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ArcHalfCellMock-up Meeting #12
Description
This meeting follows the internal review and the presentation at the ATDC meeting, it will focus on the 1:1 scale Mock-up and on support design updates.
Agenda:
1) Feasibility report outlines (F. Carra)
2) Arc Half Cell 1:1 Mock-up - Status (A. Piccini)
3) Collider and Booster support design updates (M. Timmins)
1)
F. Carra presented outlines of the feasibility report on the contributions of the mock-up project, here are the important points:
· Arc half-cell WG is responsible for one contribution in the “Collider” section and one contribution in the “Booster” section (in the “Technical Systems” chapter).
· We will ask you support during the preparation phase and to review the draft before sending it to the management (action Arc Half Cell WG members).
2)
A. Piccini presented the Arc Half Cell 1:1 Mock-up status, here are the important points:
· Dimensions: release of the two drawings: baseline definition for the arc, approved by ATDC management (links in the ppt). Please everyone refers to these two drawings for the up-to-date cell dimensions and coordinates.
· Installation site: Integration work in building 355-358 is still ongoing. The IRP due diligence has been submitted and will be reviewed during the next SCE internal regular IRP follow-up meeting. A memo about the transfer of part of building 355/358 from SY to FCC management has been prepared and is circulating on EDMS.
· Structure: The steel structure has been validated. Calculations are being finalised to prepare a file to be reviewed by HSE (mid-December). The anchoring assessment and seismic is carried out by SCE team. The drawings of the structure are being finalised to launch manufacturing.
· What will be installed: Procurement process launched (DAIs, tenders, etc.). Discussions with groups ongoing to define orders to be placed.
Comments:
à TSO definition:
O. Rios mentioned that a dedicated TSO for the mock-up is mentioned in the memo. It has been confirmed that the building can be ‘split’ in two, requiring the definition of a TSO for the FCC part and one for the SY part (X. Genillon today). Action F. Carra to investigate with the FCC/ATS-DO management.
à What will be installed:
M. Morrone mentioned that for the Pre-TDR phase, they plan to build a 12-m long vacuum chamber to be installed in the mock-up. This can eventually be installed in the mock-up.
J-P Burnet highlighted that it is the aim of the Pre-TDR work package definition: to define the objectives and the needs for this phase. Prototyping is one of the main objectives for the technical systems, for example vacuum and magnet elements.
à Work on the building:
J-P Burnet asked: what work needs to be done on the building?
For the RF part, the floor must be closed. For the mock-up part, there is no major work to be done, but for the anchors it will be necessary to check for traces of lead paint, potentially open one of the pillars if it is not load-bearing, plus restore it for the visits: paint, ventilation etc. And we are also looking into the possibility of fixing the slab on springs – under discussion with SCE.
à Anchoring of structures:
E. Bernard noted that the anchoring of all the structures may not be necessary at first, as many dummy elements will be installed. This could maintain flexibility, but when vibration measurements are carried out, the structures will have to be fixed to the ground. This specific point will be tackled at one of the next mock-up core team weekly meetings (action A. Piccini).
à Ground motion measurement:
J-P Burnet asked if ground motion measurement can be done in building 355-358 to find out where the SSS should be installed, whether the environment is desirable etc. M. Guinchard confirmed that this was possible and could be used to determine the impact of the installation of heavy structures on the ground motion (action M. Guinchard).
3)
M. Timmins presented the updated designs of collider and booster supports, here are the important points:
· The design of the supports has been updated following the layout modifications and the magnets updates.
· The new layout follows the baseline drawings released on the 30th of October 2024 (Optic V24.3 GHC ttbar).
· The collider girder and booster support assembly have been optimised structurally and in terms of stability after several design and calculation iterations.
· The production of the collider girder has been launched in HMC-3 Pakistan.
· The SSS of the booster is following the same principles as the SSS of the collider: girder supporting quadrupole and sextupoles.
· The alignment is currently achieved using existing jacks (SPS/PSI jacks) but for the pre-TDR phase discussions are ongoing with BE/GM (Survey team) to jointly develop new jacks considering FCC requirements and to target a cost reduction. F. Carra mentioned that this task will be included in either the mock-up WP, or in the Geodesy and Survey WP. He will send to J. P. Burnet an updated version of the pre-TDR WP after discussion with BE-GM in the next days (action F. Carra).
Comments:
à Shifting of the booster magnetic axis towards the outside of the ring:
M. Guinchard noticed that the first booster mode remains quite low. And that there is a risk of crosstalk between the collider and booster systems. A. Piccini indicated that what would really help from a stability point of view would be to shift the magnetic axis of the booster towards the outside of the ring to reduce the lever arm, because optimising the structure has its limits. G. Roy noted that during the pre-TDR phase, we could try to optimise this from an optical point of view.
à Shifting of the booster cell longitudinally:
M. Timmins highlighted the fact that with the current arc half-cell length of the collider 26.055m and of the booster 27.125m, some elements are clashing when the cell is repeated. G. Roy confirmed that work is in progress to adapt the optics of the booster to obtain the same circumference as the collider.
J-P Burnet remarked that the SSS supports on the booster should not be in the same place as the shielding on the collider. G. Roy confirmed that we can play with the longitudinal position.
à New structures – impact on transport:
F. Carra asked D. Lafarge whether the weight of the new collider SSS might cause problems in terms of transport? D. Lafarge replied that yes, the increase in weight modifies the machine used, but what seems problematic is the installation of the collider dipole under the booster's SSS. It would be necessary to discuss this in more detail (action A. Piccini to organise a dedicated meeting with EN-HE).
à Synchrotron absorber placements:
J. Bauche noted that the position of the synchrotron absorber absorbers needs to be determined (possibly targeting a constant repetition rate across cells). In fact, their position impact the type of shielding and its position, the yoke of the dipole, the design of supports and their positions. A. Lechner organized a discussion on this for Friday this week.
à Feasibility report:
J-P Burnet proposed, for the images of the feasibility report, to stick to the configuration showed at the FCC week, therefore with the “slender” supports for the booster, as there is no time for all the teams to include a new support design in the report. But in the support optimisation section, the new design and the booster girder can already be introduced. The attendees agreed, we will stick to the images that will be shared by Fani after the EDMS approval process which is ongoing.
Actions follow up
1) We will ask you support during the preparation phase and to review the draft before sending it to the management (Arc Half Cell WG members).
2) F. Carra will check with SCE what is the status of the IRP due diligence.
3) F. Carra and A. Piccini will investigate a solution for the mock-up TSO, together with FCC and ATS-DO management.
4) Discuss the anchoring of the different structures in the mock-up (A. Piccini).
5) M. Guinchard, F. Carra and A. Piccini will organise ground motion measurements in building 355-358.
6) F. Carra will send to J. P. Burnet an updated version of the pre-TDR WP after discussion with BE-GM in the next days.
7) A. Piccini will organize a meeting with D. Lafarge to discuss about the installation of the different elements following their updates.
8) Organize a meeting to discuss the synchrotron absorber positions (done by A. Lechner 22/11).
Minutes written by: Audrey Piccini
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