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FCC-FS EPOL group and FCCIS WP2.5 meeting 26
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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.
FCC-FS EPOL group meeting
Zoom Meeting ID
63437787216
Host
Alain Blondel
Alternative host
Jacqueline Keintzel
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J. Keintzel presents open questions for the EPOL team. D. Barber comments that the spin tune change with orbit errors could be calcualted using first order perturbation theory which could be compared with spin tracking studies. For LEP fluctuations in the order of about 100 keV where observed. Furthermore, a new software called JULIA is currenlty being developed for spin tracking.
Z. Duan presents on intrinsic resonances through the FCC-ee booster. 2 lattices (FODO and HFD) are studied. The first super strong resonance occurs between H and top energy. He notes that for the CEPC booster the first super strong resonance occurs at 40 GeV, caused by a lower vertical betatron tune. J. Wenninger suggests to not use a Gaussian energy ramp but a linear one, which should further improve these results. Z. Duan point out that depolarization resonances caused by imperfections could have severe impact on the polarization transmission which remains to be studied for the FCC-ee. J. Wenninger suggests to also study the polarization transmission through the transfer lines, since horizontal and vertical bending angles could lead to spin rotation.
R. Kieffer presents open questions and ongoing tasks for the FCCee polarimeter and beamstrahlung monitor. Furthermore, he points out that for measuring longitudinal polarization the laser could disturb the colliding bunches. A. Blondel remarks that a beamstrahlung monitor is also important in precise determination of collission offsets, caused by beam-beam deflection kicks during collisions. J. Wenninger remarks that the placement question of the polarimeter is mainly driven by accessability and integration constraints (main rings plus booster).
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