FCC-ee top-up injection

Thursday 24 Jul 2025, 14:00 → 15:00 Europe/Zurich

Present: Y. Dutheil, G. Gonen, M.A. Jebramcik, A. Lechner, T. Mori, G. Nigrelli, G. Roy, K. Skoufaris, S. Yue

• Top-up injection tracking with Xsuite and SAD (Sen)
  • Change in the injection efficiency was due to the change in the makethin strategy
    • In ABP, now using thick elements and no longer thin elements
    • Only not done for collimation due to differences in the loss maps, which are being investigated
  • Question of the emittance blow-up
    • Also present in the SR-only case, not observed by ABP simulations
    • All the lattice preparation and tracking settings are present in the Xutil repository
    • In SAD, the H emittance shows a stair-pattern; this is an artifact due to particles lost at high amplitudes
  • Differences with beam-beam may be caused by differences in the beam-beam effect between the two codes
  • For the longitudinal emittance
    • Some increase is expected due to filamentation beforehand
  • For the LCC lattice
    • Tracking done with a single RF cavity
    • May require a flip of the crab-sextupole sign
    • ABP is working on this lattice with beam-beam to identify matched parameters of the circulating beam
  • Tracking with injection bump has been noticed to have a small effect on the circulating beam
  • A presentation by a WG member should be planned for a future optics meeting, following Frank’s request for updates on the top-up injection
• Injection with non-linear kicker (Sen)
  • Comparison of odd and even fields with sextupole and octupole
  • MIK is subject to the same
  • The concept of the MIK could use off-axis injection?
    • In such a case, no dispersion would be needed
    • A study was carried out by Takashi with sextupole and with compensation, but couldn't be implemented due to the presence of the abort system in the same region
• Mismatched injection/injected beam distributions (Giulia)
  • Injection at lower momentum offset is better even when ending on the wrong orbit
    • This corresponds to the hybrid scheme selected as the baseline for the FSR and is consistent with the FSR results
    • The opposite offset also corresponds to a hybrid scheme, although without expected gain
  • A study on the injected kick failure shows it causes betatron oscillations when one kicker is OFF
  • A comprehensive study of failure cases in injection/extraction systems
    • Will start later this year by Chiara and a new post-doc in ABT
    • Further discussions on detailed scenarios will be initiated later this year.

1 Tracking results and Multipole injection kicker

Speaker: Sen Yue (CERN)

Tracking and MIK.pdf

Tracking and MIK.pptx

2 Mismatched injection injected beam distributions studies

Speaker: Giulia Nigrelli (Sapienza Universita, INFN-LNF, CERN)