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FCC EPOL group meeting 56
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Europe/Zurich
42/R-001 (CERN)
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 15:00 on Friday.
FCC-FS EPOL group meeting
Zoom Meeting ID
63437787216
Host
Alain Blondel
Alternative host
Jacqueline Keintzel
Useful links
Join via phone
Zoom URL
News:
- Tuned lattice repository -> Ongoing work within the tuning working group
- Polarimeter dipole discussion:
- Alcove discussion and meeting in TI on 23 September: Vibrations could be a problem for laser stability in the alcoves (water, airflow, PC, etc), which must be studied. If so, a specific alcove for the laser would be required. If not, alcoves would need to be moved.
- New project by EPFL has been approved, EPOL and ELSA are parts of that.
J. Wenninger presents on the polarization transmission through the HFD booster. Up to W basically 99% polarization can be preserved. At 110 GeV beam energy polarization of on average 80% can be transported (some seeds much lower). Optics differences cannot explain the spread in transmission. Strong resonances appear at nx250 (integer tune contribution from arc). FS can explain only good seeds.
A. Blondel comments that at ZH there is some flexibility of defining the exact energy, within a few GeV.
A. Chance is working on new booster optics. Maybe a different optics could be designed with (higher vertical phase)/without polarization.
A. Blondel comments that the linear colliders propose polarization at ZH, which could be considered also for the FCC.
Z. Duan asks about transmission to higher energies.
A. Blondel presents. Depolarization is slower than lumi life time.
J. Bendavid asks about radiative return events and possible spin flip.
J. Bendavid presents news on the integration. Optimistically 2 keV error could be achieved. Pressure bump should be localized.
Actions and follow-ups:
- Actions for polarimeter dipole:
- Luke: check with magnet colleagues and provide field map
- Robert, Aurelien: evaluate polarimeter performance using realistic field map, including dipole stability and roll error
- Actions for polarimter general:
- Integration of laser alcoves
- Polarimeters up to ZH to perform RDP and best compromise
- Polarimeters in booster and injectors
- Error estimate at each energy mode assuming different set ups
- Fitting activities
- Actions for polarizer ring L
- Longitudinal polarization to be studied for special Higgs Run
- Operational scenario (regularity of RDP, lifetime, etc.)
- Actions for RDP scans
- Overlap RDP scans with detector resolution
- Check lifetime and polarization lifetime of bunches up to ZH in addition to transmission
- Single exciter vs 1 arc vs bump: impact on SR, impact on spin tune, background
- Actions for Ecm model
- Add impendance losses
- Difference between pilot and colliding bunches
- Calibration with cosmic muons and shaft locations
- Actions ee->H run
- Evaluate monochromatization vs longitudinal polarization for 125 GeV Ecm (physics, max pol and lumi from accelerator)
- Actions absolute energy measurements
- Integration (close to polarimeter, detector, cross-talks, etc)
- Actions in-situ calibration
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