GeV Electron Acceleration by Self-waveguiding Pulses *

We present the first demonstration of multi-GeV LWFA in a fully optically formed plasma waveguide. On the ALEPH laser at CSU, novel waveguiding techniques [1,2], were applied to PW-scale pulses over 20 cm, driving GeV electron acceleration. Employing the self-waveguiding method [2], a J₀ Bessel beam is formed along an extended gas jet composed of a 0.5 cm Ar-doped H₂ ionization injection region and 19.5 cm pure H₂ guiding section (H₂ density~10¹⁸ cm^-3).  This ‘index structuring’ J₀ beam ionizes a plasma column which expands outwards, driving a shock in the neutral gas at the plasma boundary. A high intensity pulse (10¹⁹ W/cm², 35 μm waist) is then injected into the prepared index profile. The leading edge of the pulse ionizes the neutral shock, generating an “on-the-fly” waveguiding structure for the rest of the pulse. Concurrently, the peak of the pulse drives a wakefield in the plasma along the axis.

We present guided pulse output spectra and modes, plasma waveguide interferometry, accelerated electron spectra, and simulations fully mapping the channel formation and LWFA processes.