[论文解读] CEPC Technical Design Report - Accelerator

Abdallah, Waleed, de Freitas, Tiago CarlosAdorno+1107 more|arXiv (Cornell University)|Jan 1, 2023

Particle Accelerators and Free-Electron Lasers被引用 4

一句话总结

《CEPC技术设计报告 - 加速器》提出了对CEPC对撞机的全面设计，重点聚焦于Z玻色子共振能量下的束流动力学、晶格光学及极化控制。报告详细描述了康普顿极化计在束流极化测量中的集成应用，实现了低于1%的系统不确定度，并为未来在对撞机晶格中实现极化束流奠定了框架。

ABSTRACT

The Circular Electron Positron Collider (CEPC) is a large scientific project initiated and hosted by China, fostered through extensive collaboration with international partners. The complex comprises four accelerators: a 30 GeV Linac, a 1.1 GeV Damping Ring, a Booster capable of achieving energies up to 180 GeV, and a Collider operating at varying energy modes (Z, W, H, and ttbar). The Linac and Damping Ring are situated on the surface, while the Booster and Collider are housed in a 100 km circumference underground tunnel, strategically accommodating future expansion with provisions for a Super Proton Proton Collider (SPPC). The CEPC primarily serves as a Higgs factory. In its baseline design with synchrotron radiation (SR) power of 30 MW per beam, it can achieve a luminosity of 5e34 /cm^2/s^1, resulting in an integrated luminosity of 13 /ab for two interaction points over a decade, producing 2.6 million Higgs bosons. Increasing the SR power to 50 MW per beam expands the CEPC's capability to generate 4.3 million Higgs bosons, facilitating precise measurements of Higgs coupling at sub-percent levels, exceeding the precision expected from the HL-LHC by an order of magnitude. This Technical Design Report (TDR) follows the Preliminary Conceptual Design Report (Pre-CDR, 2015) and the Conceptual Design Report (CDR, 2018), comprehensively detailing the machine's layout and performance, physical design and analysis, technical systems design, R&D and prototyping efforts, and associated civil engineering aspects. Additionally, it includes a cost estimate and a preliminary construction timeline, establishing a framework for forthcoming engineering design phase and site selection procedures. Construction is anticipated to begin around 2027-2028, pending government approval, with an estimated duration of 8 years. The commencement of experiments could potentially initiate in the mid-2030s.

研究动机与目标

• 为CEPC对撞机在Z玻色子共振能量下开发一种技术上可行且精确的束流极化测量系统。
• 设计并模拟一种康普顿极化计，能够以高精度测量横向束流极化。
• 识别并减轻由偶极子强度、束流能量展宽和探测器位置引起的极化测量系统不确定度。
• 实现未来将极化束流集成到CEPC晶格中，包括自旋旋转器和极化计。
• 通过共振去极化和极化监测，为物理计划提供精确的束流能量校准支持。

提出的方法

• 基于激光-电子散射的康普顿极化计，用于测量横向束流极化。
• 采用1.165 eV（或在V3版本中为2.3305 eV）激光，平均功率5 W，重复频率1–10 Hz，使用5 ns或5 ps脉冲。
• 建模束流参数，包括σE = 0.13%、βy = 40 m、σx = 98 μm、σy = 7.5 μm、σz = 8.7 mm。
• 采用硅探测器模拟散射粒子的探测，同时考虑金刚石和像素探测器等替代方案。
• 量化系统不确定度来源：偶极子强度（0.062%）、漂移距离（0.007–0.051%）、束流能量（0.0001%）、探测器能量分辨率（0.278%）以及激光极化（0.2%）。
• 提出集成极化先导束和脉冲激光运行，以实现常规束流能量校准。

实验结果

研究问题

• RQ1 如何在CEPC对撞机中实现低于1%系统不确定度的束流极化测量？
• RQ2 康普顿极化测量中的主要系统误差来源是什么？如何将其最小化？
• RQ3 康普顿极化计能否适配以测量未来极化束流运行中的纵向极化分量？
• RQ4 为实现稳定、高精度的极化测量，所需的激光和光学系统参数是什么？
• RQ5 如何在不干扰束流动力学的前提下将极化计集成到CEPC晶格中？

主要发现

• 横向极化测量的系统不确定度保持在1%以下，关键参数（如偶极子强度和探测器分辨率）的累积影响为0.6%。
• 主要系统贡献来自偶极子强度（0.062%）和L2漂移距离（0.051%），均在可接受范围内。
• 激光极化不确定度为0.2%，束流能量展宽仅贡献0.0001%，表明系统具有高度稳定性。
• 该设计支持未来扩展以测量纵向极化分量，从而实现极化对撞束流。
• 模拟结果证实，硅、金刚石或像素探测器均可用于散射粒子探测，但最终选择仍需详细电子学和模拟支持。
• 该框架支持通过共振去极化实现束流能量校准，并支持极化先导束的集成。