Platform positioning duringMDT construction

Tool for the platformpositioning

Ph.

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J.-C

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PRAXIAL ALIGNMENT SYSTEM (barrel)po

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calibration of PRAXIAL part

ATLAS Align. PDRPh. Schune (Saclay)

QA/QC: in production site and at the CERN X-ray tomograph

calibration of AXIAL part

conclusionPRAXIAL activeoptical elements

1

Principle:• The PRAXIAL system is used to unite a layer of chambers (about 6 MDT) to form a single “rigid” layer. It is composed by two systems. The precision on the positioning of both systems are:

±25 m (y,z), ±200 m (x), < 80 rad (x,z), ±200 rad (y).

Goal (for the positioning):• Positioning of the (four) platforms at their nominal position on the MDT

chambers (no position measurement in a database). The calibration of the active optical elements is done elsewhere

Method: • Use four precisely adjusted template squares (precision < 20 m) to hold the platform at their nominal position, during the glue curing, w.r.t. the end plugs (2 pts) and the outer tube surface (or on the jig, BOS only)

at the level of the first comb.

PRAXIAL ALIGNMENT SYSTEM Tool for the platform positioning

PRAXIAL Platform

Template squarescalibration (CMM)

ATLAS Align. PDRPh. Schune (Saclay)

J.-Ch.B., C.G. andH.v.d.G. presentations

red = proj.blue = praxialgreen= ref.

2

Y

Z

Atlas axis

X 3D view.

The platform is glued at its nominal position during the glue curing of the first MDT layer.

ATLAS Align. PDRPh. Schune (Saclay)

Flat surface on MDT end plugs

Half sphere on MDT end plugs

6 adjustable (on CMM) balls for the platform positioning (< 20 m)

Half sphere on the

MDT tube outer surface

(or on the jig, BOS)

Template square

PRAXIAL ALIGNMENT SYSTEM Platform positioning during MDT construction

PRAXIAL platform

template square with its precise positioning sphere

end-plug of the tube(circularity: < 20 m)

jig

glue

Gluing of the platform(detail)

3

ATLAS Align. PDRPh. Schune (Saclay) PRAXIAL ALIGNMENT SYSTEM

QA/QC: in production site and at the CERN X-ray tomographGoal:Control the chamber mechanical deformation (sag angular displacement of the platform) coming from the assembly of the different layer (e.g. BIS-Thessaloniki).

Method:Use four control tower (one on each platform) each equipped with 4 LED and 2 CCD ( two crossed BCAM).The towers calibrate (relative) platform position: x, y and z.Special software distributed to all labs.

mra

d

Rotation angle vs step (BIS-0): sag. of the chamber

Calibration benchof the tools (in each

lab., if possible)

CCD image of the 2LED from the opposite tower: ~ 0.5 pixel < 100 rad

J.B.

Control tower in position

distance adjusted to ± 2 mm

CCD LEDs

marble table

Platform angle ~ (X/Y(pixel) - X0/Y0) * pixel_size / f

4

ATLAS Align. PDRPh. Schune (Saclay) PRAXIAL ALIGNMENT SYSTEM

QA/QC: in production site and at the CERN X-ray tomograph

4 W/Au wires(Ø = 100 m)

microscope

spheres for the positioning

2D table

support only needed during the calibration

X

Z

Y

After the calibration (“optical CMM”) of the four masks, we know the wires and spheres position with the following precision: wires (4):

• = 100 m 2 m• straightness < 5 m

positioning spheres (6):• = 8 mm 5 m

RO

sid

e

MASK 3MASK 1

MASK 6MASK 2

BML chamber

HV

sid

e

Optical CMM

Chamber on tomograph (top view)

Goal:Verify the final platform position w.r.t. to MDT wires.

Method:Use four masks (one on each platform) equipped with wires. The masks wires are precisely located w.r.t. to the positioning spheres (< 10 m). Four X-ray tomo scans ( ) are needed for measuring the platforms position. These masks calibrate absolute platforms position: x, y, z and y, z.

Mask with its4 wires

5

Y of the mask wires w.r.t. the platform:< > ~ 5 m< 11 m

Z of the mask wires w.r.t. the platform:< > < 1 m< 6 m

These measurements include errors from: repositioning, X-tomo measurement error and uncertainty from local frame

-40 0 40 (m)

-10 0 10 (m)

PRAXIAL ALIGNMENT SYSTEM QA/QC with the X-ray tomograph (with BML-0)

top

view

B M L

Z

X

Atlas axis

ATLAS Align. PDRPh. Schune (Saclay) 6

exchange of masks position

Difficulty in interpreting X-tomo results but more generally difficulty of the alignment:muons are measured using the wires but alignment elements are positioned on the tubes. we have to understand the tube sag w.r.t. wire sag with a precision < 30 m in all conditions: position in the exp., flexo, T gradient… (see ATLAS-TDR)

platform

2) CERN X-tomo or ATLAS conditions:

1) Lab. conditions: (marble table, T=cte)

X-tomo results (sag. compensation up to 600 m):Ysag. comp.-Yno sag. comp ~ 40 m

marble table

tube

Y

PRAXIAL ALIGNMENT SYSTEMPositioning precision

Positioning tool (CMM): < 20 m

Platform quality + repeatability of the positioning: ~ 10 m

(special tools will be designed/made to help for the positioning)

End-plug circularity: < 20 m

Mask for X-tomo (absolute): trans.< 10 m and rot.< 100 rad

(first complete measurement: BML-1, April 2001)

optical sensor calibration J.-Ch. B. presentation

Pos

itio

ning

Con

trol

Control tower (relative angular movement): < 100 rad

ATLAS Align. PDRPh. Schune (Saclay) 7