Laser-driven, quasimonoenergetic electron beams of up to $\sim 200\mathrm{MeV}$ in energy have been observed from steady-state-flow gas cells. These beams emitted within a low-divergence cone of $2.1\pm 0.5\mathrm{mrad}$ FWHM display unprecedented shot-to-shot stability in energy (2.5% rms), pointing (1.4 mrad rms), and charge (16% rms) owing to a highly reproducible gas-density profile within the interaction volume. Laser-wakefield acceleration in gas cells of this type provides a simple and reliable source of relativistic electrons suitable for applications such as the production of extreme-ultraviolet undulator radiation.

Laser-plasma wakefield accelerators have seen tremendous progress, now capable of producing quasi-monoenergetic electron beams in the GeV energy range with few-femtoseconds bunch duration. Scaling these accelerators to the nanocoulomb range would yield hundreds of kiloamperes peak current and stimulate the next generation of radiation sources covering high-field THz, high-brightness X-ray and γ-ray sources, compact free-electron lasers and laboratory-size beam-driven plasma accelerators. However, accelerators generating such currents operate in the beam loading regime where the accelerating field is strongly modified by the self-fields of the injected bunch, potentially deteriorating key beam parameters. Here we demonstrate that, if appropriately controlled, the beam loading effect can be employed to improve the accelerator’s performance. Self-truncated ionization injection enables loading of unprecedented charges of ∼0.5 nC within a mono-energetic peak. As the energy balance is reached, we show that the accelerator operates at the theoretically predicted optimal loading condition and the final energy spread is minimized.

Laser-driven particle and photon beams and some applications K W D Ledingham and W Galster-Robust energy enhancement of ultrashort pulse laser accelerated protons from reduced mass targets K Zeil, J Metzkes, T Kluge et al.-Recent citations Marco Borghesi-Enhanced target normal sheath acceleration using colliding laser pulses J. Ferri et al-Detection and analysis of laser driven proton beams by calibrated Gafchromic HD-V2 and MD-V3 radiochromic films X. H.

We present a general expression for the maximum ion energy observed in experiments with thin foils irradiated by high-intensity laser pulses. The analytical model is based on a radially confined surface charge set up by laser accelerated electrons on the target rear side. The only input parameters are the properties of the laser pulse and the target thickness. The predicted maximum ion energy and the optimal laser pulse duration are supported by dedicated experiments for a broad range of different ions.