论文标题
未来的循环e $^+$ e $^ - $ collider与4 IP的阻抗建模和集体效果
Impedance modelling and collective effects in the Future Circular e$^+$e$^-$ Collider with 4 IPs
论文作者
论文摘要
在真空室设计和参数演化之后，FCC-EE阻抗模型正在不断地密切更新。尤其是，目前，真空专家提出了更厚的负涂层（而不是以前的100 nm），并且已经研究了波纹管的更现实的阻抗模型。此外，考虑到与纵向情况相同的来源，横向阻抗也进行了更新。因此，FCC-EE阻抗数据库正在越来越完整，并且阻抗模型正在完善。在本文中，我们描述了纵向和横向平面中目前可用的机器耦合阻抗，并研究了具有4个相互作用点（IPS）的新的FCC-EE参数集（IPS）的新FCC-EE参数集（IPS）。将结果与先前获得的结果进行了比较，并提出了对梁梁头尾不稳定（X-Z不稳定性）的进一步缓解。
The FCC-ee impedance model is being constantly updated closely following the vacuum chamber design and parameters evolution. In particular, at present, a thicker NEG coating of 150 nm (instead of previous 100 nm) has been suggested by the vacuum experts, and a more realistic impedance model of the bellows has been investigated. Moreover, also the transverse impedance has been updated by considering the same sources as for the longitudinal case. Therefore, the FCC-ee impedance database is getting more complete and the impedance model is being refined. In this paper we describe the presently available machine coupling impedance in both longitudinal and transverse planes, and study the impedance-driven single bunch instabilities (with and without beam-beam interaction) for the new FCC-ee parameter set with 4 interaction points (IPs). The results are compared with the previously obtained ones and a further possible mitigation of the beam-beam head-tail instability (X-Z instability) is proposed.
