FCC-ee top-up injection

Name: FCC-ee top-up injection
Start: 2026-02-12T09:00:00+01:00
End: 2026-02-12T10:35:00+01:00
Location: No location set

Thursday 12 Feb 2026, 09:00 → 10:35 Europe/Zurich

66156014911

Yann Dutheil

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D. Calzolari, Y. Dutheil, J. Keintzel, S. Kostoglou, G. Nigrelli, A. Potet, P. Raimondi, K. Skoufaris, S. Yue

Concerted results documented in the comparison report -> injection efficiency only with SR
Concerns arose on the status of injection efficiency in the presence of more complex modelling

Focus in ABT on the injection concept and following evolution of tracking results in a collaborative repository https://gitlab.cern.ch/abt-optics-and-code-repository/projects/collider-injection-fcc-e
In ABP mostly focused on Xsuite, although with benchmarks on SAD and superKEKb at injection presented by G. Nigrelli https://indico.cern.ch/event/1588696/contributions/6856980/
The WG members have many more simulations, with injection bump, beam-beam, optics perturbation due to the bump, non-linear dispersion

Q1 : What is the injection efficiency modelled in the presence of beam-beam and collimation ?

No resources identified are listing efficiencies of 0%
This remain an ongoing topic of discussion with continuous progress on both performance and inclusion of more physics processes
Besides including all physics processes, the injection process must be tested under perturbed conditions (corrected lattice) to test and quantify the robustness of the injection process.
Latest simulations conducted and presented by G. Nigrelli https://indico.cern.ch/event/1588696/contributions/6856980/

Q2 : Is the injected beam position and Twiss parameters including both linear and non-linear dependency with momentum offset ?

Discussed during the WG meetings of 10/2026 and 12/2026 as well as by G. Nigrelli at the tune-up meeting in October
But need to understand and fix specific parameters -> Important to find the parameters and communicate them
Important to find the optimum injected beam parameters -> We need to establish a methodology to find new parameters with a new lattice

Giulia will discuss with Sen on how to incorporate or associate her simulation to a repository, for instance the https://gitlab.cern.ch/abt-optics-and-code-repository/projects/collider-injection-fcc-e
Marc-Andre on LCC

Previous lattices not optimised for injection or non linear dynamics
It would be important to conduct optimisation from a corrected lattice with errors (request to tune-up WG ?)
Conducting MOGA at large dE

voltage presently using 150 MV which is slightly away from the baseline set to 90 MV (convergence needs to be done on ABP-RF side)
Optimisation conducted to dispersion-free straight section
Optimised lattice is able to maintain the DA w/ beam-beam and epsY
At the location of the septum the optimisation includes up to DDX2 which may be the source of limited DA -> agreement that included higher order is important

Present point selected for higher MA but could be optimised for slightly larger DA for hybrid injection
How do we proceed from here ?

90MV or stay at 150 MV for now ?
Should we switch to negative dE ? -> This is needed because we need lower RF voltage from the booster
Kyriacos asks if optimise directly on lifetime instead MA

MA should be a good proxy to lifetime but one scan should be conducted to confirm this

Marc-Andre will publish and make available a new lattice version, note this is not a new lattice but optimised element strength on LCC106

No time during the discussion, only conclusion with promising zero-phase-advance concept
The beam stay clear definition remains in question, Giulia will circulate the definition with beta and dispersion contributions
The pi-phase advance concept requires contributions from Marc-Andre to establish the feasibility in PB
Detailed discussion deferred to the next meeting

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