Evidence for Microbunching “Sidebands” in a Saturated Free-Electron Laser Using Coherent Optical Transition Radiation

Lumpkin, A.H.; Dejus, Roger J.; Lewellen, John W.; Berg, William J.; Biedron, Sandra; Borland, M.; Chae, Yong-Chul; Erdmann, M.; Huang, Zhirong; Kim, K.-J.; Li, Y.; Milton, S.V.; Moog, E. R.; Rule, D.W.; Sajaev, V.; Yang, Bingxin

doi:10.1103/physrevlett.88.234801

Cited by 42 publications

(8 citation statements)

References 15 publications

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“…This results in the generation of coherent optical transition radiation (COTR) at the surface of two thin foils located just downstream of the bubble when the beam transits them. Such effects were first observed from microbunched electrons in a self-amplified spontaneous emission (SASE) free-electron laser (FEL) experiment [7]. In that case, the increase in microbunching fraction was inherent to the exponential gain regime of the SASE FEL.…”

Section: Introductionmentioning

confidence: 96%

Observations of Coherent Optical Transition Radiation Interference Fringes Generated by Laser Plasma Accelerator Electron Beamlets

Lumpkin

Laberge

Rule³

et al. 2018

2018 IEEE Advanced Accelerator Concepts Workshop (AAC)

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We report initial observations of coherent optical transition radiation interferometry (COTRI) patterns generated by microbunched electrons from laser-driven plasma accelerators (LPAs). These are revealed in the angular distribution patterns obtained by a CCD camera with the optics focused at infinity, or the far-field, viewing a Wartski two-foil interferometer. The beam divergences deduced by comparison to results from an analytical model are sub-mrad, and they are smaller than the ensemble vertical beam divergences measured at the downstream screen of the electron spectrometer. The transverse sizes of the beamlet images were obtained with focus at the object, or near field, and were in the few-micron regime as reported by LaBerge et al. [8]. The enhancements in intensity are significant relative to incoherent optical transition radiation (OTR) enabling multiple cameras to view each shot. We present two-foil interferometry effects coherently enhanced in both the 100-TW LPA at 215 MeV energy at Helmholtz-Zentrum Dresden-Rossendorf and the PW LPA at 1.0-GeV energy at the University of Texas-Austin. A transverse emittance estimate is reported for a microbunched beamlet example generated within the plasma bubble.

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Section: Introductionmentioning

confidence: 96%

Observations of Coherent Optical Transition Radiation Interference Fringes Generated by Laser Plasma Accelerator Electron Beamlets

Lumpkin

Laberge

Rule³

et al. 2018

2018 IEEE Advanced Accelerator Concepts Workshop (AAC)

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“…To our knowledge and despite its great potential, coherent Cherenkov diffraction radiation (CChDR) has not been exploited for beam diagnostic purposes [17], and even if many groups working with short bunches have been using in the past coherent radiation, the detection systems were mainly based on coherent transition radiation (CTR) [18][19][20][21][22], coherent diffraction radiation (CDR) [23], coherent Smith Purcell radiation [24] or electro-optical sampling (EOS) [25].…”

Section: Introductionmentioning

confidence: 99%

Noninvasive bunch length measurements exploiting Cherenkov diffraction radiation

Curcio

Bergamaschi

Corsini

et al. 2020

Phys. Rev. Accel. Beams

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We present the observation and the detailed investigation of coherent Cherenkov diffraction radiation (CChDR) in terms of spectral-angular characteristics. Electromagnetic simulations have been performed to optimize the design of a prismatic dielectric radiator and the performance of a detection system with the aim of providing longitudinal beam diagnostics. Successful experimental validations have been organized on the CLEAR and the CLARA facilities based at CERN and Daresbury laboratory respectively. With ps to sub-ps long electron bunches, the emitted radiation spectra extend up to the THz frequency range. Bunch length measurements based on CChDR have been compared to longitudinal bunch profiles obtained using a radio frequency deflecting cavity or coherent transition radiation (CTR). The retrieval of the temporal profile of both Gaussian and non-Gaussian bunches has also been demonstrated. The proposed detection scheme paves the way to a new kind of beam instrumentation, simple and compact for monitoring short bunches of charged particles, particularly well-adapted to novel Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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“…In the case of the Advanced Photon Source (APS) FEL operating in the UV-visible regime, we have used standard CCD imaging cameras to obtain near-field, far-field, and spectral information on the COTR [9][10][11][12]. In addition to the unprecedented signal strength in the near-field images (used to measure beam size), we have found noticeable structure and θ x -θ y asymmetry in the far-field images plus narrow-band spectral emission.…”

Section: Introductionmentioning

confidence: 99%

Advanced Intraundulator Electron Beam Diagnostics Using COTR Techniques

Lumpkin¹,

Berg²,

Biedron³

et al. 2002

AIP Conference Proceedings

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Abstract. A significant advance in intraundulator electron-beam diagnostics has recently been demonstrated based on coherent optical transition radiation (COTR) imaging. We find signal strengths from a microbunched beam in a UV-visible free-electron laser to be several orders of magnitude higher than that of incoherent optical transition radiation. In addition we report that the far-field images of COTR interferograms carry information about beam size and asymmetry, divergence, and pointing.

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Evidence for Microbunching “Sidebands” in a Saturated Free-Electron Laser Using Coherent Optical Transition Radiation

Cited by 42 publications

References 15 publications

Observations of Coherent Optical Transition Radiation Interference Fringes Generated by Laser Plasma Accelerator Electron Beamlets

Observations of Coherent Optical Transition Radiation Interference Fringes Generated by Laser Plasma Accelerator Electron Beamlets

Noninvasive bunch length measurements exploiting Cherenkov diffraction radiation

Advanced Intraundulator Electron Beam Diagnostics Using COTR Techniques

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