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Coherent radiation of ultrashort electron-bunches from linear acceleration

R. J. McGuigan and S. P. Jamison

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Phys. Rev. Accel. Beams 29, 041003 – Published 13 April, 2026

DOI: https://doi.org/10.1103/pbv5-nw8c

Abstract

We consider the radiation emitted by a purely longitudinally accelerated relativistic electron bunch and find, contrary to the usual expectation of negligible emission, that for ultrashort compact bunches within reach of current experiments, a significant and measurable radiation pulse is produced. The underlying mechanism for the enhanced emission is coherence in the single-electron emission over O(108) electrons. We derive analytic descriptions of the emission spectrum and energy for acceleration fields and bunch conditions encountered in rf-driven particle accelerators, and in the extreme high-gradient conditions of plasma-driven acceleration. Both the bunch duration and the duration of the acceleration have a role in describing a phase-matching limitation to the coherence, with the latter dependent on the acceleration field strength and the initial energy of the electrons. In extremely compact bunches, just beyond those currently realized in the laboratory, the radiation losses approach the Larmor radiation for a massively charged particle (Q∼109e). In such conditions, the implied energy of the longitudinal acceleration radiation may approach the energy available from the electric field driving the acceleration, raising questions about a connection to mechanisms of field depletion.

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References (23)

  1. R. P. Walker, Synchrotron radiation, in CAS - CERN Accelerator School: 5th General Accelerator Physics Course (1994), pp. 437–459.
  2. H. C. Pollock, The discovery of synchrotron radiation, Am. J. Phys, 51, 278 (1983).
  3. J. D. Jackson, Classical Electrodynamics (John Wiley & Sons, New York, NY, 1999).
  4. C. Pellegrini, A. Marinelli, and S. Reiche, The physics of x-ray free-electron lasers, Rev. Mod. Phys. 88, 015006 (2016).
  5. J. Schwinger, On the classical radiation of accelerated electrons, Phys. Rev. 75, 1912 (1949).
  6. G. Geloni, E. Saldin, E. Schneidmiller, and M. Yurkov, Longitudinal wake field for an electron beam accelerated through an ultrahigh field gradient, Nucl. Instrum. Methods Phys. Res., Sect. A 578, 34 (2007).
  7. R. A. Bosch, Longitudinal wake of a bunch of suddenly accelerated electrons within the radiation formation zone, Phys. Rev. ST Accel. Beams 10, 050701 (2007).
  8. T. Nakazato et al., Observation of coherent synchrotron radiation, Phys. Rev. Lett. 63, 1245 (1989).
  9. U. Arp, G. T. Fraser, A. R. Hight Walker, T. B. Lucatorto, K. K. Lehmann, K. Harkay, N. Sereno, and K.-J. Kim, Spontaneous coherent microwave emission and the sawtooth instability in a compact storage ring, Phys. Rev. ST Accel. Beams 4, 054401 (2001).
  10. W. P. Leemans, B. Nagler, A. J. Gonsalves, C. Tóth, K. Nakamura, C. G. R. Geddes, E. Esarey, C. B. Schroeder, and S. M. Hooker, GeV electron beams from a centimeter scale accelerator, Nat. Phys. 2, 696 (2006).
  11. R. Bingham, Basic concepts in plasma accelerators, Phil. Trans. R. Soc. A 364, 559 (2006).
  12. J. Götzfried, A. Döpp, M F. Gilljohann, F M. Foerster, H. Ding, S. Schindler, G. Schilling, A. Buck, L. Veisz, and S. Karsch, Physics of high-charge electron beams in laser-plasma wakefields, Phys. Rev. X 10, 041015 (2020).
  13. E. A. Nanni, W. R. Huang, K.-H. Hong, K. Ravi, A. Fallahi, G. Moriena, R. J. Dwayne Miller, and F. X. Kärtner, Terahertz-driven linear electron acceleration, Nat. Commun. 6, 8486 (2015).
  14. J. Franklin and D. J. Griffiths, The fields of a charged particle in hyperbolic motion, Am. J. Phys. 82, 755 (2014).
  15. Max Born, The theory of the rigid electron in the kinematics of the relativity principle, Ann. Phys. (Berlin) 30, 1 (1909).
  16. A. Zangwill, Modern Electrodynamics (Cambridge University Press, Cambridge, England, 2012).
  17. A. Novokhatski, Coherent synchrotron radiation: Theory and simulations, ICFA Beam Dyn. Newslett. 57, 127 (2012).
  18. G. Geloni, Acceleration-induced self-interactions within a relativistic electron bunch: An analytical study, Ph.D. thesis, Eindhoven University of Technology, 2003, 10.6100/IR567528, p. 146.
  19. G. L. Carr, S. L. Kramer, J. B. Murphy, R. P. S. M. Lobo, and D. B. Tanner, Observation of coherent synchrotron radiation from the NSLS VUV ring, Nucl. Instrum. Methods Phys. Res., Sect. A 463, 387 (2001).
  20. R. Li, C. L. Bohn, and J. J. Bisognano, Shielded transient self-interaction of a bunch entering a circle from a straight path, in Proceedings of the 1997 Particle Accelerator Conference (1997), Vol. 2, pp. 1641–1643, 10.1109/PAC.1997.750786.
  21. Y. S. Derbenev, J. Rossbach et al., Microbunch radiative tail—head interaction, Report No. TESLA FEL 1995-05, DESY, Hamburg, Germany, 1995, 10.3204/PUBDB-2018-04128.
  22. G. Stupakov and Z. Huang, Space charge effect in an accelerated beam, Phys. Rev. ST Accel. Beams 11, 014401 (2008).
  23. R. J. McGuigan (2026), Lancaster University Research Repository at 10.17635/lancaster/researchdata/573.

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Phys. Rev. Accel. Beams 29, 041003– Published 13 April, 2026
  • Received 27 November 2025
  • Accepted 3 March 2026
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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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