Figure (a) Schematic representation of the laser pulse propagating through the preformed guiding channel. (b) Electron density during the interaction of the 10 PW laser pulse focused to a₀ = 85 interacting with the channel with the density at the center n_e = 0.1 n_c and the laser pulse transverse magnetic field component after ≈ 1 mm of propagation.

ABSTRACT: The direct laser acceleration (DLA) of electrons in underdense plasmas can provide hundreds of nC of electrons accelerated to near-GeV energies using currently available lasers. Here we demonstrate the key role of electron transverse displacement in the acceleration and use it to analytically predict the expected maximum electron energies. The energy scaling is shown to be in agreement with full-scale quasi-3D particle-in-cell simulations of a laser pulse propagating through a preformed guiding channel and can be directly used for optimizing DLA in near-future laser facilities. The strategy towards optimizing DLA through matched laser focusing is presented for a wide range of plasma densities paired with current and near-future laser technology. Electron energies in excess of 10 GeV are accessible for lasers at I ∼ 10²¹ W / cm².

More information: R. Babjak, L. Willingale, A. Arefiev, and M. Vranic, Phys. Rev. Lett. 132, 125001, DOI: https://doi.org/10.1103/PhysRevLett.132.125001