Abstract
X-ray free-electron lasers can generate intense and coherent radiation at wavelengths down to the sub-ångström region1,2,3,4,5, and have become indispensable tools for applications in structural biology and chemistry, among other disciplines6. Several X-ray free-electron laser facilities are in operation2,3,4,5; however, their requirement for large, high-cost, state-of-the-art radio-frequency accelerators has led to great interest in the development of compact and economical accelerators. Laser wakefield accelerators can sustain accelerating gradients more than three orders of magnitude higher than those of radio-frequency accelerators7,8,9,10, and are regarded as an attractive option for driving compact X-ray free-electron lasers11. However, the realization of such devices remains a challenge owing to the relatively poor quality of electron beams that are based on a laser wakefield accelerator. Here we present an experimental demonstration of undulator radiation amplification in the exponential-gain regime by using electron beams based on a laser wakefield accelerator. The amplified undulator radiation, which is typically centred at 27 nanometres and has a maximum photon number of around 1010 per shot, yields a maximum radiation energy of about 150 nanojoules. In the third of three undulators in the device, the maximum gain of the radiation power is approximately 100-fold, confirming a successful operation in the exponential-gain regime. Our results constitute a proof-of-principle demonstration of free-electron lasing using a laser wakefield accelerator, and pave the way towards the development of compact X-ray free-electron lasers based on this technology with broad applications.
This is a preview of subscription content, access via your institution
Access options
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$29.99 / 30 days
cancel any time
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
Data availability
All data are available upon reasonable request from the corresponding authors. Source data are provided with this paper.
Code availability
All codes written for use in this study are available upon reasonable request from the corresponding authors.
References
Madey, J. M. J. Stimulated emission of bremsstrahlung in a periodic magnetic field. J. Appl. Phys. 42, 1906–1913 (1971).
Ackermann, W. et al. Operation of a free-electron laser from the extreme ultraviolet to the water window. Nat. Photon. 1, 336–342 (2007).
Emma, P. et al. First lasing and operation of an angstrom-wavelength free-electron laser. Nat. Photon. 4, 641–647 (2010).
Ishikawa, T. et al. A compact X-ray free-electron laser emitting in the sub-angstrom region. Nat. Photon. 6, 540–544 (2012).
Allaria, E. et al. Highly coherent and stable pulses from the FERMI seeded free-electron laser in the extreme ultraviolet. Nat. Photon. 6, 699–704 (2012).
Bostedt, C. et al. Linac Coherent Light Source: the first five years. Rev. Mod. Phys. 88, 015007 (2016).
Tajima, T. & Dawson, J. M. Laser electron accelerator. Phys. Rev. Lett. 43, 267–270 (1979).
Mangles, S. P. et al. Monoenergetic beams of relativistic electrons from intense laser-plasma interactions. Nature 431, 535–538 (2004).
Geddes, C. G. R. et al. High-quality electron beams from a laser wakefield accelerator using plasma-channel guiding. Nature 431, 538–541 (2004).
Faure, J. et al. A laser-plasma accelerator producing monoenergetic electron beams. Nature 431, 541–544 (2004).
Nakajima, K. Towards a table-top free-electron laser. Nat. Phys. 4, 92–93 (2008).
Faure, J. et al. Controlled injection and acceleration of electrons in plasma wakefields by colliding laser pulses. Nature 444, 737–739 (2006).
Corde, S. et al. Observation of longitudinal and transverse self-injections in laser-plasma accelerators. Nat. Commun. 4, 1501 (2013).
Gonsalves, A. J. et al. Tunable laser plasma accelerator based on longitudinal density tailoring. Nat. Phys. 7, 862–866 (2011).
Buck, A. et al. Shock-front injector for high-quality laser-plasma acceleration. Phys. Rev. Lett. 110, 185006 (2013).
Liu, J. S. et al. All-optical cascaded laser wakefield accelerator using ionization-induced injection. Phys. Rev. Lett. 107, 035001 (2011).
Wang, W. T. et al. High-brightness high-energy electron beams from a laser wakefield accelerator via energy chirp control. Phys. Rev. Lett. 117, 124801 (2016).
