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    8th Run II FiDeL meeting

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    Minutes of the 8th FiDeL RunII meeting

     

     

    Date: 2016-03-08

    Place: 30-7-10

     

    Presents:

      Ezio Todesco, Rogelio Tomas Garcia, Per Hagen, Vittorio Remondino, Massimo Giovannozzi, Agnieszka Szczotka, Piotr Skowronski.

     

    Main topics for 2016 run [E. Todesco]

     

    Ezio outlines the main topics coming in 2016 for the FiDeL team.

    • Squeeze to 40 cm:
      • Check of the impact of hysteresis in the MQM and MQY [Per, on input of Riccardo]
      • Follow up of the squeeze at 40 cm, and feedback from the beam based corrections on the magnetic model [info from Rogelio team]
      • Commissioning of the triplet correctors and follow up of their use (do we need all? Are settings correct?)
    • Precycle at 3.5 TeV
      • Implementation of the agreed strategy [Matteo]
      • Analysis of special measurements on 4001 [Ezio, Lucio]
      • Commissioning of dynamic corrections on chroma and tune [Matteo, Michaela]
      • Faster ramps: are they possible? Try special measurements to quantify the effect
    • LHC chromaticity: there is a missing unit of b3 persistent current from 2015 data. Analysis of the other data of 2015, modification of the model, and follow up of the evolution of the chroma during ramp in 2016 [Matteo, Ezio]
    • LHC nonlinearities MD: understand the correction of Q’’ and Q’’’ and b4/b5 in the dipoles [Ewen]
    • Injection at 225 GeV
      • Review of the model at 225 GeV and check if some components diverge [Per]
      • Analysis of special measurements on 4001 [Lucio, Ezio]
      • Analysis of what available for the 11 T and proposal/analysis for the QXF in terms of b2/b3 decay and snapback [Susana, Lucio]
    • WISE
      • Preparation and debugging of WISE 2.0 (Agnieszka, Piotr, Per)
      • Review of calibration errors (Per)
    • Energy calibration
      • Precision of the magnetic model is asked by the HEP community to give calibration of mass (Jorg, Ezio)

     

    Upgrade of WISE [A. Szczotka]

     

    Agnieszka informs the team of the activities in BE ABP to build a new version of WISE, available as a Java tool, to generate the best model of the machine using the FiDeL parameters. Until now this project (WISE, Windows Interface for Sequence of Errors) has been steered by Per, on a Windows platform with an Excel code. This new piece of code should perform the same task in an easier environment, without the need to go through the manual generation of error tables (by Per) as it is today. This also allows to further validate this complex piece of hardware, used not only for LHC but also in HL LHC and future projects.

     

    After Massimo comments on the higher order to be used in simulations, Per remarks that WISE is limited to order 11 but in principle this could be extended to order 15. Measurements are available but the FiDeL coefficients have been extracted only up to order 11, so this would involve some additional work (probably not to heavy since it would include only allowed systematic multipoles).

     

    Agnieszka presents the advancement of the tool, showing that most steps are completed, with the exception of the GUI (graphic user interface) and the geometric errors. The error are propagated with the linear assumption, and both Gaussian and sum approaches will be implemented. A guideline on which of the two assumptions is better would be welcome.

     

    An update on the project status will be given in a couple of months.

     

    Hysteresis errors in the squeeze at 40 cm [P. Hagen]

     

    Per starts from the Riccardo optics files to understand if the neglected hysteresis of the MQM and MQY will be larger than in 2015. Per focused on these two families of magnets since for the other ones the problem is negligible (triplet and main quadrupole have a nearly constant and large current during squeeze).

     

    Per recalls the measurements analysed by Walter Venturini Delsolaro many years ago. When the magnet ramps down, since FiDeL neglects the hysteresis the magnetic model will be underestimate the transfer function for the MQM (the MQM ramping down provide more gradient than when ramping up at the same current). On the other hand, for the MQY the situation is reversed, and a lower gradient is provided when ramping down. The effect starts to be sizeable (above 0.1%) for current below 1000 A.

     

    Since the manual analysis of all IPQ is rather cumbersome, Per has developed a code to estimate the error on the TF induced by this effect (it will be positive for MQM and negative for MQY). Since in some cases the current is oscillating with small amplitudes, Per considers the error only if the change in current is larger than 5 A. Results show that we can expect at most 50 units errors in two Q6 circuits (see table in the last slide).

     

    A second optics will be issued by Riccardo, with reduced decrease of currents (so the error should be lower). Rogelio will estimate the impact on beta beating.

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