Linac and damping ring designs for the FCC-ee

Salim Ogur , Alexey Barnyakov , Iryna Chaikovska (1) , Robert Chehab (1) , Kazuro Furukawa , Naoko Iida , Takuya Kamitani , Alexey Levichev , Pavel Martyshkin , Fusashi Miyahara , Danila Nikiforov , Katsunobu Oide , Erkcan Ozcan , Yannis Papaphilippou , Sergey Polozov , Louis Rinolfi , Fatih Yaman , Frank Zimmermann

1 LAL - Laboratoire de l'Accélérateur Linéaire

We report the design of the pre-injector chain for the Future Circular e$^+$e$^−$ Collider (FCC-ee) system. The electron beam from a low-emittance RF gun is accelerated by an S-band linac up to 6 GeV. A damping ring at 1.54 GeV is required for emittance cooling of the positron beam. The intermediate energy step from the exit of the S-band linac at 6 GeV to the 20 GeV injection energy of the top-up booster can be provided by the modified Super Proton Synchrotron (SPS), serving as a pre-booster ring (PBR). An alternative option to reach 20 GeV energy would be to extend the S-band linac with a C- or X-band linac. An overall cost optimisation will determine the choice of the final configuration. Beam loss and emittance dilution in the linac due to space charge effects, wakefields, and misalignment of accelerator components can be mitigated by RF phasing and orbit steering. Start-to-end simulations examine the beam transport through the linac up to either 6 GeV or 20 GeV. The results indicate large design margins. Simulations of the beam dynamics in the damping ring (DR) demonstrate a sufficiently large momentum acceptance. Effects of intrabeam scattering and electron cloud instability in the DR are also studied.

Mots clés: linac; emittance; positron; gun; electron; energy: injection; electron: cloud; electron: beam; positron: beam; electron: particle source; accelerator: alignment; momentum: acceptance; effect: space charge; linear accelerator; FCC-ee; proton synchrotron; beam transport; beam dynamics; wake field; scattering; beam loss; stability; CERN SPS

Domaines: Physique des accélérateurs [physics.acc-ph]

Salim Ogur, Alexey Barnyakov, Iryna Chaikovska, Robert Chehab, Kazuro Furukawa, et al.. Linac and damping ring designs for the FCC-ee. 10th International Particle Accelerator Conference, May 2019, Melbourne, Australia. pp.MOPMP002, ⟨10.18429/JACoW-IPAC2019-MOPMP002⟩. ⟨hal-02223006⟩