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李波, 刘华昌, 王云, 吴小磊, 瞿培华, 李阿红, 樊梦旭, 陈强. CSNS-II超导椭球腔失谐研究[J]. 原子核物理评论, 2020, 37(2): 186-190. DOI: 10.11804/NuclPhysRev.37.2020013
引用本文: 李波, 刘华昌, 王云, 吴小磊, 瞿培华, 李阿红, 樊梦旭, 陈强. CSNS-II超导椭球腔失谐研究[J]. 原子核物理评论, 2020, 37(2): 186-190. DOI: 10.11804/NuclPhysRev.37.2020013
Bo LI, Huachang LIU, Yun WANG, Xiaolei WU, Peihua QU, Ahong LI, Mengxu FAN, Qiang CHEN. Detuning Analysis of the Superconducting Elliptical Cavity for CSNS-II Linac[J]. Nuclear Physics Review, 2020, 37(2): 186-190. DOI: 10.11804/NuclPhysRev.37.2020013
Citation: Bo LI, Huachang LIU, Yun WANG, Xiaolei WU, Peihua QU, Ahong LI, Mengxu FAN, Qiang CHEN. Detuning Analysis of the Superconducting Elliptical Cavity for CSNS-II Linac[J]. Nuclear Physics Review, 2020, 37(2): 186-190. DOI: 10.11804/NuclPhysRev.37.2020013

CSNS-II超导椭球腔失谐研究

Detuning Analysis of the Superconducting Elliptical Cavity for CSNS-II Linac

  • 摘要: 中国散裂中子源二期束流功率升级到500 kW,直线加速器H-的能量增益由现在的80 MeV提高到300 MeV以上,其中150 ~ 300 MeV能量段采用648 MHz βg=0.60的5-cell超导椭球腔结构。超导椭球腔具有加速梯度高、结构简单、后处理容易等优点,缺点是结构强度弱、易失谐。本文主要研究该椭球腔的失谐特性。利用COMSOL Multiphysics软件进行了计算分析,在两端固定边界条件下,裸腔的氦压敏感性系数KP=–45.705 Hz/mbar(1 mbar=100 Pa),洛伦兹力失谐因子KL=1.574 Hz/(MV/m)2。增加加强环并优化其位置来改善氦压敏感性系数和洛伦兹力失谐因子,通过计算分析最终确定选择双加强环方案来减小椭球腔的失谐。两个加强环位置分别取在75和120 mm的位置,腔体失谐的改善最大,KP=6 Hz/mbar,KL=0.43 Hz/(MV/m)2。为了更准确地计算椭球腔的氦压敏感性系数和洛伦兹力失谐因子,本文引入调谐刚度边界条件进行失谐分析,在椭球腔调谐器端设置30 kN/mm边界条件,另一端固定,计算得到氦压敏感性系数为4.8 Hz/mbar,洛伦兹力失谐因子1.99 Hz/(MV/m)2,满足工程要求。另外,用CST软件对椭球腔的动态洛伦兹力失谐进行了初步分析,用软件Workbench计算了椭球腔的振动本征频率,结果显示,振动本征频率离射频脉冲重复频率及环境振动频率较远,不易发生共振失谐。

     

    Abstract: China Spallation Neutron Source(CSNS) beam power will upgrade to 500 kW(CSNS-II), energy gain of H- linac will up to 300 MeV from 80 MeV, and the 648 MHz βg=0.6 5-cell superconducting elliptical cavity will be adopted to accelerate the H- from 150 to 300 MeV. Accompanied with the advantage of high accelerating gradient, simple structure, easy post-processing, weak stiffeness and detuning is the shortcoming of elliptical cavity, this study analysis detuning characteristic of the elliptical cavity. With code COMSOL Multiphysics, helium pressure sensitivity coefficient KP and lorentz force detuning factor KL of bare cavity was calculated under two end fixed conditions, KP=–45.705 Hz/mbar(1 mbar=100 Pa) and KL=1.574 Hz/(MV/m)2. Stiffener ring was designed and optimized to reduce the Helium pressure sensitivity coefficient and lorentz force detuning factor, and double ring was chosen to improve the detuning of elliptical cavity at last by vast calculation and analysis, the position of stiffener ring was optimized at 75 and 120 mm under two end fixed boundary, Helium pressure sensitivity coefficient drop down to KP=6 Hz/mbar, lorentz force detuning factor drop down to KL=0.43 Hz/(MV/m)2. Moreover, elastic boundary was used to analyze helium pressure sensitivity coefficient and lorentz force detuning factor, more realistic results were got under tuner end 30 kN/mm boundary and the other end fixed condition, KP=4.8 Hz/mbar and KL=1.99 Hz/(MV/m)2, meet engineering requirements. In addition, dynamic lorentz force detuning was analyzed qualitatively with code CST. And natural frequency of cavity was calculated by code Workbench, results show that nature frequency is far from RF pulse repetition rate and ambient vibration frequency, no resonance happen.

     

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