Steinke, S. et al. Multistage coupling of independent laser-plasma accelerators. Nature 530, 190–193 (2016).
Gonsalves, A. J. et al. Petawatt laser guiding and electron beam acceleration to 8 GeV in a laser-heated capillary discharge waveguide. Phys. Rev. Lett. 122, 084801 (2019).
Ta Phuoc, K. et al. All-optical Compton gamma-ray source. Nat. Photon. 6, 308–311 (2012).
Sarri, G. et al. Ultrahigh brilliance multi-MeV γ-ray beams from nonlinear relativistic Thomson scattering. Phys. Rev. Lett. 113, 224801 (2014).
Yu, C. et al. Ultrahigh brilliance quasi-monochromatic MeV γ-rays based on self-synchronized all-optical Compton scattering. Sci. Rep. 6, 29518 (2016).
Schroeder, C. B., Esarey, E., Geddes, C. G. R., Benedetti, C. & Leemans, W. P. Physics considerations for laser-plasma linear colliders. Phys. Rev. Spec. Top. Accel. Beams 13, 101301 (2010).
Pellegrini, C., Marinelli, A. & Reiche, S. The physics of X-ray free-electron lasers. Rev. Mod. Phys. 88, 015006 (2016).
Huang, Z. & Kim, K.-J. Review of X-ray free-electron laser theory. Phys. Rev. Spec. Top. Accel. Beams 10, 034801 (2007).
Anania, M. P. et al. An ultrashort pulse ultra-violet radiation undulator source driven by a laser plasma wakefield accelerator. Appl. Phys. Lett. 104, 264102 (2014).
Fang, M. et al. Long-distance characterization of high-quality laser-wakefield-accelerated electron beams. Chin. Opt. Lett. 16, 040201 (2018).
van Tilborg, J. et al. Active plasma lensing for relativistic laser-plasma-accelerated electron beams. Phys. Rev. Lett. 115, 184802 (2015).
Maier, A. R. et al. Demonstration scheme for a laser-plasma-driven free-electron laser. Phys. Rev. X 2, 031019 (2012).
Huang, Z., Ding, Y. & Schroeder, C. B. Compact X-ray free-electron laser from a laser-plasma accelerator using a transverse-gradient undulator. Phys. Rev. Lett. 109, 204801 (2012).
Loulergue, A. et al. Beam manipulation for compact laser wakefield accelerator based free-electron lasers. New J. Phys. 17, 023028 (2015).
Khojoyan, M. et al. Transport studies of LPA electron beam towards the FEL amplification at COXINEL. Nucl. Instrum. Methods Phys. Res. A 829, 260–264 (2016).
Seggebrock, T., Maier, A. R., Dornmair, I. & Grüner, F. Bunch decompression for laser-plasma driven free-electron laser demonstration schemes. Phys. Rev. Spec. Top. Accel. Beams 16, 070703 (2013).
Schlenvoigt, H. P. et al. A compact synchrotron radiation source driven by a laser-plasma wakefield accelerator. Nat. Phys. 4, 130–133 (2008).
Fuchs, M. et al. Laser-driven soft-X-ray undulator source. Nat. Phys. 5, 826–829 (2009).
André, T. et al. Control of laser plasma accelerated electrons for light sources. Nat. Commun. 9, 1334 (2018).
Ratner, D. et al. FEL gain length and taper measurements at LCLS. In Proc. 2009 Free-Electron Laser Conference 221–224 (JACoW, 2009).
Wu, F. X. et al. Performance improvement of a 200TW/1Hz Ti:sapphire laser for laser wakefield electron accelerator. Opt. Laser Technol. 131, 106453 (2020).
Reiche, S. GENESIS 1.3: a fully 3D time-dependent FEL simulation code, Nucl. Instrum. Methods Phys. Res. Nucl. Instrum. Methods Phys. Res. 429, 243–248 (1999).
Hogan, M. et al. Measurements of high gain and intensity fluctuations in a self-amplified, spontaneous-emission free-electron laser. Phys. Rev. Lett. 80, 289–292 (1998).
