Design of beam transport system integrating active plasma lens for laser-plasma-driven EUV free-electron lasers

Laser-plasma accelerators (LPAs) produce high-quality electron beams with the GeV-level of the energy, the high peak currents and low emittance, making them ideal for compact novel free-electron lasers (FELs). However, the large angular divergence and energy spread of these beams pose challenges for efficient beam transport and overall FEL performance. This study explores the use of an active plasma lens (APL) as a capture block to improve the transport of LPA-generated beams into an undulator. Initial beam parameters were based on published results from LWFA studies. In this report, we present the results of the modeling conducted to design an efficient LPA-based electron beamline and optimize the FEL regime for the extreme ultraviolet (EUV) range. Our goal is to achieve saturation of the photon beam power within a single unit. The results show that the APL enables efficient beam transport and facilitates the generation of high-brightness coherent X-rays. This work underscores the potential of APLs in developing compact FELs and advancing LPA beams. This technology is essential for creating a new generation of FELs at ELI-ERIC in the Czech Republic and within the EuPRAXIA project.