Kazu AkibaOn behalf of the Velo Group
LHCb VErtex LOcator
Operation Experience
2
beauty at the LHC
π+
B0
B0
K+
K-
D-
Beam 2Beam 1
PV
IP
LHCbb production at low angle and in the same direction.A B experiment at the LHC needs forward acceptance!High b production cross section @ TeV energies
Even Higher background ratesLHCb’s scientific mission statement:
To precisely measure CP-violation in the B-system To find Rare B Decays To seek out New Physics
Key points: Vertexing Particle identification. Trigger
Kazu Akiba Rust, Austria
LHCb σ(pp → Hb X) = ( 75 ± 5 ± 13 ) µbPhys. Lett. B 694, 209-216 (2010)
The LHCb Experiment
Large Hadron Collider beauty Experiment for CP violation and Rare B Decays.
TTSi
Muon
MWPCGEM
HCAL
ECAL RICH2 Outer Tracke
r straw Tubes
Magnet
RICH1
VELO&PUSi
Inner Tracke
r Si
Closed For
physics Open during
injection
Zoom in the interaction
region
Kazu Akiba 4
2 Retractable halves21 Modules /half1R & 1φ sensors/module2048 strips/sensor 172k channels300 µm n-on-n sensors!
1 n-on-p Active @ 8 mm.Operated in a secondary vacuum,
sensors and front-end
Rust, Austria
Designed for:Minimal material budget.Excellent primary and secondary vertexing… and
tracking. Outstanding impact parameter resolution.
Vacuum !
VELO
Contains 1 Velo half
Rf Foil300 mm
Kazu Akiba 5Rust, Austria
Vacuum !
VELO
Contains 1 Velo half
2 Retractable halves21 Modules /half1R & 1φ sensors/module2048 strips/sensor 172k channels300 µm n-on-n sensors!
1 n-on-p Active @ 8 mm.Operated in a secondary vacuum,
sensors and front-end
Designed for:Minimal material budget.Excellent primary and secondary vertexing… and
tracking. Outstanding impact parameter resolution.
Rf Foil300 mm
Kazu Akiba 6Rust, Austria
Vacuum !
VELO
Contains 1 Velo half
2 Retractable halves21 Modules /half1R & 1φ sensors/module2048 strips/sensor 172k channels300 µm n-on-n sensors!
1 n-on-p Active @ 8 mm.Operated in a secondary vacuum,
sensors and front-end
Designed for:Minimal material budget.Excellent primary and secondary vertexing… and
tracking. Outstanding impact parameter resolution.
Rf Foil300 mm
Kazu Akiba 7
2 Retractable halves21 Modules /half1R & 1φ sensors/module2048 strips/sensor 172k channels300 µm n-on-n sensors!
1 n-on-p Active @ 8 mm.Operated in a secondary vacuum,
sensors and front-end
Designed for:Minimal material budget.Excellent primary and secondary vertexing… and
tracking. Outstanding impact parameter resolution.
Rust, Austria
Designed for:Minimal material budget.Excelent Primary and Secondary Vertexing… and
tracking. Outstanding Impact Parameter resolution.
Vacuum !
VELO
Contains 1 Velo half
Rf Foil
Beam vacuum
Velomba
rm
bar
Kazu Akiba 8Rust, Austria
Sensors/Modules
x42DataConfig
SensorFront-end:40 MHz clock, 1 MHz readout
HybridActive CoolingBiphase CO2
Analogue readout from ASICS (Beetle)on hybrids
Repeater cards outside tank – inaccessible when LHC is ON
Digitization 60m away – safe zone
FPGA processing106 parametersInteger pedestals and CM subtractionsClustering + Zero suppression
Carbon
fibre
-sensor
R-side circuit
-sidecircu
it
R-sensor
Carbon fibre support
Kapton cables
Kazu Akiba 9Rust, Austria
Sensors Modules
x42DataConfig
SensorFront-end:40 MHz clock, 1 MHz readout
HybridActive CoolingBiphase CO2
Analogue from ASICS on hybridsRepeater cards outside tank – inaccessible when LHC is ON
Digitization 60m away – safe zone
FPGA processing 106 parametersInteger pedestals and CM subtractionsClustering + Zero suppression
Carbon
fibre
-sensor
R-side circuit
-sidecircu
it
R-sensor
Carbon fibre support
Kapton cables -30oC
10
0
-10
-5
5
silicon [oC]
-5oC
-15oC
-25oC
-35oC
VELO fully powered
Silicon temperature as function of cooling setpoint
Stable behaviour. Work point: -30 oC nice low silicon work temperature of -10oC
-30oC
Cooling performance very stable so far
Time AlignmentFine tune timing is an automated procedureOverall precision of ± 1 nsAim for
Maximum signal/noise Minimal neighbouring bunch cross talk.
