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AD realignment during LS3
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AD realignment during LS3
The possible realignment of the AD optics during LS3 is discussed. The measurements performed regularly show long term movements and also known positioning errors of some magnets, which in the long run could become problematic. Camille suggests to take advantage of LS3 to come back to a “0” situation.
During LS3, all vacuum sectors of the ring plus the injection line will be brought to atmospheric pressure.
The refurbishment process has been the occasion in the last years to realign a significant fraction of t he magnets, usually performing some “lissage” with respect to the surrounding magnets. The strategy has proven to be correct if we see the regular improvement of the machine performance.
Nevertheless, the aperture model does not show any potential significative gain in a general re-alignment, and cannot exclude the risk to even potentially degrade the current situation.
The work involved in realigning the magnets (potentially only the quadrupoles as the dipoles have a large aperture and play a smaller role in fine tuning the beam position) mainly concerns the vacuum team. Indeed, all magnets before they can be moved much be disconnected and then reconnected after swapping the seals for new ones. The cost of this can be evaluated to some 500 CHF per magnet to be moved. Also the availability of the VSC team at this stage is not guaranteed.
For the MSC team, this job is not unusual in other machines and is considered acceptable. LS3 program includes that 10 main quadrupoles will be refurbished, and 4 magnets in the injection line will be replaced. Some space would have to be found for the temporary storage of the magnets connections covers. Unused positioning motors would have to be removed in some cases.
Camille will refine the proposal, to be discussed in an upcoming ADTC meeting.
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