Rossbach, J. et al. 10 years of pioneering X-ray science at the free-electron laser FLASH at DESY. Phys. Rep. 808, 1–74 (2019).
Maier, R. et al. Decoding sources of energy variability in a laser-plasma accelerator. Phys. Rev. X 10, 031039 (2020).
Lehe, R. et al. A spectral, quasi-cylindrical and dispersion-free Particle-In-Cell algorithm. Comput. Phys. Commun. 203, 66 (2016).
Jalas, S. et al. Accurate modeling of plasma acceleration with arbitrary order pseudo-spectral particle-in-cell methods. Phys. Plasmas 24, 033115 (2017).
Borland, M. ELEGANT: A flexible SDDS-compliant code for accelerator simulation. Technical Report No. LS-287 (Argonne National Laboratory, 2000).
Flöttmann, K. ASTRA. A space charge tracking algorithm. https://www.desy.de/~mpyflo/ (DESY, 2007).
Xie, M. Exact and variational solutions of 3D eigenmodes in high gain FELs. Nucl. Instrum. Methods Phys. Res. Sect. A 445, 59–66 (2000).
Acknowledgements
We thank D. Wang and B. Liu for discussions and assistance. This work was supported by the Strategic Priority Research Program (B) (grant no. XDB16) and Center for Excellence in Ultra-intense Laser Science of Chinese Academy of Sciences (CAS), the National Natural Science Foundation of China (grant nos. 11127901, 11875065 and 11991072), the Natural Science Foundation of Shanghai (nos 18JC1414800 and 18ZR1444500) and the State Key Laboratory Program of the Chinese Ministry of Science and Technology and CAS Youth Innovation Promotion Association (Y201952).
Author information
Authors and Affiliations
Contributions
R.L., Jiansheng Liu and Z.X. conceived the project. R.L., W.W. and K.F. designed the experiments. W.W., K.F., L.K., C.Y., R.Q., Y.C., Z.Q., Z.Z., M.F., Jiaqi Liu, K.J., H.W., C.W. and Jiansheng Liu performed the experiments and collected the data. Y.L., Y.X., F.W. and X.Y. constructed and ran the Ti:sapphire laser system. K.F. conducted the simulations. K.F. and L.K. analysed the experimental data. K.F., W.W. and R.L. co-wrote the paper. All authors contributed to the experiments and discussions.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Peer review information Nature thanks Luca Giannessi, James Rosenzweig and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Extended data figures and tables
Extended Data Fig. 1 Electron-beam spectra from LWFA.
Energy spectra of the accelerated electron beams for 50 shots measured in spectrometer 1 located 2.3-m downstream of the gas target. Electron beams with an average peak energy of about 490 MeV, r.m.s. energy spread of 0.2–1.2%, r.m.s. divergence of 0.1–0.4 mrad and charges of 10–50 pC were experimentally obtained. The associated fluctuations of the electron beam peak energy were estimated to be less than 3%.
Extended Data Fig. 2 Particle-in-cell simulation results for single-stage LWFA.
a, b, Measured fringe pattern for plasma density diagnosis and the corresponding density profile along the optical axis. c–e, Longitudinal phase space of the trapped electrons and the corresponding accelerating electric field at different positions. f, Longitudinal phase space of the accelerated electrons at the exit of the plasma and the corresponding energy spectrum shown in red. s is the longitudinal position of the electron in an electron beam in the co-moving coordinate. The simulated electron beam had a peak energy of 495 MeV, charge of 25.4 pC, global energy spread of 0.67% in r.m.s. (93% of the total electrons), and normalized projected emittance of 0.23 mm mrad and 0.73 mm mrad in the horizontal and vertical directions, respectively.
Extended Data Fig. 3 Properties of simulated electron beam at the exit of the plasma.
a, Coordinate space distribution of accelerated electrons, with various colours representing the various energies. b, Beam current (blue) and slice energy spread (red) within the beam. RES, relative energy spread. c, Normalized slice emittance of the beam in the horizontal (enx, red) and vertical (eny, blue) directions. Each slice has a length of 31.25 nm, which was set as the grid size in the particle-in-cell simulation.
