Author: Wu, J.
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TUP020 Recent Study in iSASE 393
  • K. Fang, C. Pellegrini, J. Wu
    SLAC, Menlo Park, California, USA
  • C. Emma, C. Pellegrini
    UCLA, Los Angeles, California, USA
  • S. Hsu
    University of California, San Diego (UCSD), La Jolla, California, USA
  The Improved Self-Amplified Spontaneous Radiation (iSASE) scheme has potential to reduce SASE FEL bandwidth. This is achieved by repeatedly delaying the electrons with respect to the radiation pulse using phase shifters in the undulator break sections. It has been shown that the strength, locations and sequences of phase shifters are important to the iSASE performance. Particle swarm optimization algorithm is used to explore the phase shifters configuration space globally.  
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WEB01 A Two-Color Storage Ring FEL 571
  • 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.Y. Li
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • N. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
  • J. Wu
    SLAC, Menlo Park, California, USA
  Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
Using different undulator configurations on the Duke storage ring, we have successfully achieved lasing with a novel two-color storage ring FEL. Using a pair of dual-band FEL mirrors, simultaneous lasing was realized in IR (around 720 nm) and in UV (around 360 nm). With this two-color FEL, we have demonstrated independent wavelength tuning of either IR or UV lasing. With careful tuning, we have also realized harmonic lasing with the UV lasing tuned to the second harmonic of the IR lasing. The tuning of harmonic two-color lasing has also been demonstrated with the locked wavelengths. Furthermore, we have demonstrated good control of the FEL power sharing between the two colors. The two-color FEL has created new opportunities to drive a two-color Compton gamma-ray beam at the High Intensity gamma-ray Source at Duke.
slides icon Slides WEB01 [18.975 MB]  
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WEP076 Tapering Studies for TW Level X-ray FELs with a Superconducting Undulator and Built-in Focusing 726
  • C. Emma
    UCLA, Los Angeles, USA
  • K. Fang, C. Pellegrini, J. Wu
    SLAC, Menlo Park, California, USA
  Funding: U.S. Department of Energy DE-SC0009983.
Tapering optimization schemes for TeraWatt (TW) level X-ray Free Electron Lasers (FELs) are critically sensitive to the length of individual undulator and break sections. Break sections can be considerably shortened if the focusing quadrupole field is superimposed on the undulator field increasing the filling factor and the overall extraction efficiency of the tapered FEL. Furthermore, distributed focusing reduces the FODO length and allows one to use smaller beta functions. This reduces particle de-trapping due to betatron motion from the radial tails of the electron beam. We present numerical calculations of the tapering optimization for such an undulator using the three dimensional time dependent code GENESIS. Time dependent simulations show that 8 keV photons can be produced with over 3 TW peak power in a 100m long undulator. We also analyze in detail the time dependent effects leading to power saturation in the taper region. The impact of the synchrotron sideband growth on particle detrapping and taper saturation is discussed. We show that the optimal taper profile obtained from time independent simulation does not yield the maximum extraction efficiency when multi-frequency effects are included. A discussion of how to incorporate these effects in a revised model is presented.
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