单谐振腔束团长度监测器耦合结构设计与仿真

庹还湘; 孙葆根; 罗箐; 吴芳芳; 周天雨; 卢平

doi:10.11884/HPLPB202234.210261

单谐振腔束团长度监测器耦合结构设计与仿真

doi: 10.11884/HPLPB202234.210261

中国科学技术大学国家同步辐射实验室，合肥 230029

基金项目: 国家重点研发计划(2016YFA0401900, 2016YFA0401903)；国家自然科学基金项目(12075236)

详细信息

作者简介:
庹还湘，tuohx@mail.ustc.edu.cn

通讯作者:
孙葆根，bgsun@ustc.edu.cn

中图分类号: TL506
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- 文章访问数: 901
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- PDF下载量: 38
- 被引次数: 0
出版历程
- 收稿日期: 2021-07-08
- 修回日期: 2021-12-25
- 录用日期: 2022-01-04
- 网络出版日期: 2022-01-08
- 刊出日期: 2022-03-19

Design and simulation of the coupler of single resonant cavity bunch length monitor

National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China

摘要

摘要: 单谐振腔束团长度监测器利用谐振腔内的两个本征模式测量ps量级的电子束团长度，它的关键是如何将两个不同频率的模式互不干扰地耦合提取出来。为解决这个问题，基于低通和带通滤波器的理论，提出了同轴滤波耦合结构和膜片加载波导滤波结构，借助CST微波工作室对滤波器进行建模并仿真得到其S参数。为测试耦合器的应用效果，设计了一套带有该耦合结构的单谐振腔束团长度监测器探头，根据国家同步辐射实验室基于可调谐红外激光的能源化学研究大型实验装置FELiChEM的束流特点，在CST内对所设计的探头进行束流模拟仿真。仿真结果表明，该耦合器可以实现对特定模式的耦合，并有效降低其它模式的干扰，采用同轴滤波耦合结构和膜片加载波导滤波结构的谐振腔监测器可以实现对FELiChEM装置束团长度的高精度测量，测量误差小于2 %。
- 谐振腔 /
- 束团长度 /
- 滤波器 /
- CST /
- 束流 /
- 自由电子激光
Abstract: The single-cavity bunch length monitor uses two eigenmodes in the resonant cavity to measure the bunch length in the order of picoseconds. The key is how to couple and extract two modes of different frequencies without interfering with each other. To solve this problem, based on the theory of low-pass and band-pass filters, a coaxial filter coupling structure and a diaphragm-loaded waveguide filter structure are proposed. The filters are modeled and simulated in CST Microwave Studio to obtain S parameters. In order to test the effect of the coupler, a bunch length monitor with the coupling structure is designed. According to the beam characteristics of the National Synchrotron Radiation Laboratory based on the tunable infrared laser energy chemistry research large-scale experimental device (FELiChEM), a beam simulation is performed on the designed monitor in CST. The simulation results show that the coupler can realize the coupling of specific modes and effectively reduce the interference of other modes. The resonant cavity monitor adopting the coaxial filter and the diaphragm-loaded waveguide filter can achieve high-precision measurement of the bunch length of the FELiChEM, and the measurement error is less than 2%.
- resonant cavity /
- bunch length /
- filters /
- CST /
- beam /
- free electron laser

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图 1 低通原型滤波器集总电路

Figure 1. Lumped circuit of low-pass prototype filter

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图 2 低通原型滤波器的衰减-频率特性

Figure 2. Attenuation-frequency characteristics of low-pass prototype filter

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图 3 低通滤波器的结构

Figure 3. Structure of low pass filter

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图 4 低通滤波器的S参数

Figure 4. S parameters of low pass filter

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图 5 膜片加载波导带通滤波器的电路

Figure 5. Circuit of diaphragm-loaded waveguide band-pass filter

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图 6 带通滤波器的三维模型结构

Figure 6. 3D model of band pass filter

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图 7 带通滤波器的剖面图

Figure 7. Cutaway view of band pass filter

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图 8 带通滤波器的S参数

Figure 8. S parameters of band pass filter

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图 9 单谐振腔束团长度监测器结构

Figure 9. Structure of bunch length monitor

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图 10 耦合模式的场分布

Figure 10. Electric field distribution of coupling mode

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图 11 端口输出信号

Figure 11. Port output signals

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表 1 FELiChEM的束流参数

Table 1. Electron beam parameters of FELiChEM

	energy/MeV	energy spread/keV	bunch charge/nC	bunch length/ps	micro-pulse repetition rate/GHz
	25−60	＜240	1.0	2−5	0.476

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表 2 带通滤波器参数

Table 2. Parameters of band pass filter

d₀₁/mm	d₁₂/mm	a/mm	b/mm	l₀/mm	l₁/mm	l₂/mm	t/mm
10.54463	6.26978	28.499	12.624	15	21.19	22.47	1.2

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表 3 束团长度仿真结果

Table 3. Simulation results of bunch length

bunch length/ps	V_TM010/10⁻⁷	V_TM030/10⁻⁷	V_TM010/V_TM030	measured bunch length/ps	relative error/%
2	2.175	0.966	2.251	2.03	1.50
3	2.174	0.959	2.266	2.99	0.33
5	2.168	0.937	2.313	4.91	1.80
10	2.147	0.840	2.557	9.93	0.70
15	2.116	0.700	3.024	14.94	0.40
20	2.074	0.542	3.828	19.97	0.15

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参考文献(15)

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