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Description
Operating at 45.6 GeV with high beam current, low emittances, and long damping times, the FCC-ee low-energy collider configuration is particularly sensitive to collective effects and impedance-induced beam instabilities. Controlling these effects requires a continuously refined impedance model to guide design choices and to establish reliable instability thresholds. Recent studies identify the collimation system as a dominant contributor to the total machine impedance, with geometric effects playing a key role in beam stability.
Within this framework, a flexible, modular, and comprehensive impedance model enables targeted optimization and systematic stability assessments. The total impedance model includes the beam pipe, collimators, RF cavities, bellows, tapers, and beam position monitors.
This work presents the latest FCC-ee impedance model with a full evaluation of collimator impedance, addressing current limitations related to the challenging simulation regime. It provides an in-depth analysis of the contribution of collimators to beam stability, comparing different optics configurations, novel materials, and advanced design solutions, as well as highlighting ongoing progress in impedance modelling, intensity threshold evaluation, and instability mitigation.
| Paper status | Resubmitted proceeding files received and assigned to an editor. Accepted. |
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