Demonstration of electron acceleration in a laser-driven dielectric microstructure

Abstract

The enormous size and cost of current state-of-the-art accelerators based on conventional radio-frequency technology has spawned great interest in the development of new acceleration concepts that are more compact and economical. Micro-fabricated dielectric laser accelerators (DLAs) are an attractive approach, because such dielectric microstructures can support accelerating fields one to two orders of magnitude higher than can radio-frequency cavity-based accelerators. DLAs use commercial lasers as a power source, which are smaller and less expensive than the radio-frequency klystrons that power today’s accelerators. In addition, DLAs are fabricated via low-cost, lithographic techniques that can be used for mass production. However, despite several DLA structures having been proposed recently1,2,3,4, no successful demonstration of acceleration in these structures has so far been shown. Here we report high-gradient (beyond 250 MeV m−1) acceleration of electrons in a DLA. Relativistic (60-MeV) electrons are energy-modulated over 563 ± 104 optical periods of a fused silica grating structure, powered by a 800-nm-wavelength mode-locked Ti:sapphire laser. The observed results are in agreement with analytical models and electrodynamic simulations. By comparison, conventional modern linear accelerators operate at gradients of 10–30 MeV m−1, and the first linear radio-frequency cavity accelerator was ten radio-frequency periods (one metre) long with a gradient of approximately 1.6 MeV m−1 (ref. 5). Our results set the stage for the development of future multi-staged DLA devices composed of integrated on-chip systems. This would enable compact table-top accelerators on the MeV–GeV (106–109 eV) scale for security scanners and medical therapy, university-scale X-ray light sources for biological and materials research, and portable medical imaging devices, and would substantially reduce the size and cost of a future collider on the multi-TeV (1012 eV) scale.

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Figure 1: DLA structure and experimental set-up.
Figure 2: Demonstration of energy modulation.
Figure 3: Measurement of acceleration gradient in the 400-nm gap structure.

Change history

  • 06 November 2013

    Minor changes were made to the Acknowledgements section.

References

  1. 1

    Lin, X. E. Photonic band gap fiber accelerator. Phys. Rev. Spec. Top. Accel. Beams 4, 051301 (2001)

    ADS  Article  Google Scholar 

  2. 2

    Mizrahi, A. & Schachter, L. Optical Bragg accelerators. Phys. Rev. E 70, 016505 (2004)

    ADS  Article  Google Scholar 

  3. 3

    Cowan, B. M. Three-dimensional dielectric photonic crystal structures for laser-driven acceleration. Phys. Rev. Spec. Top. Accel. Beams 11, 011301 (2008)

    ADS  Article  Google Scholar 

  4. 4

    Plettner, T., Lu, P. P. & Byer, R. L. Proposed few-optical cycle laser-driven particle accelerator structure. Phys. Rev. Spec. Top. Accel. Beams 9, 111301 (2006)

    ADS  Article  Google Scholar 

  5. 5

    Ginzton, E. L., Hansen, W. W. & Kennedy, W. R. A linear electron accelerator. Rev. Sci. Instrum. 19, 89–108 (1948)

    CAS  ADS  Article  Google Scholar 

  6. 6

    Plettner, T. et al. Visible-laser acceleration of relativistic electrons in a semi-infinite vacuum. Phys. Rev. Lett. 95, 134801 (2005)

    CAS  ADS  Article  Google Scholar 

  7. 7

    Shimoda, K. Proposal for an electron accelerator using an optical maser. Appl. Opt. 1, 33–35 (1962)

    ADS  Article  Google Scholar 

  8. 8

    Piestrup, M. A., Rothbart, G. B., Fleming, R. N. & Pantell, R. H. Momentum modulation of a free electron beam with a laser. J. Appl. Phys. 46, 132–137 (1975)

    ADS  Article  Google Scholar 

  9. 9

    Palmer, R. B. Interaction of relativistic particles and free electromagnetic waves in the presence of a static helical magnet. J. Appl. Phys. 43, 3014–3023 (1972)

    CAS  ADS  Article  Google Scholar 

  10. 10

    van Steenbergen, A., Gallardo, J., Sandweiss, J. & Fang, J.-M. Observation of energy gain at the BNL inverse free-electron-laser accelerator. Phys. Rev. Lett. 77, 2690–2693 (1996)

