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Successful Implementation of Simultaneous Tune and Coupling Feedback in RHIC Run 6

This paper presents the groundbreaking implementation of simultaneous tune and coupling feedback during the RHIC Run 6, marking a milestone in accelerator research. Acknowledging contributions from key figures like Tom Shea and teams from BNL C-AD, it discusses system architecture, the 3D AFE's sensitivity to beam noise, and the complexities of maintaining feedback during ramping. The findings open avenues for further developments in simultaneous feedback mechanisms, enhancing performance in future LHC operations.

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Successful Implementation of Simultaneous Tune and Coupling Feedback in RHIC Run 6

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  1. Simultaneous Tune and Coupling Feedback during RHIC Run 6 Peter Cameron BIW 2006

  2. BIW 2006

  3. 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 BIW 2006

  4. 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 BIW 2006

  5. BIW 2006

  6. BIW 2006

  7. 10nm BIW 2006

  8. special case general case eigenmodes rotated wrt horizontal and vertical planes due to coupling. BIW 2006

  9. 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 BIW 2006

  10. Set and Measured Tunes set measured set measured BIW 2006

  11. tune feedback would break here BIW 2006

  12. Manual Decoupling Skew chrom 0 Chrom measurement BIW 2006

  13. dQmin < .001 BIW 2006

  14. BIW 2006

  15. 1 sec ½ synchrotron period .02 Coupling coefficient ‘C’ 0 Coupling Echoes BIW 2006

  16. 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 BIW 2006

  17. First Ramp with Feedbacks BIW 2006

  18. First Ramp with Feedbacks 2 BIW 2006

  19. Last Blue Ramp with Feedbacks BIW 2006

  20. Next Ramp with Feedbacks Off BIW 2006

  21. Beam Noise • Steve Peggs – “declare Victory” • Peter Cameron – “Mission Accomplished” • One messy little detail • 3D AFE sensitivity to ‘beam noise’ • No free lunch BIW 2006

  22. 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

  23. 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

  24. 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

  25. Back-up slides BIW 2006

  26. 3D on the Ramp - 1 Jan 05 dominant spacing is 180Hz 60Hz onset 60Hz end IPM every 100 turns (780 Hz) BIW 2006

  27. Transverse instability • Not fixed by chrom • Frequently present at a level not detectable by anything other than BBQ • Upper half of sideband BIW 2006

  28. chrom - good results under sequencer control Summary of Chromaticity gt +5 Q' ramp 6380 -5 dp/p of +/-10-4 gives ~+/-100m radial modulation (RHIC&LHC) vert +5 Q' horiz ramp 6381 -5 gt in RHIC modulation is at 1Hz +5 Q' ramp 6382 -5 BIW 2006

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