1. SSD offline status Offline week CERN, 7 July 2008 Enrico Fragiacomo on behalf of ALICE SSD

2. Run statistics The SSD was one of the detectors that participated in the majority of the global runs (Panos). Calibration runs were extensively tested and used. Many standalone runs to check: 1.The DDL mapping 2.The hardware/software adc map 3.The output of the pedestal run Global runs: 1.In the same partition with the SPD, later with layer 3 and recently with part of layer 4 of the SDD triggered by the SPD FastOR when SPD was able to provide it. 2.In the same partition with the TPC triggered by the combination ACORDE.OR.SCINTILLATOR 3.In the same partition with the rest of the ITS subsystems and TPC triggered by the combination FastOR.OR.ACORDE.OR.SCINTILLATOR See https://twiki.cern.ch/twiki/bin/view/AliceSSD/WebHome

3. Top three debated items Wrong coordinates on layer 6 Overlaps in geometry  Memory consumption of calibration objects

4. Wrong coordinates on lay6  The problem has shown up after reconstructing the cosmic data. No problem with simulations.  Recpoints coordinates on layer 6 were wrong!  It looked like a local x->-x inversion but it was in fact more entangled  Due to a wrong assumption in the segmentation (swapped stereo angles between lay5 and lay6) ( see next slide )

5. Two examples of local vs global coordinate

6. How modules are installed in hw LAY5 MODULE LAY6 MODULE 2.Moreover, readout from positive x! Marco Bregant 1.Stereo angles (unlike in the sw) are the same but lay6 module is up-side-down!

7.  AliRoot simulation modified according to the new local coordinates  Two classes modified: AliITSsimulationSSD, where the actual response simulation is implemented: small changes -> stereo angles no longer swapped between lay5 and lay6 AliITSsegmentationSSD, where the details (e.g. stereo angle, width, pitch,...) about the SSD module are plugged in GetPadTxz (which returns P and N strips for given local coordinates) has changed  Effective since trunk 26/06/08 and ported back to the v4-13-Release  Simulation and reconstruction are again compatible (see next slides)

8. Global x-y projection Reconstructed point Geant hits Scale in cm Simulated cosmic rays (muons) via AliGenCosmicParam class Straight line fit through SPD points via AliEveCosmicRayFitter Only SPD+SSD geometry shown x y Note the many hits in y

9. Global x-z projection x z

10. Global z-y projection z y

11. Problems in the geometry Volumes breaking the simulation! Due to volumes created with TGeoXTRU. Too many vertices gave unpredictable results (negative volumes)!  Overlaps (149) obtained with the “s” checking option. Many were repeated due to the hierarchy. Almost all of them have been fixed (see next slides), 13 remaining (see also Mario’s talk)  Many of the overlaps (39) due to a request of infinite precision  enrico.cattaruzza@ts.infn.it

12. Overlap Fixing Overlap between ITSssdSensor e Ladder Segment Replacement of Physical Mother Volumes with TGeoVolumeAssemblies (TGeoXtru Problem)

13. Overlap Fixing Overlaps between adiacent Ladder Segments: fgkSSDTorelance variable has been introduced Carbon Fiber Overlaps Cooling Tube Overlaps

14. Overlap Fixing Overlaps between adiacent Ladder Segments and EndLadder Segment: fgkSSDTorelance variable has been introduced Cooling Tube Overlaps Carbon Fiber Overlaps

15. Overlap Fixing Overlaps between adiacent ladders Cooling Tube Overlaps

16. What Remains? Overlap between Ladder Cables and Hybrid Flex

17. What Remains? Overlap between LadderSupport And Layer

18. Top three debated Wrong coordinates on layer 6 Overlaps in geometry  Memory consumption of calibration objects

19. Next-todo item  There are 1698 AliITSCalibrationSSD objects (one for each SSD module)  Each AliITSCalibrationSSD has pointers to the calibration objects AliITSNoiseSSD, AliITSGainSSD and AliITSBadChannelsSSD  Each of these objects has 2 TArrays of 768 values (as many as the strips on each side)  Simple implementation of the calibration scheme but memory consumption!  TArray to be replaced by arrays and one object for all the modules (in place of 1698)