Chromaticity correction (without RCS.A78B2) Thanks to: F. Roncarolo, E.Todesco, M.Lamont,...
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Transcript of Chromaticity correction (without RCS.A78B2) Thanks to: F. Roncarolo, E.Todesco, M.Lamont,...
Chromaticity correction (without RCS.A78B2)
Thanks to: F. Roncarolo, E.Todesco, M.Lamont, J.Wenninger
Matteo Solfaroli 2
Outline & Measurement method
• 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 rampQ’ decay at flat-topB3 to Q’ measurementsQ’ knob verification
(OP w/o RCS.A78B2)
Matteo Solfaroli 3
OP without RCS.A78B2
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
Matteo Solfaroli 4
B3 decay at injection
B1• Q’H ~ +2.5• Q’V ~ -2
B2• Q’H ~ +2.5• Q’V ~ -2
0.058 B3 units
B3 decay not correctly compensated (kind of
expected), but the good news is that there is no
visible difference between the beams
Dec_tau 600Dec_d 0.28dec_delta 0.32
Trims on lattice sext to get Q’~8 before going into the ramp
Matteo Solfaroli 5
B3 decay at injection
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
Jul 4th Aug 8thDec_tau 850 600Dec_d 0.32 0.28dec_delta 0.26 0.32
July 4th
Matteo Solfaroli 6
Ramping w/o RCS.A78B2
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)
Matteo Solfaroli 7
Ramp
• 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
Matteo Solfaroli 8
Flattop
• 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)
Matteo Solfaroli 9
B3 to Q’ measurement Old assumption: 1 B3 unit =
• -43 Q’ units in H• 35 Q’ units in V
Values measured during Run1
New measurements1 B3 unit =
B1• H ~ -42.6 Q’ unit• V ~ 35.3 Q’ unit
B2• H ~ -42 Q’ unit• V ~ 35 Q’ unit
0.3 B3 units swing in 10 stepscrosscheck with 1 unique step back (not shown)
Matteo Solfaroli 10
Q’ knob check
Knob measurements2 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 Solfaroli 11
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)
B1HB1V
B2HB2V
+12 (+15)+10
(+13)
+10(+13)
sec
sec
sec
sec
Q’
Q’
Q’
Q’
Linear Fit:
On-momentum tune
Chroma
Momentum- Offset
Problematic when frequency acquisition () and tune (Q) are not well aligned
Sine modulation of RF frequency Acquire Tune (Q) and momentum offset
Online Q’ estimate V1 -> the naïve approach
𝑄 (𝑡 )=𝑄on+𝑄′ .Δ𝑝𝑝
(𝑡)
Matteo Solfaroli 12
K.Fuchsberger
Individual Harmonic Fits on and
Δ𝑝𝑝
(𝑡 )=𝐴𝑝 . sin (𝜔 𝑡+𝜑𝑝)+𝐵𝑝
4 Fit parameters
Initial guess
4 Fit parameters
𝑄 (𝑡 )=𝐴𝑄 .sin (𝜔𝑡+𝜑𝑄)+𝐵𝑄
, with
Online Q’ estimate V2
Matteo Solfaroli 13
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
Matteo Solfaroli 15
Conclusions 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)
Decay @flat-top 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))