The Performance of the Outer Tracker Detector at LHCb

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The Performance of the Outer Tracker Detector at LHCb

Barbara Storaci on behalf of the OT group

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The mission

Precise Alignment

High tracking performace

Excellent mass resolution

High Performanceat the tracking detector

(Raphael Marki’s talk)

(Andreas Jaeger’s talk)

3-7 Octorber 2011 Barbara Storaci 13th ICATPP Conference , Como Villa Olmo

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LHCb

Outer Tracker :This Talk

SiTracker: (Mark Tobin’s talk)

VELO: (Alexander Leflat’s talk)



OT: the detectoro Drift Chambers detector based on straw

tube technology:o Anode wire at 1550 Vo Cathode straw connected to ground

o Gas Mixture Ar/CO2/O2 (70/28.5/1.5)

Straw tubes packed in double-layered modulesType F

2400 mm

S1

3070 mm

S3S2

2900 mm

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• 3 stations for each side• Each station 4 layers (central layers tilted by ± 5°)

OT: the readout

Readout Electronics hosted in aluminum frames installed at both ends of the detector (FE-box).

o HV distributiono Preamplification and

discrimination (ASDBLR)

o Time to Digital convertion (OTIS) (TDC has to operate synchronous with 40MHz bunch crossing clock)

o Data serialization for optical transmission (GOL)

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HV

TFC & ECSLV

Data Fiber

ASDBLR

OTIS

GOL/AUX


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Quality assurance

Module Classification (1st choice, 2nd choice, etc.) based on: Dead channels: in general disconnected shorts (0.6‰) “Noisy” Channels: high dark current (0.7‰), often “cured”

after HV training)

Quality Assurance during production:o Wire tensiono Dark currento Wire pitch

Quality Assurance after production:o Gas Tightness, Dark currento detector response to 90Sr β-

sourceFull scan (every cm2) of all

OT modulesExcellent uniformity of the response for all modules


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Nasty Surprise: AgeingPeculiar characteristics:

• Gas flow dependence: • most of the damage upstream the source • half-moon shape

• Intensity dependence:• Maximum damage NOT at the highest

intensity

Gas flow

Ratio Plot: Iafter/Ibefore

Irradiated with a 2 mCi 90Sr source


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Nasty Surprise: AgeingPeculiar characteristics:

• Gas flow dependence: • most of the damage upstream the source, • half-moon shape

• Intensity dependence:• Maximum damage places NOT at the highest

intensity

Gas flow

Ratio Plot: Iafter/Ibefore

Irradiated with a 2 mCi 90Sr source

CULPRITC16H22O4 C16H20

dibutyl phthalatediisopropyl-naphthalene

AY103 AY103-1

Supplier produced the glue with a different plastifier:

same mechanical properties… but AY103-1 causes ageing!!!


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Ageing Monitoring SystemLaboratory System:

•Irradiation of a 6x6 cm2 area with 2mCi 90Sr source•Current read every centimeter•Scanning source: 20mCi 90Sr source

2 90Sr sources

Current-meter connectors

Safety garage

Scanning Frame

System in Situ:

•Irradiation with 90Sr sources (74MBq)•Current read every centimeter•Scanning source: 2 90Sr sources (74MBq)• Can be used only during technical stop

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Living with ageing

• Outgassing:– Flushing – Heating

• Addition of Oxygen to the gas mixture:

– Production of ozone • HV training:

– Induce high current in the module• Typical currents:

– 10 μA per straw at 1900V Wire with carbon deposit


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Recovery and Prevention: HV training

Before training(previous damages clearly visible)

After 15h training at 1900V in situ(only wires 33-64)

The HV training procedure:• Reset of the gain value• Prevent from further ageing (up to a certain dose)From optical and SEM inspection:• Deposit removed• Wire undamaged

recovery

immunity


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Threshold Scan with beam• Error function (assuming

gaussian noise) to describe hit-efficiency vs threshold– Point at 50% of efficiency: half-

efficiency point (HEP)• Variation of the HEP sign of gain

loss (ageing)PROCEDURE:

1 scan every 200 pb-1

Ten threshold for 12 layers (full detector) 150000 events per step

No gain loss beyond 10% observed yet

Readout Monitoring

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Online-offline calibration software

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o Noise Threshold Scan:o Identifying channels that have an “abnormal”

level of noise



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level of noise

Noise level for the full detector <8*10-4 at working threshold



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level of noiseo Threshold Scan:

o Identifying dead channels, gain deteriorating effects, etc.




