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TT20 survey
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866/2-D05 (CERN)
TT20 survey
Participants:
- Alex
- Matthew
- Anne-Valerie
- Patrick
- Jules
- Camille
Summary:
- There are ~ 50 mm offsets between the initial conditions applied in the SURVEY commands for TT22 and TT25 and between TT23 and TT24 in the MADX optics model from acc-models .
- acc-models MADX model of TT20 agrees quite well with GEODE data, except for the end of TT21 (~ 10 mm error) and TT24 (~ 2-3 mm error). Most probably the discrepancy is caused by rounding error of the initial conditions, TBC.
- Initial conditions from Anne-Valérie agree with GEODE except for the TT25. Most probably because of the location of the chosen starting point on the line.
- It is assumed (although not verified) that the center of the MSSB and TCSC blades (lowest point of the V shape aperture) are aligned with the upstream beam axis given in GEODE.
- The centre of the up and downstream flanges on the MSSB vacuum chamber as a transverse offset with respect to the beam line defined above. From old measurements on a West Area spare this is estimated at 49.5 mm in H towards Saleve and 5.5 mm above in V: this means that that the horizontal plane of the blade of the splitter appear slightly below the centre of the vacuum flange (seen on the drawings without dimensions)
- Old vacuum chamber drawings: https://edms.cern.ch/ui/file/244254/AA/sps8097001132-v.AA.pdf
- The flange position (roll) is adjustable, we can change it if needed to adjust the relative height of the apertures
- Today we don't know the installed vacuum chamber configuration nor the actual position of beam lines around the splitters.
- The splitters may have unknown roll error.
- We agreed with Patrick and Camille that it would be prudent to measure select points on each beam line before the MSSBs are removed at the beginning of LS3
Actions:
- Layout database to be updated with best knowledge of vacuum chambers Action Alex to contact Anthony Harrison to understand timeline
- Check if discrepancy between GEODE and MADX are caused but the initial conditions or the sequence by launching identical initial conditions Action Alex
- Double-check TT25 initial point and specify exact starting position (or element to which the point belongs to) Action Patrick / Anne Valérie
- Double-check fiducialisation used in the past and the reference drawing used for alignment of the MSSB Action Patrick
- Check with Jeremie Bauche and Philip Schwarz (TE-MSC) if we have drawings locating the MSSB yoke inside its vacuum chamber (with dimensions) Action Jules
- Take into account the geometry of the vacuum chamber(s) around the MSSBs and its flanges, add corresponding apertures to MADX model Action Alex
- Propose optimal position of the flange to maximise aperture in the future for a given splitting ratios Action Alex
- Vary initial conditions in TT21 and TT24 to match survey to Geode data, or conclude that the original sequence to generate the data in GEODE has changed Action Alex (also check strategy with Francesco)
- Investigate possibility to measure the vacuum chamber positions in the YETS25/26 when accessing to measure the position of T2 Action Camille / Anne Valérie
- Check LSA for the bump shapes applied in the machine and discuss with Francesco how the separation between the lines is defined (especially of the TT25 angle to bring the beamline back to the same height at the targets) Action Alex
- Prepare to request and keep a minimum amount of time in NA-CONS planning before LS3 to measure select points on the beam lines: Action Camille
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