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FCC-FS EPOL group and FCCIS WP2.5 meeting 33
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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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Zoom URL
J. Keintzel reminds that the FCC physics workshop will take place from 13 to 16 January 2025 at CERN with 2 EPOL sessions. Furthermore, an IPAC contribution on the general EPOL effort will be submitted.
W. Hofle presents updates on the depolarizer. With the new RF scheme more gaps would be available, but smaller. Currently 100 ns bunch spacing is still foreseen, but he warns it could be reduced to 50 ns, which then needs to be studied for the depolarizer. For symmetry reasons it is proposed to have this system integrated in the return arcs of 2-4 IPs. 26 mm diameter of the vacuum chamber is proposed, with 4x 1 m length of each kicker, providing a 10 µrad kick. Currently 2 of these systems are foreseen, constraining the phase advance to n x pi. Possibile risks have been discussed within a machine protection task force. It is not yet clear if the depolarizer should be combined with the feedback system. K. Oide comments that the bending angle in the return arc is about 5% lower than in the normal arc. I. Koop agrees to look into the optics of the return arc. In the proposed modified arc the bending angle between quads would be increased, two times longer cells, leading to a more effective spin rotation. RDP will be more efficient with larger dispersion function with larger Qs. K. Oide reminds that the current design foresees twin quadrupoles in the arcs, but the return arcs could be different. R. Kieffer adds that there could also be the extraction line of the SR monitor. K. Oide adds that the bunch spacing should be as short as 25 ns.
R. Kieffer presents updates on the polarimeter, including energy deposition in proposed silicon sensors and deadzones. SImulations with polarized particles have commences in BDSIM. J. Wenninger wonders about the power deposited on the outside window, to be clarified.
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