Author: Ianconescu, R.
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MOP078 Sub-Radiance and Enhanced-Radiance of Undulator Radiation from a Correlated Electron Beam 221
  • R. Ianconescu
    Shenkar College of Engineering and Design, Ramat Gan, Israel
  • A. Gover
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  • E. Hemsing, A. Marinelli
    SLAC, Menlo Park, California, USA
  • A. Nause
    UCLA, Los Angeles, USA
  Funding: We acknowledge the United States - Israel Binational Science Foundation (BSF)
The radiant intensity of Synchrotron Undulator Radiation (UR) depends on the current noise spectrum of the electron beam injected into the wiggler. The current noise spectrum and intensity can be controlled (suppressed or enhanced relative to the shot-noise level) by the effect of collective longitudinal space charge interaction in a drift and dispersion sections[1]. This new control lever is of significant interest for possible control of SASE in FEL, since UR is the incoherent seed of SASE. Thus, control of spontaneous UR is a way to enhance the coherence of seeded FEL [2], or alternatively, obtain enhanced radiation from a cascade noise-amplified electron beam [3]. The dependence of UR emission on the current noise is primarily a result of the longitudinal correlation of the e-beam distribution due to the longitudinal space charge effect. However, at short wavelengths, 3-D effects of transverse correlation and effects of emittance disrupts the proportionality relation between the UR intensity and e-beam current noise. We present analysis and simulation of UR subradiance/superradiance under various ranges of beam parameters, and compare to recent experimental observations [1].
[1] D. Ratner et al., PRST - ACCELERATORS AND BEAMS 18, 050703 (2015)
[2] E. Allaria et al., Nat. Photonics 7, 913 (2013)
[3] A. Marinelli et al., Phys. Rev. Lett. 110, 264802 (27 June 2013)
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WEP085 Conceptual Theory of Spontaneous and Taper-Enhanced Superradiance and Stimulated Superradiance 746
  • A. Gover, R. Ianconescu
    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: We acknowledge partial support by the U.S. Israel Binational Science Foundation (BSF)Jerusalem, Israel
In the context of radiation emission from an electron beam Dicke's superradiance (SR) is the enhanced radiation emission from a pre-bunched beam. Stimulated Superradiance (ST-SR) is the further enhanced emission of the bunched beam in the presence of a phase-matched radiation wave. These processes were analyzed for Undulator radiation in the framework of radiation field mode-excitation theory[1]. In the nonlinear saturation regime the synchronism of the bunched beam and an injected radiation wave may be sustained by wiggler tapering [2]. Same processes are instrumental also in enhancing the radiative emission in the tapered wiggler section of seeded FEL[3]. In a long tapered wiggler the diffraction of the emitted radiation wave is not negligible even at Angstroms wavelengths (as in LCLS). A Fresnel diffraction model was provided in [4] for the SR process only. Here we outline the fundamental physical concepts of Spontaneous Superradiadce (SR), Stimulated Superradiance (ST-SR), Taper-Enhanced Superradiance (TES) and Taper-Enhanced Stimulated Superradiance Amplification (TESSA), and compare their Fourier and Phasor formulations in the radiation mode expansion and free-diffraction models. Detailed further analysis can provide better design concepts of high power FELs and improved tapering strategy for enhancing the power of seeded short wavelength FELs
1. A. Gover, PR ST-AB 8, (030701) ; (030702) (2005)
2. J. Duris et al., arxiv 2015.
3. Y. Jiao et al., PR ST-AB 15 050704 2012
4. E.A. Schneidmiller, M.V. Yurkov, PR ST-AB 18, 030705 (2015)
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