Next-generation plasma-based accelerators can push electron beams to GeV energies within centimeter distances. The plasma, excited by a driver pulse, is indeed able to sustain huge electric fields that can efficiently accelerate a trailing witness bunch, which was experimentally demonstrated on multiple occasions. Thus, the main focus of the current research is being shifted towards achieving a high quality of the beam after the plasma acceleration. In this paper we present a beam-driven plasma wakefield acceleration experiment, where initially preformed high-quality witness beam was accelerated inside the plasma and characterized. In this experiment the witness beam quality after the acceleration was maintained on high level, with 0.2% final energy spread and $3.8\mu \mathrm{m}$ resulting normalized transverse emittance after the acceleration. In this article, for the first time to our knowledge, the emittance of the plasma wakefield accelerated beam was directly measured.

中文翻译：

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束流驱动的等离子体尾流场加速电子束的首次发射率测量

下一代基于等离子体的加速器可以将电子束推向厘米范围内的GeV能量。由驱动器脉冲激发的等离子体确实能够维持巨大的电场，该电场可以有效地加速尾随的目击者束，这在多次场合下都得到了实验证明。因此，当前研究的主要焦点正转向在等离子加速后实现光束的高质量。在本文中，我们提出了一个光束驱动的等离子体尾场加速实验，该实验最初是在等离子体内部加速了高质量的目击光束，并对其进行了表征。在该实验中，加速后的见证光束质量保持在较高水平，最终能量散布为0.2％，$3.8\mu \mathrm{米}$加速后得到的归一化横向发射率。在本文中，就我们所知，这是首次直接测量了等离子体尾波加速束的发射率。