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 (1st and 2nd 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 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.

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.

#3121 Observations16 MHz, 100 us (1600 bunch) trains, 30 pCLattice 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 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.

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

#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 #3169 6th October 2012.

• Strange instability seen on ST2-BPM-03, 1 every 30 refreshes

• Alignment data again.