FCC-ee中使用多极注入冲击磁铁的同轴补充注入
On-axis top-up injection with multipole injection kicker in FCC-ee
AI总结：
本研究针对FCC-ee的同轴补充注入，提出补偿型多极注入冲击磁铁方案，可将Z模式下循环束水平发射度增长控制在约7%、垂直方向低于2%，是有潜力的候选方案。
AI中文摘要：
由于束流寿命较短，FCC-ee需要补充注入来维持高亮度。当前基线方案依赖于带有常规轨道 bump 的同轴非能量注入；本研究调查了一种基于多极注入冲击磁铁（MIK）的替代同轴方案。FCC-ee的束流参数对MIK的场分布提出了挑战性要求，其必须兼具用于循环束的大无场区、窄过渡区，以及所有运行模式下注入区足够均匀的场。为缓解这些挑战性要求同时限制对循环束的残余 kick，提出了补偿型MIK方案，其中在主MIK上游放置一个补偿型MIK（CMIK），并针对不同相位推进推导了两个装置间所需的光学和场对称性条件。采用脉冲导体冲击磁铁作为首选设计，并针对Z运行模式评估其对循环束的影响及注入性能。在Z模式下，近零相位推进补偿方案将循环束的单次通过发射度增长限制为水平方向约7%、垂直方向低于2%，而注入束则需要传输线预补偿以缓解注入区的场梯度。这些结果表明，补偿型MIK注入是FCC-ee同轴补充注入的有潜力候选方案。
英文摘要：
Top-up injection is required in FCC-ee to maintain high luminosity given the short beam lifetime. The present baseline relies on on-axis off-energy injection with a conventional orbit bump; in this work, an alternative on-axis scheme based on a multipole injection kicker (MIK) is investigated. The FCC-ee beam parameters place challenging demands on the MIK field distribution, which must combine a large field-free region for the circulating beam, a narrow transition region, and a sufficiently uniform field in the injection region across all operation modes. To relax these challenging requirements while limiting the residual kick on the circulating beam, a compensated MIK scheme is proposed, in which a compensation MIK (CMIK) is placed upstream of the main MIK, and the required optics and field-symmetry conditions between the two devices are derived for different phase advances. The pulsed-conductor kicker is adopted as the preferred design, and its influence on the circulating beam and its injection performance are evaluated for the Z operation mode. In the Z mode, the near-zero phase-advance compensated scheme limits the single-pass emittance growth of the circulating beam to about $7\%$ horizontally and below $2\%$ vertically, while the injected beam requires transfer-line pre-compensation to mitigate the field gradient in the injection region. These results indicate that compensated MIK injection is a promising candidate for FCC-ee on-axis top-up injection.
