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ArcHalfCellMock-up Meeting #9
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Notes of Meeting Arc Half Cell Mock-up #9
7th November 2023
List of people attending the meeting:
F. Carra (chairman), J. Bauche, J. Coupard, C. Eriksson, H. Gamper, M. Guinchard, P. Lersnimitthum, K. Hanke, E. R. Howling, L. Hutin, K. Oide, A. Piccini, C. Tetrault, M. Timmins, J.-P. Tock, F. Valchkova-Georgieva, L. Von Freeden.
Slides of the presentations are available in the Indico page related to the meeting (ArcHalfCellMock-up Meeting #9 (7 novembre 2023) · Indico (cern.ch)).
Agenda:
- General information on the Mock-up project (F. Carra)
- Presentation of the first phase of the experimental campaign: vibration results of the prototype quadrupole (M. Guinchard)
- Comparison between simulation and experimental results (A. Piccini)
- Next steps (F. Carra)
1)
F. Carra introduced the meeting by explaining that there had been no AHCM plenary meeting recently, but that the team had organised many parallel meetings, in particular concerning the experimental campaign to determine the stability of the short straight sections. The first step of this campaign has been completed and the results will be presented today.
2)
M. Guinchard presented the experimental vibration measurement results of the 1m long quadrupole prototype produced by TE-MSC before the FCC CDR. Two types of measurements have been done:
- An experimental modal analysis: this involves exciting the magnet using a shaker to generate white noise, and the vibrations are analysed using a 3D scanning vibrometer, which meshes the structure and analyses its vibration modes.
- Transfer function measurements: measure the Power Spectral Density at the ground level and at the level of the system whose transfer function needs to be determined (magnet – setup #01, marble – setup #02, magnet + marble – setup #03).
The important points are that rigid modes of the quadrupole can be found below 100Hz while natural modes are above 300Hz. It is therefore important to think about how the magnet will be fixed, whereas its stiffness looks pretty good.
The transfer functions still need to be evaluated, and the next step is to carry out the same measurements, but on a survey supporting table.
K. Oide asked how to obtain these results but for a magnet that will in reality be longer? M. Guinchard explained that this was the purpose of benchmarking with simulations and that this would be covered in Audrey’s presentation. F. Carra pointed out that the bending frequencies will scale with the square of the length, therefore they should remain still quite high also for a real-length magnet. K. Oide remarked that not only the bending frequency is critical, but also the other frequencies observed will go down with the length, since a higher length also corresponds to higher mass.
F. Carra noted that the geometry of the quadrupole is still evolving, Jeremie confirmed by explaining that the envelope of the quadrupole would remain the same, but the cross section will evolve.
3)
A. Piccini presented the comparison between simulation and experimental results. Modal analyses were carried out using finite elements method with Ansys software. It can be concluded that for mode shape results simulation and experimental results are consistent! It is then possible to carry out FEM studies to analyse new magnet geometries. The mode shapes have relatively high frequencies, even for a 2.9m long quadrupole, the geometry of this magnet is thus stiff. For the rigid body modes, they are of lower frequency. They are more difficult to identify in simulations because they are dependent on the boundary conditions, hence the importance of working on magnet fixation.
K. Oide asked if the position of the magnet's feet had been optimised? A. Piccini explained that for the moment no position optimisation had been carried out, and Jeremie confirmed, but it is something that can be done also with the help of the simulations.
F. Carra note that it would be useful to check the simulations of the quadrupole adding the coil mass, because even if the contribution should be small, it could be interesting to monitor the contribution.
4)
F. Carra detailed the ongoing and next steps activities, partly with the collaboration of partner institutes. The next step is to continue with the experimental campaign, and to produce two girders to be assembled in the dummy mock-up of the SSS, which will be installed at CERN in building 112. F. Carra also mentioned that A. Piccini will participate in the FCCIS workshop, the link of the presentation is the following: FCCIS_141123_Status_vibration_dynamic_stability_V1.pdf (cern.ch).
Actions follow up
- The MME team will find an available marble girder to pursue the measurements.
- M. Guinchard and D. Thuliez will evaluate the transfer functions following the measurements.
Opened actions
- F. Carra and A. Piccini will organise a meeting with T. Raubenheimer and K. Oide to discuss about the specifications. (Meeting #7)
Minutes written by: Audrey Piccini
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