Plasma lens for the focusing of positron bunches

Abstract: The development of effective focusing schemes for positron bunches in plasma accelerators remains a significant challenge, as nonlinear regimes fail to create stable focusing channels for positrons. This work presents a method for focusing and improving the quality of positron bunches using a plasma lens operating in the linear regime. Through numerical simulations, we investigate two distinct focused positron bunch profiles: a purely Gaussian bunch and an elongated, flat-top bunch with Gaussian rising and falling edges. For both configurations, the results demonstrate the capability to achieve high-quality transverse focusing. Furthermore, beyond focusing, the proposed system enables potential possibility to reduce energy spread of positron bunches of the sequence after precursor.