Optimized Design of Hefei Infrared Free Electron Laser Beam Injector

Peng Xiaoyu; Zhang Haoran; Hu Hao; Hu Tongning; Deng Jianjun; Feng Guangyao

doi:10.11884/HPLPB202537.250022

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Peng Xiaoyu, Zhang Haoran, Hu Hao, et al. Optimized Design of Hefei Infrared Free Electron Laser Beam Injector[J]. High Power Laser and Particle Beams. doi: 10.11884/HPLPB202537.250022

Citation:

Peng Xiaoyu, Zhang Haoran, Hu Hao, et al. Optimized Design of Hefei Infrared Free Electron Laser Beam Injector[J]. High Power Laser and Particle Beams. doi: 10.11884/HPLPB202537.250022

Peng Xiaoyu, Zhang Haoran, Hu Hao, et al. Optimized Design of Hefei Infrared Free Electron Laser Beam Injector[J]. High Power Laser and Particle Beams. doi: 10.11884/HPLPB202537.250022

Citation:

Peng Xiaoyu, Zhang Haoran, Hu Hao, et al. Optimized Design of Hefei Infrared Free Electron Laser Beam Injector[J]. High Power Laser and Particle Beams. doi: 10.11884/HPLPB202537.250022

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Optimized Design of Hefei Infrared Free Electron Laser Beam Injector

doi: 10.11884/HPLPB202537.250022

Peng Xiaoyu^{1, 4
,},
Zhang Haoran¹,
Hu Hao²,
Hu Tongning^{2
,
,},
Deng Jianjun³,
Feng Guangyao^{1
,
,}

1.
National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
2.
State Key Laboratory of Advanced Electromagnetic Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
3.
Institute of Fluid Physics, CAEP, Mianyang 621900, China
4.
Zhangjiang Laboratory, shanghai 201204, China

Received Date: 2025-02-10
Accepted Date: 2025-07-29
Rev Recd Date: 2025-07-29

Available Online: 2025-08-13

Abstract

Abstract

Background
Free electron lasers have emerged as significant advanced light sources owing to their unique advantages, including high power, excellent coherence, and wavelength tunability. Given that the peak and average brightness of an FEL depend on the quality of the electron beam generated by its injector, the optimization of the beam injector constitutes a key technical challenge in FEL development. The Hefei Infrared Free Electron Laser facility, a state-of-the-art, oscillator-type user facility providing continuously tunable mid-to-far-infrared radiation.
Purpose
The injector structure of Hefei Infrared Free Electron Laser is optimized to obtain electron beams with lower emittance, shorter beam length, smaller energy spread and higher peak current intensity, so as to improve the performance of driving infrared free electron laser light source.
Methods
The optimization research is carried out by combining beam dynamics simulation with numerical simulation. Based on the previous optimization of the electron gun’s grid structure, the improved design is carried out. A new 12th sub-harmonic buncher is added to the front stage of the existing 6th sub-harmonic buncher, and then the beam is bunched and accelerated by using the appropriate traveling-wave buncher. Key parameters including the beam injection phase and the phase velocity variation in the traveling-wave buncher’s tapered section are systematically scanned to achieve 100% bunch capture efficiency and accelerate the electron beam to near-light-speed energy during the bunching stage.
Results
Finally, the beam energy is increased to 64 MeV, and the root mean square length of the whole bunch reaches 8.5 ps. The high-energy scattered electrons are filtered out, and the electron beams scattered by ±1% bunch energy are counted. The optimized beam core achieves a root-mean-square longitudinal bunch length of 3.1 ps with an energy spread below 0.23 MeV, while the normalized transverse emittance is reduced to 9.8 mm·mrad. At the same time, the peak current intensity reaches 270 A, which is 2.7 times that of the original optimization results.
Conclusions
The simulation shows that the longitudinal length, energy dispersion and emittance of the core region of the bunch are significantly reduced after optimization, and the peak current intensity is greatly improved. Compared with the original structure, this scheme has significant advantages in the key performance of free electron laser, which has important engineering value for light source upgrading. The optimization method can be extended to the design of other light source injectors.
- free electron laser,
- electron beam,
- injector,
- electron gun,
- sub-harmonic buncher

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References(18)

