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BPMs period 13-14

BPMs period 13-14. General BPM Tasks/Projects. New single bunch BPM electronics on ALICE AR1 + ST2 They had been tested already last year by Alex and Ian Beam based calibration of AR1-BPM-03, see \Dlfiles03aliceAnalysisPeriod 14 dataAP_period13and14BPMAR1BPM1Calibration

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BPMs period 13-14

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  1. BPMs period 13-14

  2. General BPM Tasks/Projects • New single bunch BPM electronics on ALICE AR1 + ST2 • They had been tested already last year by Alex and Ian • Beam based calibration of AR1-BPM-03, see \\Dlfiles03\alice\Analysis\Period 14 data\AP_period13and14\BPM\AR1BPM1Calibration • Analysis of AR1-SEXT-01 and QUAD-01,02 misalignment • Beam position, interbunch, intertrain, transients, ripples etc • Variation of bunch position over train on several shifts • Dispersion (1st and 2nd order) measurement throughout ARC-1

  3. Summary of 2011 Tests • See \\dlfiles03\apsv4\Astec\Projects\ALICE\ALICE_Physics_Meeting\2011_09_20 • Some Key Points • Basic BPM resolution/noise is 20-30 um. • Initial train transient seen over 50 bunchers (~5 us) • Ripples seen at different frequencies. • horizontal: • period of (150 to 200) bunches, (80 to 110)kHz, two kinds: a single triangle wave for bunches 100 to 600 and a regular sine-like oscillation for bunches 600 to 1600, where the amplitude is (40 to 60)um; • period about <70 bunches, >230kHz, for bunches 100 to 600, amplitude (20 to 30)um; • vertical: • oscillations for 100 to 600 bunches are similar to that in the horizontal plane; • practically no oscillation of the second kind.

  4. First Shifts #3091-#3123 • Initial shifts #3091, #3121-3123 were used for looking at transients, droop, and ripple. • But the shifts above were problematic for several reasons • Attenuation on buttons set differently to each other • Problems with bunch charge (scope set-up problems) • However, despite problems ripples and transient evident, as in 2011. • Much of the data on these shifts is doubtful because of the problems. A separate ppt for these files … • \\Dlfiles03\alice\Analysis\Period 14 data\AP_period13and14\BPM\bpms3091-3123.pptx • … However, some of this data was valid (attenuation set correctly) and was used for input to IBIC 2012 paper.

  5. #3121 Observations 16 MHz, 100 us (1600 bunch) trains, 30 pC Lattice from a THz-like set-up AR1 probably not closed … (strong-ish AR1Q1/4=2.22 A) Knowledge of beta functions poor/non-existent. mean values subtracted

  6. #3121 Observations • General observations, from a single shot: • bunch to bunch position variation; larger in x than y • various ripples seen on x, y, sum_V • initial “transient”, always on sum_V, sometimes on x, y. • The first observation might be naively expected, since any bunch energy variation would show in x but noty • But since beta functions so poorly understood, not possible to confirm this.

  7. #3121 Analysis. A very rich pictures of ripples, for IBIC 2012! • This data was the basic for the IBIC paper • Fourier-analysed the various frequency components • In x and y • Biggest feature is a ~ 100 kHz oscillation (170 bunches, 10 us) oscillation. Magnet ripple? • Other peaks in the 20-200 kHz range not exactly the same in x and y • Smaller ~300 kHz and 6 MHz signal on both and x and y. Hard to see the 300 kHz on the x,y plots. • In sum_voltage signal • 60-80 kHz signal. Laser pulse power variation? • 300 kHz quite visible on the sum_V. DC-DC converter? • 6 MHz as in x,y • So the biggest effects are the ~100 kHz ripple seen on x,y, and the ~ 60 KHz ripple on charge. I would suggest these are the highest priority to investigate.

  8. AP ‘block’ #3133, 3136, 3141, Week 17th 23rd September • Attenuation set correctly, charge 50-60 pC, 16 MHz • AR1-BPM-01, 03, 04, 05 • Check the x,y sign convention • Varying AR1-Q1-4 to try and generate high dispersion on 1 or more bpms to look for energy transients on trains. • 150-200, 100 kHz bunch oscillation seen very obviously in both x and y, on all BPMs • And similar amplitude in x on BPM-01 as BPM-05, suggesting this is not an energy oscillation • Identical oscillation on x and y on BPM-03. • Able to manipulate amplitude of y amplitude on BPM-05 by ST1-Q2

  9. #3133 • See \\Dlfiles03\alice\Analysis\Period 14 data\AP_period13and14\BPM\3133\3133.ppt • Struck by how regular the oscillation was compared to earlier shifts

  10. #3136 • ~1/2 a shift after FELIS/SNOM problems • Not much intra-train studies on this shift • Trying to measure dispersion, crudely, on AR1-BPM-05 by varying beam energy, and study how AR1-SEXT-01 affects the dispersion here (ideally, it shouldn’t affect dispersion). • Get some decent agreement between theory and measurement • Also can see the T166 component quite easily

  11. #3141 • Some software tweaks for automatic dispersion measurements • Changed beam energy to observe effect on ripple. 100 kHz (and lower freq) enhanced significantly by reducing the energy. • Higher order dispersion T166 observations • Measuring dispersion with single bunch vswhole_train_mean doesn’t make much difference • More detailed effect of sextupole vs. bpm-05 dispersion. • AR1-quad alignment data. • Recording many (1000) trains for train-to-train jitter measurements.

  12. #3168 #3169 6th October 2012. • Strange instability seen on ST2-BPM-03, 1 every 30 refreshes • Alignment data again.

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