Tutorial
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TUT01 Superradiance and Stimulated-Superradiant Emission of Bunched Electron Beams 288
 
  • A. Gover, R. Ianconescu
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  • C. Emma, P. Musumeci, C. Pellegrini, N.S. Sudar
    UCLA, Los Angeles, USA
  • A. Friedman
    Ariel University, Ariel, Israel
  • R. Ianconescu
    Shenkar College of Engineering and Design, Ramat Gan, Israel
 
  Funding: We acknowledge support of the Israel Science Foundation and the German Israeli Projects Foundation (DIP).
We outline the fundamental processes of coherent radiation emission from a bunched charged particles beam [1]. In contrast to spontaneous emission of radiation from a random electron beam that is proportional to the number of particles N, a pre-bunched electron beam emits spontaneously coherent radiation proportional to N2 through the process of (spontaneous) superradiance (SP-SR) (in the sense of Dicke’s [2]). The SP-SR emission of a bunched electron beam can be even further enhanced by a process of stimulated-superradiance (ST-SR) in the presence of a seed injected radiation field. These coherent radiation emission processes are presented in term of a radiation mode expansion model, applied to general free electron radiation schemes: Optical-Klystron, HGHG, EEHG, and coherent THz sources based on synchrotron radiation, undulator radiation or Smith-Purcell radiation. The general model of coherent spontaneous emission is also extended to the nonlinear regime - Tapering Enhanced Stimulated Superradiance (TESSA) [3], and related to the tapered wiggler section of seed-injected FELs. In X-Ray FELs these processes are convoluted with other effects, but they are guidelines for strategies of wiggler tapering efficiency enhancement.
[1] A. Gover et al., Rev. Mod. Phys. https://arxiv.org/abs/1810.07566v3 (2019)
[2] R. H. Dicke, Physical Review 93, 99 (1954)
[3] N. Sudar et al., P.R.L. 117, 174801 (2016)
 
slides icon Slides TUT01 [11.391 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUT01  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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WET01
Photon Transport Beamline Design  
 
  • H. Sinn
    EuXFEL, Hamburg, Germany
 
  Free Electron Lasers produce X-ray light with almost perfect coherence. The optical elements of the beam transport system have to fulfill therefore much more stringent - and in part also different - specifications compared to similar optics at synchrotron radiation sources. Another aspect of X-ray laser light is that it is generated in very intense and short pulses, which leads to the effect that the heat pile-up in anything intercepting the beam and can outrun the thermal transport on different time scales. This poses strong limitations on the suitable materials that can be used for mirror coatings, slits, attenuators and absorbers. Under certain conditions the beam can drill very fast through thick slabs of material, which opens up new possibilities for technical applications but poses also new challenges to the radiation safety system. This tutorial gives an overview of the basic relations needed to understand the physics of X-ray optics at free electron lasers and illustrates also experiences from the first two years of operation of the European XFEL.  
slides icon Slides WET01 [53.050 MB]  
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