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JITTER

JITTER. IMPACT ON CLOCK DISTRIBUTION IN LHC EXPERIMENTS S. BARON - TWEPP 2012. Understand the contributions of all the systems to the bunch clock jitter RF system Long distance transmission Digital electronics within experiments (TTC) Compare orders of magnitude of

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JITTER

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  1. JITTER IMPACT ON CLOCK DISTRIBUTION IN LHC EXPERIMENTS S. BARON - TWEPP 2012

  2. Understand the contributions of all the systems to the bunchclockjitter RF system Long distance transmission Digital electronicswithinexperiments (TTC) Compare orders of magnitude of Jitter of the beam Jitter of the BunchClock Put them in perspective to jittersensitivity of systems in LHC detectors AIM OF this talk Manythanks to ThemistoklisMastoridis (BE/RF), Philippe Baudrenghien (BE/RF) and Jan Troska (PH/ESE) TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  3. OUTLINE • Twowords about Jitter • QuantifyingJitter • Jitter Types • Jittersensitivity of electronics in LHC experiments • TraditionalElectronics • LHC detector exoticsusceptibility • Jitter sources • BeamJitter • BunchClockJitter • RF system • Long distance transmission • Electronic components withinexperiments • Conclusion TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  4. Measuring, Quantifying and RepresentingJitter Jitter Types Two WORDS ABOUT JITTER TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  5. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… Measuring, Quantifying, RepresentingJitter Jitter Types σ= stddeviation = rmsjitter pkpkjitter TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  6. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… Measuring, Quantifying, RepresentingJitter Jitter Types PiPi+1 Pi+2 TIE(n)=T(n)-nT0 TIE(n+1)=T(n+1)-(n+1)T0 ΔPi=Pi-Pi+1 ΔPi+1= Pi+1-Pi+2 S(n+1)=T(n+1)-T0(n+1) S(n-1)=T(n-1)-T0(n-1) S(n+2)=T(n+2)-T0(n+2) S(n)=T(n)-T0(n) Cycle-to-cycle jitter: • short term variation in clockperiodbetween adjacent clock cycles. • Containshighestfrequency components of jitter. Periodjitter: • short term variation in clockperiod over all measuredclock cycles, compared to the averageclockperiod. • Containsrelativelyhighfrequency components of jitter. TIE jitter (Time IntervalError or accumulated/phase Jitter): • Actualdeviationfrom the idealclockperiod over all clockperiods. • includesjitterat all modulation frequencies. • Calculation on itspdfgivesmany information on jitter sources. Skewjitter: • Deviationfromreference signal (source, adjacent channel) over all clockperiods. Phase noise: • Plots the Phase Spectral Density (Sφ(Fφ)=|F(φ(t)|²) in dBc/Hz, over a frequency domain of the offset frequency fφ=f-fc. • Veryuseful to have a full picture of the jitter contributions. • Full integration of the plot gives the phase jitter. Wander: • jitterlessthan 10Hz from the carrier. • Any of the abovejitters, whenvery slow isconsidered as wander. TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  7. TraditionalElectronics LHC Detectors ExoticSusceptibility JITTER SENSITIVITY OF ELECTRONICS IN EXPERIMENTS TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  8. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… TraditionalElectronics LHC Detectors ExoticSusceptibility Digital Systems (flip-flops): • Very sensitive to setup and hold time • basicallyrelated to pkpk cy2cy and periodjitter. PLLs: • Track the slow variations of the clocks, and filter out the highfrequency components. • Can not deal withsuddenjumpswhichunlockthem. • pkpk cy2cy jitter • Wandercanalsobe a problemwhenitmeansfrequencydrifting out of the locking range. ADCs: • Very sensitive to timing errors as theydirectlyconvertintosamplingerrors, and SNR. • Unregularsamplingedgescandistort of the shape of digitized pulses. • This isthus more about pkpk cy2cy and periodjitterthan about TIE. Serial Data Links: • Need to combine low Bit Error Rate (BER) and good ClockRecovery for further uses. • BER isrelated to the quality of the clock • Transmitterisvery sensitive to anyclockjitter(because of clock multiplication). • On the channel, data jitteriscorrelated to Duty Cycle Distortionof the clock (DCD) • Receiver and CDR are highly sensitive to highfrequencyjitter • Quality of the ClockRecoveryis a trade off betweenlow BER (requireshighbandwidth) and noise rejection (requiresnarrowbandwidth) • Serial Data Links understandingrequires TIE decomposition and oftenfrequencydomainanalysis TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  9. