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Simultaneous Tune and Coupling Simultaneous Tune and Coupling Feedback during RHIC Run 6Feedback during RHIC Run 6

Peter Cameron

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BIW 2006

AcknowledgementsAcknowledgements

• Tom Shea – the foundation and foresight• Mike Harrison, Steve Peggs, Alex Ratti

– US LHC Accelerator Research Program

• RHIC HF Instrumentation – Earlier efforts

• BNL C-AD Instrumentation – Tom Russo et al– The present effort

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OutlineOutline

• System Architecture• Direct Diode Detection (3D) AFE• Eigenmodes, set and measured tunes,…• Coupling and de-coupling

– essential for tune feedback

• Ramping with and w/o feedbacks• 3D AFE ‘Beam Noise’ Susceptibility• Plans

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10nm

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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

eigenmodes rotated wrt horizontal and vertical planes

due to coupling.

special case general case

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Set and Measured TunesSet and Measured Tunes

• Measured tunes– The ‘eigenvalues’ – physical observables– Rotated from H and V by coupling

• Set tunes– What tune would be in the absence of coupling

– dQmin – forbidden zone• complicates tune control without feedback• breaks feedback

– can be calculated with knowledge of coupling

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Set and Measured TunesSet and Measured Tunes

set measured

yxxy

y

x

y

x

x

y

x

y

dd

C

A

Ar

C

A

Ar

,2,22,1,11

,2

,22

,1

,11

,

,2

,2

21

2121

21

212122

1

1,

1

2,

2

1

rr

rrQQ

rr

QQrrCC

2221

21

20,

2221

21

10, , CQQCQQ yx

set measured

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tune feedback would break here

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Manual DecouplingManual DecouplingSkew chrom

0

Chrom measurement

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dQmin < .001

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Coupling Echoes Coupling Echoes

½ synchrotron period

1 sec

Coupling coefficient ‘C’

0

.02

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OutlineOutline

• System Architecture• Direct Diode Detection (3D) AFE• Eigenmodes, set and measured tunes,…• Coupling and de-coupling

– essential for tune feedback

• Ramping with and w/o feedbacks• 3D AFE ‘Beam Noise’ Susceptibility• Plans

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First Ramp with FeedbacksFirst Ramp with Feedbacks

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First Ramp with Feedbacks 2First Ramp with Feedbacks 2

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Last Blue Ramp with FeedbacksLast Blue Ramp with Feedbacks

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Next Ramp with Feedbacks OffNext Ramp with Feedbacks Off

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Beam NoiseBeam Noise

• Steve Peggs – “declare Victory”

• Peter Cameron – “Mission Accomplished”

• One messy little detail– 3D AFE sensitivity to

‘beam noise’– No free lunch

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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

– Beam loss– High frequencies - longitudinal ‘hot spots’– Low frequencies

• quadrupole cryostat vibrations• mains harmonics

– Instabilities (weak – not noticed by anything except 3D AFE)– Long range beam-beam

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Immediate plans Immediate plans

• Further investigation of ‘beam noise’, and how to cope with this

• Chromaticity measurement and feedback• Movement of the system into the CERN

architecture – DAB board

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Conclusions Conclusions

• World’s first implementation of simultaneous tune and coupling feedback is successful

• The door remains open for simultaneous tune, coupling and chromaticity feedback at LHC

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Back-up slides Back-up slides

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3D on the Ramp - 1 Jan 05

dominant

spacing

is 180Hz

60Hz onset

60Hz end

IPM every

100 turns

(780 Hz)

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• Transverse instability• Not fixed by chrom• Frequently present at a

level not detectable by anything other than BBQ

• Upper half of sideband

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Summary of Chromaticity

t

t

vert

horiz

+5

-5

dp/p of +/-10-4 gives ~+/-100 radial modulation (RHIC&LHC)

-5

-5

+5

+5

Q'

Q'

Q'ramp 6380

ramp 6382

ramp 6381

in RHIC modulation is at 1Hz

chrom - good results under sequencer control