1. Platform positioning during MDT construction Tool for the platform positioning Ph. Schune J.-Ch. Barrière P RAXIAL A LIGNMENT S YSTEM (barrel) positioning calibration calibration of P RAXIAL part A TLAS Align. PDR Ph. Schune (Saclay) QA/QC: in production site and at the CERN X-ray tomograph calibration of A XIAL part conclusion P RAXIAL active optical elements 1

2. Principle : The P RAXIAL 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. P RAXIAL A LIGNMENT S YSTEM Tool for the platform positioning P RAXIAL Platform Template squares calibration (CMM) A TLAS Align. PDR Ph. Schune (Saclay)  J.-Ch.B., C.G. and H.v.d.G. presentations red = proj. blue = praxial green= ref. 2 Y Z Atlas axis X 3D view.

3. The platform is glued at its nominal position during the glue curing of the first MDT layer. A TLAS Align. PDR Ph. 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 P RAXIAL A LIGNMENT S YSTEM Platform positioning during MDT construction P RAXIAL platform template square with its precise positioning sphere end-plug of the tube (circularity:  < 20  m) jig glue Gluing of the platform (detail) 3

4. A TLAS Align. PDR Ph. Schune (Saclay) P RAXIAL A LIGNMENT S YSTEM QA/QC: in production site and at the C ERN X-ray tomograph Goal: 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. mrad Rotation angle vs step (BIS-0): sag. of the chamber Calibration bench of the tools (in each lab., if possible) CCD image of the 2 LED 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) - X 0 /Y 0 ) * pixel_size / f 4

5. A TLAS Align. PDR Ph. Schune (Saclay) P RAXIAL A LIGNMENT S YSTEM QA/QC: in production site and at the C ERN 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 side MASK 3 MASK 1 MASK 6MASK 2 BML chamber HV side 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 its 4 wires 5

6. 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) P RAXIAL A LIGNMENT S YSTEM QA/QC with the X-ray tomograph (with BML-0) top view B M L Z X Atlas axis A TLAS Align. PDR Ph. 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 A TLAS -TDR) platform 2) C ERN X-tomo or A TLAS conditions: 1) Lab. conditions: (marble table, T=cte) X-tomo results (sag. compensation up to 600  m): Y sag. comp. -Y no sag. comp ~ 40  m marble table tube Y

7. P RAXIAL A LIGNMENT S YSTEM Positioning 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 Positioning Control Control tower (relative angular movement):  < 100  rad A TLAS Align. PDR Ph. Schune (Saclay) 7