Present: R. Bruce, C. Carli, Y. Dutheil, A. Lechner, T. Mori, G. Nigrelli, K. Skoufaris, S. Yue

• Injection losses (Giulia)
  • On-axis scheme with injection on chromatic orbit
  • Model includes the bump, uses Xsuite + BDSIMA
  • New framework being developed by Giulia and Kyriacos to make simulation more general, implementation of the bump now lattice independent
  • For injected beam simulation
    • Injected beam efficiency of 87%
    • Loss pattern primarily at the IP and the collimators
  • For circulating beam simulation
    • Split between core and halo (5-12 sigma), 1% of the beam is in the halo
    • halo uses a ring distribution, but a more realistic distribution is under study
    • Some losses are seen at the injection point for the core of the beam
    • For the halo almost 50% of the beam is lost at the injection, with significant leaking at collimation and around the ring
  • Next steps
    • Question on the failure cases
  • Need to add an absorbers,
    • would benefit from a dedicated absorber from STI
    • Need to protect the equipment and localize the losses that would be incurred every time the beam is bumped, which folds into the allowed impedance
  • Need to clarify the bump amplitude
  • The injection efficiency of 87% is very similar to the model of Kyriacos, likely because the particles are any lost in both simulation. In particular in the vertical plane the DA is smaller than the collimation in the vertical plane
  • The initial distribution is presently fully matched to the ring conditions at the injected beam energy offset
• Quasi strong-strong simulation with top-up injection (Takashi)
  • Planning update on earlier strong-strong simulation that used simpler model
  • Presently using the stored beam distribution, not tested with the injected distributions
  • After 1k turns, BB is turned-on and effects on beta functions can be seen
  • Next steps : increase the number of turns and beam-beam force
  • Kyriacos will organize a discussion in ABP for strong-strong simulation with the various teams working on the topic
• Evolution of the vertical emittance in the injected beam (Kyriacos)
  • Question if the emittance increase is a question of matching
  • It appears that the vertical emittance increase is caused by the beam-beam effect
  • It is important to measure and control this contribution from beam-beam
• Injection studies on V25.1 GHC (Sen)
  • Observed significant changes of the beta function with energy offset in the arc, but not at the injection point
  • Injection optimization with lower beam size clearance for both circulating and injected beams
  • Energy offset could be reduced down to 0.71% or 0.75%