Energy spread minimization in a beam-driven plasma wakefield accelerator

Next-generation plasma-based accelerators can push electron bunches to gigaelectronvolt energies within centimetre distances1,2. The plasma, excited by a driver pulse, generates large electric fields that efficiently accelerate trailing witness bunch3–5, enabling the realization of laboratory-scale applications ranging from high-energy colliders6 ultrabright light sources7. So far, several experiments have demonstrated accelerations8–10 but resulting beam quality, particularly energy spread, is still far state-of-the-art conventional accelerators. Here we show results beam-driven plasma acceleration experiment where used an bunch as followed ultrashort bunch. By setting positive chirp on bunch, its longitudinal phase space rotated during acceleration, in ultralow spread even lower than at entrance. This result will significantly impact optimization process and implementation forthcoming compact machines for user-oriented applications. In wakefield accelerator, reduced with respect entrance, which achieved through rotates bunches’ space.