- Regarding the magnetic measurements
- It was recalled that there is more superconductor in the conductor used for SP105. The Cu/Sc ratio is comprised between 0.97 and 0.98 (strand RRP 150/169) whereas it is comprised between 1.22 and 1.27 for the previous models (strand RRP 108/127 and 132/169);
- The model SP105 has the best field quality, amongst the models made to date;
- E. Todesco suggests having a careful look at the harmonics during a decay, and at the waviness along the coil as it was done for the LHC magnets.
- Regarding the mechanical aspects
- E. Todesco has questioned the relevance of targeting only 9 MPa of stress reduction in the mid-plane, as this is likely insufficient to affect, in the good direction, the conductor performance. Also, this is of the same order as the uncertainty we have in the FEA. C. Löffler answered that the 9 MPa are not a proposed target, rather a study case to understand feasibility;
- G. de Rijk asked whether there could be a shimming error (as b3 is different from the other models, …)? This is unlikely, as we have only one shim at the pole along the straight part. The magnetic measurements will be repeated with shorter pick-up coils (there are coils of 130 mm length);
- D. Tommasini suggested redoing the assembly of the model with Fuji paper installed on the entire length of the mid-plane, using smaller shims, or smaller collaring keys, to compensate for the presence of the Fuji paper, in order to verify what is the actual stress distribution in the mid-plane. This should tell us whether there are excessive stresses at the location of the mid-plane quenches;
- B. Bordini recalled the importance of looking at the thermal contraction coefficients, which are of the order of 3.3 (average) on a cable, and of the order of 1.6 on a filament. As there is more superconductor in the strand used for SP105, there might be an impact;
- Discussion
- The relevance of a thermal cycle was discussed. If we are facing a reversible degradation, the magnet may not perform better after a thermal cycle (if there is no action to change the stress/strain conditions), may be even worst. On the contrary, if we are facing permanent degradation then, the magnet is anyway lost. There was a consensus on the fact that a thermal cycle was not needed, and that the magnetic measurements (short pick-up coils), and the collaring test with Fuji paper, were of higher interest;
- B. Bordini informed us that tests will be carried out at Twente on the specific cable used in SP105, at increasing pressure up to 200 MPa. Similar tests were already done in the past and there are indications that the results are relevant;
- B. Bordini: if we would redo the model SP105 with a higher pre-stress then, we would see how much it degrades further;
- F. Savary presented a preliminary schedule for the reconstruction of two new apertures, SP104 Bis with the coils #109 and #112, and SP105 Bis with the same coils #114 and #115 assuming that it would be decollared for implementation of a new shimming plan. The collared coils could be put together, without going again in a single aperture structure, in the two-in-one model DP102. In the best case (meaning that priority would be given to this plan, which needs to be verified w.r.t. the other activities on-going in bldg.927), the two-in-one model could possibly be delivered to SM18 for cold tests in late March 2017;
- S. Izquierdo Bermudez underlined the importance of testing the two-in-one model DP102 in order to learn about the protection behaviour in presence of an unbalanced assembly like it will be the case in the prototype (in terms of conductor, which will be different in the two apertures). These tests are of utmost importance to predict the behaviour of the prototype.
- Conclusion
- The model SP105 shall be removed from the test station, and moved to bldg.927 for warm magnetic measurements (with short pick-up coils). Thereafter, it shall be moved to bldg.180 for the cutting of the shells/end plates. The work to be carried out in bldg.180 shall be done by the end of the year, as a big part of the team will not be available after Christmas because of EYETS 2016/2017;
- As soon as the collared coils of SP105 are available, they shall be moved back to bldg.927 for decollaring, and collaring test with Fuji paper in the mid-plane;
- The plan will then be fine-tuned depending on the results of the collaring test.
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