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    SHANGHAI SOFT X-RAY FREE ELECTRON LASER TEST FACILITY
    Transverse wakefields due to asymmetric protrusionsinto a vacuum chamber
    Wakefields studies for the SXFEL user facility
    Fresh-slice multicolour X-ray free-electron lasers
    合肥光源高亮度运行模式研究
    Harmonic Generation in High-GainFELs
    Free electron lasers: Present status and future challenges
    Analytic model of 3D beam dynamics in a wakefield device
    Experimental demonstration of energy-chirp control in relativistic electron bunches using a corrugated pipe. Emma P,Venturini M,Bane K L F,Stupakov G,Kang H-S,Chae M S,Hong J,Min C-K,Yang H,Ha T,Lee W W,Park C D,Park S J,Ko I S Physical review letters The first experimental study is presented of a corrugated wall device that uses wakefields to remove a linear energy correlation in a relativistic electron beam (a "dechirper"). Time-resolved measurements of both longitudinal and transverse wakefields of the device are presented and compared with simulations. This study demonstrates the feasibility to employ a dechirper for precise control of the beam phase space in the next generation of free-electron-lasers. 10.1103/PhysRevLett.112.034801
    High-Power Femtosecond Soft X Rays from Fresh-Slice Multistage Free-Electron Lasers. Lutman Alberto A,Guetg Marc W,Maxwell Timothy J,MacArthur James P,Ding Yuantao,Emma Claudio,Krzywinski Jacek,Marinelli Agostino,Huang Zhirong Physical review letters We demonstrate a novel multistage amplification scheme for self-amplified spontaneous-emission free electron lasers for the production of few femtosecond pulses with very high power in the soft x-ray regime. The scheme uses the fresh-slice technique to produce an x-ray pulse on the bunch tail, subsequently amplified in downstream undulator sections by fresh electrons. With three-stages amplification, x-ray pulses with an energy of hundreds of microjoules are produced in few femtoseconds. For single-spike spectra x-ray pulses the pulse power is increased more than an order of magnitude compared to other techniques in the same wavelength range. 10.1103/PhysRevLett.120.264801
    Control of the Lasing Slice by Transverse Mismatch in an X-Ray Free-Electron Laser. Chao Yu-Chiu,Qin Weilun,Ding Yuantao,Lutman Alberto A,Maxwell Timothy Physical review letters We demonstrated selective slice-dependent lasing by controlling the matching to the undulator of different slices within an electron bunch. The slice-dependent mismatch was realized through quadrupole wakefield generated in a corrugated structure. A deterministic procedure based on empirical beam transport and phase space information is used to match selected slices by turns to lase in the undulator while keeping all other slices from lasing, thus staying fresh. Measurements of time-resolved electron bunch energy loss by a transverse deflecting cavity confirmed the predicted behavior. 10.1103/PhysRevLett.121.064802
    Self-Amplification of Coherent Energy Modulation in Seeded Free-Electron Lasers. Yan Jiawei,Gao Zhangfeng,Qi Zheng,Zhang Kaiqing,Zhou Kaishang,Liu Tao,Chen Si,Feng Chao,Li Chunlei,Feng Lie,Lan Taihe,Zhang Wenyan,Wang Xingtao,Li Xuan,Jiang Zenggong,Wang Baoliang,Wang Zhen,Gu Duan,Zhang Meng,Deng Haixiao,Gu Qiang,Leng Yongbin,Yin Lixin,Liu Bo,Wang Dong,Zhao Zhentang Physical review letters The spectroscopic techniques for time-resolved fine analysis of matter require coherent x-ray radiation with femtosecond duration and high average brightness. Seeded free-electron lasers (FELs), which use the frequency up-conversion of an external seed laser to improve temporal coherence, are ideal for providing fully coherent soft x-ray pulses. However, it is difficult to operate seeded FELs at a high repetition rate due to the limitations of present state-of-the-art laser systems. Here, we report a novel self-modulation method for enhancing laser-induced energy modulation, thereby significantly reducing the requirement of an external laser system. Driven by this scheme, we experimentally realize high harmonic generation in a seeded FEL using an unprecedentedly small external laser-induced energy modulation. An electron beam with a laser-induced energy modulation as small as 1.8 times the slice energy spread is used for lasing at the seventh harmonic of a 266-nm seed laser in a single-stage high-gain harmonic generation (HGHG) setup and the 30th harmonic of the seed laser in a two-stage HGHG setup. The results mark a major step toward a high-repetition-rate, fully coherent x-ray FEL. 10.1103/PhysRevLett.126.084801