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the 60Hz Harmonics Problem

the 60Hz Harmonics Problem. Peter Cameron. Outline. Old Stuff – rehashing what almost everyone has seen at least once “tell them what you are going to tell them, then tell them, then tell them what you told them” New stuff another look at May APEX experiment data

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the 60Hz Harmonics Problem

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  1. the 60Hz Harmonics Problem Peter Cameron APEX 2 Nov 06

  2. Outline • Old Stuff – rehashing what almost everyone has seen at least once • “tell them what you are going to tell them, then tell them, then tell them what you told them” • New stuff • another look at May APEX experiment data • harmonics beyond the betatron line • Plans for Run 7 • Common mode??? • Ramping supply at injection – definitive? • Repeat the APEX of last May • DAQ APEX 2 Nov 06

  3. 60Hz Harmonics • direct excitation of betatron resonance by high harmonics of power supply frequencies • mechanism is not yet understood • large amplitude • ~40dB above 3D AFE noise floor during injection and store (~1m) • ~70dB above 3D AFE noise floor during ramping (~30m) • three definitive measurements • increase/decrease coincides with ramping supplies • coupling moves harmonics into vertical • main dipole 12 phase power supply tweak modifies spectrum • Concerns • makes BBQ/TF system refinement at RHIC difficult • emittance growth??? APEX 2 Nov 06

  4. the good news – if 60Hz harmonic are not blowing up emittance on the ramp (?), then BBQ certainly won’t APEX 2 Nov 06

  5. Effect of 60Hz Harmonics on BBQ PLL locked on 60Hz harmonic APEX 2 Nov 06

  6. coupling variation shows excitation is in horizontal plane horizontal vertical APEX 2 Nov 06

  7. 12 phase power supply balancing • At injection, tweak one phase of 12 phase power supply • Causal relation was observed with pattern of 60Hz harmonics • The tweak was large – 150msec, or ~3 degrees at 60Hz • Pattern changed, but total 60Hz harmonics power remained constant • not likely to be eliminated by better balancing? • problem is complex – 12 free parameters, not reasonable to expect improvement from random tweaks • fact that line amplitudes decreased suggests there is no other comparable source • This phenomenon is not understood APEX 2 Nov 06

  8. NI DSA 755am 806am 807am HP DSA APEX 2 Nov 06

  9. Correlations correlation coefficients determination coefficients • Coefficient of Determination • square of correlation coefficient • more intuitively meaningful than correlation coefficient • defined as ‘the proportion of variation in common between two data sets’ • with no noise, no machine drifts, perfect reproducibility of magnets… would be “1” for 755am and 807am data sets • Random probability of observed determination coefficients is < 1 part in 105 APEX 2 Nov 06

  10. firing order: A1, A2 B1, B2 A3, A4 B3, B4 A5, A6 B5, B6 Phase between A and B bridges depends on mains voltage (booster on/off, ???...) With phase shift between A and B bridges, this reproduces the pattern used in the simulation. LOAD RHIC 6 phase 12 pulse 1 3 5 A 4 6 2 Df=30 deg 1 3 5 B 4 6 2 APEX 2 Nov 06

  11. 3D AFE M Turn BPM Simulation APEX 2 Nov 06

  12. DC to 20KHz on the ramp only 720Hz lines high-lighted position of minimum determined by amount of SCR overlap note – amplitude at betatron line ~ amplitude at 720Hz according to million turn BPM APEX 2 Nov 06

  13. Outline • Old Stuff – rehashing what almost everyone has seen at least once • “tell them what you are going to tell them, then tell them, then tell them what you told them” • New stuff • another look at May APEX experiment data • harmonics beyond the betatron line • Plans for Run 7 • Common mode??? • Ramping supply at injection – definitive? • Repeat APEX of last May • DAQ APEX 2 Nov 06

  14. Baseband data from Carl Schultheiss APEX 2 Nov 06

  15. APEX experiment baseline • baseband data arbitrarily ‘renormalized’ for display, ‘renormalization’ the same for all graphs • 60Hz harmonics at betatron line (h~340) aligned with main dipole PS baseband spectrum • spectra are quite different • APEX experiment – one phase tweaked • power in betatron spectrum remains ~constant • power in baseband spectrum goes up a lot (~15dB on average) APEX 2 Nov 06

  16. baseband data arbitrarily ‘renormalized’ for display, ‘renormalization’ the same for all graphs • difference between spectra at baseband and betatron line with one phase tweaked • ‘baseline’ difference between spectra at baseband and betatron line • difference between tweaked and baseline spectra at baseband • power goes up a lot (~15dB on average) • difference between tweaked and baseline spectra at the betatron line APEX 2 Nov 06

  17. Conclusions – May APEX experiment • clear causal relation between main dipole PS phasing and 60Hz harmonics • Simulation of 12 phase power supply and Comparison with Data • imbalance between the two 6-phase bridges reproduces one observed spectral pattern • overlap between phases reproduces observed null at ~10KHz • Comparison of baseband and betatron spectra • they are quite different - what does this imply about the source? also see following slides • power in baseband goes up a lot with single (large) tweak APEX 2 Nov 06

  18. Yellow horiz span 5KHz 60Hz harmonics evident at ~31KHz Blue horiz span 50KHz additional ‘resonances in yellow, not at the betatron line? Yellow horiz Yellow vert APEX 2 Nov 06

  19. spectral pattern a function of frequency overlaps of 12 phase power supply? proposed new p-p working pt 20dB enhancement at betatron line – effective Q of betatron resonance is ~100? Blue horiz – span 39KHz, center 21KHz APEX 2 Nov 06

  20. Outline • Old Stuff – rehashing what almost everyone has seen at least once • “tell them what you are going to tell them, then tell them, then tell them what you told them” • New stuff • another look at May APEX experiment data • harmonics beyond the betatron line • Plans for Run 7 • Common mode??? • Ramping supply at injection – definitive? • Repeat the APEX of last May • DAQ APEX 2 Nov 06

  21. Plans for Run 7 • Carl – additional filtering, gain ~5dB • Fritz Caspers - Common mode excitation??? will check (also capacitance to ground) • Eduard - measure PS ripple – AC couple, no magnetic core • Ramping supply at injection – definitive? • George Ganetis/Kevin Brown – trivial to switch to ramping supply while at injection • look for changes in spectral pattern, amplitudes,… • Repeat last May’s APEX with more refinement, systematic attempt to tune out harmonics • additional DAQ helpful – presently just FFT APEX 2 Nov 06

  22. Bunch-by-bunch turn-by-turn system for Run 7 (Tom Russo’s talk tomorrow) 1m Stripline BH in BH out BV up BV down YH in YH out YV up YV down D hybrids HP VME Mux 14 bit A/D ch1 ch2 clock/3 trigger Control System GPMs, archiving,… SNAP 28MHz RF local 1TB hard drive (archiving) optional ext trigger (Artus,…) Windows PC running LabVIEW APEX 2 Nov 06

  23. Bunch-by-bunch turn-by-turn system for Run 7 modified to be sampling synchronous to selectable 60Hz harmonic boxcar average the data to improve S/N idea is to be able to observe effect of phase tweaks in time domain 1m Stripline BH BV YH YV 3D AFE BH BV YH YV 14 bit A/D ch1 ch2 clock/n trigger Control System GPMs, archiving,… SNAP 60Hz n x h x PLL local 1TB hard drive (archiving) optional ext trigger Windows PC running LabVIEW APEX 2 Nov 06

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