For future linear colliders, a nanometer-scale beam size at the interaction point (IP) is one of the most challenging technical aspects. To explore the feasibility of a final focus system with a high chromaticity level, comparable to that of the Compact Linear Collider, the ultralow ${\beta }^{*}$ optics has been proposed and tuned at the KEK Accelerator Test Facility 2. In this paper, the recent experimental results are presented, which demonstrate the capability of achieving and stabilizing a vertical average beam size of 60 nm and below at the virtual IP. The observed vertical beam size is about 20 nm above the numerical predictions in the presence of static and dynamic imperfections. We interpret this discrepancy as beam size growth due to multipole fields, beam jitters and wakefield effects, and diagnostic errors.

中文翻译：

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在KEK加速器测试设施2上调节超低β*光学元件

对于未来的线性对撞机，在相互作用点（IP）处的纳米级光束尺寸是最具挑战性的技术方面之一。探索具有高色度水平，与紧凑型线性对撞机相媲美的超低色散最终聚焦系统的可行性${\beta }^{*}$已经在KEK加速器测试设施2上提出并调整了光学元件。在本文中，本文给出了最近的实验结果，这些结果证明了在虚拟IP上实现并稳定60 nm以下垂直平均光束尺寸的能力。在存在静态和动态缺陷的情况下，观察到的垂直光束尺寸比数值预测值高约20 nm。我们将这种差异解释为由于多极场，光束抖动和尾波场效应以及诊断错误导致的光束尺寸增长。