JITTER IMPACT ON CLOCK DISTRIBUTION IN LHC EXPERIMENTS S. BARON
- TWEPP 2012
Slide 2
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
Slide 3
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
Slide 4
TWO WORDS ABOUT JITTER Measuring, Quantifying and Representing
Jitter Jitter Types Sophie Baron - CERN 4 TWEPP2012 - Jitter On
Clock Distribution - 19.09.12
Slide 5
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
Slide 6
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
Slide 7
JITTER SENSITIVITY OF ELECTRONICS IN EXPERIMENTS Traditional
Electronics LHC Detectors Exotic Susceptibility Sophie Baron - CERN
7 TWEPP2012 - Jitter On Clock Distribution - 19.09.12
Slide 8
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
Slide 9
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
Slide 10
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
Slide 11
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
Slide 12
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
Slide 13
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
Slide 14
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
Slide 15
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
Slide 16
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
Slide 17
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
Slide 18
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
Slide 19
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
Slide 20
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
Slide 21
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
Slide 22
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
Slide 23
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
Slide 24
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
Slide 25
CONCLUSION Sophie Baron - CERN 25 TWEPP2012 - Jitter On Clock
Distribution - 19.09.12