Positron transport and acceleration in beam-driven plasma wakefield accelerators using finite radius plasmas*

The transport and acceleration of positron beams is a crucial challenge on the path towards plasma-based particle colliders. In this work, a finite radius plasma is proposed to generate wakefields that can focus and accelerate positron beams in a plasma wakefield accelerator. The finite radius plasma reduces the restoring force acting on the plasma electrons forming the plasma wakefield, resulting in an elongation of the on-axis return point of the electrons and, hence, creating a long, high-density electron filament. This results in a region with accelerating and focusing fields for positrons, allowing for the acceleration and quality-preserving transport of high-charge positron beams.