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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Present : C. Carli, Y. Dutheil, A. Lechner, G. Nigrelli, P. Raimondi, G. Roy, K. Skoufaris, S. Yue, 

 

  • Comparison of the lattices for injection (S. Yue)
    • Question if we want to conduct tracking w/ beam-beam for the comparison
      • Beam-beam is an important parameter but may not have to take part of the injection simulation
      • Kyriacos is observing different effects w/ beam-beam between the two lattices but this can be seen as part of the optimisation
      • The more data the better but no significant resources are available to conduct the beam-beam study
      • The beam-lens, weak-strong, could be easily added : observed that it adds the filamentation process which causes the emittance growth
    • Tracking is conducted for all hybrid energy offsets, down to 0% which is off-axis injection
    • Optics compared at the injection point shows a large distortion of the dispersion with energy offset
      • Optics parameters used are the on-momentum ones
      • Is there agreement to use the all the off-axis Twiss parameters and chromatic offsets ?
        • Is it the best solution because the of the synchrotron oscillations ?
        • Maybe another orbit would be best, and the same with beta functions -> this should be tested -> to be discussed over the next few weeks
    • Behaviour in the longitudinal plane is different between GHC and LCC
      • That could be caused by higher order eta, and path lengthening with amplitude
    • In the LCC, recently noticed a second order vertical dispersion which could be addressed/debugged
    • Also proposes to conduct tracking with the matched injected beam distribution which pushed the geometrical condition
    • Shared oscillations at injection could be studied at some point
      • May be less than ideal since only 10% of the bunches are refilled per injection, while kickers would offset all the circulating bunches
    • For the report the conclusion presented is clear with a good injection efficiency for both cases
      • One question is the possible effect of the synchrotron radiation flash sent into the detector in case of horizontal emittance increase as observed on the GHC
      • This was a major concern for off-axis injection during the LEP time
      • This is addressed by Giulia in her slides
  • Injection efficiency study update on losses (G.Nigrelli)
    • Significant twiss distortion with energy
    • Also reaching significant second order vertical dispersion due to the non-closure on D''y of the vertical separation dogleg -> this should be solved by moving the quad out of the dogleg
    • Question of the horizontal offset at the final doublet
      • One particle tracked of 100 turns shows up to 2 sigma offset
      • Results are not concerning wither for GHC or LCC
    • Distributions projected over a 100 turns show significant sizes at Q2-Q3
      • Due to non-linear behaviour which could impact SR but also injection efficiency
      • Shown for both lattices
    • For the lattice comparison report
      • Injection efficiency with collimation we should have it for both
      • GHC is already set and ongoing work for the LCC
      • Injection efficiency could be majorly impacted by the large emittance increases observed
  • Next meeting on 13/11 with the aim to finish converging on the writing of the lattice comparison report
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