Calibration and production of PRAXIAL (*) sensors for the ATLAS muon spectrometer Optical Metrology - SPIE Optical Measurement Systems for Industrial Inspection III Munich, June 2003 Philippe Schune CEA-Saclay, DAPNIA-SPP, Gif sur Yvette, Cedex, France (*) only proximity alignment described in this presentation 25/06/2003 1

CEA-Saclay, DAPNIA Gif sur Yvette, Cedex France J.-Ch. Barrière, O. Cloué, B. Duboué, M. Fontaine, V. Gautard, P. Graffin, C. Guyot, G. Jiolat, P. Perrin, P. Ponsot, Y. Reinert, J.-C. Saudemont, J.-P. Schuller, Ph. Schune Saclay team involved in the development of the PRAXIAL sensors 2

1.Goal of the PRAXIAL alignment sensors in the ATLAS experiment 2.How the PRAXIAL sensor works 3.Calibration of the sensors: relative and absolute 4.Stability and results of the calibration 5.PRAXIAL sensors in ATLAS: different types, where do we stand, test beam, etc… 6.Conclusion Calibration and production of PRAXIAL sensors for the ATLAS muon spectrometer

one MDT octant = 6 adjacent towers Optical alignment lines within a MDT octant red = projective alignment blue = praxial + axial alignment green= reference alignment system Alignment of ATLAS muon chambers: global alignment ~20m ~ 12 m 3 The goal is to know the transverse position of the muon chambers w.r.t. the projective axis with a ~30  m precision.

Alignment of ATLAS muon chambers: proximity alignment Top view of a PRAXIAL (and AXIAL) system made of two « half » parts. Control local position of two neighboring muon chambers. We put one PRAXIAL element at each corner of the muon chambers (~600). MDT #i MDT #i+1 Layer of (six) MDT chambers ~ 2 m Top view 3D view one MDT octant = 6 adjacent towers z x y ~ 30 cm 4

Motivations and requirements of PRAXIAL alignment PRAXIAL should control local positioning of two neighbouring ATLAS (an LHC experiment at CERN) muon chambers: precise determination of the absolute position and rotation (dominated by mechanical positioning of sensors on muon chamber):  y,  z : ~ 30  m ;  x : ~ 100  m (// chamber wires)  x : ~ 200  rad ;  y,  z ~ 500  rad relative resolution:  y,  z : ~ 10  m ;  x : ~ 100  m (// chamber wires)  x : ~ 100  rad ;  y,  z ~ 500  rad chambers installation and displacement : range of sensors ±5mm 3, ±5mrad 3 5

1.Goal of the PRAXIAL alignment in the ATLAS experiment 2.How the PRAXIAL sensor works 3.Calibration: relative and absolute 4.Stability and results of the calibration 5.PRAXIAL sensors in ATLAS (different types, where do we stand, etc…) 6.Conclusion Calibration and production of PRAXIAL sensors for the ATLAS muon spectrometer

Light source Camera: ~3×4 mm 2 (pixel size ~12×12  m 2 ) ~ 1.5mm Enlarge view of the coded mask (total area ~20×20mm 2 ) Individual component: the RASNIK alignment system (Nikhef, Amsterdam) The Rasnik system measure : x, y  to optical axis (~1  m) magnification : d(mask-lens)/d(lens/camera) : mask rotation w.r.t. camera pixel axis : ~150  rad  Rasnik is a “3.5D” measurement system 6

camera mask lens (f ~ 50 mm) lower level = proximity clamp alignment platform upper level = axial Top view of PRAXIAL 3D view PRAXIAL sensors: made with 2 crossed Rasnik => 2×4 measurements lens camera mask each Rasnik measures: x, y  to optical axis, magnification, mask rotation w.r.t. camera ~30cm 7 ~15cm

camera mask lens (f ~ 50 mm) lower level = proximity clamp alignment platform upper level = axial Top view of PRAXIAL 3D view PRAXIAL sensors: made with 2 crossed Rasnik => 2×4 measurements lens camera mask each Rasnik measures: x, y  to optical axis, magnification, mask rotation w.r.t. camera ~30cm 7 camera lens mask ~15cm

PRAXIAL sensors mechanic and electronic components (1) rasnik #1 rasnik #2 8 Top view

PRAXIAL sensors mechanics and electronics components (2) PRAXIAL sensors/elements seen from the back ~30cm 9

1.Goal of the PRAXIAL alignment in the ATLAS experiment 2.How the PRAXIAL sensor works 3.Calibration: relative and absolute 4.Stability and results of the calibration 5.PRAXIAL sensors in ATLAS (different types, where do we stand, etc…) 6.Conclusion Calibration and production of PRAXIAL sensors for the ATLAS muon spectrometer

