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ArcHalfCellMock-up Meeting #4
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Europe/Zurich
Notes of Meeting Arc Half Cell Mockup #4
13th September 2022
List of people attending the meeting:
F. Carra (chaiman), S. Atieh, J. Bauche, L. Baudin, M. Benedict, A. Bertarelli, C. Erikson, K. Hanke, R. Losito, T. Raubenheimer, C. Tetrault, M. Timmins, F. Valchkova, L. VonFreeden
Slides of the presentations are available in the Indico page related to the meeting (https://indico.cern.ch/event/1196689/)
Agenda:
- Introduction, Presentation of the senior advisors’ meeting (F. Carra)
- Status of System Interfaces Design Work (C. Tetrault)
- Status of the arc cell integration (F. Valchkova)
1)
F. Carra opened the meeting and presented slides introducing the Senior Advisors Panel review. Status and orientations of the project will be presented to the panel. The panel will advise and give propositions about the planned activities over the coming months. F. Carra asked for feedbacks and contributions for the preparation of the presentation. A dedicated time slot and date is being defined by T. Raubenheimer, together with the Panel members; currently, it is proposed to have the meeting one day of week 39. The objective of the current meeting is the establish the highlines of the presentation to the panel.
2)
C. Tetrault presented his work about the interfaces between Magnet and Vacuum systems at various location of the arc cell: Dipole, Quadrupole, Sextupole (preliminary design), Dipole to Dipole interconnection (D2D) and Dipole to Quadrupole interconnection (D2Q))
The size of the flanges used in Callum’s model correspond to flange using Shape Memory Alloy (SMA) technologie and has been validated by TE-VSC colleagues. The updated design of the SR absorbers is also implemented.
Several areas of interferences have identified between components of the magnet system (yoke or busbars) and the SR absorbers and/or the insolation layer of the vacuum chamber. F. Carra commented that the 15 mm thickness currently assumed for the insulation system looks very large, compared to solutions used in the LHC, where thicknesses down to 3-4 mm have been employed. This is to be clarified with TE-VSC.
Inputs from TE-VSC colleagues are crucial as the interferences between magnet and vacuum systems could require modifications of the magnet yoke design or update on the beam-to-beam distance. Any change of the configuration would involve new magnetic simulations and a delay of several weeks.
The busbars connecting the dipoles must go around the quadrupole (and possibly 1or 2 sextupoles). The connection routing could go underneath the quadrupoles. Investigations must be carried on identifying the optimal position of this routing in the cross section.
M. Timmins raised the question of the interest of using a girder to support on one structure Quadrupole and 1 or 2 Sextupoles:
Girders may help with pre-installation of components and vacuum system. The possibility to slide the vacuum chamber through all magnets, and weld the extremity flange, as a second step, would save space between the magnets (no flange or bellows required between each element)
The positive aspect of using the girders from the point of view of the alignment and vibration requirements must be assessed by studies on the stability. The gain of the girder is to take the “small” elements to the same vibration mode, that might not be applicable to the pretty large elements of FCC (Quadrupole are 3-m-long). Experts from survey should also be included in the study.
J. Bauche suggested single element supports:
The gain of time in alignment is not obvious, in SPS, the realignment of each single element on the girders must be performed anyway.
In synchrotron light sources, where alignment tolerances are tight, girders must be huge to be rigid enough. The cost scaled to the number of items required for FCC project could be massive.
M. Timmins: if single supports are used, could a unique chamber be slid through all the elements in-situ, in the tunnel? If not: Could the chambers be welded? Must bellows and flanges be accounted? J. Bauche discarded the possibility to used splitable magnets suggested by T. Raubenheimer. The required mechanical tolerances would not be reached with an in-situ assembly.
J. Bauche suggested to use a configuration S-Q-S instead of Q-S-S, to keep only two different lengths of dipoles. T. Raubenheimer did not see any major drawback from the optic point of view.
