Beam transverse dynamics in laser-plasma accelerators

Beyond beam energy and energy spread, transverse beam parameters are crucial in laser-plasma accelerator projects that aim to deliver a high-quality beam to a user's community. In this article, transverse beam physics is thoroughly studied throughout an entire plasma stage, including a plasma density plateau surrounded by density up-ramp and down-ramp. Physical mechanisms, analytical calculations, and numerical simulations are employed to study the evolution of the beam Twiss parameters and emittance. The key parameters and key roles of the different plasma sections are identified. Guidelines are provided for efficiently minimizing emittance growth all along the plasma acceleration stage and the coupling with upstream and downstream transport lines.