Enabling energy-doubling at CLARA FEBE: high-quality beam generation in plasma wakefield acceleration

Abstract Plasma-wakefield acceleration (PWFA) has attracted great attention due to its high accelerating gradients, which will drastically reduce the price, footprint, and carbon load of accelerators to be used for medical applications, free electron lasers (FELs), and future high-energy physics experiments. The compact linear accelerator for research and applications (CLARA) at the Daresbury Laboratory is a state-of-the-art electron accelerator for a future FEL test facility, capable of producing 250MeV electron bunches. Recently, a new beamline attached to CLARA, the so-called full energy beam exploitation (FEBE) facility, has been commissioned to provide ultra-short and low-emittance electron bunches. Here, we use the Fourier–Bessel particle-in-cell code to investigate PWFA with a two-bunch configuration at FEBE, aiming to double the energy of the witness bunch while preserving its incoming beam quality. Simulation results indicate that the driver’s trailing portion is tightly focused by the transverse wakefield, leading to a surging beam density and a transition from the linear to the non-linear regime. An appropriate flattened wakefield due to beam loading is achieved assisted with the tailoring of the plasma density. Moreover, the impact of ramping plasma density on beam quality is also discussed.