FEL2015 - List of Authors (Fang, K.)

Paper	Title	Page
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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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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Paper

Title

Page

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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reference for this paper to ※ LaTeX, ※ Text, ※ IS/RefMan, ※ EndNote (xml)

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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reference for this paper to ※ LaTeX, ※ Text, ※ IS/RefMan, ※ EndNote (xml)