TUC —  Seeded FELs   (26-Aug-14   15:30—17:00)
Chair: E. Allaria, Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
Paper Title Page
TUC01 Hard X-ray Self-Seeding Setup and Results at SACLA 603
  • T. Inagaki, N. Adumi, T. Hara, T. Ishikawa, R. Kinjo, H. Maesaka, Y. Otake, H. Tanaka, T. Tanaka, K. Togawa, M. Yabashi
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • S. Goto, Y. Inubushi, T.K. Kameshima, T. Ohata, K. Tono
    JASRI/SPring-8, Hyogo, Japan
  • T. Hasegawa, S. Tanaka
    SES, Hyogo-pref., Japan
  • H. Kimura, A. Miura, H. Ohashi, H. Yamazaki
    Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), Hyogo, Japan
  In order to improve the spectral and temporal properties of XFEL, the self-seeding option based on the transmission crystal optics has been implemented in SACLA since 2012. The self-seeding setup composed of four dipole magnets that can generate up to 50 fs temporal delay and a diamond single crystal with the thickness of 180 micro-m has been installed at the position of the 9th undulator segment, which has been moved downstream. In 2013, the installation of all the components has been completed in August and the commissioning has been started in October. After a number of tuning processes such as the beam collimation and undulator K-value optimization, significant spectral narrowing has been confirmed at 10 keV with the C(400) Bragg reflection. The spectral bandwidth of seeded FEL is about 3 eV, which is nearly one order narrower than that of SASE measured without the diamond crystal. The peak spectral intensity of seeded FEL is about 5 times higher than that of SASE. Systematic optimization on beam properties is now in progress towards experimental use of seeded XFELs. This talk gives the overview of the plan, achieved results and ongoing R&D.  
slides icon Slides TUC01 [20.337 MB]  
Soft X-ray Self-seeding Setup and Results at LCLS  
  • D.F. Ratner, J.W. Amann, D.K. Bohler, M. Boyes, D. Cocco, F.-J. Decker, Y. Ding, D. Fairley, Y. Feng, J.B. Hastings, P.A. Heimann, Z. Huang, J. Krzywinski, H. Loos, A.A. Lutman, G. Marcus, A. Marinelli, T.J. Maxwell, S.P. Moeller, P.A. Montanez, D.S. Morton, H.-D. Nuhn, D.R. Walz, J.J. Welch, J. Wu
    SLAC, Menlo Park, California, USA
  • K. Chow, L.N. Rodes
    LBNL, Berkeley, California, USA
  • U. Flechsig
    PSI, Villigen PSI, Switzerland
  • S. Serkez
    DESY, Hamburg, Germany
  The soft X-ray self seeding program was designed to provide near transform-limited pulses in the range of 500 eV to 1000 eV. The project was a three-way collaboration between SLAC, Lawrence Berkeley National Lab, and the Paul Scherrer Institute in Switzerland. Installation finished in the Fall of 2013, and after the early stages of commissioning we have measured up to 0.5mJ pulse energy and resolving powers of up to 5000 across the design wavelength range, representing a several-fold increase in the brightness compared to the normal LCLS operating mode. Future work will aim to increase the total pulse energy and establish self-seeding as a robust user operation mode.  
slides icon Slides TUC02 [10.464 MB]  
TUC03 Generation of Optical Orbital Angular Momentum Using a Seeded Free Electron Laser 609
  • P. Rebernik Ribič, G. De Ninno, D. Gauthier
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  Funding: The research was in part funded by the TALENTS UP Programme (7th R&D Framework Programme, Specific Programme: PEOPLE - Marie Curie Actions - COFUND).
We propose an effective scheme for the generation of intense extreme-ultraviolet light beams carrying orbital angular momentum (OAM). The light is produced by a high-gain harmonic-generation free-electron laser (HGHG FEL), seeded using a laser pulse with a transverse staircase-like phase pattern. The transverse phase modulation in the seed laser is obtained by putting a phase-mask in front of the focusing lens, before the modulator. The staircase-like phase pattern is effectively transferred onto the electron beam in the modulator and the microbunching structure is preserved after frequency up-conversion in the radiator. During light amplification in the radiator, diffraction and mode selection drive the radiation profile towards a dominant OAM mode at saturation. With a seed laser at 260 nm, gigawatt power levels are obtained at wavelengths approaching those of soft x-rays. Compared to other proposed schemes to generate OAM with FELs, our approach is robust, easier to implement, and can be integrated into already existing FEL facilities without extensive modifications of the machine layout.
Experimental Demonstration of Seeded Free-electron Laser Spectrum Control using Corrugated Structure  
  • H.X. Deng, C. Feng, B. Liu, D. Wang, M. Zhang, T. Zhang, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  Funding: This work was partially supported by the Major State Basic Research Development Program of China (2011CB808300) and the National Natural Science Foundation of China (11175240, 11205234 and 11322550).
Corrugated structures [*] hold promising prospects as beam linearizer, beam de-chirper and beam stabilizer for a high brightness LINAC, and thus enhance the FEL performance significantly. So far, several electron beam test experiments of corrugated structure have been carried out on LINACs at PAL [**] and BNL [***]. More recently, a passive control experiment of FEL spectrum, by using a pair of corrugated planes has been successfully accmoplished at SDUV-FEL, which is the first real FEL experimental demonstration of such wakefield structure applications. The physical design, numerical simulations, the vacuum chamber manufacture and the experiment results are presented in this paper.
* K. L. F. Bane and G. Stupakov, NIMA 690 (2012) 106-110.
** P. Emma, M. Venturini, K. L. F. Bane, et al., PRL. 112 (2014) 034801.
*** M. Harrison, et al., NaPAc 2013, Pasadena, USA.
slides icon Slides TUC04 [8.562 MB]