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Results from non-linear measurements and next steps
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Europe/Zurich
6/2-008 (CERN)
Non-linear measurements, Ewen
Beam1 2011 non-linear chromaticity agrees very well with 2015.
Beam2 horizontal disagrees a bit between 2011 and 2015, coming from larger Q''' (triple prime), a factor 2 larger now.
First corrections were not exact and needed a second iteration. This second iteration has been tested but not left in the machine. Nice decoherence.
Trims of MSS did not affect non-linear chromaticity. This trim of MSS was computed with a wrong input measurement files, like assuming it was kick but it was AC dipole. So actually MSS was trimmed but chromatic coupling remained similar order of magnitude.
Expected shifts in Q''' due to MCD trims agree with measurements. However there is a feed-down or cross-talk to MCO. A feed-down would require a 0.2mm systematic offset for all planes both beams. The consistency of these numbers might point more towards a cross-talk. Maybe this can be determined by re-analysing recentering the dp/p to zero the 0.2mm systematic offset hypothesized in the MCDs.
From the MCO changes is hard to conclude feed-down or cross talks. Maybe the fidel decay is contaminating the feeddown. Probably a DQx'=0.2 is measured in Beam1 (assuming some b3 decay of similar ammount).
To be checked how much MCO misalignment would be needed to explain a DQ'=0.2.
How does 2015 decoherence compares to 2012, seems better, actually.
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GUI news
Now it is possible to load the MQTs with date at model creation. New model construction was released.
Tests are needed.
Next GUI developments: towards automatic calculation of s-b-s, elements, beta* plus more automatic 'documentation' logging.
Other line of modification is communicating better Verena's multitrun and our GUI.
Jaime started looking at Verena's code and he found the classes but you need RBAC -> Ask Verena.
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To be done if commissining is still on: Injection with MSS, Ramp and beta*=0.65cm.
BPM rephasing to be addressed, because now we lost again many BPMs and it is unclear how
to recover them even for the expert.
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