Chromaticity correction (without RCS.A78B2) Thanks to: F. Roncarolo, E.Todesco, M.Lamont, J.Wenninger

Outline & Measurement method Matteo Solfaroli2 Q raw data Clean the data Fit a sin function with variable A Calculate Q’ Q’ function smoothing Elaborate data depending on needs  Q’ decay at injection (state of art)  Q’ during ramp  Q’ decay at flat-top  B3 to Q’ measurements  Q’ knob verification (OP w/o RCS.A78B2)

OP without RCS.A78B2 Matteo Solfaroli3 INJECTION B3 decay RAMP Snapback B3 variation (momentum change) FLATTOP B3 decay B2 compensation is calculated as for B1 then multiplied to a 8/7=1.14 factor The RCS.A78B2/B3 function has been equally distributed on the other circuits The B2 global_B3 knob has been multiplied by a 8/7=1.14 factor (effect of about 0.2 Q’ units) RCS.A78B2/B3 sec B3 Q’ min sec B3 ~7 B3 units Example of H corr

B3 decay at injection Matteo Solfaroli4 B1 Q’H ~ +2.5 Q’V ~ -2 B2 Q’H ~ +2.5 Q’V ~ B3 units B3 decay not correctly compensated (kind of expected), but the good news is that there is no visible difference between the beams Trims on lattice sext to get Q’~8 before going into the ramp

B3 decay at injection Matteo Solfaroli5 Example of horizontal corrections The problems seen during the scrubbing were likely due to: Not good control of the tune decay (due to lack of reproducibility) High precision required over a much larger window than in standard operation Q’ min July 4 th

Ramping w/o RCS.A78B2 6Matteo Solfaroli First ramp: At about 800 sec the B2Q’V starts growing and B2Q’H goes down then passes negative…B2 is dumped around 1080 sec after the ramp start Third ramp: Both beams survive! Q’ (re-)measured along the ramp (small corrections implemented) and at flattop Second ramp: Both beams survive the ramp, but are dumped about 30 sec after flattop is reached (electrical glitch caught by FMCM RD1.LR5)

Ramp 7Matteo Solfaroli B3 compensation at injection not perfect, about 2/3 Q’ units are not into the snapback correction but in the lattice sextupole Q’ along the ramp is well controlled (+-2) No visible effect from the missing RCS

Flattop 8Matteo Solfaroli Very good control of small (~0.05 units) B3 decay at flattop Small (visible on V??) effect from the missing RCS as the trim was reverted and not put back Tune decay not compensated (QFB during squeeze)

B3 to Q’ measurement Matteo Solfaroli9 Old assumption : 1 B3 unit = -43 Q’ units in H 35 Q’ units in V Values measured during Run1 New measurements 1 B3 unit = B1 H ~ Q’ unit V ~ 35.3 Q’ unit B2 H ~ -42 Q’ unit V ~ 35 Q’ unit 0.3 B3 units swing in 10 steps crosscheck with 1 unique step back (not shown)

Q’ knob check Matteo Solfaroli10 Knob measurements 2 steps of 5 units B1 H -> 2 to 12 V -> 15 to 5 B2 H -> 2.2 to 12.2 V -> 14 to 4

Matteo Solfaroli11 Q’ today +6 all along (~10) +8 the last point (~12) +6 all along (~9) +8 the last point (~12) +10 (+13) +12 (+15) +10 (+13) B1H B1V B2H B2V +12 (+15) +10 (+13) +10 (+13) sec Q’

Linear Fit: On-momentum tune Chroma Momentum - Offset Online Q’ estimate V1 -> the naïve approach Matteo Solfaroli12 K.Fuchsberger

4 Fit parameters Initial guess 4 Fit parameters Online Q’ estimate V2 Matteo Solfaroli13 K.Fuchsberger

Worked very reliably for several fills Next improvement steps: Q’ trace (e.g. to observe evolution during ramp) Feed Forward Error Estimation Online Q’ K.Fuchsberger 14Matteo Solfaroli

Conclusions 15Matteo Solfaroli  The exclusion of RCS.A78B2 has been fairly transparent (NO difference between the beams)  B3 injection decay  The B3 injection decay is correctly compensated for the operational purpose (windows of about 1 hour at constant Q’)  It would be a plus to verify the powering history dependence with some additional measurements  Snapback & ramp  Quite a good control of Q’ during ramp and snapback (+-2 units)  A measurement with slower ramp start could maybe gives us more info?? (details to be studied)   The correction for B3 decay at flat-top (0.05 units) has been implemented and the Q’ is well controlled (tune decay not negligible, but corrected with the QFB during the squeeze (if used))