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 \\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 (1 st and 2 nd order) measurement throughout ARC-1

Summary of 2011 Tests See \\dlfiles03\apsv4\Astec\Projects\ALICE\ALICE_Physics_Meeting\2011_09_20 Some Key Points – Basic BPM resolution/noise is 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 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.

First Shifts #3091-#3123 Initial shifts #3091, # 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 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\bpms pptx … However, some of this data was valid (attenuation set correctly) and was used for input to IBIC 2012 paper.

#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

#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 not y But since beta functions so poorly understood, not possible to confirm this.

#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 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 – 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.

AP ‘block’ #3133, 3136, 3141, Week 17 th 23 rd September Attenuation set correctly, charge 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 , 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

#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

#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

#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 vs whole_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.

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