BIW 2006
Simultaneous Tune and Coupling Simultaneous Tune and Coupling Feedback during RHIC Run 6Feedback during RHIC Run 6
Peter Cameron
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
BIW 2006
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
BIW 2006
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eigenmodes rotated wrt horizontal and vertical planes
due to coupling.
special case general case
BIW 2006
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
BIW 2006
Set and Measured TunesSet and Measured Tunes
set measured
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BIW 2006
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
BIW 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
BIW 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
– 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
BIW 2006
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
BIW 2006
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
BIW 2006
3D on the Ramp - 1 Jan 05
dominant
spacing
is 180Hz
60Hz onset
60Hz end
IPM every
100 turns
(780 Hz)
BIW 2006
• Transverse instability• Not fixed by chrom• Frequently present at a
level not detectable by anything other than BBQ
• Upper half of sideband