1. BARREL ALIGNMENT PLATFORM POSITIONING Goal: Positioning of the platforms at their nominal position on the MDT chambers (No position measurement in a database). Principle: Use a precisely adjusted template squares (precision < 10  m) to hold the platform at their nominal position during the glue curing w.r.t. the endplugs (2 points) and the outer tube surface or on the jig (BOS only) at the level of the first comb. Flat surface on endplugs Half sphere on end plugs 6 adjustable (on CMM) balls for the platform positioning Half sphere on the tube outer surface or on the jig (BOS) C. Guyot (Saclay) Dubna 06/2000

2. Praxial platform positioning tools: Top view Bottom view

3. Positioning in x of the template tools on the tube layer: Tube with calibrated length (+- 50  m) Ruler with straigthness < 100  m Platform screwed on the positioning square

4. The optical control tools Goal: Check the platform orientation (angles) during the tube layer assembly ( Reminder: The platforms are glued on the first layer) Register on a database the values of the angles measured after only one tube layer glued (i.e. right after the platform gluing) and the angles mesured at the end of the multilayer assembly. For the module 0 assembly, register the values after each tube layer assembly (Not possible on BIL due to the stiff back geometry). Principle: 4 tools (towers) carrying 2 cameras and 2 LEDs looking at each neighbour 2 leds CMOS image sensor lens f~ 80 mm (except for BIS transverse: 60 mm) Plateform angle ~ (X/Y(pixel) - X 0 /Y 0 ) * pixel_size / f Average led spot coordinate From the calibration on the granite table

5. Measured platform angles y 12 x 12 y 14 x 14 y 43 x 43 y 41 x 41 y 21 x 21 y 23 x 23 y 34 x 34 y 32 x 32 Tower 1 Tower 3 Tower 2 Tower 4 Z ch X ch Image sensor axis (pixel direction) Signal side HV side Rotation of platform 1 around X ch axis:  X = (X 14 -X 0 14 )/f Rotation of platform 1 around Y ch axis:  Y = - (Y 12 -Y 0 12 )/f = - (Y 14 -Y 0 14 )/f Rotation of platform 1 around Z ch axis:  Z = - (X 12 -X 0 12 )/f Rotation of platform 2 around X ch axis:  X = (X 23 -X 0 23 )/f Rotation of platform 2 around Y ch axis:  Y = (Y 21 -Y 0 21 )/f = (Y 23 -Y 0 23 )/f Rotation of platform 2 around Z ch axis:  Z = (X 21 -X 0 21 )/f Y ch

6. Control tool calibration Longitudinal lines : Distance adjusted to +- 2mm Precision wedges x z Calibrates rotations around z and y axis

7. Control tool calibration Transverse lines : Distance adjusted to +- 2mm Precision wedges z x Calibrates rotations around x axis only Square ( 90 degrees +- 1 mrad)

8. Saclay will supply each MDT lab (barrel) with a set of 4 template squares and a set of 4 control tools (with cables to the RASMUX). Each lab will have to provide: - A length calibrated tube - A straight ruler of length ~ chamber width - square width The absolute calibration of the control tools will have to done on a granite table prior to the module 0 assembly. This calibration requires a precision side on the granite table or (better) a precision wedge. If the assembly table on side does not allow such a calibration (no room or no precise side face), this calibration will be done at Saclay (hoping that the image sensor does not move during the transport).