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o Noise Threshold Scan:o Identifying channels that have an “abnormal” level

of noiseo Threshold Scan:


o Delay Scan:o Identifying defects in the timing of the OT channels

(offsets,non-linearities etc.)




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(offsets,non-linearities etc.)

1 TDC = 0.4ns; 1DAC = 0.1ns




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(offsets,non-linearities etc.)99.7 % of the channels working in June 2011

1 TDC = 0.4ns; 1DAC = 0.1ns



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RT-relation

Drift Time r 2.45 mm

• Majority of hits within 50ns readout window• RT-relation close to expectation from testbeam• Current single hit resolution (p>10GeV) of 220μm

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Drift Cell Efficiencyr

2.45 mm

Procedure:• Considered high quality track:

• χ2 / dof < 2• certain number of hits

• Looking for hits along the track


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Drift Cell Efficiencyr

2.45 mm

Characteristics:• Cell profile is symmetric• Efficiency inside the cell independent on the number of hits

99.2 - 99.5% average efficiency plateau

Procedure:• Considered high quality track:

• χ2 / dof < 2• certain number of hits

• Looking for hits along the track


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Invariant-Mass Resolution

Momentum resolution p/p~0.35-0.5% very good mass resolution world best mass measurements

[LHCb-CONF-2011-027]

Channel LHCb mass [MeV/c2] PDG [MeV/c2]5279.17 ± 0.29

5279.50 ± 0.30

5279.50 ± 0.30

5366.30 ± 0.60

5620.2 ± 1.6

6277 ± 6

Dimuon spectrum(3000-3800 MeV)

Linear interpolation of invariant mass resolution

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Upgrade Plans• run ~5 years (2011-2012 and 2014-2016), collect 5 to 6 fb-1

• upgrade ready for 2017-2018 shutdown, aim at >50 fb-1

In 2010 run LHCb worked at 7 times its design conditions


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Upgrade PlansIn 2010 run LHCb worked at 7 times its

design conditions

Requirements: 1. Transmit collision data @ 40 MHz :

• upgrade all FE to 40 MHz (new OTIS and GOL/AUX)• Re-use ASDBLR, HV board, FE mechanics (73% OT costs)

• run ~5 years (2011-2012 and 2014-2016), collect 5 to 6 fb-1



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Upgrade PlansIn 2010 run LHCb worked at 7 times its

design conditions

Requirements: 1. Transmit collision data @ 40 MHz :

• upgrade all FE to 40 MHz (new OTIS and GOL/AUX)• Re-use ASDBLR, HV board, FE mechanics (73% OT costs)

2. Higher Luminosity = new IT/OT boundary•

• keep straw-tube technology or• possible partial replacement by 1mm SciFi in central region

• Si -strips to be replaced• keep Si technology or• move to 250 m SciFi

• run ~5 years (2011-2012 and 2014-2016), collect 5 to 6 fb-1


Conclusions• OT: drift-chambers detector based on straw tube

technology• Detector performance according to expectations• Continuous monitoring and replacement of FE Electronics

guarantees efficient data taking• Excellent mass resolution• Ageing problems traced back to the plastifier in the sealing

glue– Addition of oxygen to the gas mixture to reduce gain loss– HV training technique to remove the deposit on the wire

• A lot of work ongoing to be ready for an upgrade27


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The Performance of the Outer Tracker Detector at LHCb

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