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    BOND-M Cu cable: Issues on pop-strands

    → Europe/Zurich
    180/1-N51 (CERN)

    180/1-N51

    CERN

    25
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    FINAL UPDATE;

    After checking with Susana and Juan Carlos on my side, we concluded that:

     

    • We will try to re-spool the insulated BOND-M Cu cable (received full of pop-strands after braiding) by inserting a “compaction/laminoire” tooling in the re-spooling line.

    The objective is to try to correct as much as pop-strands as possible, and to be able to use this insulated copper cable for the first trial coil (400 m) and for winding tests (400 m, lots of margin).

     

    • Concerning new potential cable runs and your proposal to re-launch a new Cu run with optimized cable transposition pitch for mechanical stability:
      • For the moment, we do not see a high added value on re-doing immediately a full copper unit length.

     

    • We see interesting, however, the exercise proposed by Susana:
      • It could be advantageous instead to consider the exercise you propose (optimizing the transposition pitch for mechanical stability) but on the Nb3Sn cable (a small cabling campaign for tests).
      • Maybe the gain is marginal, but it could help us to minimize the risk of reproducing what happened with the Cu cable (and what has been a recurrent issue in MQXFB after braiding).
      • Similarly, Juan Carlos has confirmed as well that the BOND cable underwent a slight modification of the transposition pitch for improved mechanical stability.

     

     

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    According to Jerome F. and after discussions with Angelo B., the BOND-M Copper cable showed to be a bit unstable (with a certain tendency to create pop strands) after the fabrication. This is a particular difference of Cu cables when compared to Nb3Sn ones, already seen in the past.

    However, even if the cable mechanical behaviour was such, the cable was in good state and no pop strands were identified after fabrication. The appearance of the pop-strands (all along the BOND-M unit length) seems to be due to the additional contribution of the braiding.

    Jerome stressed out that similar pop-strand issues were encountered with FalconD and Eurosig copper unit lengths:

    • For FalconD, the transposition pitch was modified to make the Cu cable more stable
    • For Eurosig, the bare cable was treated in a sort of "laminoire" tooling to correct / cure the pop-strands. The solution worked well.

     

    In terms of possible next steps for BOND-M Cu cable:

    • Removing the conductor insulation for BOND-M is discarded, since there is not any proof that re-insulating again in the same conditions could improve the situation.
    • One option would be to produce a new Cu length with improved cable twist pitch for increasing the stability. We would need to send it for insulation. The cable could be produced relatively soon, but the slots for insulation seem very tight (note that the contract with CGP is being terminated in November).
    • Our preferred solution is to try to cure as much as pop-strands as possible by using the solution of a "laminoire". We will try to get the best 400 m of cable for the Cu coil, and the rest will be used for winding trials.

     

    DECISION:

    • For the moment, the immediate production of a new copper length is not considered.
    • We will try to make our best effort to correct as much as defects as possible in our insulated Cu cable, in order to use it for the trial coil and winding tests. The "laminoire" solution will be investigated. 
    • Based on the results of this exercise we will decide on next steps. In parallel, we will check with Susana about the alternative path proposed by Jerome (who proposes to launch in parallel a new Cu run for redundancy).

     

     

    ACTION ITEMS:

    • The required length for 10-stack measurements will be cut from the present BOND-M Cu insulated cable. Popped-strands will be cured by hand.
    • Next, we will try to include the "laminoire" tooling in our re-spooling line under tension, with the objective of trying to correct as much as pop-strands as possible. Different passes could be envisaged. Jerome will ask Angelo to show us the "laminoire" tooling before the end of the week.
    • At this point, we will evaluate the results and decide for next steps.
    • In parallel, we could check with Susana the proposal from Jerome of producing a new Cu cable length with improved parameters for stability (twist pitch). This could be done very quickly in the cabling machine in coming weeks. 

     

     

    Other info in terms of cabling:

    • Jerome has announced that there are available slots for cabling before the end of the year. If we confirm the BOND-M unit length, we could produce the cable relatively soon.

     

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