A fully plasma based electron injector for a linear collider or XFEL*

We demonstrate through high-fidelity particle-in-cell simulations a simple approach for efficiently generating 20+ GeV electron beams with the necessary charge, energy spread, and emittance for use as the injector for an electron arm of a future linear collider or a next generation XFEL. The self-focusing of an unmatched, relatively low quality, drive beam results in self-injection by elongating the wakefield excited in the nonlinear blowout regime. Over pump depletion distances, the drive beam dynamics and self-loading from the injected beam leads to extremely high quality and high energy output beams.For plasma densities of  10¹⁸ cm^-3, PIC simulation results indicate that self-injected beams with 0.52 nC of charge can be accelerated to 20 GeV energies with projected energy spreads, <1% within the beam core, slice normalized emittances as low as 110 nm, a peak normalized brightness >10¹⁹ A/m²/rad², and energy transfer efficiencies >54%.