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

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AIM OF THIS TALK 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 Jitter of the beam Jitter of the Bunch Clock Put them in perspective to jitter sensitivity of systems in LHC detectors Many thanks to Themistoklis Mastoridis (BE/RF), Philippe Baudrenghien (BE/RF) and Jan Troska (PH/ESE) Sophie Baron - CERN 2 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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Two words about Jitter Quantifying Jitter Jitter Types Jitter sensitivity of electronics in LHC experiments Traditional Electronics LHC detector exotic susceptibility Jitter sources Beam Jitter Bunch Clock Jitter RF system Long distance transmission Electronic components within experiments Conclusion OUTLINE Sophie Baron - CERN 3 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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TWO WORDS ABOUT JITTER Measuring, Quantifying and Representing Jitter Jitter Types Sophie Baron - CERN 4 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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Time Domain (oscilloscope or SDA traditional views) Probability Density Function (PDF) Frequency Domain (spectrum, phase noise) = std deviation = rms jitter pkpk jitter TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION Measuring, Quantifying, Representing Jitter Jitter Types Sophie Baron - CERN 5 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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Cycle-to-cycle jitter: short term variation in clock period between adjacent clock cycles. Contains highest frequency components of jitter. Period jitter: short term variation in clock period over all measured clock cycles, compared to the average clock period. Contains relatively high frequency components of jitter. TIE jitter (Time Interval Error or accumulated/phase Jitter): Actual deviation from the ideal clock period over all clock periods. includes jitter at all modulation frequencies. Calculation on its pdf gives many information on jitter sources. Skew jitter: Deviation from reference signal (source, adjacent channel) over all clock periods. Phase noise: Plots the Phase Spectral Density (S (F )=|F((t)|) in dBc/Hz, over a frequency domain of the offset frequency f =f-f c. Very useful to have a full picture of the jitter contributions. Full integration of the plot gives the phase jitter. Wander: jitter less than 10Hz from the carrier. Any of the above jitters, when very slow is considered as wander. P i =P i -P i+1 P i+1 = P i+1 -P i+2 P i P i+1 P i+2 TIE(n)=T(n)-nT 0 TIE(n+1)=T(n+1)-(n+1)T 0 S(n-1)=T(n-1)-T 0 (n-1) S(n)=T(n)-T 0 (n) S(n+1)=T(n+1)-T 0 (n+1) S(n+2)=T(n+2)-T 0 (n+2) TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION Measuring, Quantifying, Representing Jitter Jitter Types Sophie Baron - CERN 6 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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JITTER SENSITIVITY OF ELECTRONICS IN EXPERIMENTS Traditional Electronics LHC Detectors Exotic Susceptibility Sophie Baron - CERN 7 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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Digital Systems (flip-flops): Very sensitive to setup and hold time basically related to PKPK CY2CY AND PERIOD JITTER. PLLs: Track the slow variations of the clocks, and filter out the high frequency components. Can not deal with sudden jumps which unlock them. PKPK CY2CY JITTER WANDER can also be a problem when it means frequency drifting out of the locking range. ADCs: Very sensitive to timing errors as they directly convert into sampling errors, and SNR. Unregular sampling edges can distort of the shape of digitized pulses. This is thus more about PKPK CY2CY AND PERIOD JITTER than about TIE. Serial Data Links: Need to combine low Bit Error Rate (BER) and good Clock Recovery for further uses. BER is related to the quality of the clock Transmitter is very sensitive to ANY CLOCK JITTER (because of clock multiplication). On the channel, data jitter is correlated to DUTY CYCLE DISTORTION of the clock (DCD) Receiver and CDR are highly sensitive to HIGH FREQUENCY JITTER Quality of the Clock Recovery is a trade off between low BER (requires high bandwidth) and noise rejection (requires narrow bandwidth) Serial Data Links understanding requires TIE decomposition and often frequency domain analysis TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION Traditional Electronics LHC Detectors Exotic Susceptibility Sophie Baron - CERN 8 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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Event reconstruction over a huge system 1000s of Bunch Clock destinations spread all over the detectors SKEW JITTER BETWEEN ALL CLOCK SIGNALS to guaranty channel-to-channel consistency Trade off for the PLLs in the clock tree Narrow bandwidth to clean the clock as much as possible Not too narrow bandwidth to be sure they do not drift too much from each other. stable phase between Bunch Clock and Beam Low SKEW JITTER BETWEEN CLOCK AND BUNCHES (RF) over a fill (obvious) DETERMINISTIC phase from fill to fill and between power cycles not obvious at all, as this requirement is almost never required by industry. Almost impossible to get from commercial components. The Reference of our system is moving Bunch Clock comes from the RF system which is not stable (ramps, blow-ups, trimms, feedback loops) The beam driven by the RF has its own jitter (bunch-to-bunch distance, phase noise wrt RF, bunch profile variation over a fill, etc) TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION Traditional Electronics LHC Detectors Exotic Susceptibility Sophie Baron - CERN 9 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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

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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 Themistoklis Mastoridis, BE/RF TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION BEAM JITTERBUNCH CLOCK JITTERRF JITTERLONG DISTANCETTC JITTER Sophie Baron - CERN 11 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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Bunch position jitter over a fill Consistent 0.5-1 ps rms 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). Flat BottomMiddle of RampFlat TopStable Beam Standard Deviation (rms) of each bunch over 73 turns Mean Bunch Position over 73 turns 12p s 6ps 2ps 1.3p s 20p s 8ps 6ps Courtesy of Themistoklis Mastoridis, BE/RF TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION BEAM JITTERBUNCH CLOCK JITTERRF JITTERLONG DISTANCETTC JITTER Sophie Baron - CERN 12 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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Almost NO Variation of the bunch profile over a fill Slight distortion from gaussian shape because of the blow-up during ramp Blow-up is a noise injected into the RF during the ramp to shake the beam and spread the particules within bunches Protons Ions Courtesy of Philippe Baudrenghien, BE/RF TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION BEAM JITTERBUNCH CLOCK JITTERRF JITTERLONG DISTANCETTC JITTER Sophie Baron - CERN TWEPP2012 - Jitter On Clock Distribution - 19.09.12 13

