Author: Nanni, E.A.
Paper Title Page
TUP036 A Waveguide-Based High Efficiency Super-Radiant FEL Operating in the THz Regime 127
 
  • P. Musumeci, A.C. Fisher
    UCLA, Los Angeles, California, USA
  • A. Gover
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  • E.A. Nanni, E.J. Snively
    SLAC, Menlo Park, California, USA
  • S.B. van der Geer
    Pulsar Physics, Eindhoven, The Netherlands
  
  Funding: DOE grant No. DE-SC0009914 and NSF grant PHY-1734215
In this paper we describe a novel self-consistent 3D simulation approach for a waveguide FEL operating in the zero-slippage regime to generate high power THz radiation. In this interaction regime, the phase and group velocity of the radiation are matched to the relativistic beam traveling in the undulator achieving long interaction lengths. Our numerical approach is based on expanding the existing 3D particle tracking code GPT (General Particle Tracer) to follow the interaction of the particles in the beam with the electromagnetic field modes of the waveguide. We present two separate studies: one for a case which was benchmarked with experimental results and another one for a test case where, using a longer undulator and larger bunch charge, a sizable fraction of the input beam energy can be extracted and converted to THz radiation. The model presented here is an important step in the development of the zero-slippage FEL scheme as a source for high average and peak power THz radiation. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP036  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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WEP104 A High-Power, High-Repetition Rate THz Source for LCLS-II Pump-Probe Experiments 556
 
  • Z. Zhang, A.S. Fisher, M.C. Hoffmann, Z. Huang, B.T. Jacobson, P.S. Kirchmann, W.S. Lee, A. Lindenberg, E.A. Nanni, R.W. Schoenlein
    SLAC, Menlo Park, California, USA
  • S. Sasaki, J.Z. Xu
    ANL, Lemont, Illinois, USA
  
  Experiments using a THz pump and an x-ray probe at an x-ray free-electron laser (XFEL) facility like LCLS-II require frequency-tunable (3 to 20 THz), narrow bandwidth ( ∼ 10\%), carrier-envelope-phase-stable THz pulses that produce high fields (>1MV/cm) at the repetition rate of the x rays and well synchronized with them. In this paper, we study a two-bunch scheme to generate THz radiation at LCLS-II: the first bunch produces THz radiation in a permanent-magnet or electromagnet wiggler immediately following the LCLS-II undulator that produces X-rays from the second bunch. The initial time delay between the two bunches is optimized to compensate for the path difference in transport. We describe the two-bunch beam dynamics, the THz wiggler and radiation, as well as the transport system bringing the THz pulses from the wiggler to the experimental hall.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP104  
About • paper received ※ 23 August 2019       paper accepted ※ 17 September 2019       issue date ※ 05 November 2019  
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