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PS-harmonic-saturation and LHC normal RDTs at injection (b3,b4,b5,b6)
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Europe/Zurich
6/2-004 (CERN)
Vittorio: MU studies
Vittorio performed Q and Q' measurements on a range of cycles to different extraction energies. Several have very unstable Q and Q' values due to transition crossing and then eddycurrents / overshoot at end of ramp, however in most cases can find a stable region of the platteu later in the flattop. He has considered the Q vs energy in the stable region of the platteau.
Comparing platteu measurements to a continuous measurement during the 23 gev ramp: 7 and 14 GeV cycles don't show a good agreement. Maybe down to some dynamic effect at end of ramp - to be understood - however 23 GeV cycle looks very nice and 2GeV 10GeV 18GeV all agree well.
From the opera model it also looks like the b2 is indeed saturating faster than the dipole field, qualitively consistent with the Q obs.
Tobias raised question of how to implement b3 component into sbend since the changed reference radius may cause some extra feed-down.
Action - Need to implement into madx so we can see the comparison!
Action - check the continuous measurement in e.g. 14 gev ramp to see if they agree with the observed evolution from the 23 gev cycle.
Mael: b6 RDT
Mael sees the 5Qy line in some proportion of the BPMs in latest measurements with big vertical kicks. See very noisy phase inconsistent kick to kick in some arcs, in particular 7/8 which matches up well with the arcs where you cant see the resonance line - but in the arcs where you can see the line you get a nice consistent measurement of the re and im from shot to shot
5Qy lines were clearly more visible in the 2022 studies than 2023 - see the line with smaller kicks 20% vs 35%
model and measurement seem consistent - but big error bar on the measurement
action - adding b2 errors to MB has big impact on the simulated RDT - but b2 gives big phase wave - check impact of matching to measured phase rather than using the dipole b2 errors without any correciton
felix - check if reconstruction of complex spectra depends on measured or model betas and phases. Since if using model then adding the b2 errors will also mix the +-5Qy
action - see if reducing svd can improve measurement
action - list which arcs are visible and which are not
Mael: b5 RDT
Very weird behaviour of the LHCB2 response matrix. Makes no sense there must be a bug.
Action - Check the prediction of the response matrix vs the measurement. Check simulation vs response matrix to see which part doesn't match.
Felix - maybe try a simpler a4 correction with a couple of correctors to compare to commissioning a4 correction and see if there is a similar problem.
Action - check if b4 impact on b5rdt in model is actually a b3xb4 term (turchetti table)
Sasha: b3/b4 RDT
Felix - propbably shouldn't consider the f1020_x from 2022, since it is very close to noise limit. Other measurement look good though
action - compare to madx model with the different b3 errors
action - compare the new measurement of MO rdt to the shifts
action - find a sextupole correction
Wietse: BBQ phase noise
Discussion: Documentation
MD note status 2022
MD note status 2023
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