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    12th Quench Behavior Team meeting

    → Europe/Zurich
    927/1-B23 (CERN)

    927/1-B23

    CERN

    35
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    Date: 2016-08-23, 09.00-10.00

    Place: 927

    Presents: P. Ferracin, P. Hagen, J. P. Tock, F. Savary, O. Bruning, S. Le Naour, A. Verweij, M. Modena, E. Todesco, R. Schmidt, R. V. Weelderen, G. Willering

    Updates of estimates of training to 7 TeV [E. Todesco]

    Ezio presents an update in the expected training towards 7 TeV. After recalling the method, the new elements are presented:

    • For the 1000 series, in absence of data a 5% probability to quench before 7 TeV plus 150 A (12000 A) was assumed in 2015. The analysis of the production data after thermal cycle show that a much larger fraction (18%) of the magnets quenched. The second quench in virgin conditions also shows a similar fraction. So, the new estimate of 18% is taken, thus increasing the total number of quench of ~50. Gerard points out that many magnets were also tested after 2008 – a paper will be presented at ASC, and a talk will be given in QBT in September to inject this information in the estimates.
    • The 2015 estimate was based on a slicing of the magnets according to the sector (case B): so for the 3000 series we had separate fits for the 45 sector and for the rest. The 2000 series was split in 78-81 sectors, giving most of the quenches, and the rest. Ezio presents an estimate where the fit are applied to the whole 2000 and 3000 production (case A) and where the slicing is done according to the production sequence (case C), that in principle should be a more natural way of slicing the data sample .

    The main results are the followings

    • The three estimates give a global number of quenches ranging from 520 to 580, so the number is not strongly depending on the slicing criteria.
    • All sectors require a similar number of quenches (40 to 50) to reach 7 TeV, with two exceptions: sector 56 (66 quenches) and sector 12 (26 quenches). So sector 56 should not be trained. Sector 12 would train rapidly, but should not be trained unless the problem related to the magnet quenching at low current is clarified.
    • The statistical error associated to the number of magnets over one sector (154) is ±12 quenches, and ±35 over the whole LHC (1200). One has to add on the top the error due to the precision of the estimate of the fit parameters (of the order of ±10 for one sector, and ±100 for the LHC), and the error due to the missing information for the best performing magnets, and on the second quench (of the same order of magnitude).

    Which sector to train? [all]

    It has been decided to train sector 45, mainly to see the second quench of 3000 series magnets. For the second sector to be trained, required to have a more precise final estimate, we exclude (i) sector 12 for the low current quench induced by QPS, (ii) sector 23 for the heaters, (iii) sector 56 for excessive training. There is a general consensus that a good candidate is sector 34.

     

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