WEYAT0104
CERN, Meyrin, Switzerland
LNF-INFN, Frascati, Italy
INFN-Roma1, Rome, Italy
WEXAT0104
IHEP, Beijing, People’s Republic of China
Sapienza University of Rome, Rome, Italy
KEK, Ibaraki, Japan
LNF-INFN, Frascati, Italy
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WEYAT0104 |
Collective Effects Studies in FCC-ee | |
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| The high luminosity foreseen in the future electron-positron circular collider (FCC-ee) necessitates very intense multi-bunch colliding beams with very small transverse beam sizes at the collision points. This requires emittances comparable to those of the modern synchrotron light sources. At the same time, the stored beam currents should be close to the best values achieved in the last generation of particle factories. This combination of opposite factors represents a big challenge in order to preserve a high beam quality avoiding, at the same time, a machine performance degradation. As a consequence, a careful study of the collective effects and some solutions for the mitigation of foreseen instabilities is required. In this contribution we discuss the current status of these studies. | ||
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Slides WEYAT0104 [15.810 MB] | |
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WEXAT0104 |
Beam-beam Simulations including Coupling Impedance | |
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| The design performance of future e+e− ring colliders has been pushed to new extreme based on the crab-waist scheme. The new found coherent head-tail instability (X-Z instability) may induce the horizontal beam size blowup and reduce the machine performance. The longitudinal coupling impedance would distort the phase space: lengthen the bunch and bring incoherent synchrotron tune spread. The simulation study has found the clear influence of longitudinal impedance on the X-Z instability in both CEPC and FCCee. With the evolvement of future machine design process, the transverse impedance has also been included. The results show that a vertical beam-beam TMCI-like instability may be induced when the impedance is considered. It is first found in e+e− colliders. Some similar study at SuperKEKB will also be presented. It could be expected or concluded that different effect would couple and determine the final performance together in present and future high performance crab-waist colliders. Separate effect study seems not enough to evaluate and predict the machine performance/stability. | ||
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Slides WEXAT0104 [3.976 MB] | |
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