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FCC-ee top-up injection

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FCC-ee top-up injection
Zoom Meeting ID
66156014911
Host
Yann Dutheil
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Participants H. Bartosik, C. Carli, Y. Dutheil. M. Jebramcik, J. Keintzel, G. Nigrelli, P. Raimondi, K. Skoufaris, S. Yue

 

  • Pantaleo started looking into the booster to collider transfer and may show some progress at the next meeting
  • update on beam-dynamics with 106.3
    • Work-in-progress to understand emittance blow-up and efficiency
    • Discussion on the position of the star in the MA plot
      • while this is indeed synchrotron injection that representation shows an offset because it is at a location with dispersion. The star would be at zero if looked at a position without dispersion
      • Pantaleo point the DA calculation is also impacted and this was agreed it must be reviewed, but it remains uncertain if it is only an effect of the representation
    • Tracking w and w/o BB
      • Question of the vertical emittance, which appears small. Christian pointed those numbers should be discussed with the booster team and investigated how much effect they have on top-up efficiency
      • w/o BB an
      • Computation is done at the IP, Pantaleo points it should also show the beam size and the angular divergence. A correlation wouldn't be seen in emittance, and become misleading as oscillations would remain hidden
      • Additional representation using a fit to quantify the emittance which focus on the core would be helpful
    • Tracking see oscillations of the centroid at each IP, first finding and needs to be investigated
    • At the IP the injected beam at max offset is very far from the beam, and should
    • We should also establish betatron injection for comparison : Hannes suggests at this stage without a full optics design, only injecting from another straight section
    • Could we compromise the injection settings, for instance reducing by ~23% the energy offset and reducing all the margin
    • Hybrid scheme doesn't show an improvement, may be caused by BB so should be redone w/o BB
  • The emittance produced by the booster must be looked into.
    • The ideal is to have 5 damping times, challenging
    • How to ensure the emittance is correct at every cycle, in particular if it depends on the injectors
    • The booster parameters, cycling, constraints will need to be revised but only once top-up injection and its requirements is better understood
  • The update on MIK by S. Yue wasn't discussed and the contribution is reschedule to the next meetin
There are minutes attached to this event. Show them.
    • 09:00 → 09:20
      update on beam-dynamics 20m

      efficiency optimization and understanding the emittance blow-up

      Speaker: Kyriacos Skoufaris (CERN)
      FCCee_Top-up_Injection_v106.3-1.pdf
    • 09:20 → 09:40
      FCC week actions and priorities 20m

      From FCC week talk 

       

      •Proposed timeline by the collider design pillar (F. Zimmerman, 219th Accelerator and Design Meeting)
      –10/2026 : injection lattice (geometry) consolidated
      –12/2026 : baseline top-up injection scheme
      –03/2027 : realistic top-up injection efficiency
      •List questions remaining (not exhaustive)
      ✓Injection line design with optics and operation concept (optics, performance, mode switching, collective effects) -> Pantaleo Raimondi volunteered for a first design
      –Identify the beam specs and injection settings at every mode and how to transition between modes (injection line tuning range, motorised septum, changed straight section crossing, …)
      –Machine protection concept and passive absorbers (STI aims at comprehensive list of devices with specs and location by the end of 2026)
      –Halo population distribution for the injection scheme (hardware, machine protection, concept)
      –Conventional Vs MIK concept : should we install both anyway ?
      –A dedicated injection system needed for commissioning and/or witness bunches (dedicated fast injection, alternative betatron scheme ?) (“Off-energy injection should not pose a problem for polarization.” J. Wenninger EPOL1, FCCweek 2026)
      –Commissioning and intensity ramp-up concept
      –Establish a clear injection tuning method for sharing across WGs (injection point, backtracking from IP, mismatched phase-space, …)
      –Move injection settings from dedicated repository to the main optics repo settings
      –Effects and compensation of injection bump non-closure in the vertical plane
       

      Proposed Actions and further follow-up items

      • Action Y. Dutheil (09/2026): Write a document listing the conventional top-up injection constraints and impacts of beam/hardware/changes of parameters. Including possible adjustment variable to see where we can gain ​

      • Action Y. Dutheil (10-11/2026) : Pro/cons for pi Vs 4-C bump document is needed ​

      • Action in ABT: Finalise candidate search and start PhD project on MIK hardware system​

      • Injected beam properties being dependant on booster injection parameters is a risk, further uncertainty regarding the impact of wiggler in the booster and the required vertical emittance from booster extraction​

       
       
       
       
    • 09:40 → 09:50
      MIK Injection at ttbar mode 10m
      Speaker: Sen Yue (CERN)
      MIKinjection_ttbar.pdf
      MIKinjection_ttbar.pptx