adt tune measurement

W. Hofle @LBOC 21.08.2012

ADT Tune Measurement

F. Dubouchet, W. Hofle, D. Valuch

Acknowledgement: R. Calaga, F. Roncarolo, E. Bravin, shift crews

New developments and tests on August 1st and 12th 2012


ADT Tune Measurement

Reminder (Chamonix):

Plan:implement gain modulation to selectively reduce ADT gain for witness batch (Chamonix: 12 bunches Now: 6 bunches) done, but no improvement for BBQ

situation: BBQ gating difficult, BI working on it, tests upcoming long term ADT plan: tune from residual ADT signal massive data treatment, limitations of VME technology not operational before LS1 as new hardware required

Plan B: kick beam (witness batch) selectively by ADT and record free oscillation make an operational tool by combining with already commissioned batch by batch gain modulation

use new 16384 word long dedicated study buffer on FPGA of ADT DSPU VME cardmethod gives also the ADT damping time along the cycle monitoring of performance


Timeline of tests on August 1st, 2012

1 3 542

1: 6 turns kick (16x)2: 3 turns kick (21x)3: 5 turns kick (28x)4: 5 turns kick (7x)5: 5 turns kick (500x)6: 5 turns kick (52x)

total: 624x

5: frequency trim6: tune trim

6

6 bunches, nominal intensity 1.5x1011/bunch beam measurements with 1 beam only, V-plane; both beams injected (6 bunches)using existing firmware / infrastructure (abort gap cleaning), kicking at 0.31 in tune

450 GeV, but damper gain adjusted to model situation at flat-top (damping time of 100 turns)


Lifetime during excitation of 6 bunches

start of continuous burst excitation [1 burst every 2.34 s]

BLM lifetime drops from 200 hours to below 100 hours


Lifetime cont.

end of burst mode of 500 excitations

BLM lifetime recovers after stop of excitation

excitationsre-started


Blow-up of the 6 bunches as a result of kicks

initial test (manual triggers) then500 bursts (each 5 turns)from 13:45 to 14:05 (19.5 min)2.34 seconds per burst

td = 100 turnsmax amplitude 100 mm at Q7V.B1 of damper

1st period: 45 minutes, 3.3 nm / min0.149 mm for 72 excitations + normal blow-up

2nd period: 19.5 minutes, 43.3 nm /min43.3 nm /min 0.844 mm in 19.5 min0.844 mm for 500 excitations + normal blow-up

deduce blow-up w/o excitation (assumed to be a constant rate per unit of time):0.65 nm/min, i.e. 29.25 nm during 1st period

12.68 nm during 2nd period

blow-up per trigger (excitation)1st period: 72 triggers: 1.66 nm per excitation2nd period: 500 triggers: 1.66 nm per excitation

500+5272

excitation bursts (approx)

F. Roncarolo, E. Bravin


Tune trim (data set ‘6’)

1e-3 up and down

tune

time

(hou

rs, d

ecim

al)


RF frequency trim

VCXO word

40 Hz up, i.e. from -20 Hz to +20 Hzwith respect to central frequency of 400.788’837 MHz

FGC frequency(logging on change)

time [1 min / tick]

14:03:37


RF frequency trim (data set ‘5’)

40 Hz up, i.e. from -20 Hz to +20 Hzwith respect to central frequency 400.788’837 MHz

DQ = -4.9e-4 DQ = - 4.9e-4 Dp/p = - 3.2e-4 Q’ = + 1.5

single bunch (!), single pick-up Q7.VB1, 2730 turns, 500 times kickedtune

time

(dec

imal

)

14:03:3x


2nd peak at -20 Hz also visible for FFTs of individual bunchesReal modulation of beam tune or artifact ?

