RF Design of Traveling-Wave Accelerating Structures for the FCC-ee Pre-injector Complex

Abstract

The linacs of the FCC-ee (Future Circular Electron-Positron Collider) injector complex will provide the drive beam for positron production and accelerate nominal electron and positron beams up to 6 GeV. Several linacs comprise different traveling-wave (TW) accelerating structures fulfilling the beam dynamics and rf constraints. Notably, high-phase advance large-aperture structures accelerate the positron beam at low energies. All TW structures are rotationally symmetric for easier production. Long-range wakes are damped by HOM detuning. Operating mode and HOM parameters were calculated based on lookup tables and analytic formulas, allowing for rapid scanning of large parameter spaces. In this paper, we present both methodology and realization of the rf design of the TW structures including their pulse compressors