tune/coupling/chromaticity measurement and feedforward/feedback
DESCRIPTION
Tune/Coupling/Chromaticity Measurement and Feedforward/Feedback. Peter Cameron. Outline. Decoupling Ramping 3D AFE ‘Beam Noise’ Susceptibility Plans. - PowerPoint PPT PresentationTRANSCRIPT
LARP Berkeley Apr 2006
Tune/Coupling/ChromaticityTune/Coupling/ChromaticityMeasurement and Measurement and
Feedforward/FeedbackFeedforward/Feedback
Peter Cameron
LARP Berkeley Apr 2006
OutlineOutline
• Decoupling• Ramping• 3D AFE ‘Beam Noise’ Susceptibility• Plans
LARP Berkeley Apr 2006
x
y
Q1
Q2
A1,xA2,x
A1,y
A2,y
x
y
Q1
Q2
1,x
1,y
2,x
2,y
x
y
Q1
Q2
A1,xA2,x
A1,y
A2,y
x
y
Q1
Q2
A1,xA2,x
A1,y
A2,y
x
y
Q1
Q2
1,x
1,y
2,x
2,y
Schematics showing the two eigenmodes rotated with respect to the horizontal and vertical planes due to coupling. The left hand figure shows the special case where the projections of each mode in each plane are in phase. The right hand side shows the more general case where coupling introduces a phase shift into the eigenmode projections.
C-A/AP/174 - Possible phase loop for the global betatron decoupling, Y. Luo et al C-A/AP/204 - Towards a Robust Phase Locked Loop Tune Feedback System, R. Jones et al both at http://www.rhichome.bnl.gov/AP/ap_notes/cad_ap_index.html
LARP Berkeley Apr 2006
LARP Berkeley Apr 2006
Manual DecouplingManual DecouplingSkew chrom
0
Chrom measurement
LARP Berkeley Apr 2006
LARP Berkeley Apr 2006
LARP Berkeley Apr 2006
You will see this slide again
LARP Berkeley Apr 2006
Coupling Echoes Coupling Echoes
½ synchrotron period
1 sec
Coupling coefficient ‘C’
0
.02
LARP Berkeley Apr 2006
OutlineOutline
• Decoupling• Ramping• 3D AFE ‘Beam Noise’ Susceptibility• Plans
LARP Berkeley Apr 2006
First Ramp with FeedbacksFirst Ramp with Feedbacks
LARP Berkeley Apr 2006
First Ramp with Feedbacks 2First Ramp with Feedbacks 2
LARP Berkeley Apr 2006
Last Blue Ramp with FeedbacksLast Blue Ramp with Feedbacks
LARP Berkeley Apr 2006
Next Ramp with Feedbacks OffNext Ramp with Feedbacks Off
LARP Berkeley Apr 2006
LARP Berkeley Apr 2006
OutlineOutline
• Decoupling• Ramping• 3D AFE ‘Beam Noise’ Susceptibility• Plans
LARP Berkeley Apr 2006
Beam NoiseBeam Noise
• Steve Peggs – “declare Victory”
• Peter Cameron – “Mission Accomplished”
• One messy little detail– 3D AFE sensitivity to
‘beam noise’– No free lunch
LARP Berkeley Apr 2006
3D AFE ‘beam noise’3D AFE ‘beam noise’• Beautiful when looking at amplitude
– Very sensitive ~10nm– Resistant to dynamic range problems (bunch length, beam offset,…)
• But, when you put it in a phase loop…. • Possible sources
– Radiation Damage?– Beam loss? Direct impingement on electrodes? Amplitude modulation?– High frequencies - longitudinal ‘hot spots’?– Low frequencies - broadband magnet noise? Power supply bit toggling?.....– Instabilities (weak – not noticed by anything except 3D AFE)?– Long range beam-beam?
• Complicating factors– Mains harmonics, IPM– ’10Hz noise’ – cryostat vibrations?– Anomalous tune dependence– Islands– Anomalous phase shifts– Synchrotron satellite sensitivity? Pulsed excitation?
LARP Berkeley Apr 2006
BBQ and PLL S/N ComparisonBBQ and PLL S/N Comparison- static conditions- static conditions
BBQ H
I and Q
PLL both
I and QBBQ V
I and Q
LARP Berkeley Apr 2006
Initial SymptomsInitial Symptoms• BBQ AFE problems – gain chain?
– dropouts– saturation
• First suspicion was radiation damage of the in tunnel electronics– Specifically, gain control– Move electronics out of tunnel – Bench check revealed no problems– Operation with electronics out of tunnel perhaps
showed moderate improvement – capacitance of heliax between pickup and diodes?
LARP Berkeley Apr 2006
Yellow horizontal – Yellow horizontal – ‘dropouts’ during ‘dropouts’ during fillingfilling• signal goes away completely at times• At other times attenuated
LARP Berkeley Apr 2006
Blue Vertical- ‘Saturation’ Blue Vertical- ‘Saturation’ during rampingduring ramping
LARP Berkeley Apr 2006
BV ‘Saturation’ Spectra at storeBV ‘Saturation’ Spectra at store
78KHz span 4.8KHz zoom
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APEX ExperimentAPEX Experiment
• The goal – gain understanding of the effect of beam loss on the BBQ, and specifically on the Direct Diode Detection (3D) analog front end
• The procedure– Apply a bump upstream of the BBQ pickup– Observe effect of beam loss on BBQ I and Q signals– Simultaneously observe loss monitors and Schottky
LARP Berkeley Apr 2006
Max bump ~3cm!
