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FCC-FS EPOL group and FCCIS WP2.5 meeting 36
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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 15:00 on Friday.
FCC-FS EPOL group meeting
Zoom Meeting ID
63437787216
Host
Alain Blondel
Alternative host
Jacqueline Keintzel
Useful links
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Zoom URL
J. Wenninger presents updates on solenoid compensation. Spin solenoid compensation bumps in LEP introduced strong coupling. Work has started by Y. Wu, agreeing with results from A. Blondel.
J. Wenninger presents on FCC-ee solenoids. G. Oide comments that the non-local compensation is only used in LCC. Using a solenoid with fringe fields the spin rotation is 6 murad after one IP. One reason for no depolarization is possibly from dn/dgamma.
J. Wenninger on injecting polarized beams from the linac to the HEB via the transfer line. By slightly reducing the beam energy to 19.875 GeV about 90% polarization transport could be achieved.
Z. Duan adds that the energy ramp through the HEB seem also promising.
Following a question by G. Wilkinson, J. Wenninger explains that C. Carli will start working on a dedicated polarization ring.
R. Kieffer suggests to investigate in the operation scheme with polarized bunches. Furthermore, he adds that polarization moniting must be investigated.
K. Oide suggests to include the earth curvature.
Z. Duan explains that for CEPC an electron source is foreseen, together with a damping ring, requiring 2T dipoles, for the positrons.
J. Tamazirt presents updates on simulation studies on the impact of vertical polarization on fit parameters extraction and on monolithic sensors. SR is not included.
G. Wilkinson points out that also a bias is found without deadzones. The bias is currenlty 1 MeV on the energy measurement of 45.6 GeV. Performing more complex simulations are planned in the future. R. Kieffer points out that significant computing power is required to perform these simulations. No crossing angle between the beam and the laser is included. While the current results would be already fine for RDP scans, G. Wilkinson warns that measuring polarization of colliding beams would require higher precision.
A. Korsun introduces herself. During her PhD she will work on monochromatization optics with A. Faus-Golfe.
G. Wilkinson presents the status of the EPOL note and the final report. The EPOL note will be uploaded to CDS and is currently not foreseen to be submitted to a Journal.
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