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Vacuum laser acceleration of relativistic electrons using plasma mirror injectors


Accelerating particles to relativistic energies over very short distances using lasers has been a long-standing goal in physics. Among the various schemes proposed for electrons, vacuum laser acceleration has attracted considerable interest and has been extensively studied theoretically because of its appealing simplicity: electrons interact with an intense laser field in vacuum and can be continuously accelerated, provided they remain at a given phase of the field until they escape the laser beam. But demonstrating this effect experimentally has proved extremely challenging, as it imposes stringent requirements on the conditions of injection of electrons in the laser field. Here, we solve this long-standing experimental problem by using a plasma mirror to inject electrons in an ultraintense laser field, and obtain clear evidence of vacuum laser acceleration. With the advent of petawatt lasers, this scheme could provide a competitive source of very high charge (nC) and ultrashort relativistic electron beams.

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Figure 1: Injection of relativistic electrons in ultraintense laser fields using plasma mirrors.
Figure 2: Experimental evidence of vacuum laser acceleration.
Figure 3: Initial conditions of electrons ejected from plasma mirrors.
Figure 4: 3D modelling of laser–electron interaction in vacuum.


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We are grateful to P. d’Oliveira, F. Réau, C. Pothier and D. Garzella for operating the UHI100 laser source. This work was funded by the European Research Council under Contract No. 306708, ERC Starting Grant FEMTOELEC, the Agence Nationale pour la Recherche under contract ANR-14-CE32-0011-03 APERO and LASERLAB-EUROPE (grant agreement no. 284464, EC’s Seventh Framework Programme) through the CHARPAC Joint Research Action. We acknowledge the support of GENCI for access on super computer Curie. Simulations were run using EPOCH, which was developed as part of the UK EPSRC funded projects EP/G054940/1.

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A.L. performed the experiment with S.K. and F.Q.; A.L. analysed the data; A.V. and J.F. calibrated the electron spectrometer. H.V. modified EPOCH for 1D boosted frame simulations. H.V. and M.T. performed the PIC simulations and developed the associated post-processing tools. M.T. developed and exploited the test particle model. All authors participated in the interpretation of the results. A.L. and M.T made the figures. F.Q. and J.F. designed and directed the project with equal contributions, and wrote the paper with inputs from the other authors.

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Correspondence to F. Quéré or J. Faure.

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The authors declare no competing financial interests.

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Thévenet, M., Leblanc, A., Kahaly, S. et al. Vacuum laser acceleration of relativistic electrons using plasma mirror injectors. Nature Phys 12, 355–360 (2016).

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