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Longitudinal emittance improvement at an x-ray free-electron laser by shortening the injector laser pulse duration

Anastasiia Riabchikova1,2, Philipp Dijkstal1, Wenxiang Hu3,4, Thomas G. Lucas1, Sven Reiche1, and Eduard Prat1,*

  • *Contact author: eduard.prat@psi.ch
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Phys. Rev. Accel. Beams 29, 020703 – Published 10 February, 2026

DOI: https://doi.org/10.1103/lgqn-158t

Abstract

The performance of x-ray free-electron lasers (XFELs) strongly depends on the longitudinal emittance of the electron beam. We show that by reducing the injector drive laser pulse duration, the electron beam peak current can be increased by a factor of 2 or more, resulting in a significant improvement in longitudinal emittance. Comprehensive simulations and measurements carried out at SwissFEL confirm the expected trade-off of moderately higher transverse emittance. This simple approach can be readily adapted to other XFEL facilities.

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References (42)

  1. Z. Huang and K.-J. Kim, Review of x-ray free-electron laser theory, Phys. Rev. ST Accel. Beams 10, 034801 (2007).
  2. B. W. J. McNeil and N. R. Thompson, X-ray free-electron lasers, Nat. Photonics 4, 814 (2010).
  3. C. Pellegrini, A. Marinelli, and S. Reiche, The physics of x-ray free-electron lasers, Rev. Mod. Phys. 88, 015006 (2016).
  4. S. Di Mitri, On the importance of electron beam brightness in high gain free electron lasers, Photonics 2, 317 (2015).
  5. J. S. Fraser, R. L. Sheffield, E. R. Gray, and G. W. Rodenz, High-brightness photoemitier injector for electron accelerators, IEEE Trans. Nucl. Sci. 32, 1791 (1985).
  6. C. Hernandez-Garcia, P. G. O’Shea, and M. L. Stutzman, Electron sources for accelerators, Phys. Today 61, No. 2, 44 (2008).
  7. S. G. Anderson, P. Musumeci, J. B. Rosenzweig, W. J. Brown, R. J. England, M. Ferrario, J. S. Jacob, M. C. Thompson, G. Travish, A. M. Tremaine, and R. Yoder, Velocity bunching of high-brightness electron beams, Phys. Rev. ST Accel. Beams 8, 014401 (2005).
  8. E. L. Saldin, E. A. Schneidmiller, and M. V. Yurkov, Coherence properties of the radiation from x-ray free electron laser, Opt. Commun. 281, 1179 (2008).
  9. A. Piwinski, Intra-beam-scattering, Technical Report No. CERN-1992-001.226, CERN, 1974, 10.5170/CERN-1992-001.226.
  10. Z. Huang, Intrabeam scattering in an x-ray FEL driver, Technical Report No. SLAC-TN-05-026, Stanford Linear Accelerator Center, Stanford University, Stanford, CA, 2002.
  11. S. Heifets, G. Stupakov, and S. Krinsky, Coherent synchrotron radiation instability in a bunch compressor, Phys. Rev. ST Accel. Beams 5, 064401 (2002).
  12. E. L. Saldin, E. A. Schneidmiller, and M. V. Yurkov, Klystron instability of a relativistic electron beam in a bunch compressor, Nucl. Instrum. Methods Phys. Res., Sect. A 490, 1 (2002).
  13. Z. Huang and K.-J. Kim, Formulas for coherent synchrotron radiation microbunching in a bunch compressor chicane, Phys. Rev. ST Accel. Beams 5, 074401 (2002).
  14. E. L. Saldin, E. A. Schneidmiller, and M. V. Yurkov, Longitudinal space charge-driven microbunching instability in the TESLA test facility linac, Nucl. Instrum. Methods Phys. Res., Sect. A 528, 355 (2004).
