Operation Experience

Kazu AkibaOn behalf of the Velo Group

LHCb VErtex LOcator

Operation Experience

http://vertex2011.hephy.at/

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


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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







Rf Foil300 mm



Vacuum !

VELO







Rf Foil300 mm


Kazu Akiba 7






Rust, Austria

Designed for:Minimal material budget.Excelent Primary and Secondary Vertexing… and

tracking. Outstanding Impact Parameter resolution.

Vacuum !

VELO


Rf Foil

Beam vacuum

Velomba

rm

bar



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



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!


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


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Rust, Austria

Done about 100 times this year!


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Rust, Austria

Fraction of the inefficiency due to the Velo closing procedure


Kazu Akiba 18








Rust, Austria

Partly due to a bug in the derandomizer of Beetle ASICWhich increases with the rate.


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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.


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Operational Issue: Performance


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)


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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


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VELO TDR

Observed “Fluences”


LHCb Velo Preliminary



LHCb Velo PreliminaryMinimum

bias data


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Observed “Fluences”


VELO TDR




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



BACK UP


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


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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



Radiation Damage: CCEMeasure CCE(V) Estimate the Effective Depletion Voltage:EDV = V(CCE = 80%)

Similar Zones as previously


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Radiation Damage: IV curves


Annealed at 20 o.Cover shutdown

n-on-n sensor

As well.

Not

e th

e di

ffer

ent

scal

es


Operation Experience

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