Author: Huang, S.
Paper Title Page
MOP013 Hundred-Gigawatt X-Ray Self-Seeded High-Gain Harmonic Generation 1
 
  • L. Zeng, S. Huang, K.X. Liu, W. Qin, G. Zhao
    PKU, Beijing, People's Republic of China
  • Y. Ding, Z. Huang
    SLAC, Menlo Park, California, USA
 
  Self-seeded high-gain harmonic generation is a possible way to extend the wavelength of a soft x-ray free-electron laser (FEL). We have carried out simulation study on harmonic generation within the photon energy range from 2 keV to 4.5 keV, which is difficult to achieve due to a lack of monochromator materials. In this work, we demonstrate the third harmonic FEL with the fundamental wavelength at 1.52 nm. Our results shows that, by using undulator tapering technique, sub-terawatt narrow-bandwidth FEL output can be obtained.  
 
MOP014 Harmonic Lasing Towards Shorter Wavelengths in Soft X-Ray Self-Seeding FELs 1
 
  • L. Zeng, S. Huang, K.X. Liu, W. Qin, G. Zhao
    PKU, Beijing, People's Republic of China
  • Y. Ding, Z. Huang
    SLAC, Menlo Park, California, USA
 
  In this paper, we study a simple harmonic lasing scheme to extend the wavelength of X-ray self-seeding FELs. The self-seeding amplifier is comprised of two stages. In the first stage, the fundamental radiation is amplified but well restricted below saturation, and simultaneously harmonic radiation is generated. In the second stage, the fundamental radiation is suppressed while the harmonic radiation is amplified to saturation. We performed a start-to-end simulation to demonstrate third harmonic lasing in a soft x-ray self-seeding FEL at the fundamental wavelength of 1.52 nm. Our simulations show that a stable narrow-band FEL at GW levels can be obtained.  
 
TUA05
Generating Subfemtosecond Hard X-Ray Pulses with Optimized Nonlinear Bunch Compression  
 
  • S. Huang
    PKU, Beijing, People's Republic of China
  • Y. Ding, Y. Feng, E. Hemsing, Z. Huang, J. Krzywinski, A.A. Lutman, A. Marinelli, T.J. Maxwell, D. Zhu
    SLAC, Menlo Park, California, USA
 
  Funding: This work is supported by the U.S. Department of Energy Contract No. DE-AC02-76SF00515 and the National Key Research and Development Program of China (Grant No. 2016YFA0401904).
A simple method for generating single-spike hard x-ray pulses in free-electron lasers (FELs) has been developed at the Linac Coherent Light Source (LCLS). By optimizing the electron bunch compression in experiments, we have obtained half of the hard x-ray FEL shots containing single-spike spectrum. At 5.6-keV photon energy, the single-spike shots have a mean pulse energy of about 10 J with 70% intensity fluctuation and the pulse width (full width at half maximum) is evaluated to be at 200-attosecond level.
 
 
TUC01 Polarization Control of Storage Ring FELs Using Cross Polarized Helical Undulators 1
 
  • J. Yan, H. Hao, S.F. Mikhailov, V. Popov, Y.K. Wu
    FEL/Duke University, Durham, North Carolina, USA
  • S. Huang
    PKU, Beijing, People's Republic of China
  • J.L. Li
    IHEP, Beijing, People's Republic of China
  • V. Litvinenko
    Stony Brook University, Stony Brook, USA
  • N.A. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
 
  For more than two decades, accelerator researchers have been working to gain control of polarization of synchrotron radiation and FELs using non-optical means. In 2005, the first experimental demonstration of polarization control of an FEL beam was realized with the Duke storage-ring FEL. With the recent upgrade of the undulator system, the Duke FEL can be operated with up to four helical undulators simultaneously. Using two sets of helical undulators with opposite helicities, for the first time, we have demonstrated full polarization control of a storage ring FEL. First, the helicity switch of the FEL beam has been realized with good lasing up to a few Hz. Second, the linearly polarized FEL beam has been generated with a high degree of polarization (Plin>0.95). The FEL polarization direction can be fully controlled using a buncher magnet. Furthermore, the use of non-optical means to control the FEL polarization allows us to extend polarization control to gamma-ray beams generated using Compton scattering. This has been experimentally demonstrated with the production of linearly polarized Compton gamma-ray beams with rotatable polarization direction based upon helical undulators.  
slides icon Slides TUC01 [5.916 MB]  
 
TUC05
Start-to-End Simulations for an X-Ray FEL Oscillator at the LCLS-II and LCLS-II-HE  
 
  • W. Qin, K.L.F. Bane, Y. Ding, Z. Huang, G. Marcus, T.J. Maxwell
    SLAC, Menlo Park, California, USA
  • S. Huang, K.X. Liu
    PKU, Beijing, People's Republic of China
  • K.-J. Kim, R.R. Lindberg
    ANL, Argonne, Illinois, USA
 
  The proposed high repetition-rate electron beam from the LCLS-II and LCLS-II High Energy (LCLS-II-HE) upgrade are promising sources as drivers for an X-ray FEL Oscillator (XFELO) operating at both the harmonic and fundamental frequencies. In this contribution we present start-to-end simulations for an XFELO operating at the fifth harmonic with 4 GeV LCLS-II beam and at the fundamental with 8 GeV LCLS-II-HE beam. The electron beam longitudinal phase space is optimized by shaping the photoinjector laser and adjusting various machine parameters. The XFELO simulations show that high-flux output radiation pulses with 1010 photons and 3 meV (FWHM) spectral bandwidth can be obtained with the 8 GeV configuration.  
 
WEA03
Simulation Optimization of DC-SRF Photoinjector for Low-Emittance Electron Beam Generation  
 
  • K.X. Liu, J.E. Chen, W. Cheng, L.W. Feng, J.K. Hao, S. Huang, L. Lin, W. Qin, S.W. Quan, F. Wang, H.M. Xie, F. Zhu
    PKU, Beijing, People's Republic of China
 
  A DC and superconducting rf (SRF) combined photoinjector, DC-SRF photoinjector, has been developed at Peking University to generate high repetition-rate electron bunches. At present stable operation of the DC-SRF photoinjector has been realized and the electron beam has been delivered to a SRF linac with two 9-cell TESLA-type cavities for further acceleration and experiments. Here we will present our latest progress on the DC-SRF photoinjector. We will also present our recent simulation work to decrease the emittance. The purpose is to build an upgraded DC-SRF photoinjector capable of driving CW X-ray free-electron lasers.