Pbar transverse Instability in Main Injector MingJen Yang
Pbar transverse Instability in Main Injector Ming-Jen Yang 04/12/2010
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 RTD 720 digitizer at MI 10 Digitize monitor signal supplied by FW system - Raw PMT signal - FW integrated loss signal. ✦ Independent of FW front end - Turn-by-turn. - No decimation. ✦
First data set, S 7669 x 1 Output of MI FW integrator, integrating over four pbar bunches. Break-down occurred when signal was too large.
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.
S 7685 x 1 Pbar� from RR, Vertical Flying Wire There is no apparent vertical plane oscillation at 8 -Ge. V.
150 Ge. V pbar, S 7706 x 1 Horizontal Flying Wire No apparent horizontal plane oscillation at 150 Ge. V.
S 7682 x 1, with PMT paddle replaced No break-down, but Oscillation is still as big as before.
Reconstructed horizontal beam profile bunch# 1 bunch# 2 bunch# 3 bunch# 4 Peak integrated amplitude from each successive traces, for each bunch.
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.
FFT of reconstructed profile, bunch #3 FFT spectrum from TBT BPM position at injection. 39136. 4 Hz Tune = 39136. 4 / 89815. 3 = 0. 4357 FFT spectrum of bunch#3 profile.
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.
Adjusting MI chromaticity, nominal setting S 7724, xfer #1 Chrom. H: -12 Chrom. V: -13 Oscillation: large FWH integrator signal Legend: Signal - Outside plate Signal - inside plate Signal Difference MI horizontal wide-band pickup
Adjusting MI chromaticity, -3 units S 7724, xfer #1 Chrom. H: -15 Chrom. V: -16 Oscillation: smaller FWH integrator signal Legend: Signal - Outside plate Signal - inside plate Signal Difference MI horizontal wide-band pickup
Adjusting MI chromaticity, -6 units S 7724, xfer #1 Chrom. H: -18 Chrom. V: -19 Oscillation: invisible FWH integrator signal Legend: Signal - Outside plate Signal - inside plate Signal Difference MI horizontal wide-band pickup
Adjusting MI chromaticity, -12 units S 7724, xfer #1 Chrom. H: -24 Chrom. V: -25 Oscillation: invisible FWH integrator signal Legend: Signal - Outside plate Signal - inside plate Signal Difference MI horizontal wide-band pickup
Signal of Wide-band, at injection Nearly perfect beam with no sign of beam distortion from RR.
Wall Current Monitor signal, pbar bunch #1 Long profile: at injection Long profile: when flying wire flew
Wall Current Monitor signal, pbar bunch #2 Long profile: at injection Long profile: when flying wire flew
Wall Current Monitor signal, pbar bunch #3 Long profile: at injection Long profile: when flying wire flew
Wall Current Monitor signal, pbar bunch #4 Long profile: at injection Long profile: when flying wire flew
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 Ge. V - None. - Visible, but smaller, horizontal plane oscillation. MI transverse damper is in used for these transfers. - Effective. Set chromaticity to -18 units, from nominal of -12. ❖ Pbar from Accumulator to RR ❖ Chromaticity damping
- Slides: 21