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TY - CONF AU - Kersevan, R. AU - Garion, C. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Design of the Vacuum System of the FCC-ee Electron-Positron Collider J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - The Future Circular Collider (FCC) Design Study includes the twin storage ring (FCC-ee) where electrons and positrons are stored and made to collide inside two detectors. The vacuum system of FCC-ee must be designed in order to deal with a lower-energy (45.6 GeV), high-current (1390 mA) Z-pole machine and at a later stage with a higher-energy (182.5 GeV) low-current (5.4 mA). The former machine is the most challenging one from the point of view of vacuum, since the photon-stimulated desorption (PSD) generated by the copious synchrotron radiation (SR) fans is quite large. While several concepts have been considered at the beginning, the design retained for the Conceptual Design Report (CDR) is one where the cross-section of the vacuum chamber (VC) in the arcs is a scaled-down version of the one implemented in the SUPERKEKB collider. Contrary to SUPERKEKB tough, the SR fans are absorbed by many short absorbers, with average spacing of 5.8 m. This allow a localization of the PSD gas load and to place lumped pumps in front of the SR absorbers, to maximize the pumping efficiency. The VC design is compatible with the design of the common-yoke dipoles and quadrupoles. The VC material is copper alloy. Optimization of the pressure profiles has been carried out by means of extensive coupled montecarlo simulations, for SR and molecular flow. For the higher energy versions of the machine, for which the SR spectra are characterized by critical energies well above the Compton edge, the localized absorbers facilitate also shielding the tunnel and any radiation-sensitive machine components from X-ray photon damage, by installing short high-Z material around the absorbers. The major features of the CDR relevant for vacuum will be highlighted in the paper. PB - JACoW Publishing CP - Geneva, Switzerland SP - 1319 EP - 1322 KW - collider KW - vacuum KW - photon KW - dipole KW - quadrupole DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-TUPMP035 UR - http://jacow.org/ipac2019/papers/tupmp035.pdf ER -