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 4008 Z rubyballs coordinates R1 R2 R2-R1 Survey -412.9781 412.9962 825.974 Load(db) -413.0563 412.9367 825.993 Distance between FE pads of the same module X rubyballs coordinates R1 R2 Survey -0.0082 -0.0051 Load(db) -5.9749 6.0060 CMM problem?

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 -370.3440 -370.3100 -0.0340 0.1398 0.000123 -308.5780 -308.5920 0.0140 0.2038 -0.001561 -246.8510 -246.8730 0.0220 0.1600 0.000756 -185.1250 -185.1550 0.0300 0.1303 -0.002653 -123.3780 -123.4370 0.0590 0.0874 0.000613 -61.6630 -61.7183 0.0553 0.1046 -0.000088 -0.0514 0.0000 -0.0514 0.0587 0.000058 61.6831 61.7183 -0.0352 0.0475 0.000184 123.4430 123.4370 0.0060 0.0340 -0.000090 185.1880 185.1550 0.0330 0.1081 -0.000062 246.8470 246.8730 -0.0260 0.1081 -0.000300 308.5730 308.5920 -0.0190 0.1089 -0.000595 370.2580 370.3100 -0.0520 0.0851 0.000080 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.

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 4003 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) -412.9170 412.9194 825.836 X rubyballs coordinates R1 R2 Load(db) -5.9656 6.0060

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 -369.9630 -370.3100 0.3470 0.1552 -0.001150 -308.2450 -308.5920 0.3470 0.1050 0.000214 -246.5360 -246.8730 0.3370 0.0648 0.000250 -184.7980 -185.1550 0.3570 0.0333 -0.000058 -123.0930 -123.4370 0.3440 0.0298 0.000986 -61.3880 -61.7183 0.3303 0.0085 0.000843 -0.0340 0.0000 -0.0340 0.0045 0.000307 61.4070 61.7183 -0.3113 -0.1093 0.000468 123.1160 123.4370 -0.3210 -0.0790 0.000590 184.8360 185.1550 -0.3190 -0.0822 0.000538 246.5420 246.8730 -0.3310 -0.0922 0.000759 0.0000 308.5920 0.0000 0.0000 0.000000 369.9780 370.3100 -0.3320 -0.0220 0.000747 X difference (mm) Z difference (mm)

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 4003 Z rubyballs coordinates Angles (rot. around Y) (rad) R1 R2 R2-R1 Survey 825.8 Load(db) -412.9170 412.9194 825.836 ???

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

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 !!!

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.

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).