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Generating quasi-single-cycle THz pulse from frequency-chirped electron bunch train and a tapered undulator

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High Power Laser Science and Engineering 2016年第1期4卷 5-8页

作者： Zhuoran Ma Zhe Wang Feichao Fu Rui Wang Dao Xiang Key Laboratory for Laser Plasmas (Ministry of Education) Department of Physics and AstronomyShanghai Jiao Tong University IFSA Collaborative Innovation Center Shanghai Jiao Tong University

We propose a proof-of-principle experiment to test a new scheme to produce a single-cycle radiation pulse in free-electron lasers(FELs). Here, a few α-BBO crystals will be first used to produce an equally spaced laser pulse ***, the laser pulse train illuminates the cathode to produce a frequency-chirped electron bunch train in a photocathode rf gun. Finally, the frequency-chirped electron bunch train passes through a tapered undulator to produce a quasi-single-cycle THz pulse. This experiment should allow comparison and confirmation of predictive models and scaling laws, and the preliminary experimental results will also be discussed.

关键词： electron bunch train single-cycle THz pulse tapered undulator

An analysis of undulator optimization in self-seeding free electron lasers

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Chinese Physics C 2014年第8期38卷 94-96页

作者：贾启卡 National Synchrotron Radiation Laboratory University of Science and Technology of China

A simple analysis is given for the optimum length of undulator in a self-seeding free electron laser （FEL）. The obtained relations show the correlation between the undulator length and the system parameters. The power required for the seeding in the second part of the undulator and the overall efficiency of monochromatizating the seeding determine the length of the first part of the undulator; the magnitude of seeding power dominates the length of the second part of the undulator; the whole length of the undulator in a self-seeding FEL is determined by the overall efficiency for getting coherent seed, and is about half as long again as that of SASE, not including the dispersion section. The requirement of the dispersion section strength is also analyzed.

关键词： free electron laser self-seeding undulator

A study on low emittance injector and undulator for PAL-XFEL

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High Power Laser Science and Engineering 2015年第3期3卷 41-49页

作者： J.Hong J.-H.Han S.J.Park Y.G.Jung D.E.Kim H.-S.Kang J.Pflueger Pohang Accelerator Laboratory European XFEL

For the success of PAL-XFEL, two critical systems, namely a low emittance injector and a variable gap out-vacuum undulator, are under development. In order to realize the target emittance of the PAL-XFEL injector we carried out an optimization study of various parameters, such as the laser beam transverse profile, the laser pulse length, the laser phase,and the gun energy. The transverse emittance measured at the Injector Test Facility(ITF) is εx=0.48±0.01 mm *** undulator prototype based on the EU-XFEL design and modified for PAL-XFEL was built and tested. A local-K pole tuning procedure was developed and tested. A significant reduction(90%) of the local-K fluctuation was observed. The requirement of undulator field reproducibility better than 2×10-4and the undulator gap setting accuracy below 1 μm were achieved for the prototype. The optical phase jitter after the pole height tuning at the tuning gap was calculated to be 2.6? rms, which satisfies the requirement of 5.0?.

关键词： emittance free-electron lasers(FELs) photocathode RF-gun undulator

Novel efficient THz undulator using a laser-driven wire

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Light(Science & Applications) 2017年第1期6卷 408-409页

作者： Kazuhisa Nakajima Center for Relativistic Laser Science Institute for Basic Science(IBS)Gwangju 61005Korea

Terahertz(THz=10^(12) cycles per second,or T-ray)radiation sources are indispensable for modern materials science,chemical and biomedical imaging and sensing,as well as for a broad range of applications in diagnostic systems and advanced telecommunications1,*** electromagnetic spectrum of the THz radiation is loosely characterized by the frequency range of 0.1−10 THz,or wavelengths between 30μm and 3 *** particular,a low photon energy of 4.2 meV or 48 K at 1 THz,which is less than the thermal energy at room temperature,allows precise measurements with a simplified setup and very high signal-to-noise ratio in time-domain pulsed THz *** the spectral region is located on the boundary between electronics and photonics,the diversity of the THz sources relies on either frequency up-conversion of electronic sources,such as solid-state photo-switches and radio-frequency(RF)electron-beam accelerators3,or frequency down-conversion of optical sources,such as optical rectification2,3 in nonlinear optical processes and laser-gas interaction induced by twocolor *** technologies,however,exploit ultrashort pulse lasers as a *** a recent publication,Tian et al.4 at Shanghai Institute of Optics and Fine Mechanics(SIOM)and Nankai University developed a new THz radiation source using a laser-driven wire that generates a femtosecond electron bunch and helical undulator fields to emit THz synchrotron radiation with high efficiency.

关键词： laser undulator precise

Mechanical design of a cryogenic Delta-Knot undulator for high energy photon source

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Radiation Detection Technology and Methods 2021年第1期5卷 122-127页

作者： Shuchen Sun Huihua Lu Xiaoyu Li Xiangzhen Zhang Yanwei Yang Yajun Sun Lei Zhang Yuhui Li Zhiqiang Li Wan Chen Lingling Gong Shutao Zhao Qing Guo Keyun Gong Yongsheng Huang Yufeng Yang Laboratory of Particle Acceleration Physics and Technology Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China University of Chinese Academy of Science Beijing 100049China

Introduction A novel type of pure permanent cryogenic Delta–Knot undulator was developed at IHEP to supply a high flux of full adjustable polarization synchrotron radiation with low on-axis power *** prototype was an active attempt and early exploration for future APPLE–Knot undulator,which will be used at high energy photon source(HEPS).Materials and methods There are several challenges to develop a cryogenic delta undulator,such as the complicated structure,the influence of large magnetic force,and the magnetic measurement difficulty due to the very small *** this paper,the mechanical design for overcoming these difficulties will be presented in *** A special hall measuring system is developed,and the preliminary results agree with the theoretical *** undulator prototype will provide valuable experience for angle magnetization technology,intricate magnetic attraction structure design,and magnetic field measurement under closed small space.

