The ATF2 beam line at KEK was built to validate the operating principle of a novel final-focus scheme devised to demagnify high-energy beams in future linear lepton colliders; to date vertical beam sizes as small as 41 nm have been demonstrated. However, this could only be achieved with an electron bunch intensity $\sim 10\%$ of nominal, and it has been found that wakefield effects limit the beam size for bunch charges approaching the design value of ${10}^{10}{e}^{-}$. We present studies of the impact of wakefields on the production of “nanobeams” at the ATF2. Wake potentials were evaluated for the ATF2 beam line elements and incorporated into a realistic transport simulation of the beam. The effects of both static (component misalignments and rolls, magnet strength errors and beam position monitor resolution) and dynamic (position and angle jitter) imperfections were included and their effects on the beam size evaluated. Mitigation techniques were developed and applied, including orbit correction, dispersion-free steering, wakefield-free steering, and interaction point tuning knobs. Explicit correction knobs to compensate for wakefield effects were studied and applied, and found to significantly decrease the intensity dependence of the beam size.

中文翻译：

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在KEK加速器测试设施2上产生纳米束的韦克菲尔德效应和缓解技术

位于KEK的ATF2光束线旨在验证新颖的最终聚焦方案的工作原理，该方案旨在减少未来的线性轻子对撞机中的高能光束；迄今为止，已经证明了垂直光束尺寸小至41 nm。但是，这只能通过电子束强度来实现$〜10％$ 的标称值，已经发现尾波场效应会限制束电荷的束大小接近设计的 ${10}^{10}{Ë}^{-}$。我们介绍了在ATF2上尾波场对“ nanobeams”产生的影响的研究。评估了ATF2光束线元素的唤醒电势，并将其纳入了光束的真实传输模拟中。包括静态（部件未对准和滚动，磁体强度误差和光束位置监控器分辨率）和动态（位置和角度抖动）缺陷的影响，并评估了它们对光束尺寸的影响。开发并应用了缓解技术，包括轨道校正，无色散转向，无尾场转向和交互点调整旋钮。研究并应用了显式校正旋钮来补偿尾波场效应，并发现该旋钮显着降低了光束尺寸的强度依赖性。