References

[1]	范伟杰, 冯超, 赵明华. 上海软X射线自由电子激光外种子运行模式的模拟研究[J]. 强激光与粒子束, 2022, 34:031016 doi: 10.11884/HPLPB202234.210262 Fan Weijie, Feng Chao, Zhao Minghua. Simulation studies of external seeding schemes for Shanghai soft X-ray free electron laser[J]. High Power Laser and Particle Beams, 2022, 34: 031016 doi: 10.11884/HPLPB202234.210262
[2]	陈思富, 黄子平, 石金水. 带电粒子加速器的基本类型及其技术实现[J]. 强激光与粒子束, 2020, 32:045101 Chen Sifu, Huang Ziping, Shi Jinshui. Basic types and technological implementation of charged particle accelerators[J]. High Power Laser and Particle Beams, 2020, 32: 045101
[3]	李和廷, 何志刚, 吴芳芳, 等. 合肥红外自由电子激光装置[J]. 中国激光, 2021, 48:1700001 doi: 10.3788/CJL202148.1700001 Li Heting, He Zhigang, Wu Fangfang, et al. Hefei infrared free-electron laser facility[J]. Chinese Journal of Lasers, 2021, 48: 1700001 doi: 10.3788/CJL202148.1700001
[4]	Li Heting, Jia Qika. Commissioning and first lasing of the FELiChEM: a new IR and THz FEL oscillator in China[C]//39th Free Electron Laser Conference. 2019: 15-19.
[5]	Li Heting, Jia Qika, Zhang Shancai, et al. Design of FELiChEM, the first infrared free-electron laser user facility in China[J]. Chinese Physics C, 2017, 41: 018102. doi: 10.1088/1674-1137/41/1/018102
[6]	Li Heting, Jia Qika, Zhang Shancai, et al. Design of the mid-infrared FEL oscillator in China[C]//Proceedings of FEL2015. 2015: 427-429.
[7]	He Zhigang, Xu Wei, Zhang Shancai, et al. Linac design of the IR-FEL project in China[C]//37th International Free Electron Laser Conference. 2015: 46-48.
[8]	贾启卡. 自由电子激光物理导论[M]. 北京: 科学出版社, 2021 Jia Qika. Introduction to free electron laser physics[M]. Beijing: Science Press, 2021
[9]	邓建军, 丁伯南, 王华岑, 等. "神龙一号"直线感应加速器物理设计[J]. 强激光与粒子束, 2003, 15(5):502-504 Deng Jianjun, Ding Bonan, Wang Huacen, et al. Physical design of the Dragon-I linear induction accelerator[J]. High Power Laser and Particle Beams, 2003, 15(5): 502-504
[10]	Peng Xiaoyu, Hu Tongning, Peng Yufei, et al. Optimized design of a thermionic electron gun applied to a high-power FEL injector[C]//2023 IEEE 4th China International Youth Conference on Electrical Engineering (CIYCEE). 2023: 1-6.
[11]	Peng Xiaoyu, Hu Hao, Hu Tongning, et al. Emittance optimization of gridded thermionic-cathode electron gun for high-quality beam injectors[J]. Nuclear Science and Techniques, 2024, 0482. R1.
[12]	Hu Tongning, Li Junyang, Pei Yuanjie, et al. Indirect estimations of energy and energy spread for a compact free electron laser-terahertz pre-injector using RF measuring parameters[J]. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2021, 1016: 165775. doi: 10.1016/j.nima.2021.165775
[13]	钟少鹏, 赵明华, 汪宝亮. 上海光源150 MeV直线加速器次谐波腔耦合器的设计与调试[J]. 强激光与粒子束, 2010, 22(5):1125-1128 doi: 10.3788/HPLPB20102205.1125 Zhong Shaopeng, Zhao Minghua, Wang Baoliang. Design and test of sub-harmonic cavity's coupler for 150 MeV linac of Shanghai synchrotron radiation facility[J]. High Power Laser and Particle Beams, 2010, 22(5): 1125-1128 doi: 10.3788/HPLPB20102205.1125
[14]	周文振, 李文琴, 浦德修, 等. 强流射频电子直线加速器中的分频预聚束器的研制[J]. 强激光与粒子束, 1990, 2(3):311-318 Zhou Wenzhen, Li Wenqin, Pu Dexiu, et al. Development of subharmonic prebuncher in RF electron linear accelerator with high current[J]. High Power Laser and Particle Beams, 1990, 2(3): 311-318
[15]	Hu Tongning, Pei Yuanji, Qin Bin, et al. Study of beam transverse properties of a thermionic electron gun for application to a compact THz free electron laser[J]. Review of Scientific Instruments, 2014, 85: 103302. doi: 10.1063/1.4897481
[16]	Hu Tongning, Wang Haimeng, Zeng Yifeng, et al. Fault locating for traveling-wave accelerators based on transmission line theory[J]. Nuclear Science and Techniques, 2023, 34: 116. doi: 10.1007/s41365-023-01279-z
[17]	Zeng Yifeng, Hu Hao, Hu Tongning. Improvement and correction for transverse emittance diagnosis based on Q-scanning techniques[J]. Nuclear Science and Techniques, 2025, 36: 38. doi: 10.1007/s41365-024-01597-w
[18]	杨国君, 张卓, 何小中. 750 keV射频四极注入器射频结构的优化[J]. 强激光与粒子束, 2008, 20(8):1349-1352 Yang Guojun, Zhang Zhuo, He Xiaozhong. RF optimization design of a 750 keV radio frequency quadrupole injector[J]. High Power Laser and Particle Beams, 2008, 20(8): 1349-1352