Single beam collective effects in FCC-ee due to beam coupling impedance

TL;DR

This paper analyzes the collective effects caused by beam coupling impedance in FCC-ee, focusing on resistive wall and geometrical sources, to predict and mitigate potential beam instabilities in this high-energy collider.

Contribution

It identifies and evaluates key impedance sources in FCC-ee and discusses their impact on beam stability, providing insights for future collider design and operation.

Findings

Resistive wall impedance significantly affects beam stability.

Geometrical impedance sources can induce beam instabilities.

Strategies for mitigating impedance effects are discussed.

Abstract

The Future Circular Collider study, hosted by CERN to design post-LHC particle accelerator options in a worldwide context, is focused on proton-proton high-energy and electron-positron high-luminosity frontier machines. This new accelerator complex represents a great challenge under several aspects, which involve R&D on beam dynamics and new technologies. One very critical point in this context is represented by collective effects, generated by the interaction of the beam with self-induced electromagnetic fields, called wake fields, which could produce beam instabilities, thus reducing the machines performance and limiting the maximum stored current. It is therefore very important to be able to predict these effects and to study in detail potential solutions to counteract them. In this paper the resistive wall and some other important geometrical sources of impedance for the FCC electron-positron accelera- tor are identified and evaluated, and their impact on the beam dynamics, which in some cases could lead to unwanted instabilities, is discussed.