Author: Emma, C.
Paper Title Page
TUB02
Fresh Slice Self-Seeding and Fresh Slice Harmonic Lasing at LCLS  
 
  • C. Emma, C. Pellegrini
    UCLA, Los Angeles, California, USA
  • J.W. Amann, M.W. Guetg, J. Krzywinski, A.A. Lutman, C. Pellegrini, D.F. Ratner
    SLAC, Menlo Park, California, USA
  • D.C. Nguyen
    LANL, Los Alamos, New Mexico, USA
 
  We present results from the successful demonstration of fresh slice self-seeding at the Linac Coherent Light Source (LCLS).* The performance is compared with SASE and regular self-seeding at photon energy of 5.5 keV, resulting in a relative average brightness increase of a factor of 12 and a factor of 2 respectively. Following this proof-of-principle we discuss the forthcoming plans to use the same technique** for fresh slice harmonic lasing in an upcoming experiment. The demonstration of fresh slice harmonic lasing provides an attractive solution for future XFELs aiming to achieve high efficiency, high brightness X-ray pulses at high photon energies (>12 keV).***
* C. Emma et al., Applied Physics Letters, 110:154101, 2017.
** A. A. Lutman et al., Nature Photonics, 10(11):745-750, 2016.
*** C. Emma et al., Phys. Rev. Accel. Beams 20:030701, 2017.
 
slides icon Slides TUB02 [13.759 MB]  
 
WEP079
High-Efficiency, Tapered FELs with a Pre-Bunched Electron Beam  
 
  • C. Emma, P. Musumeci, C. Pellegrini, N.S. Sudar, A. Urbanowicz
    UCLA, Los Angeles, USA
  • C. Pellegrini
    SLAC, Menlo Park, California, USA
 
  We study the 1-D physics of high gain, high efficiency tapered FELs in the post-saturation regime.*,** We derive a basic scaling formula for the FEL output power as a function of the beam current, the seed power and the trapping fraction assuming a constant resonant phase. We examine this analytic scaling using 1-D simulations for a seeded FEL starting from a large seed with a small energy spread electron beam (fresh bunch) with/without pre-bunching. We show that the efficiency improves substantially when the electron beam is suitably pre-bunched compared to the unbunched case. Finally, we study the sideband instability growth via 1-D time-dependent simulations. We confirm the inverse proportionality of the sideband power to the resonant phase as discussed in KMR. We also propose a method of sideband suppression via gain-modulation of the FEL using a modulated taper profile.***
* N. M. Kroll, P. L. Morton, and M. Rosenbluth. Quantum Electronics 17(8): 1436-1468, August 1981.
** R. Iaconescu, at this conference.
*** Marinelli et al., PRL 111: 134801 (2015).
 
 
FRA01
Fresh-Slice X-Ray Free Electron Laser Schemes for Advanced X-Ray Applications  
 
  • A.A. Lutman, R.N. Coffee, Y. Ding, J.P. Duris, M.W. Guetg, Z. Huang, J. Krzywinski, J.P. MacArthur, A. Marinelli, T.J. Maxwell, S.P. Moeller, J. Zemella
    SLAC, Menlo Park, California, USA
  • N. Berrah
    University of Connecticut, Storrs, Connecticut, USA
  • C. Emma
    UCLA, Los Angeles, USA
 
  Funding: This work was supported by Department of Energy contract nos DE-AC02-76SF00515 and DE-SC0012376
The novel fresh-slice XFEL scheme grants control on the temporal slice of the electron bunch lasing in each undulator section. The technique relies on a time-dependent electron bunch trajectory impressed by the transverse wakefield of a corrugated structure and subsequent orbit manipulation in the undulator section. Fully saturated double pulses are produced in two different undulator sections. The wavelength of each pulse is controlled by the undulator magnetic strength and the delay between the pulses can be scanned from a few femtosecond advance of the pulse generated on the bunch head in the second section to a picosecond delay provided by the magnetic chicane. Three-color saturated pulses are demonstrated by using three undulator sections and the polarization of the pulse generated in the last section can be controlled by the variable polarization Delta undulator. In this work we also show the early results for the first multi-stage amplification scheme, producing ultra-short single-pulses with a 100-GW power level in the soft X-rays. The multi-stage amplification is also demonstrated to improve the performance in power and pulse duration control for the two-color FEL scheme.
 
 
FRB03 Dynamics of Superradiant Emission by a Prebunched E-Beam and its Spontaneous Emission Self-Interaction 1
 
  • R. Ianconescu, A. Gover
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  • C. Emma, P. Musumeci
    UCLA, Los Angeles, USA
  • A. Friedman
    Ariel University, Ariel, Israel
 
  Funding: Partial support by US-Israel Binational Science Foundation (BSF) and by Deutsche-Israelische Projektkooperation (DIP).
In the context of radiation emission from an electron beam, Dicke's superradiance (SR) is the enhanced coherent spontaneous radiation emission from a prebunched beam, and Stimulated-Superradiance (ST-SR) is the further enhanced emission of the bunched beam in the presence of a phase-matched radiation wave.* These processes are analyzed for undulator radiation in the framework of radiation field mode-excitation theory. In the nonlinear saturation regime the synchronicity of the bunched beam and an injected radiation wave may be sustained by wiggler tapering: Tapering-Enhanced Superradiance (TES) and Tapering-Enhanced Stimulated Superradiance Amplification (TESSA).** Identifying these processes is useful for understanding the enhancement of radiative emission in the tapered wiggler section of seeded FELs.***,**** The nonlinear formulation of the energy transfer dynamics between the radiation wave and the bunched beam fully conserves energy. This includes conservation of energy without radiation reaction terms in the interesting case of spontaneous self-interaction (no input radiation).
* A. Gover, Phys. Rev. ST-AB 8, 030701 (2005).
** J. Duris et al., New J.Phys. 17 063036 (2015).
*** E. A. Schneidmiller et al., PRST-AB 18, 03070 (2015).
**** C. Emma et al., this conference.
 
slides icon Slides FRB03 [2.656 MB]