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… TraditionalElectronics LHC Detectors ExoticSusceptibility Event reconstruction over a huge system • 1000s of BunchClock destinations spread all over the detectors • skewjitterbetween all clocksignalsto guarantychannel-to-channelconsistency • Trade off for the PLLs in the clocktree • Narrowbandwidth to clean the clock as much as possible • Not toonarrowbandwidth to be sure they do not drift toomuchfromeachother. • stable phase betweenBunchClock and Beam • Lowskewjitterbetweenclock and Bunches(RF) over a fill (obvious) • Deterministicphase fromfill to fill and between power cycles • not obviousat all, as thisrequirementisalmostneverrequired by industry. • Almost impossible to getfrom commercial components. The Reference of our system ismoving • BunchClockcomesfrom the RF system whichis not stable (ramps, blow-ups, trimms, feedback loops) • The beamdriven by the RF has itsownjitter (bunch-to-bunch distance, phase noise wrt RF, bunch profile variation over a fill, etc…) TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  10. BEAM JITTER BUNCH CLOCK JITTER RF System (Analog) Long Distance Transmission TTC Electronics (Digital) JITTER SOURCES TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  11. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER • Bunch position jitter • The data over a turn show a peak-to-peak variation of ~7 ps. This is a single data set (no averaging involved). Each Bunch position is measured once versus 400Mhz RF. • Jitter for each bunch (Standard deviation over 73 turns) is less than 2ps rms Courtesy of ThemistoklisMastoridis, BE/RF TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  12. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER • Bunch position jitter over a fill • Consistent 0.5-1 psrms for each bunch. Increases to about 2-3 ps during the ramp due to the acceleration • At most 6 ps peak-to-peak over a turn due to beam loading (very reproducible from turn to turn). 12ps 2ps 1.3ps 6ps 20ps 8ps 20ps 6ps Courtesy of ThemistoklisMastoridis, BE/RF TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  13. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER • Almost NO Variation of the bunch profile over a fill • Slightdistortionfromgaussianshapebecause of the blow-up duringramp • Blow-up is a noise injectedinto the RF during the ramp to shake the beam and spread the particules withinbunches Protons Ions Courtesy of Philippe Baudrenghien, BE/RF TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  14. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER • New Bunch Position Plot after LS1 • “After LS1, some modulation of the cavity phase will probably be implemented to help lower the RF power requirements • The modulation of the cavity phase changes the bunch spacing and therefore the collision point. However the 65 ps displacement is small compared to the 1.2 ns 4-sigma bunch length • As the filling pattern of the two rings is very similar, the phase modulations will cancel out in IP1 and IP5 and the resulting displacement of the collision vertex will be much smaller than the above 65 ps “ Modulation of the cavity phase by the transient beam loading in physics for nominal conditions. 2835 bunches, 1.7E11 p/bunch, 25ns spacing Current Bunch position (1440 bunches). No Cavity phase modulation. Courtesy of ThemistoklisMastoridisand Philippe Baudrenghien BE/RF TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  15. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER Reproduciblefromfill to fill Modulation of the cavity phase by the transient beam loading in physics for nominal conditions. 2835 bunches, 1.7E11 p/bunch, 25ns spacing Current Bunch position (1440 bunches). No Cavity phase modulation. Courtesy of ThemistoklisMastoridisand Philippe Baudrenghien BE/RF TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  16. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER • Manyloops are managed by the lowlevelloop processor • Beam control loop (lowfrequency, < 11kHz) • Phase loop • Synchro loop • Radial loop • Cavity control loops (highfrequency) • Phase Noise Power Spectral Density Plot: • Fullyintegrated phase noise 1Hz-1MHz is 3 psrms. • Keep in mind the propagation time (>50us) between RF and detectors • Jitter on RF signal adds to bunchjitterat the level of detectors Beam Control Loops Cavities Control Loops TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  17. