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ArcHalfCellMock-up Meeting - BPM and interfaces # 2
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ArcHalfCellMock-up Meeting - BPM and interfaces # 2
Notes of Meeting Arc Half Cell Mockup – BPM and interfaces #2
4th May 2023
List of people attending the meeting:
F. Carra (chairman), J. Bauche, L. Baudin, C. Jaermyr Eriksson, E. Rose Howling, A. Piccini, S. Rorison, M. Timmins, M. Wendt.
Slides of the presentations are available in the Indico page related to the meeting (ArcHalfCellMock-up Meeting - BPM and interfaces # 2 (4 mai 2023) · Indico (cern.ch)).
Agenda:
- Presentation of the FCCee Arc Half Cell Mock-up project (F. Carra)
- Status on the design of the BPM pick-up on the vacuum chamber (S. Rorison)
- Introduction of the new PhD student: (E. Rose Howling)
- Discussion about the mechanical integration of the BPMs
1)
F. Carra and L. Baudin gave a reminder of what the Arc Half Cell Mockup project is about, i.e., build a mock-up of the most recurrent assembly of the mechanical hardware in the FCC to optimize and test several aspects.
As requested by M. Wendt, the link of the Indico page of the project will be send to the BPM team (action Audrey).
The mock-up will be 1:1 scale in cross section but the length will be shorter. As indicated by J. Bauche, it is not necessary to have 20 m of dipole.
Regarding the mock-up fabrication, L. Baudin asked if a prototype for the vacuum chamber was planned, when and how? S. Rorison explained that the first prototypes of cold extruded vacuum chamber have been manufactured, these vacuum chambers have an internal diameter of 70 mm and a lengths of 2 to 5 m.
2)
S. Rorison presented an update on the design of the BPM pick-up and the first results of the test of the additive manufacturing method for the buttons. Cold sprayed copper is added on the cold extruded vacuum chamber in order to machine the buttons. A flange made of Shape Memory Alloy (SMA) will be used to fix the BPM pick-up on the vacuum chamber.
The slides corresponding to S. Rorison’s talk will be uploaded on the Indico page (action Sam).
J. Bauche reminded that the diameter of the chamber is still not fixed and is still under discussion between 60 and 70mm. M. Wendt explained that for testing the BPM a 70 mm diameter should be fine, the results can be then scaled to 60 mm if necessary. Therefore, he asks if it would be possible to have the step file of the vacuum chamber to design the BPM (action Sam).
M. Wendt reminded that the ceramic material (alumina or glass) used in the BPM pick up is brittle, the feasibility of using SMA technology for the sealing has to assessed by tests.
M. Wendt advised design modification in order to fix the vacuum chamber inside the quadrupole. He suggested to add pins on the vacuum chamber. M. Wendt will share information about the mechanical effects of the synchrotron radiations and heat loads on the vacuum chamber (action Manfred).
M. Wendt indicated that the concept would be to fix the BPM with respect to the quadrupole and with respect to the vacuum chamber, but this requires enough space.
3)
E. Rose Howling is a physist PhD student from Oxford university. Already summer student at CERN, she has started her thesis in April 2023. She plans to perform RF simulation with CST in order to optimise the design of the BPM pick-ups, the aim is to minimise the beam coupling impedance. The design should be fixed by the end of 2023. After the simulation and design of the BPM pick-ups, Emily will perform two types of tests before the end of 2025, to characterise the BPM. One will be performed in the laboratory using a stretched wire and the other at CLEAR facility at CERN with a test electron beam, which will require at least two vacuum chambers.
4)
F. Carra proposed that E. Rose Howling and M. Wendt present next time the detailed milestones related to the thesis and that for each one they specify what will be their needs (action E. Rose Howling and M. Wendt).
J. Bauche added that it could be interesting to do the tests with a prototype of the magnet. M. Wendt indicated that this is not an objective of E. Rose Howling’s thesis, considering all the unknowns this can be difficult thus the tests might be done with the magnets but not as a priority.
L. Baudin asked if they had an idea about the relative alignment of the sextupoles compared to the quadrupole? M. Wendt stated that this was not his area of expertise, that having BPMs for each sextupole would not only increase the price but also the impedance. It might be better to consider a mechanical system that adjusts the sextupoles with respect to the quadrupole.
Actions follow up
- L. Baudin, F. Carra and A. Piccini will send the link of the Indico page of the project to the BPM team. à DONE
- M. Wendt will share information (reviewed article) on the mechanical actions on vacuum chamber due to SR.
- S. Rorison will upload hisslides on the Indico page of the event and send the step file of the vacuum chamber prototype to E. Rose Howling and M. Wendt.
- E. Rose Howling and M. Wendt will provide detailed milestones related to the thesis and that for each one they specify what will be their needs.
- L. Baudin and A. Piccini will add M. Wendt and E. Rose Howling to the FCC-ee Arc Half Cell Mockup e-group. à DONE
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