    CAS  ADS  Article  Google Scholar 

  11. 11

    Marshall, T. C. Free-Electron Lasers 24–26 (McMillan, 1985)

    Google Scholar 

  12. 12

    Takeda, Y. & Matsui, I. Laser linac with grating. Nucl. Instrum. Methods 62, 306–310 (1968)

    CAS  ADS  Article  Google Scholar 

  13. 13

    Mizuno, K., Pae, J., Nozokido, T. & Furuya, K. Experimental evidence of the inverse Smith-Purcell effect. Nature 328, 45–47 (1987)

    ADS  Article  Google Scholar 

  14. 14

    Breuer, J. & Hommelhoff, P. Laser-based acceleration of non-relativistic electrons at a dielectric structure. Phys. Rev. Lett. (in the press)

  15. 15

    Peralta, E. A. et al. Design, fabrication, and testing of a fused-silica dual-grating structure for direct laser acceleration of electrons. AIP Conf. Proc. 1507, 169–177 (2012)

    CAS  ADS  Google Scholar 

  16. 16

    Plettner, T., Byer, R. L. & Montazeri, B. Electromagnetic forces in the vacuum region of laser-driven layered grating structures. J. Mod. Opt. 58, 1518–1528 (2011)

    ADS  Article  Google Scholar 

  17. 17

    Thompson, M. C. et al. Breakdown limits on gigavolt-per-meter electron-beam-driven wakefields in dielectric structures. Phys. Rev. Lett. 100, 214801 (2008)

    CAS  ADS  Article  Google Scholar 

  18. 18

    Sears, C. M. S. et al. Production and characterization of attosecond electron bunch trains. Phys. Rev. Spec. Top. Accel. Beams 11, 061301 (2008)

    ADS  Article  Google Scholar 

  19. 19

    Ganter, R. et al. Laser-photofield emission from needle cathodes for low-emittance electron beams. Phys. Rev. Lett. 100, 064801 (2008)

    CAS  ADS  Article  Google Scholar 

  20. 20

    Duris, J. P., Musumeci, P. & Li, R. K. Inverse free electron laser accelerator for advanced light sources. Phys. Rev. Spec. Top. Accel. Beams 15, 061301 (2012)

    ADS  Article  Google Scholar 

  21. 21

    Colby, E. R., England, R. J. & Noble, R. J. A laser-driven linear collider: sample machine parameters and configuration. Proc. 24th Particle Accelerator Conf. C110328 262–264. (2011)

  22. 22

    Moulton, P. F. et al. Tm-doped fiber lasers: fundamentals and power scaling. IEEE J. Sel. Top. Quant. 15, 85–92 (2009)

    CAS  Article  Google Scholar 

  23. 23

    Siemman, R. Energy efficiency of laser driven, structure based accelerators. Phys. Rev. Spec. Top. Accel. Beams 7, 061303 (2004)

    ADS  Article  Google Scholar 

  24. 24

    Plettner, T. & Byer, R. L. Microstructure-based laser-driven free-electron laser. Nucl. Instrum. Methods A 593, 63–66 (2008)

    CAS  ADS  Article  Google Scholar 

  25. 25

    Warner, C. & Rohrlich, F. Energy loss and straggling of electrons. Phys. Rev. 93, 406–407 (1954)

    CAS  ADS  Article  Google Scholar 

  26. 26

    Roberts, T. J. & Kaplan, D. M. G4beamline simulation program for matter-dominated beamlines. Proc. 22nd Particle Accelerator Conf. C070625 3468–3470 (2007)

  27. 27

    Soong, K., Byer, R. L., Colby, E., England, R. J. & Peralta, E. A. Laser damage threshold measurements of optical materials for direct laser accelerators. AIP Conf. Proc. 1507, 511–515 (2012)

    CAS  ADS  Google Scholar 

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Acknowledgements

We thank R. Noble, J. Spencer, O. Solgaard and J. Harris for discussions, J. Nelson, D. McCormick and K. Jobe for technical assistance at SLAC, and M. Tang, M. Mansourpour, N. Latta, M. Stevens, J. Conway and U. Thumser for technical assistance at the Stanford Nanofabrication Facility (SNF). This work was supported by the US DoE (grant no. DE-FG03-92ER40693) and DARPA (grant no. N66001-11-1-4199). Device fabrication took place at SNF, which is supported by the NSF under grant ECS-9731293. Work by G.T., J.M. and E.B.S. supported by US Defense Threat Reduction Agency (DTRA) grant HDTRA1-09-1-0043.

