12th meeting on HEMAC discussions

Tuesday 1 Nov 2022, 16:45 → 17:30 Europe/Zurich

Zoom

https://cern.zoom.us/j/66586421590?pwd=TVZ4WEdtaDRQNFBkNitUTm4rTG83Zz09

meeting_saved_chat.txt

16:45 → 17:00 First HOM power considerations

Speakers: Fabian Batsch (CERN), Ivan Karpov (CERN)

MC_HEMAC_FB_221101.pdf

17:00 → 17:20 Discussion

Few open points for follow-up:

• Optimize losses in RCS chain for best overall performance, allowing different transmission in the two or three machines
  -> Prio 1, but difficult with lots of degrees of freedom: straight-forward only for constant acceleration

  • Difficulty of different magnets (ramp rate)
  • How to distribute total RF length over different machines? Minimization of overall total voltage.

• Acceptable longitudinal emittance growth in the RCS chain and how to quantify it exactly?
  -> Prio 1: Needs figure from low-energy acceleration (low energy), longitudinal emittance for colliders as a starting point. Criteria also on how much bunch is distorted. What is acceptable bunch shape deviation in the collider?

• Would two RCS be sufficient to accelerate from 60 GeV to 1.5 TeV? -> Prio 2: does not look very attractive

• What are the consequences if we want to use the LHC as the last accelerator ring? -> Prio 1: check consequences, check Shiltsev proposal: https://iopscience.iop.org/article/10.1088/1748-0221/13/10/T10003

• Cost functions per machine part: could one make an assumption for a cost per unit length of RF (plus some infrastructure cost offset per RF section), idem for unit length of magnets? -> Prio 2

• Average gradient of RF sections: Prio 1: quickly done: 30 MV/m (conservative) 45 MV/m

• How do define a reasonable synchronous phase? Prio 1: First start for constant acceleration, then real ramps

• Transient beam loading and counter-rotating bunches and multi-turn effects (Prio 2)? Power in HOMs (Prio 1). -> - Can the ILC cavity (possibly in a modified form) be used for the muon RCS? -> Prio 1

• Mauro Migliorati? Presently no code can do it.

• David has impedance model for ILC cavities

• Resistive wall impedance? -> Prio 1: David, contact with JPARC, collecting information; Luca will organize a dedicated meeting on 24th November: muon collider magnet working group

• Is transition gamma of ~20 a good number for the first RCS stage? -> Prio 2: check various transition gammas and their impact -> David to present

• FFA alternative for RCS?

• Introduce chromaticity in transverse studies, do we need sextupoles? -> Prio 1

• More detailed lattice model, beyond smooth approximation. -> Prio 2

17:20 → 17:30 Round table

Speakers: Alexej Grudiev (CERN), Antoine Chance (CEA Irfu), David Amorim (CERN), Elias Metral (CERN), Fabian Batsch (CERN), Heiko Damerau (CERN), Ivan Karpov (CERN)