Noise studies and FMAs an update Beam beam
Noise studies and FMAs: an update Beam beam and luminosity meeting 07/06/2018 H. Bartosik, L. R Carver, G. Iadarola, N. Karastathis, S. Kostoglou, Y. Papaphilippou, L. Sabato, G. Sterbini
Part 1: FMAs during squeeze
Introduction Investigation of the losses during squeeze with the e-cloud team (Gianni, Luca) q FMAs as first step with the following parameters: q Ø Ø Ø Ø 4 D & 5 D (δp/p =23. 42 e-5 ) (Qx, Qy) = (62. 31, 60. 32) 79 angles 1. 1 -10. 1σ 6. 5 Te. V εn=2 [μm] I = 1. 2 e 11 Ioct, Q’, β* var 3
Ioct = 0, Q’=0, without BB 4 D 5 D 4
Ioct = 0, Q’=15, without BB 5
Ioct = 550, Q’=0, without BB 6
Ioct = 550, Q’=15, without BB 7
Ioct = 0, Q’=0, with BB 8
Ioct = 550, Q’=15, with BB 9
10
9/26/2020 Document reference 11
9/26/2020 Document reference 12
Part 2: The investigation of the origin of the 50 Hz harmonics in the beam spectrum
In preparation for MD#3. . . • Based on the LMC_220 action, we would like to investigate the origin of the extra frequency components that perturb the beam spectrum 14
In preparation for MD#3. . . Based on the LMC_220 action, we would like to investigate the origin of the extra frequency components that perturb the beam spectrum • Preparation of proposal for MD#3 • 15
In preparation for MD#3. . . Based on the LMC_220 action, we would like to investigate the origin of the extra frequency components that perturb the beam spectrum • Preparation of proposal for MD#3 • Feedback from BI, RF, EPC (minutes from Guido https: //hackmd. web. cern. ch/s/Sy 4 F 9 l 2 zm): • Waiting for: List of PC switching frequencies Waiting for: Spectrum analyzer for converter noise Info: PC clocks are not synchronized Info: Switching frequencies may vary during the same fill according to current • • • Switching frequency RTQX 1: variable switching frequency (50. . 200 k. Hz) Switching frequency RQX and RTQX 2: 25 k. Hz → 50 th harmonic of 50 Hz Possible test: frev modulation during chromaticity scans Possible test: Change the gain of the ADT and check if lines are enhanced/suppressed Possible test: We can switch on/off filters in each arc even with beam 16
OB & BBQ spectrum: comparison • • • These components seem compatible with harmonics of 50 Hz Visible both in the Obs. Box (OB) & HS BBQ Different harmonics for different beam modes OB: sum of bunches the see the effect/ not a bunch by bunch effect Same harmonics in both instruments at the same location No modulation of the betatron tunes, probably dipolar modulation ΔQ = 4 e-3 17
BBQ: Do we see them without beam? • Not visible in the spectrum without beam (only some low harmonics) • Power of 3 larger between ramp/beamdump 18
BBQ: Do we see them without beam? • Not visible in the spectrum without beam (only some low harmonics) • Power of 3 larger between ramp/beamdump Correlation of amplitude evolution of 50 Hz lines 19
BBQ: Do we see them both in B 1/B 2 & H/V • Visible both in B 1, B 2 and H/V, mostly on H 20
Time evolution of harmonics in OB & BBQ OB 21
Time evolution of harmonics in OB & BBQ OB Time evolution of harmonics in BBQ during same period RAMP FLATTOP 22
Noise to do list: 50 Hz lines: 1. 2. 3. 4. DOROS PU, BPMs, BLMs, OB PUs (MD 2 -MD 3) Correlation of PC spectrum with beam spectrum (MD 2 -MD 3) Simulations with 50 Hz lines from OB (MD 2 -MD 3) Automatic 50 Hz-line tool for fill by fill analysis (MD 2 -MD 3) HL-LHC: 1. Following Miriam’s & Riccardo’s work, lifetime studies and tolerances for inner triplet (300 Hz, 600 Hz + real frequency spectrum*) *https: //indico. cern. ch/event/373539/contributions/886821/attachments/743975/1020555/TC-2015 -04 -16. pdf) 23
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