Status Brussels GANTRY

New measurements of pin positions New measurements of pin positions using short pins rather than long onesusing short pins rather than long ones improved the precisionimproved the precision

Cross-check of precisionCross-check of precision compare measurements in Brussels and CERN (6 modules)compare measurements in Brussels and CERN (6 modules) good agreement was foundgood agreement was found

Soft-ware for R3 modules is readySoft-ware for R3 modules is ready We lack several module components…We lack several module components…

O.Bouhali, J.D’Hondt, C.Vandervelde, L.Van Lancker, J.WickensGantry meeting CMS – March 2004

Reminder : Old procedure to determine the pin positions

+ +

Pin positions are determined relative to the fiducial markers on the plate

Measure both fiducial markers on the plate Take ~8 points around the circle of each pin hole Fit a circle through them Repeat the above at least 10 times Look if the fits are stable (small residuals)

Fits to determine the pin positions : residuals

Differences between a module measured in the 3 positions

diff ~ 1 diff ~ -5 diff ~ -3

Difference between plate level and top of the pin level scaled to 1mm thicknessreal 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 ≡ 0Translation ≡ 0

Rotation ~ -20Translation ~ -14

Rotation ~ -10Translation ~ -6

New procedure with short pins

FramePin

Plate

It was observed that the pins are not vertical (cfr. last meeting) Now we have used short pins (10mm) We determine the centre of the pin at frame level

the edge of the pin is clearly visible no influence of being non-vertical

Repeat the fit of the circle at least 10 times Residuals are smaller with the new procedure

FramePin

Plate New Old

use large pinsduring assembly

Residuals with short pins

Comparison modules measured in 3 different positions on the GANTRY

+ +

A dummy module has been measured in the 3 GANTRY positionsY( [measured – nominal]Pos.X)

Pos.1 Pos.2 Pos.3

-6 -5

2 -2

4 4

3 2

-4 7

3 8

5 17

2 6

-3 1

1 1

9 13

-2 -1

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 mT(x) = 0.6 mRot. = -0.3 mdeg

Relative to position one →T(y) = -6.4 mT(x) = 2.3 mRot. = -2.1 mdeg

Comparison between CERN and Gantry measured modulesIn total 6 modules were measured at CERN (Metrology Service)and re-measured on the Brussels Gantry (with short pins)

Both use pattern recognition Different reference system (pins or frame holes) The elongated hole in the frame is rather poor measured at CERN

some rotation is possible between both an optimal rotation can be fitted

Compare the residual translations

Position 1 Position 2 Position 3

3 Real modules

T(y) X -15.3 m -22.1 m

T(x) X 2.5 m 3.1 m

Applied rotation too 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 m 2.1 m -8.6 m

Applied rotation -1.8 mdeg -2.7 mdeg -2.2 mdeg

X

Y

Interpretation of the comparison

Using the small pins for module assembly is not precise enough repeatability of the measurements was poor use the large pins but measure the pin positions with the small ones now we have a very good repeatability ( ~ 5 m)

Taking into account the precision of the CERN measurements of both holes in the carbon frames, we observe a good agreement

We could implement ‘off-line’ corrections for the residual difference corrections are not precisely known… (small statistics)

Reminder !!

Re-write the precision cross-checks criterion for the module assembly the angular criteria are too tight and not well designed they are not robust for outliers due to bad measurements of one FM a large fraction of our modules is therefore not valied implement similar criteria as used by the Lyon and US centers

Position of the stiffener

The grove in the R6 plates for the stiffener between both sensors is wrongly positioned

shifted hence not symmetric (~ 1mm) glue could come occasionally between both sensors

will be adapted (thanks to Oliver Pooth and collaborators)

One of our R6 plates (R6.2) has to be adapted

GLUE

GLUE

S2

S1

First R3 modules are assembled

The R3 plates from Lyon have 4 module positions (we have adapted the software) have pin holes on the frame level and with sharper edges (better precision)

First module was assembled and re-measured in all four positions very good agreement (maximum difference of the FMs equals 14 m)

Need more components for further checks…

Summary

R6 modules :R6 modules : Precision of modules is Precision of modules is very goodvery good according to Gantry according to Gantry Precision of modules is Precision of modules is goodgood according to CERN according to CERN Precision of modules is Precision of modules is goodgood when placed in a different position when placed in a different position on the Gantry plateson the Gantry plates

R3 modules :R3 modules : Precision of modules is Precision of modules is very goodvery good according to Gantry according to Gantry Precision of modules to be checked with an independent Precision of modules to be checked with an independent machinemachine Precision of modules is Precision of modules is very goodvery good when placed in a different when placed in a different position on the Gantry platesposition on the Gantry plates