The Research On Multi-physics Coupling Analysis For RFQ Accelerate Structure Of Ion Accelerator

RFQ accelerator is the mostly necessary accelerate component at the low-energy and middle-energy beam transport for modern high power ion linac.For the RFQ cavity operated in continuous wave mode,the thermal dissipation control is a critical issue,which is very challenging.Because the continuous wave operation and high beam intensity,the higher demands is needed for the cooling system of RFQ accelerator.Due to its high level of average power consumption and its complex water-cooling system,it became the frontier technical problem in the accelerator field.Therefore,the multi-physics coupling analysis of electromagnetic,thermal and structure are essential to the RFQ accelerator design.CAE technology is an essential numerical calculation tool for engineering and product analysis.The topic carries out the combination between the thermal dissipation of RFQ accelerator and CAE software on multi-physics coupling of the cavity.It successfully solves the problem that the four-vane type RFQ of Chinese accelerator driven subcritical system(CADS-RFQ)unstable operation due to the high frequency heat dissipation in the strategic priority research program hosted by Chinese academy of science.The analysis of parameter supports the key theoretical data for the experiment RFQ accelerates the beam.In addition the topic simulates and analyzes four-rod type RFQ(SSC-RFQ)in the upgraded project of sector separated cyclotron of Lanzhou heavy ion national laboratory,optimizes the design of the cavity cooling system,and ensures the successful implementation of the project.The content below will describe the background of the two RFQs which researched in this dissertation,Summarize problems of the high power proton RFQ of continuous wave.The multi-physics coupling analysis is the key technology that ensures the cavity can be on stable operation;Afterwards,the author introduces the relevant theory of the multi-physics coupling analysis.The main part of this dissertation describes the research of the CADS-RFQ and SSC-RFQ multi-physics coupling.CADS-RFQ is based on the 2D and 3D simulation.The key factors are studied in the parametric scanning.The experiments are carried out to verify the results of the simulation study.The results of parametric analysis of the cavity provides theoretical guide to the stable operation of the RFQ with accelerating beam.SSC-RFQ adopts the 3D finite element simulation and the cooling water system was optimized so as to ensure the stable operation of the cavity with full power.The multi-physics coupling analysis for two types of RFQ: four-vane type RFQ and four-rod type RFQ are carried out.After the fabrication and assembling of the cavity,the experiments are designed to verify the results of the analysis.The main research work and conclusions obtained are as follows.(1)The multi-physics coupling analysis of CADS-RFQ and SSC-RFQ are the main content of the thesis.The process including the electro-magnetic simulation,thermal analysis and structure analysis is completed.Finally the optimization analysis of two RFQ cooling waterway is finished to ensure the RFQ cavity of high power to be operated with full power.(2)According to the operation conditions of CADS-RFQ,the parametric analysis of the input power of RFQ cavity,environmental temperature,flow rate of cooling water,and the temperature of cooling water was done.From the above analysis,the water pressure,flow speed and cooling water temperature are chosen to ensure the cavity operation stably under full power.The experiment is designed and implemented and the experiments results agreed well with the simulation ones.(3)According to the results of parametric analysis,the water temperature of cooling system is adjusted based on the simulation results to decrease the reflection power.This ensures the successful operation of the CADS-RFQ with high power beam.This is the first time that high power proton continuous wave beams are stably accelerated in China.(4)Due to asymmetric cavity structure of the SSC-RFQ,the 3D multi-physics coupling analysis of the whole cavity was implemented.The relationships between frequency drift and input power or water velocity was studied.From the simulation,the temperature raise and displacement of the cavity are all proportional to the changing of the input power and the variation tendency.Also when the water velocity is too fast,the cooling effect is unsatisfactory.It is the best choice to keep the water velocity at 2.0 m/s to 2.5 m/s.The experiments are carried out on the cavity and the experimental results are close to simulation results.The error between experiments results and simulation results is 10% that is an acceptable level.In this dissertation,the multi-physics coupling analysis was applied to the RFQ cavities in CADS injector ? and SSC-LINAC with CAE software in the design phase.The key parameters are specially analyzed and cooling water channel are optimized so as to ensure stable operation of RFQ cavities.The coupling experiments were implemented on the CADS-RFQ and the experimental results highly consistent with the simulation ones.It is the first time of verification of multi-physics coupling simulation between simulation and experimental results in china.Also it provides a theoretical guide for high intensity beam acceleration of CADS-RFQ.The successful operation of continuous wave RFQ is also first in china and RFQ performances reach the international leading level.The experience is the very valuable for cooling design of high power high frequency cavity in future.