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MQYYM Final Assembly Plan proposal
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Europe/Zurich
CERN
CERN
During the meeting it has been presented the status of the project, the proposed shimming plan in the straight part and in the ends. For the first assembly only the straight parts has been shimmed to control the stress in the coils and keep the stress between 90 and 120 MPa in the coils. The ends have not been shimmed because the mechanical measurement showed that for the full ends the stress is lower than in the straight part. However there is one part of the ends where the conductor has the same position than in the straight part and where the stress will be similar to the stress in the straight part. This area will be overstressed. Moreover removing some shimming on the pole could also lead to an area where the cable is not supported. Gijs warns that on the LHC dipoles some short circuits appear on 1 over 50 coils in the same location due to a lake of support of the conductor. To limit the stress in this area and to be sure that the conductor is always supported, two solutions have been proposed:
- Juan Carlos propose to create a slope in the insulated pole piece to be sure that the conductor is always supported (see figure 1). Everybody agree and it will be done before the assembly using the azimuthal shims as reference.
- Another proposition is to remove two layers of the GPI insulation over the ends trying to make a smooth change of radius. The modification of the 3rd and 4th layer of GPI will be study at CEA this week, to be done at CERN next week before assembly.
Another proposition evoked is the complete removing of one layer of GPI to decrease the overall stress in the coils. For the insulation point of view it should safe. This solution have to be looked carefully however it will change completely the shimming plan in the straight part used and validated during the first assembly.
The new assembly will begin next week at CERN (927).
Thanks to all the participants of the meeting for your time and help.
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