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LMC follow-up and MD preparation
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Europe/Zurich
6/R-012 - conference room (CERN)
Present: Andy, Maria Kuhn, Ana, Lukas, Tobias, Piotr, Rogelio, Jaime, Ewen
Andy, Comparisons to K-mod
Uncertainties from magnets calibrations have been included in segment-by-segment via an analytical equation.
Both K-mod and turn-by-turn suffered from tune and BPM problems so far.
Probability of chi2 function is used to compare measurements.
3 BPMs with very small error bar dominate the discrepancy.
K-mod errors include random errors and a constant uncertainty in the K. Why we (ac dipole) have small error bars if measurement is not good? To be followed up.
Both calculations are average beta at the quads. Andy might include averaging in s-b-s.
In IP2 there is a large discrepance, K-mod sees 20% beta-beat.
IP1 AC dipole data seems to suffer from BPM choice, very large error bars...
Actually 20% discrepancies in IP1 and IP2.
-> Try to follow up with Maria's measurements next week, Andy on Skype
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Tobias, Dispersion and chromatic coupling
Dispersion problem with large error bars in beam 2.
Orbit is stable over 2 minutes (less stable over 1 h).
Beam2 Normalized Dispersion disagrees when considering only 0 and +dp and only 0 and -dp. Source of error bar is clear. Also seen in the normal dispersion.
Computed dp/p due to the the +-50Hz trim is not symmetric, this is already a puzzle but small, it does not explain discrepancy.
To be followed up taking more measurements +, - and 0.
Simulating chromatic coupling measurement using nominal model. Adjusting chromaticity.
Driving at the same tune distance the method works very well -> Distance between driving tune and natural tune should be kept very constant. Message:
1) Use same x-y chromaticities and drive at the same distance. This is safe today
2) Change AC dipole calculation for coupling, use h1001 instead of f1001. Change also corrections.
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Ana, Beta from amplitude
Some correlations are apparent, more accurate estatistical approach needed.
Absolute amplitude signals not stable after 2 minutes! -> view in relative.
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Lukas, beam optics measurements in LSA
Optics measurements have already been put in LSA. Successful tested. Some problem with the GUI that one cannot choose different sets of beam processes, it does not react. After uploading one, you have to restart.
Tobias mentions that some buttons become unclickable -> To be submitted to Delphine, and ask for a comment where we can specify which optics we uploaded (Jaime, Lukas and Tobias).
Maria asks about injection values, however we do not have good measurement yet...
Tobias asks about downloading from on-line model. Lukas answers that this is still difficult.
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Jaime, Software updates
Beta* automatically computed displayed on GUI and in the usual sbs output.
Now the error cut can be set in the sbs element.
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Ewen, non-linear chrom, IR non-linearity, fringe fields
PTC Fringe fields do not explain discrepancies on crossing angle scans.
MD procedures discussed.
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