First HOM power considerations

• Ivan Karpov (CERN)
• Fabian Batsch (CERN)

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

Round table

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