Data Set 5, 500 measurements, FFT average over 6 bunches


Example of a single bunch, single measurement FFT (V.B1)

50 Hz

20 Hz

2730 turns resolution too limited to clearly resolve if there is a systematic peak at 20 Hz in the low frequency range


3.5 TeV, 8 MV fs=22.9 Hz

compatible with Qs and 2Qs, fs=22.9 Hz

50 Hz

Clean spectrum between 50 Hz and tune

tune

2010 data17 May 2012damper offlow bunch intensityFFT of 4 bunches(65536 turns)

10 20 100 1000 1 frequency in Hz

FFT

(B2.

V Q

7L)

4.5 Hz

broad noise @20 Hz

2010 data


Data Set 5, 500 measurements x 6 bunches


average: 1.8x10-3 in tune 20.2 Hz

cut:only measurementsare displayed in which upper and lower tune peaks are the highest peaks for at least one bunch


2nd test (12th August 2012)dedicated firmware deployed (Daniel), new dedicated fesa classes (Frederic) for excitation similar to AGC, but “skimmed down” excitation scales automatically with normalised damper gain

dedicated parameters and resources:

window (gating on part of the beam)DDS to generate excitation with programmable excitation frequency number of kicks (in turns)dedicated memory on FPGA (16384 bunch x turns)

max 2730 turns for each of the 6 bunches kicked

beam test (12th August 2012)

injected 2x6 bunches per beam with standard, i.e. minimal possible spacingsymmetric pattern with collisions in IP1 and IP5 only (bucket 1 and 651)use first 6 as witness bunches, kicked by ADT, 4 planes x beamskicked every beam and plane once per 4 seconds

(rotating kicks every second between beam and plane)4 turns kicked at 0.28 (H) and 0.31 (V), amplitude 0.8 of max

real life

no changes to operationalParameters and functions


Damping times

Fill 2956

collisionsflat top and squeeze

Beam modes:19:33 prep4ramp19:37 ramp19:50 F-top20:15 squeeze20:39 adjust21:26 dump

injection

Daniel’s tool

ramp


Horizontal Beam 1

Fill 2956

collisionswith S / pmodes

tune changeat start of squeeze

ramp

setting-upthen refill


flat bottomhigh ADT gainneed lowerADT gain for the first 6

FFTs from 6 bunchesaveraged


Horizontal Beam 2

Fill 2956

collisions

spurious at 0.3068n x frev +/- 3450 Hzmesses up spectrum need to kick harder

ramp:tune took a dive due to tune FB locking on wrong lineswitched off and corrected at FT

flat bottomhigh ADT gainneed lowerADT gain for the first 6

setting-upthen refill


spurious



Vertical beam 1

Fill 2956

collisions

flat top spurious messes up spectrum need to kick harder




Vertical Beam 2

Fill 2956

collisions

flat top withspurious messes up spectrum need to kick harder




Individual bunches

20 Hz line moves with beam tune !


F. Roncarolo, E. Bravin

Emittance blow-up


Towards making an operational tool – next steps

•implement control of parameters in sequencer, plus start / stop functionality (t.b.d.)•implement FFTs in front-end (0.45 ms/FFT, 12 FFT 5.4 ms (6 bunches, 2 PU) •average FFTs in front-end publish averaged FFT and tune (peak), fitting (?)

•make operational with 1374 bunches once sequencer work completed, andacquisition working

•explore parameter space to get desired resolution understand and decide how to deal with the spurious 20 Hz line next to the tune (!)

needs: gain modulation programmed to tailor damping time of the 6 buncheskicking harder at flat top when spurious lines perturb (kicking to larger amplitudes by increasing the number of turns kicked or by

increasing normalised gain + additional gain modulation to maintain same gain for main beam)

suggestion: use more turns of excitation when amplitude is insufficient and flat-bottom: gain modulation 16/128 for the 6, 127/128 for restramp / flat-top / squeeze: gain modulation 64/128 for the 6, 127/128 for rest

adt tune measurement

Documents

adt gain

period blowup

adt tune measurementf

nm min0

adt damping time

kick beam witness batch

kick 21x3

kick 7x5