Extended Data Fig. 4 Electron-beam properties in the beamline.
a, b, Start-to-end simulation for horizontal and vertical envelopes of the electron beam along the beamline with a beam energy of 475 MeV (blue), 490 MeV (red) and 505 MeV (black). c–e, Measured transverse profiles of the electron beam at the entrance of the undulator located 4-m downstream from the gas target without (c) and with (d) focusing and at the exit of the undulator located 9.5-m downstream from the gas target (e). With the quadrupoles installed, the measured r.m.s. size of the electron beam was reduced from approximately 0.8 mm to a minimum value of less than 0.1 mm in the horizontal and vertical directions. f–h, Shot-to-shot pointing distribution over 50 shots (f), and beam size statistics in the horizontal (g) and vertical (h) directions. The relative positions of the quadrupoles (green) and undulators (cyan) are shown in a and b.
Extended Data Fig. 5 Properties of an electron beam with a reference energy of 490 MeV along the beamline.
a–c, Simulated beam envelopes (a), normalized projected emittance (b) and Twiss parameters β (c) of the electron beam in the horizontal (red) and vertical (blue) directions. The beam used for tracking was directly derived from the FBPIC code.
Extended Data Fig. 6 Properties of the electron beam at the entrance of the undulator.
a, Beam current (blue) and slice energy spread (red) within the beam. b, Normalized slice emittance of the beam in the horizontal (red) and the vertical (blue) directions. Despite the slice emittance in the bunch tail increasing substantially (b) and causing an increase in projected emittance (Extended Data Fig. 5b), most of the electrons in the beam still showed a small slice emittance.
Extended Data Fig. 7 Electron-beam spectra detected at the exit of the undulators.
Energy spectra of electron beams for 200 consecutive shots detected with spectrometer 2. The average energy of the electron beam was estimated to be 485 MeV with energy fluctuations of 3.3% and a reproducibility of approximately 100%.
Extended Data Fig. 8 Measured spectra of undulator radiation.
a, b, Spectra of the undulator radiation with a groove density of the grating of 3,000 lines per mm (a) and 500 lines per mm (b). The radiation wavelength was typically centred at 27 nm with a corresponding electron beam energy of 492 MeV, which is reasonably consistent with the measured values shown in Extended Data Fig. 7. The minimum bandwidth was measured to be 2%, which indicated a reasonable agreement with the simulated values in the exponential-gain regime. The measured spectra of broadband spontaneous emission are also depicted with a bandwidth of approximately 7%.
Extended Data Fig. 9 Measured radiation energy at the exit of the undulator for various electron beam charges and relative energy spreads.
The black diamonds represent cases with energy spreads larger than 2% (exponential gain is typically not available under such conditions), and the corresponding linear fitting curve (black dashed line) indicates the spontaneous emission. The radiation emitted by a low-energy-spread electron beam (<1%) typically has energy one to two orders higher than that in spontaneous cases, thus indicating the operation in the exponential-gain regime in the present scheme. The exponential gain of the radiation is illustrated with the orbit kick method in the main text.
Supplementary information
Supplementary Video 1
The e beams continuously measured in the energy spectrometer I.
Supplementary Video 2
The e beams continuously measured in the energy spectrometer II.
Supplementary Video 3
Video recording for the generation of a continuous high-quality e beams.
Source data
Rights and permissions
About this article
Cite this article
Wang, W., Feng, K., Ke, L. et al. Free-electron lasing at 27 nanometres based on a laser wakefield accelerator. Nature 595, 516–520 (2021). https://doi.org/10.1038/s41586-021-03678-x
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41586-021-03678-x
This article is cited by
-
Electro-optic 3D snapshot of a laser wakefield accelerated kilo-ampere electron bunch
Light: Science & Applications (2024)
-
Coherence and superradiance from a plasma-based quasiparticle accelerator
Nature Photonics (2024)
-
Attosecond-Angstrom free-electron-laser towards the cold beam limit
Nature Communications (2023)
-
Femtosecond electron microscopy of relativistic electron bunches
Light: Science & Applications (2023)
-
400nm ultra-broadband gratings for near-single-cycle 100 Petawatt lasers
Nature Communications (2023)
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.