam is further slowed down by the second harmonic to 30Me V/u.The deceleration RF voltage,frequency and phase can also be carried out.The deceleration RF system will adopt a Magnetic Alloy(MA)-loaded quarter wavelength coaxial resonator with the advantages of high gradient,low Q factor,wide bandwidth and no tuning system.The performance of the MA sample core which produced by Qingdao Yunlu Advanced Materials Technology Co.,Ltd and Sichuan Liyuan Electronics Co,Ltd,081 Electronics Group has been researched.It has been proved the performances of the MA sample core,which produced by the optimized production process,meet the technical requirements of the deceleration RF system.And the performance of MA core is improved by 12%.According to the test,the deceleration MA cavity is calculated with the equivalent parallel circuit method.The RF system will adopt two MA cavities to establish a peak radio frequency voltage of 50 k V.Each half of the cavity unit will be loaded with four MA cores with a size of 660 mm*290 mm*25 mm,and the peak power of each cavity will be 160.4k W.The calculations of the cooling will be carried out based on the theoretical results of MA cavity.According to the fluid heat transfer,the theoretical model is established to analysis the surface temperature of MA core after air cooling.Then the fluent analysis software is used to calculate the cooling of the MA cavity and optimize the structure of the cavity.By comparing the optimized model parameters with the theoretical calculation results,the error between those two methods is less than 3?.The theoretical model can meet the engineering design under the comparison of the optimized MA cavity which proves the accuracy of the theoretical calculation method.At last we describe the power source and low level control system of the deceleration RF system,and calculate the tetrode tube working states.Finally,a radio frequency deceleration system with the voltage of 50k V and work bandwidth of1.0?0.5 MHz has been obtained.