Calibration: algorithm of the calibration install both PRAXIAL elements on the calibration bench: 1 movable, 1 fixed do ~ 100 movements: rotations  translations (range ±3mrad 3, ±3mm 3 ) for each movement records: both Rasniks (8 measurements) mechanical probes output (needed because each translation or rotation stage have small unwanted movements on other axis: e.g.  x=1mm => 1mm  ~100  rad on  x Finally determine the calibration matrix A to be used for determining the absolute position D of one praxial element with respect to the other through the relation: D = A×R+d where R is the column vector of Rasnik measurements (8 lines, 4 per Rasnik system); d is a column vector of 6 elements describing the offset of the two reference frames of the praxial elements; A is the calibration matrix (8 times 6). d is measured using the “zeroprax”. 10

linear combination + offsets coefficients computed using known displacements Step motors (limited accuracy…) Mechanical probes (typical accuracy: ~2  m) Determined in a known “reference position” “Zeroprax” Calibration: transfer matrix of the PRAXIAL calibration matrix A R column vector with 8 Rasnik measurements d offset absolute position D = +× 11

Movable stage set-up PC used for control of the set-up and for calculation of calibration constants screen for image control Calibration: calibration set-up (1) 12 Two elements of a PRAXIAL in position

y xx zz mechanical probes movable support with its (round) flat reference surfaces in contact with mechanical probes six stages elements: three for rotations and three for translations Calibration: calibration set-up (2) 13

Absolute calibration: the “zeroprax” + offsets link mechanical frame of both PRAXIAL elements. Use a common mechanical support, known at ±5  m. ~30cm 14 A×A×

1.Goal of the PRAXIAL alignment in the ATLAS experiment 2.How the PRAXIAL sensor works 3.Calibration: relative and absolute 4.Stability and results of the calibration 5.PRAXIAL sensors in ATLAS (different types, where do we stand, etc…) 6.Conclusion Calibration and production of PRAXIAL sensors for the ATLAS muon spectrometer

Stability of the set-up with time (1) Temperature variation of the hall (±0.5 deg.) induce small mechanical deformation of the calibration bench: below 5 microns. mechanical probes measurements 15

Stability of the set-up with time (2) both Rasnik measurements 16

y z x Translations (  m) Rotations (  rad) y z x Final resolution of PRAXIAL sensors r.m.s.  m r.m.s.  rad 17 After its calibration, we test a PRAXIAL sensor by doing tens random (known) displacements and we compare PRAXIAL results to mechanical probes measurements.

1.Goal of the PRAXIAL alignment in the ATLAS experiment 2.How the PRAXIAL sensor works 3.Calibration: relative and absolute 4.Stability and results of the calibration 5.PRAXIAL sensors in ATLAS (different types, where do we stand, etc…) 6.Conclusion Calibration and production of PRAXIAL sensors for the ATLAS muon spectrometer

Different PRAXIAL types for ATLAS experiment Total: more than 1000 PRAXIAL pairs. The calibration bench should be adapted for all distances… 18

glue all elements to the mechanical support (anodised aluminium profile) avoid electrical contact of camera and LED to mechanics (ground loops) use a plastic cover on the camera to avoid dust radiation hardness tests performed (to resist of 10 years of LHC, Nikhef) use bar code in order to identify PRAXIAL elements check the calibration by doing ~50 random movements in the range ±5mrad 3, ±5mm 3 use special individual boxes for transportation before installation on ATLAS chamber check all cabling check a complete (or few) lines of 12 PRAXIAL sensors together using autocollimator, laser+ transverse alignment sensors, elements calibrated with a CMM… use hard spheres for the positioning (local deformation < 5  m) screw elements on ATLAS muon chambers with a screwing torque < 2Nm …/… Features 19

Where do we stand today ? Most of the elements have already been glued on mechanical profile. PRAXIAL calibration bench finalized these days, including: transfer matrix, data base connection, special operator program, check of calibration on random mvts, etc… Still ~15 month of calibration work ahead of us at Saclay, for two to three persons. Installation of calibrated PRAXIAL elements on ATLAS muon chambers should start at CERN in October ~ 2m 20

2002 test beam set-up at CERN two outer chambers two middle chambers two inner chambers We have tested 6 PRAXIALs (and also 6 axial elements) including mechanics, etc… Relative measurements work at the 20  m level. drift tubes of muon chamber 21 between to neighbouring identical chambers

1.Goal of the PRAXIAL alignment in the ATLAS experiment 2.How the PRAXIAL sensor works 3.Calibration: relative and absolute 4.Stability and results of the calibration 5.PRAXIAL sensors in ATLAS (different types, where do we stand, etc…) 6.Conclusion Calibration and production of PRAXIAL sensors for the ATLAS muon spectrometer

Conclusion on the PRAXIAL alignment sensor development at Saclay relative resolution < 10  m for translations < 100  rad for rotations absolute calibration of the sensor : < 20  m < 150  rad at the end the global absolute accuracy is dominated by mechanical positioning on ATLAS muon chambers (platform support) the PRAXIAL is well adapted to the ATLAS experiment six of them have been successfully tested last year individual cost (not included acquisition electronics) ~200 euros/PRAXIAL pair >1000 PRAXIAL will be calibrated at Saclay for the CERN ATLAS experiment (+5% spare) 22