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FCC-FS EPOL group meeting 51

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6/2-004 (CERN)

6/2-004

CERN

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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 15:00 on Friday.

FCC-FS EPOL group meeting
Zoom Meeting ID
63437787216
Host
Alain Blondel
Alternative host
Jacqueline Keintzel
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IPAC is taking place in the following week.

FCC-week organisation is converging and speakers are expected to be invited soon.

J. Tamazirt presents on polarimeter studies at BEPC-II. Most studies are only for simulation studies. Analysis is pending. Z. Duan explains that this is for 30s for 1% precision. There is 1 Compton beam line. Pol time is 70min. Max. One electron polarization is measured. RDP is the baseline, re-use of this bunch could be explored. Foreseen to run until 2030. 

J. Burvill presents on the polarimeter photon sensor. With 100% polarization he sees 200um shift, which is already challenging. 1% error is achieved over a measurement time over 0.17s, assuming 1000 events per 1 bunch crossing. For 10% 21s is needed. Laser polarization must be shift continously, not integrated. Studies only for Z so far. J. Keintzel suggests to also study W. R. Kieffer comments even more difficult for colliding ones, since polarimeter behind the IP. 

J. Wenninger presents news on the spin tune shifts in main rings and booster. For the booster he finds reducing number of eigenvalues could improve spin tune shift in the booster. He also presents on snakes in the booster.

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