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    New tapering command and round table

    → Europe/Zurich
    New tapering command and round table
    Zoom Meeting ID
    62787732885
    Host
    Rogelio Tomas Garcia
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    01/09/2021 LNO meeting

    on new MAD-X tapering command, short news and round table discussion.

    News, Rogelio : requests for fellows in the group were sent.
    CERN is looking for volunteers to help for the Science Gateway. Also fellows and (qualified) students are welcome; thanks already to Jacqueline who will help for german speaking visitors.
    While a new record 1.6e11 bunch intensity has been reached in the PS, there have also been recently new issues in injector commissioning.
    A beam test preparation day is scheduled for the 13 September, https://indico.cern.ch/event/1033814/ with a presentation by Tobias.
    LHC: the 6 cold sectors reached the 6.8 TeV equivalent, and the two repaired sectors (23, 78) are now nearly cold.
    Helmut said there was an LPC meeting https://indico.cern.ch/event/1068719/ re-iterating on the experiments requests including special runs in preparation of the LHCC this week https://indico.cern.ch/event/1062348/ . ATLAS, CMS and TOTEM are interested that the LHC runs at the highest possible energy.

    New MADX tapering command, Ghislain Roy, slides
    -----------------------------------------------
    A tapering option in TWISS and MATCH has already been implemented by Leon/Tobias.
    Ghislain reported on the proposal and tests for the implementation of a separate TAPER command in MAD-X, which could allow for more flexibility
    and potentially unify some aspects by using a single relative KTAP scaling parameter rather then K1TAP, K2tap,..
    He shows the documentation of the functionality of the TAPER command. The choice of STEPSIZE in TAPER allows to perform the tapering in steps for groups of adjacent magnets to explore different tapering strategies. The implementation works with a copy of the orbit. The results can be saved as a MAD-X file, that could be modified or reloaded.
    Discussion:
    Tobias reminds about the importance of re-matching RF-phases after tapering.
    Riccardo reminds that different from quadrupole and sextupole magnets with k1, k2 strengths, angle is used to specify bends but k0 is also used in LHC sequences and overriding K0 for tapering is a problem.
    The proposed new TAPER command appears interesting, but requires still more work and cannot be expected to already be integrated in the new MAD-X release planned for this month.
    Ghislain will make a test version available as extra MAD-X branch.
    The MAD-X team will look into details and in particular decide on the possible use of a relative or absolute KTAP parameter and check the consistency of scaling strength parameters with deltap :  factor 1+deltap or  1/(1-deltap).

    Round table discussion:
    Tobias says there is good progress on expanding the MAD-X drift around the orbit.
    Riccardo and Laurent say (permanent) misalignments are becoming more important and require a clear, well documented strategy on how to define the physical reference of the machine. This is important also as basis for the the survey/alignment team and should also be useful for non-CERN machines like SuperKEKB or linear colliders which may require patches.

    Topics for next meeting(s): MAD-NG, injectors, MAD-X for LHC

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