Electron bunch generation from a plasma photocathode
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Electron bunch generation from a plasma photocathode

  • Author(s): Deng, Aihua
  • Karger, Oliver
  • Heinemann, Thomas
  • Knetsch, Alexander
  • Scherkl, Paul
  • Manahan, Grace Gloria
  • Beaton, Andrew
  • Ullmann, Daniel
  • Wittig, Gregor
  • Habib, Ahmad Fahim
  • Xi, Yunfeng
  • Litos, Mike Dennis
  • O'Shea, Brendan D
  • Gessner, Spencer
  • Clarke, Christine I
  • Green, Selina Z
  • Lindstrøm, Carl Andreas
  • Adli, Erik
  • Zgadzaj, Rafal
  • Downer, Mike C
  • Andonian, Gerard
  • Murokh, Alex
  • Bruhwiler, David Leslie
  • Cary, John R
  • Hogan, Mark J
  • Yakimenko, Vitaly
  • Rosenzweig, James B
  • Hidding, Bernhard
  • et al.

Plasma waves generated in the wake of intense, relativistic laser or particle beams can accelerate electron bunches to giga-electronvolt (GeV) energies in centimetre-scale distances. This allows the realization of compact accelerators having emerging applications, ranging from modern light sources such as the free-electron laser (FEL) to energy frontier lepton colliders. In a plasma wakefield accelerator, such multi-gigavolt-per-metre (GV m$^{-1}$) wakefields can accelerate witness electron bunches that are either externally injected or captured from the background plasma. Here we demonstrate optically triggered injection and acceleration of electron bunches, generated in a multi-component hydrogen and helium plasma employing a spatially aligned and synchronized laser pulse. This ''plasma photocathode'' decouples injection from wake excitation by liberating tunnel-ionized helium electrons directly inside the plasma cavity, where these cold electrons are then rapidly boosted to relativistic velocities. The injection regime can be accessed via optical density down-ramp injection, is highly tunable and paves the way to generation of electron beams with unprecedented low transverse emittance, high current and 6D-brightness. This experimental path opens numerous prospects for transformative plasma wakefield accelerator applications based on ultra-high brightness beams.

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