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER • Up to 14km of burriedfiberfrom SR4 to ALICE, ATLAS, CMS (1m deep) • The fibre length changes withcoretemperatureby 7ppm/degC, whichinduces variation of the propagation delay by about 0.5ns/degC/14km • Obviouslyvery slow variation of the phase betweenbeam and clock (wander) 5ns/full year/9km • 3ns per season • for 14km TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  18. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER RF Tx Rx RF 2TTC TTCvi/ex TTCrq RF Phase Jitter=2ps rms TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  19. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER RF Tx Rx RF 2TTC TTCvi/ex TTCrq RF Phase Jitter=2ps rms Rx Phase Jitter=1.9ps rms TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  20. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER RF Tx Rx RF 2TTC TTCvi/ex TTCrq RF Phase Jitter=2ps rms Rx Phase Jitter=1.9ps rms RF2TTC Phase Jitter=10ps rms TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  21. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER RF Tx Rx RF 2TTC TTCvi/ex TTCrq RF Phase Jitter=2ps rms Rx Phase Jitter=1.9ps rms RF2TTC Phase Jitter=10ps rms TTCex Phase Jitter=4.9psrms TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  22. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER RF Tx Rx RF 2TTC TTCvi/ex TTCrq OFF site RF Phase Jitter=2ps rms Rx Phase Jitter=1.9ps rms RF2TTC Phase Jitter=10ps rms TTCex Phase Jitter=4.9psrms TTCrq Phase Jitter=8ps rms TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  23. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER RF Tx Rx RF 2TTC TTCvi/ex TTCrq TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  24. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  25. conclusion TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  26. JITTER SENSITIVITY JITTER SOURCES CONCLUSION TWO WORDS… BEAM JITTER BUNCH CLOCK JITTER RF JITTER LONG DISTANCE TTC JITTER TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  27. REFERENCES TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  28. A Primer on Jitter, JitterMeasurement and Phase-LockedLoops, SiLabs AN687, 2012 • Practical pointers to measurejitters and phase-noise accurately, EDN Asia, Nov 2011 • Jitter – Understandingit, Measuringit, Eliminatingit, High FrequencyElectronics, 2004 • UsingClockJitterAnalysis to Reduce BER in Serial Data Applications, Agilent Application Note, 2006 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  29. SpARE SLIDES TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  30. BunchClockJourney Jitterconcerns … and sources LLRF loop [Jitter of interest] RF clockgeneration Traditional Source of Jitter RJ and DJ [Skewjitterbetween source and destination clock] 40MHz clockpath LHC specific Source of Jitter TDC Jittervictim Beam life time, bunch profile, cavity noise Phase shift withTemperature (wander) [low cy2cy jitter to keep PLL locked] [Phase jitterbetween Bunch and Clock] RJ and DJ TDC QPLL [Skewjitterbetweenchannels] TTCrx DDJ RJ and DJ TTCex ECL FANOUT RF2TTC RF-Rx ECL FANOUT TTCrx QPLL TDC Propagation delay = 46.7 us for 14 km = 1/2 LHC turn = 21kHz TTCoc [lowrandomjitter for good ADC performance] DDJ TTCrx ADC QPLL [lowjitter to allow frequency multiplication] PLL x60 Beam life time, bunch profile, cavity noise TTCrx Tx DDJ QPLL Trig RF-Rx RJ and DJ Rx DAQ RF-Tx [periodjitter, related to setup and hold time for digital systems] Fanout [low TIE jitter for good BER] RJ and DJ TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  31. BunchClockJitter Added by detectors electronics Gaussian and unbounded PDF, quantityisoften « rms » Usuallyperiodic or narrowband, the PDF isbounded, quantityisoften « pkpk » • Randomjitter sources • Caused by accumulation of a hugenumber of uncorrelatedprocessesthat have small magnitude • Random noise phenomena • Thermal noise, Shot noise, Pink noise, etc… • Occur in all semiconductors and components (PLLs, Oscillators, Tx, Rxetc…) • Typicalrepresentation of inducedjitter: gaussian & unbounded PDF • Quantified as Standard Deviation (rms) • Deterministicjitter sources • caused by a comparativelysmallnumber of processesthatneed not beindependent and may have large amplitudes, • Systematic & Data Dependentphenomena • Crosstalk, dispersion, impedancemismatch • InterSymbolInterference (ISI), Duty-Cycle Distortion (DCD), Bit sequenceperiodicity • Typicallydetected as distortion of the PDF fromgaussianshape • Quantified as pkpk, as theyinducebounded phase deviation (DJ) (RJ) Periodicjitter (PJ) (DDJ) TWEPP2012 - Jitter On Clock Distribution - 19.09.12

  32. Typicaljitter values of TTC system New Electronics for Upgrade TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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