New Journal of Physics (Jan 2022)

Effect of driver charge on wakefield characteristics in a plasma accelerator probed by femtosecond shadowgraphy

  • Susanne Schöbel,
  • Richard Pausch,
  • Yen-Yu Chang,
  • Sébastien Corde,
  • Jurjen Couperus Cabadağ,
  • Alexander Debus,
  • Hao Ding,
  • Andreas Döpp,
  • F Moritz Foerster,
  • Max Gilljohann,
  • Florian Haberstroh,
  • Thomas Heinemann,
  • Bernhard Hidding,
  • Stefan Karsch,
  • Alexander Köhler,
  • Olena Kononenko,
  • Thomas Kurz,
  • Alastair Nutter,
  • Klaus Steiniger,
  • Patrick Ufer,
  • Alberto Martinez de la Ossa,
  • Ulrich Schramm,
  • Arie Irman

DOI
https://doi.org/10.1088/1367-2630/ac87c9
Journal volume & issue
Vol. 24, no. 8
p. 083034

Abstract

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We report on experimental investigations of plasma wave structures in a plasma wakefield acceleration (PWFA) stage which is driven by electron beams from a preceding laser plasma accelerator. Femtosecond optical probing is utilized to allow for direct visualization of the plasma dynamics inside the target. We compare two regimes in which the driver propagates either through an initially neutral gas, or a preformed plasma. In the first case, plasma waves are observed that quickly damp after a few oscillations and are located within a narrow plasma channel ionized by the driver, having about the same transverse size as the plasma wakefield cavities. In contrast, for the latter robust cavities are recorded sustained over many periods. Furthermore, here an elongation of the first cavity is measured, which becomes stronger with increasing driver beam charge. Since the cavity length is linked to the maximum accelerating field strength, this elongation implies an increased field strength. This observation is supported by 3D particle-in-cell simulations performed with PIConGPU. This work can be extended for the investigation of driver depletion by probing at different propagation distances inside the plasma, which is essential for the development of high energy efficiency PWFAs.

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