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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

JITTER

IMPACT ON CLOCK DISTRIBUTION IN LHC EXPERIMENTS

S. BARON - TWEPP 2012

aim of this talk
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

outline
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

two words about jitter
Measuring, Quantifying and RepresentingJitter

Jitter Types

Two WORDS ABOUT JITTER

TWEPP2012 - Jitter On Clock Distribution - 19.09.12

slide5

JITTER SENSITIVITY

JITTER SOURCES

CONCLUSION

TWO WORDS…

Measuring, Quantifying, RepresentingJitter

Jitter Types

σ= stddeviation = rmsjitter

pkpkjitter

TWEPP2012 - Jitter On Clock Distribution - 19.09.12

slide6

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

jitter sensitivity of electronics in experiments
TraditionalElectronics

LHC Detectors ExoticSusceptibility

JITTER SENSITIVITY OF ELECTRONICS IN EXPERIMENTS

TWEPP2012 - Jitter On Clock Distribution - 19.09.12

slide8

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

slide9

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

jitter sources
BEAM JITTER

BUNCH CLOCK JITTER

RF System (Analog)

Long Distance Transmission

TTC Electronics (Digital)

JITTER SOURCES

TWEPP2012 - Jitter On Clock Distribution - 19.09.12

two words

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

two words1

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

two words2

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

two words3

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

two words4

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

two words5

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

two words6

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

two words7

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

two words8

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

two words9

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

two words10

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

two words11

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

two words12

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

two words13

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

conclusion
conclusion

TWEPP2012 - Jitter On Clock Distribution - 19.09.12

two words14

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

references
REFERENCES

TWEPP2012 - Jitter On Clock Distribution - 19.09.12

slide28

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

spare slides
SpARE SLIDES

TWEPP2012 - Jitter On Clock Distribution - 19.09.12

bunch clock journey
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

bunch clock jitter
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

typical jitter values of ttc system
Typicaljitter values of TTC system

New Electronics for Upgrade

TWEPP2012 - Jitter On Clock Distribution - 19.09.12