Simultaneous Tune and Coupling Feedback during RHIC Run 6

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Simultaneous Tune and Coupling Feedback during
RHIC Run 6

• Peter Cameron

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Acknowledgements

• 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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Outline

• 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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special case
general case
eigenmodes rotated wrt horizontal and vertical
planes due to coupling.
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Set 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 Tunes

• set measured

• set measured

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• tune feedback would break here

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Manual Decoupling
Skew chrom
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Chrom measurement
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• dQmin lt .001

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Coupling Echoes
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Outline

• 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 Feedbacks
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First Ramp with Feedbacks 2
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Last Blue Ramp with Feedbacks
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Next Ramp with Feedbacks Off
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Beam 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

• 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

• 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

• Worlds 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
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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
chrom - good results under sequencer control
gt
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Q'
ramp 6380
-5
dp/p of /-10-4 gives /-100m radial modulation
(RHICLHC)
vert
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Q'
horiz
ramp 6381
-5
gt
in RHIC modulation is at 1Hz
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Q'
ramp 6382
-5