APEX 2 Nov 06 the 60Hz Harmonics Problem Peter Cameron

APEX 2 Nov 06Outline 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 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 (~1  ) –~70dB above 3D AFE noise floor during ramping (~30  ) 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 the good news – if 60Hz harmonic are not blowing up emittance on the ramp (?), then BBQ certainly won’t

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

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

APEX 2 Nov 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 – 150  sec, 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 am 806am 807am NI DSA HP DSA

APEX 2 Nov 06Correlations 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 10 5

APEX 2 Nov 06 LOAD A B  =30 deg 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. RHIC 6 phase 12 pulse

APEX 2 Nov 06 3D AFE M Turn BPM Simulation

APEX 2 Nov 06 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 06Outline 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 Baseband data from Carl Schultheiss

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

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

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

APEX 2 Nov 06 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 14 bit A/D ch1 ch2 clock/n trigger Windows PC running LabVIEW Control System GPMs, archiving,… SNAP local 1TB hard drive (archiving) 60Hz optional ext trigger 3D AFE BH BV YH YV 1m Stripline BH BV YH YV n x h x PLL