1 / 48

Tune/Coupling/Chromaticity Measurement and Feedforward/Feedback

Tune/Coupling/Chromaticity Measurement and Feedforward/Feedback. Peter Cameron. Outline. Decoupling Ramping 3D AFE ‘Beam Noise’ Susceptibility Plans.

nitza
Download Presentation

Tune/Coupling/Chromaticity Measurement and Feedforward/Feedback

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Tune/Coupling/ChromaticityMeasurement and Feedforward/Feedback Peter Cameron LARP Berkeley Apr 2006

  2. Outline • Decoupling • Ramping • 3D AFE ‘Beam Noise’ Susceptibility • Plans LARP Berkeley Apr 2006

  3. 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

  4. LARP Berkeley Apr 2006

  5. Manual Decoupling Skew chrom 0 Chrom measurement LARP Berkeley Apr 2006

  6. LARP Berkeley Apr 2006

  7. LARP Berkeley Apr 2006

  8. You will see this slide again LARP Berkeley Apr 2006

  9. Coupling Echoes 1 sec ½ synchrotron period .02 Coupling coefficient ‘C’ 0 LARP Berkeley Apr 2006

  10. Outline • Decoupling • Ramping • 3D AFE ‘Beam Noise’ Susceptibility • Plans LARP Berkeley Apr 2006

  11. First Ramp with Feedbacks LARP Berkeley Apr 2006

  12. First Ramp with Feedbacks 2 LARP Berkeley Apr 2006

  13. Last Blue Ramp with Feedbacks LARP Berkeley Apr 2006

  14. Next Ramp with Feedbacks Off LARP Berkeley Apr 2006

  15. LARP Berkeley Apr 2006

  16. Outline • Decoupling • Ramping • 3D AFE ‘Beam Noise’ Susceptibility • Plans LARP Berkeley Apr 2006

  17. Beam 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

  18. 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

  19. BBQ and PLL S/N Comparison- static conditions PLL both I and Q BBQ H I and Q BBQ V I and Q LARP Berkeley Apr 2006

  20. Initial 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

  21. Yellow horizontal – ‘dropouts’ during filling • signal goes away completely at times • At other times attenuated LARP Berkeley Apr 2006

  22. Blue Vertical- ‘Saturation’ during ramping LARP Berkeley Apr 2006

  23. BV ‘Saturation’ Spectra at store 78KHz span 4.8KHz zoom LARP Berkeley Apr 2006

  24. APEX 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

  25. Max bump ~3cm! Schottky BBQ pickup LARP Berkeley Apr 2006

  26. Total beam loss was ~3X1010 effect Schottky Bump BBQ LARP Berkeley Apr 2006

  27. 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

  28. Schottky also showed effect only early in the bump, and only in horizontal Schottky horiz times of large losses Schottky vert LARP Berkeley Apr 2006

  29. 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

  30. Zoom on effect of beam loss next slide LARP Berkeley Apr 2006

  31. Further zoom on effect of beam loss ~180 degree phase shift = temporary ‘loss of lock’ LARP Berkeley Apr 2006

  32. Similar data from fill 7614, showing progressive deterioration of lock quality as beam loss increases LARP Berkeley Apr 2006

  33. ~0.5%/turn Effect of beam loss on signal amplitude – ‘AM effect’ LARP Berkeley Apr 2006

  34. Actual loss rate 5 amp/sec (Don Bruno) ~0.025T-m/s ~150mrad/sec at 25GeV, b~100 ~0.5%/turn 1 sec for bump 10-4 loss gives 10-9/turn LARP Berkeley Apr 2006

  35. Polarimeter Effect LARP Berkeley Apr 2006

  36. 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

  37. Effect of filtering in front of diodes 100MHz Hi-Pass no filter 100MHz Hi-Pass plus 50MHz Lo-Pass 50MHz Lo-Pass LARP Berkeley Apr 2006

  38. BTF 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

  39. 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

  40. Effect of long range beam-beam on the ramp LARP Berkeley Apr 2006

  41. 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

  42. 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

  43. LARP Berkeley Apr 2006

  44. coupling excitation is horizontal horizontal vertical LARP Berkeley Apr 2006

  45. Anomalous 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

  46. BBQ during tune scan (x const) Vert I and Q ~.01 units of tune Horiz I and Q Effect of beam loss? Tunes and beam decay LARP Berkeley Apr 2006 decoupled!!! dqmin<.001

  47. 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

  48. 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 LARP Berkeley Apr 2006

More Related