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 curingw.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 thetube outer surface oron the jig (BOS)

C. Guyot (Saclay) Dubna 06/2000

Praxial platform positioning tools:Top view

Bottom view

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

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) - X0/Y0) * pixel_size / f

Average led spot coordinate From the calibration on the granite table

Measured platform angles

y12

x12

y14

x14

y43

x43

y41

x41

y21

x21

y23x23

y34

x34

y32

x32

Tower 1

Tower 3

Tower 2

Tower 4

Zch

Xch

Image sensor axis (pixel direction)

Signal sideHV side

Rotation of platform 1 around Xch axis: X = (X14-X014)/f

Rotation of platform 1 around Ych axis: Y = - (Y12-Y012)/f = - (Y14-Y0

14)/f Rotation of platform 1 around Zch axis: Z = - (X12-X0

12)/f

Rotation of platform 2 around Xch axis: X = (X23-X023)/f

Rotation of platform 2 around Ych axis: Y = (Y21-Y021)/f = (Y23-Y0

23)/f Rotation of platform 2 around Zch axis: Z = (X21-X0

21)/f

Ych

Control tool calibration

Longitudinal lines :

Distance adjusted to +- 2mm

Precision wedges

x

zCalibrates rotations around z and y axis

Control tool calibration

Transverse lines :

Distance adjusted to +- 2mm

Precision wedges

z

x

Calibrates rotations around x axis only

Square ( 90 degrees +- 1 mrad)

•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 doneon 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).