scaling laser-driven electron acceleration
Laser-driven electron acceleration has reached the GeV frontier, by the production of quasi-monoenergetic beams from cm-long plasmas. Besides the longer-term objective of establishing this technique for future high-energy accelerators, our primary goal is to apply these beams to brilliant X-ray generation, by using them to drive an undulator or free-electron laser (FEL). This application places stringent demands on the shot-to shot reproducibility, bunch charge and the energy spread. We have demonstrated both GeV-scale acceleration in a discharge capillary waveguide, and <2% energy spread with unprecedented shot-to-shot reproducibility from a non-turbulent gas target.
By improving these technologies and using 100-TW sub-30-fs pulses from ATLAS-100, we pursue advancing laser-driven acceleration towards several GeV energies, nanocoulomb charges, ever smaller (→ < 1%) energy spread and divergence, and ever better constancy of bunch parameters. In our dedicated HF-4/5 beamline, we plan to investigate the acceleration process in a variable-length gas cell, giving insight into the evolution of the electron pulse with propagation distance as a function of gas density and laser parameters, allowing to choose optimum conditions for a stable capillary accelerator.
Other injection mechanisms (injection laser, density ramp) will also be studied in conjunction with this techniqe in order to identify optimum conditions. By employing staging scenarios we expect to be able to improve the energy spread and the degree of control over the acceleration process and bunch parameters. After its commissioning in 2010, PFS will create ideal prerequisites for generating stable several-GeV mono-energetic electron bunches, wich will open the door for a new generation of compact brilliant X-ray sources and pave the way towards next-generation large-scale accelerators.
contact: S. Karsch
, Zs. Major
contact: S. Karsch
, Zs. Major
references:
Generation of stable, low divergence electron beams by laser-wakefield acceleration in a steady-sate-flow gas cell, J. Osterhoff et al. Phys. Rev. Lett. 101, 085002 (2008)
GeV-scale electron acceleration in gas-filled capillary discharge waveguide, S. Karsch et al. New J. Phys. 9, 415 (2007)
GeV electron beams from a centimetre-scale accelerator, W.P. Leemans et al. Nature Phys. 2, 696 (2006)
Fig. 1. Plasma wave field acceleration in a steady-state-flow gas cell driven by LAP’s ATLAS source results in unprecedented simultaneous stability of electron bunch parameters: divergence ∼0.9 mrad, pointing ∼1.4 mrad, bunch charge ∼15%, peak energy ∼2.5%.