  15. E. Prat, P. Craievich, P. Dijkstal, S. Di Mitri, E. Ferrari, T. G. Lucas, A. Malyzhenkov, G. Perosa, S. Reiche, and T. Schietinger, Energy spread blowup by intrabeam scattering and microbunching at the SwissFEL injector, Phys. Rev. Accel. Beams 25, 104401 (2022).
  16. L. H. Yu, Generation of intense UV radiation by subharmonically seeded single-pass free-electron lasers, Phys. Rev. A 44, 5178 (1991).
  17. G. Stupakov, Using the beam-echo effect for generation of short-wavelength radiation, Phys. Rev. Lett. 102, 074801 (2009).
  18. E. Allaria, D. Castronovo, P. Cinquegrana, P. Craievich, M. D. Forno, M. B. Danailov, G. D’Auria, A. Demidovich, G. D. Ninno, S. D. Mitri, B. Diviacco, W. M. Fawley, M. Ferianis, E. Ferrari, L. Froehlich et al., Two-stage seeded soft-x-ray free-electron laser, Nat. Photonics 7, 913 (2013).
  19. P. R. Ribič, A. Abrami, L. Badano, M. Bossi, H.-H. Braun, N. Bruchon, F. Capotondi, D. Castronovo, M. Cautero, P. Cinquegrana, M. Coreno, M. E. Couprie, I. Cudin, M. B. Danailov, G. D. Ninno et al., Coherent soft x-ray pulses from an echo-enabled harmonic generation free-electron laser, Nat. Photonics 13, 555 (2019).
  20. S. Di Mitri, Bunch length compressors, in Proceedings of the CAS—CERN Accelerator School: Free Electron Lasers and Energy Recovery Linacs, Hamburg, Germany, edited by R. Bailey, CERN Yellow Reports: School Proceedings (CERN, Geneva, 2018), Vol. 1/2018, CERN-2018-001-SP.
  21. Y. Ding, P. Emma, Z. Huang, and V. Kumar, Optical klystron enhancement to self-amplified spontaneous emission free electron lasers, Phys. Rev. ST Accel. Beams 9, 070702 (2006).
  22. E. Prat, E. Ferrari, M. Calvi, R. Ganter, S. Reiche, and T. Schmidt, Demonstration of a compact x-ray free-electron laser using the optical klystron effect, Appl. Phys. Lett. 119, 151102 (2021).
  23. N. R. Thompson and B. W. J. McNeil, Mode locking in a free-electron laser amplifier, Phys. Rev. Lett. 100, 203901 (2008).
  24. B. W. J. McNeil, N. R. Thompson, and D. J. Dunning, Transform-limited x-ray pulse generation from a high-brightness self-amplified spontaneous-emission free-electron laser, Phys. Rev. Lett. 110, 134802 (2013).
  25. E. Prat, W. Hu, C. Arrell, M. Calvi, P. Dijkstal, R. Follath, and S. Reiche, Experimental demonstration of mode-coupled and high-brightness self-amplified spontaneous emission in an x-ray free-electron laser, Phys. Rev. Lett. 133, 205001 (2024).
  26. E. Prat, R. Abela, M. Aiba, A. Alarcon, J. Alex, Y. Arbelo, C. Arrell, V. Arsov, C. Bacellar, C. Beard, P. Beaud, S. Bettoni, R. Biffiger, M. Bopp, H.-H. Braun et al., A compact and cost-effective hard x-ray free-electron laser driven by a high-brightness and low-energy electron beam, Nat. Photonics 14, 748 (2020).
  27. E. Prat, A. A. Haddad, C. Arrell, S. Augustin, M. Boll, C. Bostedt, M. Calvi, A. L. Cavalieri, P. Craievich, A. Dax, P. Dijkstal, E. Ferrari, R. Follath, R. Ganter, Z. Geng et al., An x-ray free-electron laser with a highly configurable undulator and integrated chicanes for tailored pulse properties, Nat. Commun. 14, 5069 (2023).
  28. E. Prat, A. Malyzhenkov, G. L. Orlandi, T. Weilbach, and S. Reiche, Enhanced generation of single-spike hard x-ray free-electron laser pulses with lower charge and shorter electron beams in the injector, Phys. Rev. Res. 7, L042060 (2025).
