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45th FCC-ee Optics Design meeting
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Europe/Zurich
6/R-012 - conference room (CERN)
Present: Katsunobu Oide, Dima El Khechen, Jorg Wenninger, Mike Koratzinos, Salim Ogur, Mauro Migliorati, Demin Zhou, Frank Zimmermann, Sandra Aumon, Eleonora Belli.
Frank Zimmermann: Summary of the MDI mini-workshop at CERN
This workshop was triggered by the last FCC-ee project review in October 2016, in order to discuss and validate the baseline of the MDI layout. In particular, a symmetric L* of 2.2m was discussed and the mitigation of a strong instability at the Z energy which would impact the optics at IP was presented with a betx of 10cm.
Concerning the IR layout, 15mm radius has been set for all beam pipes, with 12.5mm length for the central detector beam pipe. It was proposed to have a Be beam pipe for the luminosity monitor window, in order to minimize the high order mode power and the radiation length in this region.
At high energy, the LumiCal window will increase the synchrotron radiation detector background due to the higher energy of the photons and its need at higher energy is still under discussion. Local shielding of the detector magnet will be needed in the IR to protect the central detector. An option about the diameter for the solenoid (2T with 4mx6m) were described. The workshop summarized the status about the different prototypes of quadrupole magnet coil technology at the IR, and no prototype will be needed for the CDR. Sergey with Mike the emittance blow up due to the present IR layout with solenoid-anti-solenoid field, with/without iron, which contributes to 0.32pm in vertical emittance.
The last model used for high mode studies very close to the one from Sullivan design. Trapped modes were found in IR to be investigated, so there is a need high order mode absorbers.
New requests arose from the workshop such as a 3D CAD model of the IR region for realistic impedance calculations, and there is a need for a cryostat designer.
Mike Koratzinos: Report from Hong-Kong
Mike Koratzinos went to Honk-Kong to the conference on High Energy Physics. CEPC project changes their baseline with a new layout, very similar now the FCC layout. The cicumference of the ring was increased from 50 to 100km. The energy of the proton-proton collider has been upgraded to at least 125 TeV center of mass. The conference covered also the baseline of the main future electron-positron colliders (ILC, CLIC, CEPC and FCC-ee): ILC baseline is changed to 250 GeV, CLIC phase 1 to 380GeV, FCC-ee changed its Linac to a 6 GeV Linac. Finally, the different projects have more or less the same cost (FCC-ee had no cost estimation~5-6B$). A MDI collaboration between CERN, IHEP, BINP and KEK will be form.
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