Observation of monoenergetic electrons from two-pulse ionization injection in quasilinear laser-wakefields.

The generation of low emittance electron beams from laser-driven wakefields is crucial for the development of compact X-ray sources. Here, we show new results for the injection and acceleration of quasi-monoenergetic electron beams in low amplitude wakefields, both experimentally and using simulations. This is achieved by using two laser pulses which decouples the wakefield generation from the electron trapping via ionization injection in addition with temporally limited constructive interference of the driven wakefields. By changing the polarization of the injector pulse, reducing the ionization volume, the electron spectra of the accelerated electron bunches are improved.

The possibility of using a two-pulse approach [1] to inject electrons allows reaching higher electron energies by using a linear drive pulse which is compatible with propagation in a pre-formed channel [2].



[1] N. Bourgeois, J. Cowley, and S. M. Hooker, Phys. Rev. Lett. 111, 155004 (2013).

[2] A. Picksley et al., Phys. Rev. Accel. Beams 23, 081303 (2020).