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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 Themistoklis Mastoridis and Philippe Baudrenghien BE/RF TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION BEAM JITTERBUNCH CLOCK JITTERRF JITTERLONG DISTANCETTC JITTER Sophie Baron - CERN 14 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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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 Themistoklis Mastoridis and Philippe Baudrenghien BE/RF Reproducible from fill to fill TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION BEAM JITTERBUNCH CLOCK JITTERRF JITTERLONG DISTANCETTC JITTER Sophie Baron - CERN 15 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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Many loops are managed by the low level loop processor Beam control loop (low frequency, < 11kHz) Phase loop Synchro loop Radial loop Cavity control loops (high frequency) Phase Noise Power Spectral Density Plot: Fully integrated phase noise 1Hz- 1MHz is 3 ps rms. Keep in mind the propagation time (>50us) between RF and detectors Jitter on RF signal adds to bunch jitter at the level of detectors Beam Control LoopsCavities Control Loops TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION BEAM JITTERBUNCH CLOCK JITTERRF JITTERLONG DISTANCETTC JITTER Sophie Baron - CERN 16 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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Up to 14km of burried fiber from SR4 to ALICE, ATLAS, CMS (1m deep) The fibre length changes with core temperature by 7ppm/degC, which induces variation of the propagation delay by about 0.5ns/degC/14km Obviously very slow variation of the phase between beam and clock (wander) 5ns/full year/9km 3ns per season for 14km TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION BEAM JITTERBUNCH CLOCK JITTERRF JITTERLONG DISTANCETTC JITTER Sophie Baron - CERN 17 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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TxRxRF 2TTC TTCvi/ ex TTCrq RF Phase Jitter=2ps rms TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION BEAM JITTERBUNCH CLOCK JITTERRF JITTERLONG DISTANCETTC JITTER Sophie Baron - CERN 18 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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TxRxRF 2TTC TTCvi/ ex TTCrq TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION BEAM JITTERBUNCH CLOCK JITTERRF JITTERLONG DISTANCETTC JITTER Sophie Baron - CERN 19 TWEPP2012 - Jitter On Clock Distribution - 19.09.12 RF Phase Jitter=2ps rms Rx Phase Jitter=1.9ps rms

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TxRxRF 2TTC TTCvi/ ex TTCrq TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION BEAM JITTERBUNCH CLOCK JITTERRF JITTERLONG DISTANCETTC JITTER Sophie Baron - CERN 20 TWEPP2012 - Jitter On Clock Distribution - 19.09.12 RF Phase Jitter=2ps rms Rx Phase Jitter=1.9ps rms RF2TTC Phase Jitter=10ps rms

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TxRxRF 2TTC TTCvi/ ex TTCrq TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION BEAM JITTERBUNCH CLOCK JITTERRF JITTERLONG DISTANCETTC JITTER Sophie Baron - CERN 21 TWEPP2012 - Jitter On Clock Distribution - 19.09.12 RF Phase Jitter=2ps rms Rx Phase Jitter=1.9ps rms RF2TTC Phase Jitter=10ps rms TTCex Phase Jitter=4.9ps rms

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TxRxRF 2TTC TTCvi/ ex TTCrq TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION BEAM JITTERBUNCH CLOCK JITTERRF JITTERLONG DISTANCETTC JITTER Sophie Baron - CERN 22 TWEPP2012 - Jitter On Clock Distribution - 19.09.12 RF Phase Jitter=2ps rms Rx Phase Jitter=1.9ps rms RF2TTC Phase Jitter=10ps rms TTCex Phase Jitter=4.9ps rms TTCrq Phase Jitter=8ps rms OFF site

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TxRxRF 2TTC TTCvi/ ex TTCrq Jitter MeasurementTTCrq 40 MHz output rmspkpk TIE974 Cy2Cy13119 Per1866 TJ (BER 10-12)116 RJ7 PJ720 Phase146mdeg1.1deg Phase noise rms jitter8 ps rms TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION BEAM JITTERBUNCH CLOCK JITTERRF JITTERLONG DISTANCETTC JITTER Sophie Baron - CERN 23 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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New Electronics for TTC Upgrade TTCrq 40 MHz output TTC PON very basic proof of concept TTC FMC board (no PLL) GBT Serdes Prototype Measurement type rmsPkpkrmspkpkrmspkpkrmspkpk TIE252391179418974 Cy2cy Agilent242068731211013119 TJ11684116 RJ457 PJ1511.558210720 Skew368mde g 3.3deg190mdeg1.5deg146mdeg1.1deg Phase Noise Jitter23.512.7158 TWO WORDSJITTER SENSITIVITYJITTER SOURCESCONCLUSION BEAM JITTERBUNCH CLOCK JITTERRF JITTERLONG DISTANCETTC JITTER Sophie Baron - CERN 24 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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CONCLUSION Sophie Baron - CERN 25 TWEPP2012 - Jitter On Clock Distribution - 19.09.12

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JITTER VictimsJITTER Sources Jitter Victim Quality Criteria Ideal reference Jitter type sensitivity Typical requiremen ts at the input ElectronicsBeamRF phase noise Temper ature drift Usual RJ contribution Usual PJ contribution ADCSampling quality Intrinsiccy2cy