11/06/201110
Sensors individually tuned to account for differences in
Time of flight Cable length
Kazu Akiba 11
Running 2010-11
Rust, Austria
Higher Occupancy, collisions/crossing, then designed for.Nominal Instantaneous luminosity achieved in May/2011!
12
Running 2010-11Higher Occupancy, collisions/crossing, then designed for.Nominal Instantaneous luminosity achieved in May/2011!
Kazu Akiba Rust, Austria
ATLAS/CMS
LHCbUpgrade
Nominal
Now
Vis
Col
lisio
n
Pile-UP
Lumi LevelingDisplacing the beams
13
Running 2010-11Higher Occupancy, collisions/crossing, then designed for.Nominal Instantaneous luminosity achieved in May/2011!Running with 24/7 shifters in 2010.
Safety of the detector ensured. Careful HV ramping and moving the detector upon stable beams Front-end configured at all times except “MD” Data quality constantly checked.
Stability in 2010 pushed toward no VELO shifter operations in 2011: 2 people on call 24/7: data quality + hardware experts. Powering and moving are now automated, but human confirmed.
Interfill time is used for standard checks. IV curves and calibration runs constantly taken Checks for any increase of noisy/dead strips.
DAQ parameters determination and uploading streamlined Problems found with pedestal drifting Complete retuning of the system can be done within a day. NZS data taken all the time: all detectors together in separate
stream => CM studies to be performed.Kazu Akiba Rust, Austria
HV and LVstable through 2010-11
Kazu Akiba 14
Running 2010-11Higher Occupancy, collisions/crossing, then designed for.Nominal Instantaneous luminosity achieved in May/2011!Running with 24/7 shifters in 2010.
Safety of the detector ensured. Careful HV ramping and moving the detector upon stable beams Front-end configured at all times except “MD” Data quality constantly checked.
Stability in 2010 pushed toward no VELO shifter operations in 2011: 2 people on call 24/7: data quality + hardware experts. Powering and moving are now automated, but human confirmed.
Interfill time is used for standard checks. IV curves and calibration runs constantly taken Checks for any increase of noisy/dead strips.
DAQ parameters determination and uploading streamlined Problems found with pedestal drifting Complete retuning of the system can be done within a day. NZS data taken all the time: all detectors together in separate
stream => CM studies to be performed.Rust, Austria
HV and LVstable through 2010-11Problem showed to be highly correlated
to the trigger rate…
Kazu Akiba 15
Operational Issue: Closing
The flags “stable beams” and “movable devices allowed in” set to TRUE by the LHC.
HV is ramped up. Temperatures, bias currents, occupancies are checked.
Closing manager “asks” to close the VELO
Calculation of the beam position relative to each half and global.
Four steps in x: 29 mm - 14 mm - 5 mm - 1 mm – closed
Constant check of the safety listCalculation of the next positionHuman re-confirmation at 1 mm.movement in y if request > 50 mm
Rust, Austria
Kazu Akiba 16
Operational Issue: Closing
The flags “stable beams” and “movable devices allowed in” set to TRUE by the LHC.
HV is ramped up. Temperatures, bias currents, occupancies are checked.
Closing manager “asks” to close the VELO
Calculation of the beam position relative to each half and global.
Four steps in x: 29 mm - 14 mm - 5 mm - 1 mm – closed
Constant check of the safety listCalculation of the next positionHuman re-confirmation at 1 mm.movement in y if request > 50 mm
Rust, Austria
Done about 100 times this year!
Kazu Akiba 17
Operational Issue: Closing
The flags “stable beams” and “movable devices allowed in” set to TRUE by the LHC.
HV is ramped up. Temperatures, bias currents, occupancies are checked.
Closing manager “asks” to close the VELO
Calculation of the beam position relative to each half and global.
Four steps in x: 29 mm - 14 mm - 5 mm - 1 mm – closed
Constant check of the safety listCalculation of the next positionHuman re-confirmation at 1 mm.movement in y if request > 50 mm
Rust, Austria
Fraction of the inefficiency due to the Velo closing procedure
Kazu Akiba 18
Operational Issue: Closing
The flags “stable beams” and “movable devices allowed in” set to TRUE by the LHC.
HV is ramped up. Temperatures, bias currents, occupancies are checked.
Closing manager “asks” to close the VELO
Calculation of the beam position relative to each half and global.
