中能衍射极限环中电阻壁和高频系统阻抗计算与优化  

Calculation and Optimization of Resistive Wall and RF Cavity Impedance in Medium Energy Diffraction Limit Storage Ring

作　　者：王猛[1,2] 张文志 田顺强[2,3] 蔡传兵 刘新忠[2,3] WANG Meng;ZHANG Wenzhi;TIAN Shunqiang;CAI Chuanbing;LIU Xinzhong(Shanghai Key Laboratory of High Temperature Superconductivity,Department of Physics,College of Science,Shanghai University,Shanghai 200444,China;Shanghai Institute of Applied Physics,Chinese Academy of Sciences,Shanghai 201800,China;Shanghai Advanced Research Institute,Chinese Academy of Sciences,Shanghai 201204,China)

机构地区：[1]上海大学上海市高温超导重点实验室,理学院物理系,上海200444 [2]中国科学院上海应用物理研究所,上海201800 [3]中国科学院上海高等研究院,上海201204

出　　处：《原子能科学技术》2022年第9期1821-1831,共11页Atomic Energy Science and Technology

摘　　要：在衍射极限环中,由于采用了高梯度小孔径磁铁,真空盒尺寸相对于第3代同步辐射光源大幅减小,全环阻抗明显增大,因此在设计阶段需要对真空元件阻抗进行精准的评估与模型优化。本文计算了中能衍射极限环的多层电阻壁阻抗,针对衍射极限环给出了优化的电阻壁的材料选择;利用数值模拟程序,完成了对高频腔与三次谐波腔的设计、优化与阻抗计算;分析了由电阻壁阻抗、高频腔和三次谐波腔中的高次模引起的束流不稳定性,并对不稳定性问题提出了抑制方案。In the diffraction limit storage ring,the size of the vacuum chamber was greatly reduced compared with the third-generation synchronous light source due to the high-gradient small-aperture magnet,and the impedance of ring is significantly increased.Therefore,it is necessary to accurately evaluate and optimize model of the impedance of the vacuum elements in the design stage.In the impedance budget,the resistance wall impedance accounts for a high proportion of the whole ring impedance,and a sharp resonance peak will appear when the frequency is close to 0,which has a great impact on the beam motion.In the RF system,the high-order mode of the cavity is an important source of the narrow-band impedance.Therefore,in the accelerator design stage,it is necessary to select the resistance wall of appropriate materials,accurately model of the RF cavity and the third harmonic cavity,calculate the impedance,and evaluate instability that may be caused.In this paper,the multi-layer resistance wall impedance of the medium energy diffraction limit storage ring was calculated and the optimized material of resistance wall was chosen for the diffraction limit storage ring.A vacuum chamber with distributed exhaust is required in the storage ring,and the thickness of copper coating of 1μm film is the optimized material.For special vacuum chamber components,the internal structure is complex and it is impossible or difficult to implement NEG coating,or the centralized arrangement of air pump can meet the vacuum requirements,the stainless-steel internal coating with 5μm copper film is considered.The impedance models of RF cavity and the third harmonic cavity were established and optimized by using numerical simulation program.The fluted beam tube can effectively transmit the high-order modes generated in the RF cavity and the third harmonic cavity to ensure the stability of the beam.The collective effects were caused by resistive wall impedance,the high order modes of RF cavity and the third harmonic cavity were analyzed and summariz

关 键 词：衍射极限环 阻抗壁 高频腔 三次谐波腔 束流集体效应 

分 类 号：O57[理学—粒子物理与原子核物理]