Operation Experience

LHCbVErtexLOcator Operation Experience KazuAkiba On behalf of the Velo Group

beauty at the LHC K+ • LHCbb 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 rates • LHCb’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 B0 PV Beam 1 K- π+ Beam 2 IP B0 D- LHCb σ(pp → Hb X) = ( 75 ± 5 ± 13 ) µb Phys. Lett. B 694, 209-216 (2010) Kazu Akiba

The LHCb Experiment RICH2 TT Si Outer Tracker straw Tubes ECAL HCAL Magnet Zoom in the interaction region VELO&PU Si Closed For physics Muon MWPCGEM Inner Tracker Si Open during injection RICH1 Large HadronColliderbeauty Experiment for CP violation and Rare B Decays.

VELO • 2 Retractable halves • 21 Modules /half • 1R & 1φ sensors/module • 2048 strips/sensor  172k channels • 300 µm n-on-n sensors! • 1 n-on-p • Active @ 8 mm. • Operated in a secondary vacuum,sensors and front-end Vacuum ! • Designed for: • Minimal material budget. • Excellent primary and secondary vertexing… and tracking. • Outstanding impact parameter resolution. Contains 1 Velo half Rf Foil 300 mm Kazu Akiba

VELO • 2 Retractable halves • 21 Modules /half • 1R & 1φ sensors/module • 2048 strips/sensor  172k channels • 300 µm n-on-n sensors! • 1 n-on-p • Active @ 8 mm. • Operated in a secondary vacuum,sensors and front-end mbar Beam vacuum Velo mbar Vacuum ! • Designed for: • Minimal material budget. • Excelent Primary and Secondary Vertexing… and tracking. • Outstanding Impact Parameter resolution. • Designed for: • Minimal material budget. • Excellent primary and secondary vertexing… and tracking. • Outstanding impact parameter resolution. Contains 1 Velo half Rf Foil Kazu Akiba

Sensors/Modules Sensor • Analogue readout from ASICS (Beetle) • on hybrids • Repeater cards outside tank – inaccessible when LHC is ON • Digitization 60m away – safe zone • FPGA processing • 106 parameters • Integer pedestals and CM subtractions • Clustering + Zero suppression Front-end: 40 MHz clock, 1 MHz readout Hybrid Active Cooling Biphase CO2 Carbon fibre support Kapton cables R-side circuit R-sensor Carbonfibre -sidecircuit x42 Data Config -sensor Kazu Akiba

Sensors Modules silicon [oC] Sensor • Analogue from ASICS on hybrids • Repeater cards outside tank – inaccessible when LHC is ON • Digitization 60m away – safe zone • FPGA processing • 106 parameters • Integer pedestals and CM subtractions • Clustering + Zero suppression -5oC Front-end: 40 MHz clock, 1 MHz readout Silicon temperature as function of cooling setpoint 10 Hybrid VELO fully powered -15oC Active Cooling Biphase CO2 5 0 Carbon fibre support -25oC Kapton cables -5 -30oC R-side circuit R-sensor -30oC Carbonfibre -10 Cooling performance very stable so far -sidecircuit -35oC x42 Data Stable behaviour. Work point: -30 oC nice low silicon work temperature of -10oC Config -sensor Kazu Akiba

Time Alignment • Fine tune timing is an automated procedure • Overall precision of ± 1 ns • Aim for • Maximum signal/noise • Minimal neighbouring bunch cross talk. • Sensors individually tuned to account for differences in • Time of flight • Cable length

Running 2010-11 • Higher Occupancy, collisions/crossing, then designed for. • Nominal Instantaneous luminosity achieved in May/2011! Kazu Akiba

Running 2010-11 • Higher Occupancy, collisions/crossing, then designed for. • Nominal Instantaneous luminosity achieved in May/2011! Vis Collision Pile-UP ATLAS/CMS Upgrade LumiLeveling Displacing the beams LHCb Now Nominal KazuAkiba

Running 2010-11 • Higher 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. HV and LV stable through 2010-11 KazuAkiba

Running 2010-11 • Higher 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. HV and LV stable through 2010-11 Problem showed to be highly correlated to the trigger rate… Kazu Akiba

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 list • Calculation of the next position • Human re-confirmation at 1 mm. • movement in y if request > 50 mm Kazu Akiba

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 list • Calculation of the next position • Human re-confirmation at 1 mm. • movement in y if request > 50 mm Done about 100 times this year! Kazu Akiba

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 list • Calculation of the next position • Human re-confirmation at 1 mm. • movement in y if request > 50 mm Fraction of the inefficiency due to the Velo closing procedure Kazu Akiba

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 list • Calculation of the next position • Human re-confirmation at 1 mm. • movement in y if request > 50 mm Partly due to a bug in the derandomizer of Beetle ASIC Which increases with the rate. Kazu Akiba

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. Kazu Akiba

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. Kazu Akiba

Operational Issue: Performance • R -sensors: • Noise increases with strip length (radius). • 4 sectors of 512 strips cross talk from Beetle header • All S/N > 17... Still. • But 1/pb per hour... 3 types of strips in f sensors • outer – WITHOUT • overlaid routing lines • inner – routed over • outer strips • outer – WITH • overlaid routing lines KazuAkiba

Operational Hazards: Radiation Damage Disclaimer: Depletion voltage around 40-80V initially. Depletion voltage decreases with fluence till type inversion (n-on-n) • Current vs Voltage (IV) • Taken weekly • Current increases with bulk damage, linearly related to fluence • Does not study depletion voltage • Noise vs applied bias Voltage • Taken monthly • Sensors decrease capacitance and hence noise when depleted, so sensitive to depletion voltage at least during early running • 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

Radiation Damage: IV curves n-on-n sensor n-on-p sensor (similar z position) Annealed at 20 o.C over shutdown As well. Kazu Akiba

Radiation Damage: Noise Vs Voltage Measure the change in the Effective Minimal Noise Voltage EMNV, when 1/noise passes 80% of final noise . Innermost strips on R sensor most irradiation Ratio < 1, i.e. , smaller EMNV Outermost strips on R sensor less irradiation Ratio ~ 1, i.e. no change in EMNV Kazu Akiba

Observed “Fluences” LHCbVelo Preliminary Minimum bias data LHCbVelo Preliminary LHCbVelo Preliminary LHCbVelo Preliminary VELO TDR KazuAkiba

Summary • Smooth 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)! Kazu Akiba

Kazu Akiba

BACK UP Kazu Akiba

Common Mode Kazu Akiba

Radiation Damage: CCE Charge Collection Efficiency – The Method: • Blue – tracking sensors at full bias voltage • Red – 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

Radiation Damage: CCE Measure CCE(V)  Estimate the Effective Depletion Voltage: EDV = V(CCE = 80%) Similar Zones as previously Kazu Akiba

Radiation Damage: IV curves n-on-n sensor Annealed at 20 o.C over shutdown As well. Note the different scales KazuAkiba

Operation Experience