  29. A. Malyzhenkov, Y. P. Arbelo, P. Craievich, P. Dijkstal, E. Ferrari, S. Reiche, T. Schietinger, P. Juranić, and E. Prat, Single- and two-color attosecond hard x-ray free-electron laser pulses with nonlinear compression, Phys. Rev. Res. 2, 042018(R) (2020).
  30. E. Prat, A. Malyzhenkov, C. Arrell, P. Craievich, S. Reiche, T. Schietinger, and G. Wang, Coherent sub-femtosecond soft x-ray free-electron laser pulses with nonlinear compression, APL Photonics 8, 111302 (2023).
  31. L. Serafini and J. B. Rosenzweig, Envelope analysis of intense relativistic quasilaminar beams in rf photoinjectors: mA theory of emittance compensation, Phys. Rev. E 55, 7565 (1997).
  32. Z. Huang, M. Borland, P. Emma, J. Wu, C. Limborg, G. Stupakov, and J. Welch, Suppression of microbunching instability in the linac coherent light source, Phys. Rev. ST Accel. Beams 7, 074401 (2004).
  33. P. Craievich, R. Ischebeck, F. Löhl, G. L. Orlandi, and E. Prat, Transverse deflecting structures for bunch length and slice emittance measurements on SwissFEL, in Proceedings of the FEL 2013, New York, USA (JACoW, Geneva, Switzerland, 2013), pp. 236–241, TUPS014.
  34. E. Prat, P. Dijkstal, E. Ferrari, A. Malyzhenkov, and S. Reiche, High-resolution dispersion-based measurement of the electron beam energy spread, Phys. Rev. Accel. Beams 23, 090701 (2020).
  35. E. Prat, Z. Geng, C. Kittel, A. Malyzhenkov, F. Marcellini, S. Reiche, T. Schietinger, and P. Craievich, Attosecond time-resolved measurements of electron and photon beams with a variable polarization x-band radiofrequency deflector at an x-ray free-electron laser, Adv. Photonics 7, 026002 (2025).
  36. E. Prat, C. Kittel, M. Calvi, P. Craievich, P. Dijkstal, S. Reiche, T. Schietinger, and G. Wang, Experimental characterization of the optical klystron effect to measure the intrinsic energy spread of high-brightness electron beams, Phys. Rev. Accel. Beams 27, 030701 (2024).
  37. A. A. Sorokin, Y. Bican, S. Bonfigt, M. Brachmanski, M. Braune, U. F. Jastrow, A. Gottwald, H. Kaser, M. Richter, and K. Tiedtke, An x-ray gas monitor for free-electron lasers, J. Synchrotron Radiat. 26, 1092 (2019).
  38. G. Geloni, M. Guetg, S. Serkez, and E. Schneidmiller, Revision of optical klystron enhancement effects in self-amplified spontaneous emission free electron lasers, Phys. Rev. Accel. Beams 24, 090702 (2021).
  39. E. Prat, Symmetric single-quadrupole-magnet scan method to measure the 2D transverse beam parameters, Nucl. Instrum. Methods Phys. Res., Sect. A 743, 103 (2014).
  40. K. Flötmann, astra, A Space Charge Tracking Algorithm (DESY, Hamburg, 2017).
  41. T. Liu, N. Huang, H. Yang, Z. Qi, K. Zhang, Z. Gao, S. Chen, C. Feng, W. Zhang, H. Luo, X. Fu, H. Liu, B. Faatz, H. Deng, B. Liu et al., Status and future of the soft x-ray free-electron laser beamline at the shine, Front. Phys. 11, 1172368 (2023).
  42. J. Yan, W. Qin, Y. Chen, W. Decking, P. Dijkstal, M. Guetg, I. Inoue, N. Kujala, S. Liu, T. Long, N. Mirian, and G. Geloni, Terawatt-attosecond hard x-ray free-electron laser at high repetition rate, Nat. Photonics 18, 1293 (2024).

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Phys. Rev. Accel. Beams 29, 020703– Published 10 February, 2026
  • Received 8 October 2025
  • Accepted 14 January 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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