LARP Berkeley Apr 2006 Tune/Coupling/Chromaticity Measurement and Feedforward/Feedback Peter Cameron

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

LARP Berkeley Apr 2006 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

LARP Berkeley Apr 2006

Manual Decoupling Skew chrom 0 Chrom measurement

LARP Berkeley Apr 2006

You will see this slide again

LARP Berkeley Apr 2006 Coupling Echoes ½ synchrotron period 1 sec Coupling coefficient ‘C’ 0.02

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

LARP Berkeley Apr 2006 First Ramp with Feedbacks

LARP Berkeley Apr 2006 First Ramp with Feedbacks 2

LARP Berkeley Apr 2006 Last Blue Ramp with Feedbacks

LARP Berkeley Apr 2006 Next Ramp with Feedbacks Off

LARP Berkeley Apr 2006

Outline Decoupling Ramping 3D AFE ‘Beam Noise’ Susceptibility Plans

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

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

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

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

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

LARP Berkeley Apr 2006 BBQ Schottky Bump effect Total beam loss was ~3X10 10

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

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

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

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

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

LARP Berkeley Apr 2006 Actual loss rate 5 amp/sec (Don Bruno) ~0.025T-m/s ~150  rad/sec at 25GeV,  ~100 ~0.5%/turn 1 sec for bump loss gives /turn

LARP Berkeley Apr 2006 Polarimeter Effect

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

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

LARP Berkeley Apr D 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 D on the Ramp - 1 Jan 05 dominant spacing is 180Hz 60Hz onset 60Hz end IPM every 100 turns (780 Hz)

LARP Berkeley Apr 2006

coupling excitation is horizontal vertical horizontal

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

LARP Berkeley Apr 2006 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 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