1. Status Brussels GANTRY Ê New measurements of pin positions 4 using short pins rather than long ones 4 improved the precision Ë Cross-check of precision 4 compare measurements in Brussels and CERN (6 modules) 4 good agreement was found Ì Soft-ware for R3 modules is ready Í We lack several module components… O.Bouhali, J.D’Hondt, C.Vandervelde, L.Van Lancker, J.Wickens Gantry meeting CMS – March 2004

2. Reminder : Old procedure to determine the pin positions ++ Pin positions are determined relative to the fiducial markers on the plate Ê Measure both fiducial markers on the plate Ë Take ~8 points around the circle of each pin hole Ì Fit a circle through them Í Repeat the above at least 10 times Î Look if the fits are stable (small residuals)

3. Fits to determine the pin positions : residuals

4. Differences between a module measured in the 3 positions diff ~ 1diff ~ -5diff ~ -3 Difference between plate level and top of the pin level scaled to 1mm thickness real pin position shifted (in  m) in direction indicated 2.5 2.0 -0.3 3.7 0.9 1.6 -3.9 -7.0 2.8 4.6 3.6 5.5 Brussels-Aachen (3 dummy modules assembled in Brussels) Rotation ≡ 0 Translation ≡ 0 Rotation ~ -20 Translation ~ -14 Rotation ~ -10 Translation ~ -6

5. New procedure with short pins Frame Pin Plate Ê It was observed that the pins are not vertical (cfr. last meeting) Ë Now we have used short pins (10mm) Ì We determine the centre of the pin at frame level ï the edge of the pin is clearly visible ï no influence of being non-vertical Í Repeat the fit of the circle at least 10 times Î Residuals are smaller with the new procedure Frame Pin Plate NewOld use large pins during assembly

6. Residuals with short pins

7. Comparison modules measured in 3 different positions on the GANTRY ++ A dummy module has been measured in the 3 GANTRY positions  Y( [measured – nominal] Pos.X ) Pos.1Pos.2Pos.3 -6-5 2-2 44 32 -47 38 517 26 -31 11 913 -2 All can be explained by a rotation and a translation of the module between GANTRY positions  measured shape of module is the same smaller residuals than with pin positions determined with old procedure X Y T(y) = -5.9  m T(x) = 0.6  m Rot. = -0.3 mdeg Relative to position one → T(y) = -6.4  m T(x) = 2.3  m Rot. = -2.1 mdeg

8. Comparison between CERN and Gantry measured modules In total 6 modules were measured at CERN (Metrology Service) and re-measured on the Brussels Gantry ( with short pins ) Ê Both use pattern recognition Ë Different reference system (pins or frame holes) Ì The elongated hole in the frame is rather poor measured at CERN ï some rotation is possible between both ï an optimal rotation can be fitted Í Compare the residual translations Position 1Position 2Position 3 3 Real modules T(y)X -15.3  m-22.1  m T(x)X 2.5  m3.1  m Applied rotationtoo large ( > 20 mdeg)3.9 mdeg-1.4 mdeg 3 Dummy modules T(y) -2.0  m-13.7  m-5.5  m T(x) -3.2  m2.1  m-8.6  m Applied rotation-1.8 mdeg-2.7 mdeg-2.2 mdeg X Y

9. Interpretation of the comparison Ê Using the small pins for module assembly is not precise enough ï repeatability of the measurements was poor ï use the large pins but measure the pin positions with the small ones  now we have a very good repeatability (  ~ 5  m) Ë Taking into account the precision of the CERN measurements of both holes in the carbon frames, we observe a good agreement Ì We could implement ‘off-line’ corrections for the residual difference ï corrections are not precisely known… (small statistics) Reminder !! Ê Re-write the precision cross-checks criterion for the module assembly 4 the angular criteria are too tight and not well designed 4 they are not robust for outliers due to bad measurements of one FM 4 a large fraction of our modules is therefore not valied è implement similar criteria as used by the Lyon and US centers

10. Position of the stiffener Ê The grove in the R6 plates for the stiffener between both sensors is wrongly positioned ï shifted hence not symmetric (~ 1mm) ï glue could come occasionally between both sensors ï will be adapted (thanks to Oliver Pooth and collaborators) Ë One of our R6 plates (R6.2) has to be adapted GLUE S2 S1

11. First R3 modules are assembled Ê The R3 plates from Lyon ï have 4 module positions (we have adapted the software) ï have pin holes on the frame level and with sharper edges (better precision) Ë First module was assembled and re-measured in all four positions  very good agreement (maximum difference of the FMs equals 14  m) Ì Need more components for further checks…

12. Summary R6 modules : R6 modules : Ê Precision of modules is very good according to Gantry Ë Precision of modules is good according to CERN Ì Precision of modules is good when placed in a different position on the Gantry plates on the Gantry plates R3 modules : R3 modules : Ê Precision of modules is very good according to Gantry Ë Precision of modules to be checked with an independent machine Ì Precision of modules is very good when placed in a different position on the Gantry plates position on the Gantry plates