Upload
barry-goodwin
View
219
Download
0
Tags:
Embed Size (px)
Citation preview
SSD offline status
Offline weekCERN, 7 July 2008
Enrico Fragiacomoon behalf of ALICE SSD
Run statisticsThe 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 mapping2. The hardware/software adc map3. 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
Top three debated items
Wrong coordinates on layer 6Overlaps in geometryMemory consumption of calibration objects
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)
How modules are installed in hw
LA
Y5 M
OD
UL
E
LA
Y6 M
OD
UL
E2. Moreover, readout from positive x!
Marco Bregant
1. Stereo angles (unlike in the sw) are the same but lay6 module is up-side-down!
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)
Global x-y projection
Reconstructed pointGeant 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
Global x-z projection
x
z
Global z-y projection
z
y
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
Overlap Fixing Overlap between ITSssdSensor e Ladder
Segment
Replacement of Physical Mother Volumes withTGeoVolumeAssemblies (TGeoXtru Problem)
Overlap Fixing Overlaps between adiacent Ladder Segments:
fgkSSDTorelance variable has been introduced
Carbon Fiber Overlaps
Cooling Tube Overlaps
Overlap Fixing Overlaps between adiacent Ladder Segments and
EndLadder Segment: fgkSSDTorelance variable has been introduced
Cooling Tube Overlaps
Carbon Fiber Overlaps
Overlap Fixing Overlaps between adiacent ladders
Cooling Tube Overlaps
What Remains?
Overlap between Ladder Cables and Hybrid Flex
What Remains?
Overlap between LadderSupportAnd Layer
Top three debated
Wrong coordinates on layer 6 Overlaps in geometry Memory consumption of calibration
objects
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)