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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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K. Andre, H. Bartosik, C. Carli, Y. Dutheil, P. Raimondi, K. Skoufaris

 

 

  • MIK Injection at ttbar mode (S. Yue)
    • Using ttbar beam parameters from booster table already 2 years old, sigma showed without dispersion contribution
    • Strong non-linear field components for the injected beam, would be improved with larger beam separation (2.8->4mm proposed)
    • Present simulations are limited to <1 turn tracking
    • The beam stay-clear is an important input but the cuts for ttbar remains
    • Hannes comments that the linear matching is already
    • Pantaleo comments on the effect of multipole elements in the transfer line that would cause large amplitude to hit the septum. Need to ensure we plot the phase space at the septum entrance to assert the (at least) 3 sigma matches
    • Pantaleo comments that a MIK was just installed and we should follow-up on their experience
    • Kyriacsos comments that the ring phase space should consider non-linear dynamics of the ring
  • Booster-to-Collider transfer line design (P. Raimondi)
    • Based on Pantaleo's experience minimization of optics function excursion is important
    • The concept uses an H-dogleg inside a V-dogleg with different constraints
      • V-phase advance needs to be -I for zero Dy
      • All H-dipoles dispersion contributions need to add coherently to reach the required dispersion at injection
    • The layout doesn't indicate likely interference with the other ring
    • Proposed specifications for septa design using low fields, and hopefully reaching thinner blade of 1mm
    • Limited freedom, could the booster optics SS be adapted ? (discussion took place here on the booster for injection/extraction).
    • Proposition to shift horizontally the collider SS to obtain both BTC be exactly (anti) symmetric (favored option)
    • What freedom do we want for the beta and what tunability range ?
      • On-momentum should be checked but may be working too
    • This preliminary design could be added to the repository (to be followed w/ Giani and Mark)
    • Transfer the lattice to ABT colleagues for first machine protection concept
  • Update on tracking studies for top-up injection (K. Skoufaris)
    • Results showed for 106.3, but Kyriacos also has initiated studies with other parameters
    • For off-axis, used a position without dispersion at RF where beta are smaller
    • Why do we start losing particles after 1-damping time (of 0.3s)
    • Is it the beam-beam that either on- or off- axis makes the emittance blow-up
    • Pantaleo recommends to reduce beyond matching the injected beam beta function
    • What is the source of the injected beam emittance blow-up ? This is under study
    • In case of thinner septum and less than 5sigma from the previous presentation
  • Question of separation and
    • Pantaleo comments that in light sources 3 sigma is considered, but with additional 1mm on both sides of the septum for unknown and margins
    • For circulating 5sigma, the halo population modelling. Presently one assumption from the collimation team using single-planes and worst case scenario lifetime. Pantaleo mentions another approach from M. Sidel that considers two gaussians with different halo distributions
    • We should also consider some margin on both sides of the septum blade, maybe 0.5mm on each side
    • For injected beam, a 5sigma envelope was considered early on. It could be reviewed but should add also the uncertainties
    • A review of those numbers, with details on margin and assumptions needs to be documented by the end of the year
  • Meeting to be move to even weeks and with 2-weeks periodicity
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