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FCC-FS EPOL group and FCCIS WP2.5 meeting 31
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Europe/Zurich
Description
The FCC technical and financial feasibility study comprises a work package (EPOL) on precision determination of the centre of mass energy at FCCee. using resonant depolarisation of the beams, in conjunction with precise measurement of the energy spread and other parameters using physics events in the detectors, and other beam diagnostics in particular to control the collision parameters. Specific equipment involves polarimeters for both beams, polarisation wigglers, and depolarising RF kickers. The possible mono-chromatization of the beams in view of a measurement of the e+ e- —> H (125) process will also be studied and special requirements investigated.
Short group meetings are foreseen at 16:30 on Thursday typically every three weeks.
Videoconference
FCC-FS EPOL group meeting
- Zoom Meeting ID
- 63437787216
- Host
- Alain Blondel
- Alternative host
- Jacqueline Keintzel
- Useful links
- Join via phone
- Zoom URL
-
G. Wilkinson reminds that the FS report consists of 3 chapters. The EPOL team will also update the "requirements document" as complementary material for the final report.
R. Kieffer presents on FCC polarimeter running modes specifications. The goal for the polarimeter is having a 95% availability. The laser room must be accessible 24/7. 10% polarization is required to detect depolarization within 100 turns. A. Blondel comments that for the phyiscs bunches they should be constantly monitored, where R. Kieffer suggests to target a few bunches, since they could create background for the experiment. He proposed a scheme e.g. 10s measurements, followed by 10min no RDP measurement on colliding bunches. A. Blondel comments that polarization build-up is a much bigger concert at Z, than at higher energies. G. Wilkinson suggests to keep that running mode at WW, but with more relaxed tolerances. A. Blondel comments that the Z-pole calibration runs could be roughly monthly, aimed to achieve ~1MeV precision. G. Wilkinson comments that we should strick to depolarize only up to WW. R. Kieffer adds that if it would be required for ZH onwards, the polarimeter design must be reevaluated. Concerning the direct energy measurements, it is suggested to have ~1MeV precision requiring 10 µm alignment of the detectors. If we would inject polarized beams, polarimeters in the injectors would also need to be included. It is concluded that the baseline is 1 polarimeter per beam in PA with 2 laser systems each. D. Barber comments that at very high energies (higher than ZH) a polarization of a few % could be feasible (published September 2023).
I. Koop presents on accuracies of FSP.
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