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    2nd Run III FiDeL meeting

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    Minutes of the 2st FiDeL Run III meeting

    Date: 2020-02-04

    Place: 6-R-018

    Presents:

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

    The b4 correction in IR1 and IR5 [E. Todesco, E. Maclean]

    Ewen has recomputed the b4 correction in IR1 and IR5 using the MQXA and MQXB errors presented by Ezio (data present in FiDeL reports). Using only MQXA, one finds a 0.8 m-4 octupole gradient correction for all IP and all sides; this is ~30% of the maximum correction strength, i.e. 2.3 m-4. Beam measurements provide values within 20% from this correction. Adding the effect of MQXB, the expected correction increases (in absolute value) by 0.2-0.4 m-4, and the agreement gets slightly worse (within 20-35%). In general, the beam-based correction is smaller (in absolute value) than the computed correction, in all IP and sides. Further investigation is ongoing to estimate the end-field effect (B. Dalena at al.).

    The cross-check of the data shows inconsistencies in some ID cards, manually corrected by Massimo (but not at the EDMS level) and in data provided by WISE for the model-based correction. Both discrepancies will be investigated for the other multipoles. Also, a plan for the finalization of JISE will be discussed and presented in a future FiDeL meeting.

     

    11 T magnetic measurements towards FiDeL [L. Fiscarelli]

    Lucio reports on the available data for the 11 T. For the short models, we have data of one double aperture with final iron yoke. For the 5.5-m-long magnets, we have one full set of data (two apertures MBHB-002) and one partial set of data (up to 8 kA, MBHA-002).

    • Transfer function variation with current (slide 9) is in agreement within 10 units for the three cases (short model, MBHA-002 and MBHB-002), so this component is well assessed. This is the most critical one for operational settings since it gives the current in the trim. A decay of the TF at injection of 4 units is observed.
    • b3 has an important change of 25 units (negative) from injection to 1.2 kA (slide 14 and 15); this could give sizable effects on chromaticity control during the ramp. Saturation component at 7 TeV has a large variability (about ±1 units) but this should not pose problems for operation.
    • b2 saturation is 10 to 15 units: the impact of this change of tune should also be evaluated (see slide 15). On the other hand, a corresponding correction could be implemented in the nearby IPQ.
    • Multipole decay and snapback are lower than in the MB.

    Next steps are (i) the evaluation of the components that could be critical for the beam control, (ii) the construction of the FiDeL of the 11 T based on the available data, and (iii) to decide what to implement in LSA and how.

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