First demonstration of a hybrid laser-electron-beam driven plasma wakefield accelerator

Plasma based electron acceleration is widely considered as a promising concept for a compact electron accelerator with broad range of future applications from high energy physics to photon science.
These accelerators can be powered by either ultra-intense laser beams (LWFA) or relativistic high-current-density particle beams (PWFA).
Here, we report on a novel approach which combines both schemes in a truly compact experimental setup.
In our “LWFA + PWFA” hybrid accelerator, the electron beam generated by a LWFA stage drives a subsequent PWFA stage where a witness beam is trapped and accelerated.
This strategy aims to combine the unique features of both plasma acceleration techniques, the LWFA stage provides with a compact source of high-current electron beams required as PWFA drivers, while the PWFA stage acts as an energy and brightness transformer for the LWFA output.
In this work, we show the first experimental evidence of accelerating a distinct witness bunch in a LWFA-driven PWFA (LPWFA), within only about one millimeter acceleration distance.
In the beam self-ionizing case, we observe witness energies of around 50 MeV.
By utilizing a counter-propagating pre-ionization laser, the interaction with the plasma becomes stronger, increasing the final energies to around 120 MeV.
Thus, yielding a field gradient of (46+-11) GeV/m which is comparable to what has been shown at large scale facilities.