ArcHalfCellMock-up Meeting - Alignment and girder #1

Wednesday 26 Oct 2022, 09:00 → 10:00 Europe/Zurich

Federico Carra (CERN)

Notes of Arc Half Cell Mockup Meeting - Alignment and girder #1

 

List of people attending the meeting: 

L. Baudin, H. MainaudDurand, W. Niewniem C. Tetrault, 

 

Visit of TT61 planned at the same time of the dry-run visit organised for the IWAA conference

 

Here are some figures noted down after our meeting, please don’t hesitate to correct or further comment them:

• +/- 20 mm radial and vertical range of motion for the jacks
• observed LHC ground motion: 1 mm/year (at most critical location, over a distance of 800 m)
• The reference systems for the radial position of the magnets will take some space in any case 
• WPS sensors have horizontal sag of the straight wire compared to the circular trajectory
• WPS sensors need a reference to gravity to be able to re-compute the vertical sag.
• Structured Laser Beam (SLB) need a vacuum chamber of 20/25 mm of diameter, in the currently foreseen configuration.
• SLB might also need reference to gravity (not sure yet)
• The redundancy of the reference systems (on right and left of each accelerator) is needed to control the roll angle of the magnets
• Other techniques might allow to control this roll angle, such as inclinometers and multiDOF sensors, but they are not yet ready.
• The reference system should be installed as close as possible to the magnets. A metrological plate should connect the sensor to the magnet, it has to be rigid enough.
• Seeing the booster alignment requirement (150 um, to be further investigate), it does not seem possible to use the same reference systems than the collider.
• Requirements from physicists are given on 100/1500 m long moving window 
• The longitudinal overlap of the reference systems (which could be 200 m long) has to be foreseen
• HLS is used to control the vertical position, controlling the liquid level difference, therefor by principle it requires some vertical space.
• A reference system will be required even if a Beam based alignment strategy is used
• State of the art over 50 m = 100 um
• State of the art over 7 m = 30 um (but the size of the girder makes the alignment of  the components challenging as CMM machine cannot be used for such large structure)
• On 2-m-long girder 2um per meter alignment can be reach using 3D scanning technic
• Time consuming! 5h, 4 guys, for the fidusialisation of elements on a 2 m long girder in the frame work of Pacman, and CLIC Project
• Size of the fidualisatin targets: 1 and ½ inch or only a sticker
• Radiation level is a huge concern which has to be accounted

I add here a sketch about the overall layout (as I understood it, at least…)

Reference: 
Overall booster configuration : FCC Accelerator Pillar meeting #05 hold on September 22nd https://indico.cern.ch/event/1161632/

Overall collider configuration : FCC Arc Half Cell Mock-up meeting #01 hold on May 24th https://indico.cern.ch/event/1163471/