1. Stave 4008 Z rubyballs coordinates
Genova stave
Measurement accuracy (check):
Distance between crosses of the same module
Measurement accuracy: X ~4m Z ~10m Z X
Stave Z rubyballs coordinates R1 R2
R2-R1
Survey
Load(db)
Distance between FE pads of the same module
X rubyballs coordinates R1 R2
Survey
Load(db)
6.0060
CMM problem?

2. Genova stave Survey data translated to load reference frame
Coordinates of centers of modules
Angles (rot. around Y) (rad)
Zmeas Ztheor Zmeas-Ztheo Xmeas Angle
Z difference (mm)
X difference (mm)
Load and Survey coordinate systems are defined up to statistical measurement errors (transformation accuracy ~10m now). To improve accuracy the rubyball positions must be measured several times in both systems.

3. Wuppertal stave “stave coordinate system” data
2 measurement datasets exist for one stave:
“survey coordinate system” data with shift in X z=0 : at rubyball centre Z axis joins rubyball centers
“stave coordinate system” data z=0 : edge of stave side A x=0 : centerline of the stave
Measurement accuracy: X ~4m Z ~7m
Stave Z rubyballs coordinates from database (no measurements of rubyballs in this dataset)
Measurement accuracy:
Distance between crosses of the same module Z X R1 R2
R2-R1
Load(db)
X rubyballs coordinates R1 R2
Load(db)
6.0060

4. Wuppertal stave “stave coordinate system” data
Coordinate transformation: -no transformation in X direction -z=0 is placed in the middle between 2 rubyballs (Zrb-Zedge=3.151mm)
Coordinates of centers of modules
Angles (rot. around Y) (rad)
Zmeas Ztheor Zmea-Ztheo Xmeas Angle
X difference (mm)
Z difference (mm)

5. Wuppertal stave “survey coordinate system” data
Measurement accuracy:
Distance between crosses of the same module
Measurement accuracy: X ~62m(???) Z ~7m Z X
“survey coordinate system” data have a bad resolution in X direction???
Z positions are close to the “stave coordinate system” ones
Stave Z rubyballs coordinates
Angles (rot. around Y) (rad) R1 R2
R2-R1
Survey
825.8
Load(db)
???

6. Wuppertal stave “survey coordinate system” data
Crosses positions
Wuppertal “survey coordinate system” data definitely have problems. Are they really the results of survey measurements?

7. Alignment
Sin(200)=0.34 Y
100m X
200
30m
Bowed module X Z
100m bow of the module produces a 30m shift of pixel positions in the most sensitive direction (50m pitch). Bad for alignment with required <10m accuracy !!!

8. Alignment
2D crosses measurements seem not enough for alignment. 3D information is required – bow, deposition angle (deviation from nominal 1.10 ), twist (probably) and glue thickness(probably).
Genova stave(no data on twist and glue thickness)
Having 3D module positions measurements with ~10m accuracy (seems possible) one needs to measure only a global stave position and stave shape distortions to obtain a good initial pixel position accuracy.

9. Some conclusions
Accuracy of Load<->Survey system transformation is ~10m ( precision of survey checks). Difference in rubyballs distance seems due to Genova CMM problems.
Genova and Wuppertal data seem ok (with above accuracy) except for Wuppertal “survey coordinate system” dataset. Problem of measurement procedure or stave?
For alignment of Pixel Barrel modules definitely a 3D module position on stave and module shape information are needed. This information can be easily obtained during survey and stored in database ( but it is very difficult to find it in alignment procedure itself).