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    FCC EPOL group meeting 53

    → Europe/Zurich
    354/1-019 (CERN)

    354/1-019

    CERN

    30
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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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    J. Keintzel shows the proposal for Bonn University. Following a question by C. Carli, R. Kieffer comments that the workforce requested would be located at Bonn. In addition the links to CERN should be clarified. If positively evaluated funding could start mid next year. R. Kieffer comments that first simulations have started regarding the laser and polarimeter requirements for Bonn in order to aim for testing NRPM.  

    J. Wenninger comments that a bug has been fixed in xsuite for spin tracking. 

    To Do: clarify resources and collaboration with ELSA, check requirements to perform NRPM at ELSA, error table on errors on beam and ecm energy

    J. Bendavid presents news on the absolute energy calibration located at the polarimeter location. Without in-situ calibration, 100 um over 2m would need to be known inside the detector (silicon sensors). From the gas pressure 30 to 50 % of the vacuum emittance increase could be tolerated from this measurements. This technique measures the local energy over about 200 h for 10 keV.  Absolute accuracy should be e-5, calibrated by in-situ measurements. 

    To Do: in-situ detector calibration, integration close to polarimeter, detector design next to beam pipe (stray fields, etc)

    J. Wenninger presents on polarization transmission through the booster. No thin elements should be used for spin simulations. For the new HFD optics strong depolarization occurs at a*gamma = 251, stemming from a smaller vertical tune (only arc contribution). Emittance is result of simulations, tuning is not optimized yet. 

    D. Barber comments at RCS they use a high super period (80) in the lattice.

    To Do: CERNbox for tuned lattices, more realistic errors, possible optimize lattice or polarization

    A. Martens presents tolerances for the dipole for the polarimeter. One 17m long dipole is assumed. Assuming this needs to be split in 3 parts, in total 12 units would be needed:

    • 2.3 e-4 field stability over the full aperture and full length
    • horizontal beam field 2.9 e-5 Tm
    • longitudinal bending field 7.4e-3 Tm
    • Dipole roll 94 mu rad (factor 10 smaller as for tuning)

     

    M. Liebsch comments it could be special magnets. Since it is only 3 magnets per polarimeter, systemtatic errors could be cured. Random errors are more challenging. M. Liebsch suggests to arrange a meeting with J. Bauche, D. Mergelkuhl, M. Liebsch, R. Kieffer, EPOL conveners et al. 

    To Do: Meeting to discuss magnet, field map to polarimeter BI colleagues for full simulations

     

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