Figure 4.

Schematic of the double-jet plasma target for the LPWFA proof-of-concept experiment at HZDR. In the first gas jet an LWFA stage is driven by the DRACO laser for the generation of a high-current electron beam. In the second gas jet, the LWFA-produced electron beam drives a PWFA for the production of a new electron beam with largely improved energy and brightness. A thin foil made of kapton is placed at the entrance of the second jet in order to reflect the main laser, while letting the electron beam go through into the second stage. A counter-propagating low-intensity laser can be used in order to fully preionize the hydrogen to facilitate the beam refocusing and enhance the blowout formation in the second stage. (Online version in colour.)