M. Timmins: the length of the interconnection (the longitudinal distance between the yokes) must be increased to fit the BPM.
Main action: answer opened questions about vacuum system:
A meeting must be organized to discuss the interfaces between Magnet and Vacuum systems. Samuel Rorison, Roberto Kersevan and Cedric Garion from TE-VSC will been invited. Here are some of the questions that we need to address during the meeting:
- Minimum required thickness of the insolation layer? Is it possible to reduced it from 15 mm to 5 mm for instance?
- Presence of the SR absorber in Quadrupoles?
- Possibility of modifying the design of the absorbers? (vertical shift of the position of the cooling pipe out of the bending plan)
- Space allocation for the tools used to operate the SMA flanges to evaluate the needed clearance? (Especially on D2Q interconnections)
- Need of bellows? Possibility of SMA flanges? Or in-situ weld of the vacuum chambers between Quadrupole and Sextupoles
3)
F. Valchkova presented the status of the arc cell integration (which has evolved compared to the CDR version but not compared to the FCC week in Paris). The diameter of the tunnel is 5.5 m.
The vertical configuration (with the booster ring on the top of the collider ring) has been accepted by RF colleagues (cryomodules of the booster ring will be suspended to the ceiling).
With the current status of the space reservation for different systems, the horizontal configuration (with the booster ring on the same plan than the collider ring) would lead to a tunnel diameter of 6 m, which discards this option.
It is proposed to re-evaluate the space reservation dedicated to the different systems, to reconsider the possibility to place the collider and the booster on the same horizontal plan while keeping the tunnel cross section at 5.5-m-diameter.
F. Valchkova has discussed with Guillermo Peon about the re-evaluation of the encumberment of the water-cooling system: no major changes are expected if the users do not decrease their needs.
The space reservation for survey has been discussed with Mark Jones. T. Raubenheimer raised questions about space allocation for alignment: verify the space allocated to the wire alignment systems in the side-by-side layout. Is similar space allocated in the vertical layout? Is the wire system applicable to the quadrupole spacing of 50 m (in Z and W configurations)? Can the laser alignment techniques be used? What is the space allocation in this situation? Is there enough line-of-sight space to do laser alignment of the main ring magnets?
T. Raubenheimer asked on which basis the number of cable trays has been evaluated. F. Valchkova tooks the same number of cable trays than the one estimated for FCC-hh. Space reservation for power supply should be verified.
F. Carra pointed out that one possible problem for the vertical configuration is the vibration of the booster (although this should be more relaxed than the one of the collider ring). Stability and dynamic behavior of the booster ring using the preliminary design already provided by F. Valchkova.
T. Raubenheimer will provide first estimate on horizontal tolerance and vibration requirements for the booster ring.
Actions follow up
- Organise the meeting with the Senior Advisors Panel à T. Raubenheimer
- Prepare the presentation for the Senior Advisors Panel à F. Carra
- Meeting with TE-VSC colleagues to assess the points raised in Callum’s presentationà L. Baudin (for organisation) Follow up: See Minutes from ArcHalfCellMock-up Meeting - VSC MSC Interfaces #1 (https://indico.cern.ch/event/1203783/)
- Re-evaluate space reservation with the component or system owners (Guillermo Peon, Roberto Kersevan, Mark Jones). à F. Carra and L. Baudin
- Re-evaluate of the number of cable trays necessary for the power supply à F. Carra and L. Baudin
- Get in touch with Irene from Survey team à F. Valchkova
- Stability study on the girder configuration à L. Baudin
- Stability study on the booster ring à L. Baudin
- Investigate the possibility of a configuration SQS instead of QSS à ALL Follow up: SQS configuration has been discarded by O. Katsunobo during the FCC Accelerator Pillar meeting #05 (https://indico.cern.ch/event/1161632/)
- A node is created in the FCC hardware baseline a document should be added gathering all the links of the presentations and materiel used on the project à L. Baudin
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