The achromatic telescopic squeezing (ATS) scheme has brought an essential conceptual foundation to the HL-LHC project, making possible a strong and clean (achromatic) reduction of ${\beta }^{*}$, an important parameter with respect to which several HL-LHC sub-systems were dimensioned (e.g., the 150 mm aperture of the new inner triplet quadrupoles) or justified (crab-cavities for mitigating the geometric luminosity loss factor at low ${\beta }^{*}$ and subsequent large crossing-angle). The basic mechanics of the scheme is shortly reminded, highlighting as well some of its by-products (Landau damping, long-range beam-beam mitigation with octupoles), and a recent improvement which made possible an early, but still partial, implementation of ATS optics in the LHC for the 2017 and 2018 LHC physics runs. The main focus of the paper will be on the experimental validation of the scheme, via the development of dedicated machine configurations and high-intensity beam tests which took place in Run 2. The paper will conclude on the configuration presently in mind to operate the LHC during its third exploitation period (Run 3), while trying to ensure a smooth enough transition toward the HL-LHC, in terms of optics, beam parameters, and dedicated beam manipulations (${\beta }^{*}$-leveling).

中文翻译：

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消色差伸缩式压缩方案和副产品：从概念到验证

消色差伸缩式压缩（ATS）方案为HL-LHC项目带来了重要的概念基础，从而有可能实现强而干净的消色差 ${\beta }^{*}$，是确定几个HL-LHC子系统的尺寸（例如，新的内部三重态四极杆的150毫米孔径）或调整后的合理参数（用于缓解低几何发光度损失的蟹形腔）的重要参数 ${\beta }^{*}$以及随后的大交叉角）。简短地提醒了该方案的基本原理，重点介绍了该方案的一些副产品（Landau阻尼，使用八极杆的远距离光束缓解）以及最近的改进，这使得该方案的早期但仍部分实施成为可能。 LHC中用于2017年和2018年LHC物理的ATS光学器件运行。本文的主要重点将是通过开发专用的机器配置以及在运行2中进行的高强度光束测试，对方案进行实验验证。本文将就目前操作LHC的配置得出结论。在第三个开发阶段（运行3）期间，同时尝试在光学，光束参数和专用光束操纵方面确保向HL-LHC足够平稳的过渡（${\beta }^{*}$-级）。