关键词： Insertion device undulator Synchrotron radiation photon source Low-emittance storage ring Mechanical design

Pulsed-wire system for undulator measurement

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Radiation Detection Technology and Methods 2022年第2期6卷 150-158页

作者： Zhiqiang Li Huihua Lu Wan Chen Yuhui Li Yongsheng Huang Peng Liu Lingling Gong Laboratory of Particle Acceleration Physics and Technology Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China University of Chinese Academy of Sciences Beijing 100049China

Purpose More undulators are required of HEPS in *** efficiency of traditional Hall-probe measurement method is relatively low,which is difficult to meet the measurement needs of large quantities of *** order to improve debugging efficiency,the pulsed-wire method is required further *** A pulsed-wire method is an effective method to achieve magnetic field distribution through narrow aperture of *** pulsed-wire method works by sending a square current pulse through the wire,which will induce an interaction with the magnetic field due to the Lorentz *** force causes the wire to be displaced,and this displacement travels along the wire in both directions as an acoustic *** of the displacement in the wire over time using a motion detector yields the first or second integrals of the magnetic *** The accuracy and repeatability are the important *** repeatability of the first field integral of the pulsed-wire system is better than 1‰which meets the design *** This paper illustrates the effectiveness of pulsed-wire system by test *** comparison,the accuracy of the system is *** provides a new important measurement system for undulators in future.

关键词： Magnetic field measurement undulator Pulsed wire Integral field measurement Displacement

Single-blockmeasurement for the cryogenic permanent magnet undulator sorting

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Radiation Detection Technology and Methods 2021年第1期5卷 83-89页

作者： Ling-Ling Gong Xiao-Yu Li Yu-Hui Li Ya-Jun Sun Hui-Hua Lu Ke-yun Gong Qing Guo·Shu-Chen Sun Zhi-qiang Li Wan Chen Laboratory of Particle Acceleration Physics and Technology Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China University of Chinese Academy of Sciences Beijing 100049China

Purpose The magnet sorting is a standard step in the undulator fabrication *** shortest undulators period used in the High Energy Photon Source(HEPS)is only 12 *** the short period undulator,the sorting may be more important than the long-period ***,the Helmholtz measurement is used as the input for the *** is the averaged orthogonal magnetization of each *** order to investigate whether the Helmholtz coil measurement is enough for the sorting,a careful study has been *** Firstly,a magnetic camera was used to scan the 3D surface field of a ***,its field integral ismeasured by the stretched *** the measurement,the magnetwas placed at different *** results were checked to seewhether they are consistent with expected features supposing a homogeneous magnetized ***,the results measured by the Helmholtz coil and the stretched wire were *** The surface field scan demonstrates that the field over a magnet block is ***,the field integral measurement by the stretched wire also shows big difference when the different magnet sides toward *** comparison between the stretched wire and the Helmholtz coil measurement shows no *** The study presented in this paper reveals that the homogeneity of the magnetization is ***,the Helmholtz coil data are insufficient to the short-period undulators sorting.

关键词： Magnet sorting undulator Stretched wire Helmholtz coil

ANGULAR SPECTRUM PROPERTY OF SPONTANEOUS EMISSION IN A TWO-DIMENSIONAL undulator FREE-ELECTRON LASER

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Journal of Electronics(China) 1994年第1期11卷 64-70页

作者：彭良福杨中海刘盛纲 University of Electronic Science and Technology of China Chengdu 610054

The angular spectrum of spontaneous emission in a two-dimensional undulator free-electron laser is analyzed theoretically. Numerical calculation shows that the 3-th harmonic spontaneous emission power density can be greatly enhanced by using a two-dimensional undulator, for which l=s, so the harmonic number can be selected by selecting l. Therefore, the higher harmonic operation of a free-electron laser can be realized selectively.

关键词： Free-electron laser Two-dimensional undulator Spectrum property Higher harmonic

Investigation of a method to calculate spontaneous radiation spectra from relativistic electrons in undulators

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Chinese Physics C 2009年第1期33卷 58-64页

作者：陈鸣之何建华 Shanghai Institute of Applied Physics Chinese Academy of Sciences

undulators are key devices to produce brilliant synchrotron radiation at the synchrotron radiation facilities. In this paper we present a numerical computing method, including the computing program that has been developed to calculate the spontaneous radiation emitted from relativistic electrons in undulators by simulating the electrons＇ trajectory. The effects of electron beam emittance and energy spread have also been taken into account. Comparing with other computing methods available at present, this method has a few advantages with respect to several aspects. It can adopt any measured or arbitrarily simulated 3D magnetic field and arbitrary electron beam pattern for the calculation and it＇s able to analyze undulators of any type of magnetic structure. It＇s expected to predict precisely the practical radiation spectrum. The calculation results of a short period in-vacuum undulator and an Elliptically Polarized undulator （EPU） at Shanghai Synchrotron Radiation Facility （SSRF） are presented as examples.

关键词： undulator spontaneous radiation electron trajectory Runge-Kutta method