基于高品质因数波导型缩比例船形腔的多物理场耦合仿真研究

Multi-physical Field Coupling Simulation of High Quality Factor Waveguide Scaled Boat Shape Cavity

高能强流质子加速器有着十分广泛而重要的应用,中国原子能科学研究院提出1台2 GeV连续波固定场交变梯度质子加速器,该加速器采用44.4 MHz的大功率高品质因数、高分路阻抗的船形高频腔。为掌握船形高频腔的加工工艺,研制了频率为177.6 MHz的1∶4缩比例船形高频腔样机。本文采用固热分析和流固热分析两种热分析方法对该腔体样机进行多物理场耦合仿真计算,经比较发现,流固热分析方法计算得到的腔体温度分布较固热分析方法更符合实际物理过程,但后者对模型的处理和计算速度更快,两种方法得到的温度和频率调节范围略有差异。对于缩比例腔而言,两种热分析方法得到的结果大体一致,实际应用中稳态热分析已足够满足工程设计需求。

High-energy and high-intensity proton accelerators in the range of several MW are widely applied in the fields of the nuclear industry,civil applications and fundamental researches.In this scenario,a high power circular accelerator complex consisting of a 100 MeV pre-injector cyclotron,a 800 MeV injector ring cyclotron and a 2 GeV continuous wave(CW)fixed field alternating gradient accelerator(FFA)was proposed at China Institute of Atomic Energy.The development of the 44.4 MHz high power waveguide type RF cavity with high quality factor and high shunt impedance is extremely important for 2 GeV CW FFA.In order to acquire the fabrication technology and operation experience of the boat shape cavity,R&D on a 177.6 MHz quarter scaled prototype cavity was conducted.The power dissipated on the prototype surface can reach hundreds of kW,resulting in thermal stress of the cavity.Under the combined action of thermal stress,gravity,atmospheric pressure and mechanical constraint,the cavity frequency shifts.Therefore,it is necessary to resist the deformation of the cavity through various measures such as cooling water and changing the external forces on the cavity,and adjust the frequency to the design range.Solid-thermal coupling method and fluid-solid-thermal coupling method were used to carry out the multi-physical simulation of the cavity respectively,and the distribution of power loss in the surface,temperature field,stress field and deformation field of the boat shape cavity was calculated in the process.The effect of different force and the influence of the deformation of the cavity on the frequency were analyzed.The result by the fluid-solid-thermal coupling method shows that the cavity temperature near the inlet area is lower than that in the outlet area.However,the results calculated by solid-thermal coupling method show that the cavity temperature distribution on the two regions is almost equal.The above results show that the fluid-solid-thermal coupling method are more consistent with the actual physical process.The temperature field distribution obtained by the two methods has slightly different influence on the deformation field and the frequency adjustment range,but the solid-thermal coupling method requires less computer configuration,simpler model processing and slightly faster calculation speed.For the quarter scaled cavity,the results obtained by the two thermal simulation methods are generally consistent,and the solid-thermal coupling simulation methods in practical application are sufficient to meet the requirements of engineering design.