Visible-Laser Acceleration of Relativistic Electrons in a Semi-Infinite Vacuum

We demonstrate a new particle acceleration mechanism using 800 nm laser radiation to accelerate relativistic electrons in a semi-infinite vacuum. The experimental demonstration is the first of its kind and is a proof of principle for the concept of laser-driven particle acceleration in a structure loaded vacuum. We observed up to 30 keV energy modulation over a distance of $1000\lambda$, corresponding to a $40\mathrm{MeV}/\mathrm{m}$ peak gradient. The energy modulation was observed to scale linearly with the laser electric field and showed the expected laser-polarization dependence. Furthermore, as expected, laser acceleration occurred only in the presence of a boundary that limited the laser-electron interaction to a finite distance.

Figure 1

The laser beam, electron beam, and boundary configuration.

Figure 2

(a) Layout of the experiment. The tape was moved to a new, not-yet damaged surface for each laser shot. (b) Experimentally observed laser-driven energy modulation.

Figure 3

The experimental confirmation of the Lawson-Woodward theorem.

Figure 4

Dependence of $⟨M⟩$ on $E_z$.

Figure 5

(a) Diagram of the laser electric field orientation. (b) Dependence of $⟨M⟩$ on the polarization angle.