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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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.
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). https://doi.org/10.1038/nphys3597
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