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FCC-FS EPOL group and FCCIS WP2.5 meeting 35

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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. 

FCC-FS EPOL group meeting
Zoom Meeting ID
63437787216
Host
Alain Blondel
Alternative host
Jacqueline Keintzel
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J. Keintzel reminds that the FCC Physics workshop will take place at CERN fromm 13 to 17 January 2025 with 2 EPOL sessions. 

G. Wilkinson reports on the progress of the FSR in Volume 1 (physics) and J. Keintzel on Volume 2 (accelerators). The deadline for these reports is Christmas. They remind that the supporting document should also be published by March 2025.

G. Narvaez presents on the polarimeter laser polarization studies for the polarimeter. Following a question by R. Kieffer, G. Narvaez answers that the assymmetry is calculated by substraction of events for both laser polarizations. G. Wilkinson suggests to study the bias on the polarization in addition to zeta. A. Martens adds changing the pixel size will be studied. 

J. Wenninger presents on solenoid spin compensation with orbit bumps. Following a question by G. Wilkinson, J. Wenninger coments that the SAD result should indeed by cross-checked. D. Barber suggests to include material by M. Signorelli (the Bagels algorithm). 

R. Kieffer reports that I. Debrot presents on the laser compton scattering for intensity control of colliding bunches. If this is used in the collider ring thsi could disturb the polarimeter reading. E. Granados comments that since compton backscattering has a low cross-section, it will be challenging to remove a few percent of the beam. 

The EPOL group discusses on tentative Workpackages (WP) for the EPOL working group:

  • 1 Coordination
  • 2 Beam and spin dynamics in main rings (solenoid compensation, spin tune shifts, depolarization process, ...)
  • 3 Injector for polarized beams (source, damping ring modifications, spin transport, ...)
  • 4 Wiggler and spectrometer magnets (specification, shielding, vacuum, tolerances, ...)
  • 5 RF Kickers (lattice modifications, machine protection, specification, integration, ...)
  • 6 Laser and optical lines (laser transport, towards fully remote control, integration, polarization control, ...)
  • 7 Interaction chamber and detectors (polarimeter detector, vacuum, integration, polarization extraction, analysis, ...)
  • 8 In-situ physics measurements
  • 9 Monochromatization (optics design, lattice implications, monochromatization measurements and operation, possibly combined with longitudinal polarization, ...) --> maybe this should go to FCC-ee optics or even stand-alone working group?
  • 10 Dynamic ECM model (each IP, info from RDP and detectors, corrections from pilot to colliding bunches, ...)

 

It is aimed to finalize this list, including person power estimates and cost estimtes early 2025.

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