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    1st Run III FiDeL meeting

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    Minutes of the 1st FiDeL RunIII meeting

    Date: 2020-01-07

    Place: 927 conference room

    Presents:

      R. Tomas Garcia, M. Giovannozzi, J. P. Tock, J. Wenninger, M. Solfaroli Camillocci, L. Fiscarelli, J. Dilly, F. Soubelet, E. Todesco, E. Maclean

     

    Field model topics for 2020 and RunIII [E. Todesco]

    After a hibernation phase, the FiDeL team is preparing the RunIII preparation. Moreover, there are pending issues in the analysis of RunII data that deserve attention

    • RunIII preparation:
      • Model update due to magnet (19 dipoles and 3 quadrupoles) replacement during LS2; this should have no practical impact on LHC settings, but it is deemed be necessary to keep the consistence and to verify all the chain of modifications after more than 3 years.
      • Extension to 7 TeV; we should review all fit and trims to verify if something could become critical at 7 TeV.
      • Complete the WISE implementation from ABP side in Java.
      • Construction of the field model of the MBH (11 T).
    • Open issues from RunII
      • Linear coupling decay indicating sextupole spool piece systematic vertical misalignment of 0.2-0.5 mm (downwards); this was seen in beam measurements and ABP required to explore the possibility of having special measurements of dipoles.
      • Decay of tune is far from being reproducible, and source in not yet clarified (from M. Solfaroli Camillocci)
      • The octupole correction in IP5, that has a much worse agreement between model and measurement than in IP1
      • The revision of the hysteretic part of the b3 model in the dipole, to better fit the measure change of chromaticity (from M. Solfaroli Camillocci).
      • The decapole correction of spool pieces at injection, half of what expected (from E. Maclean). This suggests a measurement of the transfer function of the combined MCDO magnets (from M. Giovannozzi).

     

    Discrepancies in b2 errors [R. Tomas Garcia]

    Rogelio reports on a small discrepancy in the b2 errors in between the 2011 and 2015 WISE version, the more recent one being closer to Gaussian and slightly more peaked. It is also noted that there are no error tables for 7 TeV in the 2015 release. These points will be clarified with Per Hagen in the coming weeks. It is recalled that in 2018-2019 it was agreed to have the .xls version of WISE, steered by the magnet group, replaced by a Java version, steered by ABP, which has progressed towards a final implementation that requires full validation. This is a non-trivial task, due to the complexity of the code, especially for the part that accounts for the random components in the field model. A special effort should be dedicated in 2020 both from the MSC/MPA side and from ABP side to conclude and validate the transition.

     

    b4 errors in the LHC triplet [E. Todesco]

    This is a follow up of the analysis started by E. Maclean, showing that the settings (determined on the basis of the known field quality) of the octupole in the triplet agree very well with beam measurements for IP1, whereas for IP5 they are approximately half of what expected. Ezio shows that MQXAs have 1.30 unit of systematic component in all magnets, with a sigma of 0.11 units. This should be the dominating effect, as the MQXBs have a 10 times smaller systematic component of 0.12 units, with a sigma of 0.14 units.

    A possible source of additional nonlinearity could be the solenoid of CMS; the modeling is far from being trivial, and a proposal of a dedicated MD to measure the amplitude detuning and feed-down with the magnet switched off was done by M. Giovannozzi in the past.

    Ezio also verified the consistency of the numbers in the reports and the installation sequence between the reports and WISE. Last year, ABP reported on discrepancies between WISE and ID cards values of the multipoles, that should be cured. This includes also wrong installation slots in the ID cards.

    Investigation will be done by Ezio and Ewen to (i) find the origin of the variations between the IP sides and to (ii) check the data consistency on the ID cards side

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