Pbar Transverse Instability in Main Injector
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Transcript of Pbar Transverse Instability in Main Injector
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Pbar Transverse Instability
in Main Injector
Ming-Jen Yang, Main InjectorJim Zagel, Instrumentation
04/12/2010
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Study
Initially motivated by Noisy in MI flying wire beam profile
- Changed PMT high voltage- Replaced PMT paddle in the tunnel- Noisy only on pbar from RR.
Installed RTD720 digitizer at MI10 Digitize monitor signal supplied by FW system
- Raw PMT signal- FW integrated loss signal.
Independent of FW front end - Turn-by-turn.- No decimation.
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First data set, S7669x1
Output of MI FW integrator, integrating over four pbar bunches.Break-down occurred when signal was too large.
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Acc. to RR transfer, for comparison
Scale of oscillation is quite a bit smaller.MI transverse plane damper are in use for this type of transfers.
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S7685x1 Pbarfrom RR, Vertical Flying Wire
There is no apparent vertical plane oscillation at 8-GeV.
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150 GeV pbar, S7706x1 Horizontal Flying Wire
No apparent horizontal plane oscillation at 150 GeV.
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S7682x1, with PMT paddle replaced
No break-down, butOscillation is still as big as before.
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Reconstructed horizontal beam profile
Peak integrated amplitude from each successive traces, for each bunch.
bunch# 1 bunch# 2
bunch# 3 bunch# 4
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Horizontal beam profile, as reported by FW
bunch# 1 bunch# 2
bunch# 3 bunch# 4
Good agreement with the reconstructed profiles shown in previous slide.
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FFT on reconstructed profile, bunch #3
FFT spectrum of bunch#3 profile.
FFT spectrum from TBT BPM position at injection.
39136.4 Hz
Tune = 39136.4 / 89815.3 = 0.4357
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Observation
Hashing in the profile Result of betatron oscillation
- Give the same Tune as measured with TBT BPM. Bunch # 1
- Minimal oscillation.- Clean profile from both version.
Bunch #3 - Substantial oscillation.- Noisy FW profile.
Bunch #2 & #4- Comparison not as clear-cut.
Double peak feature- Caused by PMT break-down.- Disappeared with reduced high voltage.- FW profiles are similar to the reconstructed profiles.
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Adjusting MI chromaticity, nominal setting
Color legend:Outside plateInside plateDifference
S7724, xfer #1 Chrom. H: -12Chrom. V: -13
MI horizontal wide-band pickup
Oscillation: large
FWH integrator signal
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Adjusting MI chromaticity, -3 units
Legend:Signal - Outside plateSignal - inside plateSignal Difference
S7724, xfer #1 Chrom. H: -15Chrom. V: -16
MI horizontal wide-band pickup
FWH integrator signal
Oscillation: smaller
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Adjusting MI chromaticity, -6 units
Legend:Signal - Outside plateSignal - inside plateSignal Difference
S7724, xfer #1 Chrom. H: -18Chrom. V: -19
MI horizontal wide-band pickup
FWH integrator signal
Oscillation: invisible
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Adjusting MI chromaticity, -12 units
Legend:Signal - Outside plateSignal - inside plateSignal Difference
S7724, xfer #1 Chrom. H: -24Chrom. V: -25
MI horizontal wide-band pickup
FWH integrator signal
Oscillation: invisible
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Signal of Wide-band, at injection
Nearly perfect beam with no sign of beam distortion from RR.
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Wall Current Monitor signal, pbar bunch #1
Long profile: at injection Long profile: when flying wire flew
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Wall Current Monitor signal, pbar bunch #2
Long profile: at injection Long profile: when flying wire flew
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Wall Current Monitor signal, pbar bunch #3
Long profile: at injection Long profile: when flying wire flew
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Wall Current Monitor signal, pbar bunch #4
Long profile: at injection Long profile: when flying wire flew
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Summary
At injection- No visible beam profile distortion.- Neither longitudinal nor horizontal.
At the time when flying wire flew Horizontal plane
- Bunch #1 show the least amount of distortion.- Bunch #3 & #4 are the worst.- Profiles deteriorated, horizontal and longitudinal.
Vertical plane- None.
At 150 GeV- None.
Pbar from Accumulator to RR- Visible, but smaller, horizontal plane oscillation.- MI transverse damper is in used for these transfers.
Chromaticity damping- Effective.- Set chromaticity to -18 units, from nominal of -12.