High transformer ratio electron acceleration for CEPC plasma injector

The CEPC Plasma Injector is designed as the beam energy multiplier for avoiding the dipole magnet issue of the Circular Electron Positron Collider (CEPC) booster. Besides the final energy, other requirements including the energy stability, bunch charge and energy spread all make the injector design very challenging. With respect to the electron acceleration, a high transformer ratio plasma wakefield acceleration stage is necessary if we constrain the beam energy at the end of the linac and the plasma injector are 10[Formula: see text]GeV and 45.5[Formula: see text]GeV, respectively. In this work, we use the particle-in-cell code QuickPIC to design the electron acceleration stage. Based on the current conceptual design, a comprehensive analysis of single-parameter tolerance is performed. Through the tolerance studies, we obtain some useful guidance for the further optimization of the injector.