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Contributions

E.A.P., K.S., R.J.E., E.R.C. and R.L.B. designed the experiment. E.A.P., K.S., R.J.E., E.R.C., Z.W. and B.M. built the experiment, and with the help of C.McG. and J.McN., carried out the experiment. E.A.P. designed and fabricated the structure. E.A.P. and K.S. wrote the data analysis software and analysed the results, and E.B.S. contributed to that software. K.S. developed the analytical model. K.S., B.M., J.McN, B.C. and B.S. performed supporting simulations. G.T, J.McN, E.B.S. and K.J.L. provided feedback to improve the experiment. K.S. and K.J.L. designed and constructed the vacuum damage threshold measurement set-up, and K.S. carried out such measurements. D.W. performed hardware upgrades and installation. E.A.P. wrote the manuscript with contributions from K.S. and R.J.E. and revisions by all.

Corresponding author

Correspondence to R. L. Byer.

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The authors declare no competing financial interests.

Extended data figures and tables

Extended Data Figure 1 DLA sample preparation.

a, Diagram of the structure fabrication process. In side view, the electron beam traverses the structure from left to right. In front view, the beam goes into the page. Laser is incident from above. See Methods for details. b, Picture of a completed wafer with hundreds of DLA structures. c, Diagram of a finished sample ready for beam tests including four DLA structures, alignment channels, a wedge for spatial alignment of the laser to the electron beam, and a metal coating for perpendicular alignment of the laser. d, Picture of a single DLA structure on a fingertip.

Extended Data Figure 2 Reference spectrometer screen images and spectrum.

a, Spectrometer screen image showing the 60-MeV beam with no DLA structure in place. b, Spectrometer screen image of the beam after traversing the grating structure. c, Projection of b onto the energy axis yields the energy spectrum (black crosses) in agreement with particle scattering simulations (blue dots). The corresponding least squares spectrum fit (orange curve) is also shown.

Extended Data Figure 3 Analytical treatment of laser-driven electron energy modulation.

a, Picosecond-scale electron beam partitioned into a series of finite slices over one optical cycle of the laser (for example, the green slice is at optimal phase for acceleration). b, Each slice samples a different phase of the laser pulse and therefore experiences a corresponding net energy shift with a negligible effect on the energy profile (for example, the green slice experiences net energy gain). c, When all contributions are superimposed, the initial single distribution (dashed blue line) becomes a double-peaked profile (red line), in agreement with particle tracking simulations (black crosses).

Extended Data Figure 4 Gradient measurement on 800-nm gap structure.

Calculated gradient (blue filled circles) G as a function of longitudinal electric field E0 showing expected linear dependence (dashed blue line) and reduced strength when compared to the 400-nm gap structure, as expected for a larger gap. The dashed black line is the measurement noise level. Error bars, 68% confidence interval.

Extended Data Figure 5 Experimental verification of direct laser acceleration.

a, Gradient in the 800-nm gap structure for an input pulse energy of 105.2 ± 3.6 µJ. As the laser polarization is rotated away from the direction of electron propagation by an angle ϕ, the acceleration gradient varies as G cosϕ. Data for ϕ < 0 were taken last, and beam quality had degraded. b, Gradient in the 400-nm gap structure at an input pulse energy of 29.3 ± 0.4 µJ, averaging the observed modulation over many shots taken at an optimal timing overlap. As the laser incidence angle deviates from perpendicular by an angle θ, the observed gradient decreases according to the expected relationship, equation (2) in Supplementary Information. Data are shown as blue filled circles with the corresponding least squares fit shown as green lines. The dashed black line is the measurement noise level. Error bars, 68% confidence interval.

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Supplementary Information

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Peralta, E., Soong, K., England, R. et al. Demonstration of electron acceleration in a laser-driven dielectric microstructure. Nature 503, 91–94 (2013). https://doi.org/10.1038/nature12664

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