ITS Calibration Database Requirements

UpdatedBy

Bjørn S. NilsenOn behalf of the ALICE ITS Sub-detector Group

Feb. 17 2005 ALICE February Offline Week, Calibration Database Workshop

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Outline

• Alignment• Calibration Data SPD• Calibration Data SDD• Calibration Data SSD• Assess patterns and usage• Conclusions

Feb. 17 2005 ALICE February Offline Week, Calibration Database Workshop

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AlignmentAliITSgeom & AliITSgeomMatrix2198 Detectors, 6 degrees of Freedom

• Must be fast and compact• Must allow for multiple instantiations and

easily switch between different instantiations easily and quickly

• Needs to handle different coordinate system• Needs to be useful in simulation,

reconstruction, tracking, and alignment

Feb. 17 2005 ALICE February Offline Week, Calibration Database Workshop

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AlignmentAliITSgeom & AliITSgeomMatrix

• AliITSgeomMatrix.– Sizeof(AliITSgoemMatrix) = 164Bytes (in

memory), 126Bytes on disk uncompressed.– Minimum required 64Bytes (require much

computation so slow).• AliITSgeom.

– Sizeof(AliITSgeom) = 60Bytes + allocated memory (448 776Bytes) = 448 836Bytes total.

– Minimum required 140 736Bytes.

Feb. 17 2005 ALICE February Offline Week, Calibration Database Workshop

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Response &Calibration Data

• Can, and should, be different between simulation and reconstruction.

• Will depend on run/event number in some almost unpredictable way.

• Will need to be changed with time as newer and better methods are developed.

• Will need to be able to retrieve and use older values at any point in the future.

Feb. 17 2005 ALICE February Offline Week, Calibration Database Workshop

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SPD Data240 Detectors, 40960 pixels/detector, <Occupancy> 4%

Simulation• Thresholds/cell (16bits)• Noise levels/cell (16 bits)• List of Dead Pixels and Chips

– Bit pattern 5120Bytes/detector– At 2% dead pixels +16σ

2600Bytes/detectorA dead Chip 20%

167 976Bytes/det 40 314 240Bytes total

Reconstruction• List of Dead Pixels and

Chips– Bit pattern

5120Bytes/detector– At 2% dead pixels +16σ

2600Bytes/detectorA dead Chip 20%

• List of Extra-noisy pixels?

4 136Bytes/det 992 640Bytes total

Feb. 17 2005 ALICE February Offline Week, Calibration Database Workshop

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SPD Data

• Dead pixels will not come back to life.• Small chance that new dead pixels will be

added.• Noisy pixels are very unlikely to improve.• New noisy pixels very rare.Data update will be uncommon.

Feb. 17 2005 ALICE February Offline Week, Calibration Database Workshop

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SDD Data2X256 anodes, ~200 time-bins,

6X33 injectors, 260 detectorsFor Both Simulation and Reconstruction

• For each Anode 3 Bytes.– Thresholds (Not needed for Reconstruction).

• Low (4 bits).• High (4 bits).

– Baseline (6 bits).– Gain (6 bits).– Noise ( ).

• Amplitude (4 bits). • Pedestals, 2 per detector (8 bits total)• Thermal map (sets drift velocity).

– 198 measurements (24 bits/measur. = 8 amplitude + 16 time) 594 Bytes.• Dopant concentration map (shifts in both time and anode mean values).

– 102 400 measurements (2*10 bits/cell) 256 000Bytes.– Maximum deviation of 500μm.

258 132 Bytes/detector 67 114 320 Bytes for all SDD

such a detailed measure of the noise may only bepossible for zero non-suppressed data/events

Feb. 17 2005 ALICE February Offline Week, Calibration Database Workshop

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SDD Data• Thresholds, baseline, gains.

– Set at start of run.• Noise.

– Tests show to be stable, but may change.• Temperature map.

– Transient at startup (half life ?).– Then, should remain stable.

• Dopant map.– Fixed and measured in lab.– In construction data base.

Generally Stable or minimal changes over time.

Feb. 17 2005 ALICE February Offline Week, Calibration Database Workshop

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SSD Data2X768 Anodes/cathodes, 1698 detectors

Simulation and Reconstruction• For each Anode and Cathode 4 Bytes.

– Pedestal (8 bits).– Threshold (8 bits).– Noise & always-off/on flag (8 bits).– Gain (8 bits).

6 144 Bytes/det 10 432 512 Bytes total.

Feb. 17 2005 ALICE February Offline Week, Calibration Database Workshop

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SSD Data

• Pedestal, Threshold, & Gain.– Set at beginning of run.– Will not change during run.

• Noise.– Measured in special runs.– Should not change much with time.

Generally stable or minimal changes over time.

Total ITS reconstruction data volume78 988 308Bytes

Feb. 17 2005 ALICE February Offline Week, Calibration Database Workshop

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Access PattersMy point of view

Feb. 17 2005 ALICE February Offline Week, Calibration Database Workshop

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Access PattersContinued

• Data Base.– Each Value “separate”, individually queriable.

• Value may vary by time/event/run• Value may even be represented by some function of some time/event/run

range– Full history of each value.

• When last changed• Who made change

• Calibration File.– Specific values needed to analyze specific events/runs at a give sight

and/or cpu.– Minimal size and fast access required

• Ali???Calibration (e.g. AliITSCalibrationSDD).– Class with specific data for a specific event as used inside of AliRoot.– Must be quickly updated from Calibration file for next event (possibly

next detectors)– Must be in a form efficiently usable by reconstruction.

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Conclusion• Alignment takes 448 836 Bytes• Calibration takes 78 539 472 Bytes

– Calibration data is made up of fixed, slowly changing, and rarely but abruptly changing values.

– Generally the changes in the calibration data set is expected to be rather stable.

– This is a realistic yet minimum data size (more likely to rise then drop).• The “master” calibration data is best kept in a data-base.• Usage requires much faster access, and therefore a local

copy in a form similar to that used in AliRoot.

}78 988 308Bytes