Four steps in x: 29 mm - 14 mm - 5 mm - 1 mm – closed
Constant check of the safety listCalculation of the next positionHuman re-confirmation at 1 mm.movement in y if request > 50 mm
Rust, Austria
Partly due to a bug in the derandomizer of Beetle ASICWhich increases with the rate.
Kazu Akiba 19
Once closed, then Monitor
Beam Condition Monitor (BCM), Beam Position Monitor (BPM)constantly checked.
DAQ system must “be working”.Vertex Position is monitored online at all times.
HV currents are checked for “abnormal correlated fluctuations”
If one condition is not satisfied “Grace Period” Move out to 14 mm .
32 Conditions based on 32 parameters.
Rust, Austria
Kazu Akiba 20
Once closed, then Monitor
Beam Condition Monitor (BCM), Beam Position Monitor (BPM)constantly checked.
DAQ system must “be working”.Vertex Position is monitored online at all times.
HV currents are checked for “abnormal correlated fluctuations”
If one condition is not satisfied “Grace Period” Move out to 14 mm .
Rust, Austria
32 Conditions based on 32 parameters.
21
Operational Issue: Performance
Kazu Akiba Rust, Austria
All S/N > 17... Still. But 1/pb per hour...
outer – WITHOUToverlaid routing lines
R -sensors:
Noise increases with strip length (radius).4 sectors of 512 strips
inner – routed over outer strips
outer – WITH overlaid routing lines
3 types of strips in sensors
cross talk from Beetle header
Kazu Akiba 22
Operational Hazards: Radiation Damage
Rust, Austria
Disclaimer:Depletion voltage around 40-80V initially.Depletion voltage decreases with fluence till type inversion (n-on-n)1. Current vs Voltage (IV)
Taken weekly Current increases with bulk damage, linearly related to fluence Does not study depletion voltage
2. Noise vs applied bias Voltage Taken monthly Sensors decrease capacitance and hence noise when depleted, so
sensitive to depletion voltage at least during early running3. Charge Collection Efficiency vs applied bias
voltage Direct measure of physics relevant parameter Can study radiation damage as function of position Requires beam data so only taken a few times per year
April 2010 (~none), April 2011 (40/pb)
Kazu Akiba 23
Radiation Damage: IV curves
Rust, Austria
Annealed at 20 o.Cover shutdown
n-on-n sensor
As well.
n-on-p sensor (similar z position)
Kazu Akiba 24
Radiation Damage: Noise Vs Voltage
Rust, Austria
Measure the change in theEffective Minimal Noise Voltage EMNV, when 1/noise passes 80%of final noise .
Innermost strips on R sensormost irradiationRatio < 1, i.e. , smaller EMNV
Outermost strips on R sensorless irradiationRatio ~ 1, i.e. no change in EMNV
25
VELO TDR
Observed “Fluences”
Kazu Akiba Rust, Austria
LHCb Velo Preliminary
LHCb Velo Preliminary
LHCb Velo Preliminary
LHCb Velo PreliminaryMinimum
bias data
26
Observed “Fluences”
Kazu Akiba Rust, Austria
VELO TDR
LHCb Velo Preliminary
LHCb Velo Preliminary
LHCb Velo Preliminary
LHCb Velo PreliminaryMinimum
bias data
Kazu Akiba 27
SummarySmooth Operations of the VELO over the past
~350/pb (~400/pb delivered counting 2010 too )
Troublesome at times but working fine Tracking and alignment performance reported by
S.Borghi.Hope to have much more Radiation Damage
till the end of 2011 (and 1/fb)!
Rust, Austria
Kazu Akiba 28Rust, Austria
Kazu Akiba 30
Common Mode
Rust, Austria
VELO POSITION
CM WIDTH σ
OPEN29 mm14 mm5 mm2 mmCLOSED
1,511 ± 0.011,487 ± 0.011,432 ± 0.011,607 ± 0.011,467 ± 0.011,500 ± 0.01
Kazu Akiba 31
Radiation Damage: CCE
Rust, Austria
Charge Collection Efficiency – The Method:
Blue – tracking sensors at full bias voltageRed – test sensors bias voltage scanned
10V steps, 0V-150V Rotate through patterns, fully automatic scan
procedure
Tracks fitted through tracking sensors Charge collected at intercept point on test sensors
measured as function of voltage Non-zero suppressed data taken full charge recorded
Can study regions of sensor
Kazu Akiba 32Rust, Austria
Radiation Damage: CCEMeasure CCE(V) Estimate the Effective Depletion Voltage:EDV = V(CCE = 80%)
Similar Zones as previously
33
Radiation Damage: IV curves
Kazu Akiba Rust, Austria
Annealed at 20 o.Cover shutdown
n-on-n sensor
As well.
Not
e th
e di
ffer
ent
scal
es