BBQ pickup Schottky
LARP Berkeley Apr 2006
BBQ SchottkyBump effect
Total beam loss was ~3X1010
LARP Berkeley Apr 2006
Effect of beam loss on BBQ I and Q was observed only early in the bump Change in loss pattern? Islands?
next slide
LARP Berkeley Apr 2006
Schottky also showed effect only early in the bump, and only in horizontal
times of large losses
Schottky vert
Schottky horiz
LARP Berkeley Apr 2006
Effect of beam loss on BBQ I and Q was observed only early in the bump Change in loss pattern? Islands?
next slide
LARP Berkeley Apr 2006
Zoom on effect of beam loss
next slide
LARP Berkeley Apr 2006
Further zoom on effect of beam loss
~180 degree phase shift= temporary ‘loss of lock’
LARP Berkeley Apr 2006
Similar data from fill 7614, showing progressive deterioration of lock quality as beam loss increases
LARP Berkeley Apr 2006
Effect of beam loss on signal amplitude – ‘AM effect’
~0.5%/turn
LARP Berkeley Apr 2006
Actual loss rate 5 amp/sec (Don Bruno) ~0.025T-m/s~150rad/sec at 25GeV, ~100
~0.5%/turn
1 sec for bump10-4 loss gives 10-9/turn
LARP Berkeley Apr 2006
Polarimeter EffectPolarimeter Effect
LARP Berkeley Apr 2006
3D AFE ‘beam noise’3D AFE ‘beam noise’• Beautiful when looking at amplitude
– Very sensitive ~10nm– Resistant to dynamic range problems (bunch length, beam offset,…)
• But, when you put it in a phase loop…. • Possible sources
– Radiation Damage?– Beam loss? Direct impingement on electrodes? Amplitude modulation?– High frequencies - longitudinal ‘hot spots’?– Low frequencies - broadband magnet noise? Power supply bit toggling?.....– Instabilities (weak – not noticed by anything except 3D AFE)?– Long range beam-beam?
• Complicating factors– Mains harmonics, IPM– ’10Hz noise’ – cryostat vibrations?– Anomalous tune dependence– Islands– Anomalous phase shifts– Synchrotron satellite sensitivity? Pulsed excitation?
LARP Berkeley Apr 2006
100MHzHi-Pass no filter
50MHzLo-Pass
100MHzHi-Pass plus50MHzLo-Pass
Effect of filtering in front of diodes
LARP Berkeley Apr 2006
BTF MethodBTF Method
• Excite beam ~10 microns• Phase synchronously
demodulate response to get amplitude and phase
• Can get – Direct– Coupling– Beam-beam
• Lockin plus 3D AFE gives excellent sensitivity
LARP Berkeley Apr 2006
• Transverse instability• Not fixed by chrom• Frequently present at a
level not detectable by anything other than BBQ
• Upper half of sideband
LARP Berkeley Apr 2006
Effect of long range beam-beam on the ramp
LARP Berkeley Apr 2006
3D AFE ‘beam noise’3D AFE ‘beam noise’• Beautiful when looking at amplitude
– Very sensitive ~10nm– Resistant to dynamic range problems (bunch length, beam offset,…)
• But, when you put it in a phase loop…. • Possible sources
– Radiation Damage?– Beam loss? Direct impingement on electrodes? Amplitude modulation?– High frequencies - longitudinal ‘hot spots’?– Low frequencies - broadband magnet noise? Power supply bit toggling?.....– Instabilities (weak – not noticed by anything except 3D AFE)?– Long range beam-beam?
• Complicating factors– Mains harmonics, IPM– ’10Hz noise’ – cryostat vibrations?– Anomalous tune dependence– Islands– Anomalous phase shifts– Synchrotron satellite sensitivity? Pulsed excitation?
LARP Berkeley Apr 2006
3D on the Ramp - 1 Jan 05
dominant
spacing
is 180Hz
60Hz onset
60Hz end
IPM every
100 turns
(780 Hz)
LARP Berkeley Apr 2006
LARP Berkeley Apr 2006
coupling excitation is horizontal
vertical
horizontal
LARP Berkeley Apr 2006
Anomalous tune dependenceAnomalous tune dependence
• Next slide shows odd behavior of BBQ phase noise during a tune scan– Tunes are fully decoupled– But, somehow for small tune separations tune phase
noise (fluctuations in Q) is small, and for separations greater than ~.01 it becomes large
– Additional phase noise in horizontal late in the tune scan can probably be attributed to beam loss
– ???
LARP Berkeley Apr 2006
BBQ during tune scan (BBQ during tune scan ( const) const)
Vert I and Q
Tunes and beam decay
HorizI and Q
~.01 units of tune
Effect of beam loss?
decoupled!!! dqmin<.001
LARP Berkeley Apr 2006
Summary on 3D AFE ‘beam noise’Summary on 3D AFE ‘beam noise’• We don’t know where it comes from• With other pressures of RHIC operations easing, time
available to start investigating more intensively• What we have tried
– Filtering – both in front of diodes (MHz range) and digital (tens of Hz range)
– Hybrid– Reversing diodes– Pickup centering with motion control – no effect– Changing time constants – suspicions here
• Need to make a plan
LARP Berkeley Apr 2006
Short term plan Short term plan • Investigate 3D AFE
– Rhodri visit 2 days next week– Marek visit before RHIC turns off?– 3D in phase loop at Tevatron?
• Chromaticity measurement and feedback• Implementation on DAB board
– CERN visit early July– CERN visit September – PLL on SPS
• See behavior of 3D in phase loop
• Longer term – more Tan involvement