s. m. gibson, iwaa7 november 2002 1 atlas group, university of oxford, uk s. m. gibson, p. a. coe,...
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S. M. Gibson, IWAA7 November 20021
ATLAS Group, University of Oxford, UKS. M. Gibson, P. A. Coe, A. Mitra, D. F. Howell, R. B. Nickerson
Geodetic Grids for theGeodetic Grids for the continuous, quasi real time alignment of the continuous, quasi real time alignment of the
ATLAS Semiconductor TrackerATLAS Semiconductor Tracker
S. M. Gibson, IWAA7 November 20022
OverviewOverview
• Motivation – the alignment of ATLAS
• The ATLAS SCT alignment system
• Demonstration system
• Square Grid
• Tetrahedral Grid
• Large grids for ATLAS
• Grid simulations
• Check with FEA
S. M. Gibson, IWAA7 November 20023
Motivation – the alignment of ATLASMotivation – the alignment of ATLAS
Inner detector:Physics
requires shape variations to be measured
to <10m
7m
S. M. Gibson, IWAA7 November 20024
Solution – FSI geodetic gridsSolution – FSI geodetic grids
Barrel SCT grid
Forward SCT grid
SemiConductor Trackermonitored using a
geodetic grid of 800 length measurements.
S. M. Gibson, IWAA7 November 20025
The ATLAS SCT alignment systemThe ATLAS SCT alignment system
• Frequency Scanning Interferometry (as shown earlier) will be used to simultaneously measure all lines of sight in the geodetic grids.
• Benefits: Continuous alignment during ATLAS operation. An understanding of the detector shape on day one
of physics. Corrections of short time scale motions that
degrade track-based alignment. Corrections of complex distortions, that cannot be
corrected with tracks alone.
S. M. Gibson, IWAA7 November 20026
Alignment system layoutAlignment system layout
Surface building
groundlevel
ATLAScavern
Fibre Splitter
Tree Crate
APD read out crate
Detector Cavern
ATLAS SCT gridof 800 grid-line-interferometers
Equipment Cavern
Lasers Reference Interferometer
System
Surface building
fibre coupling optics
S. M. Gibson, IWAA7 November 20027
Demonstration SystemDemonstration System
‘equipment cavern’ ‘detector cavern’
Splitter Tree and APD readout boxSplitter Tree and APD readout box
250mm
Fibres Power Square GridFibres Power Square Grid
S. M. Gibson, IWAA7 November 20028
Demonstration system: Square GridDemonstration system: Square Grid
• 6 simultaneous length measurements made between four corners of the square.
• +7th interferometer to measure stage position.
• Displacements of one corner of the square can then be reconstructed.
S. M. Gibson, IWAA7 November 20029
Square GridSquare Grid
S. M. Gibson, IWAA7 November 200210
Model Degrees of FreedomModel Degrees of Freedom
Node A defines
the origin
Node B defines
the X axis
Node C is free in X
and Y
Node D is free in X
and Y
S. M. Gibson, IWAA7 November 200211
Node ReconstructionNode Reconstruction
Reconstructed Jewel B Coordinate
-0.0010
0.0000
0.0010
253.998 253.999 254.000 254.001 254.002
X axis (defined by direction A->B) / mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel C Coordinate
253.998
253.999
254.000
254.001
254.002
253.80 253.85 253.90 253.95 254.00 254.05 254.10 254.15 254.20
X axis (defined by direction A->B) /mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel D Coordinate
253.998
253.999
254.000
254.001
254.002
-0.002 -0.001 0.000 0.001 0.002
X axis (defined by direction A->B) /mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel B Coordinate
-0.0010
0.0000
0.0010
253.998 253.999 254.000 254.001 254.002
X axis (defined by direction A->B) / mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel C Coordinate
253.998
253.999
254.000
254.001
254.002
253.80 253.85 253.90 253.95 254.00 254.05 254.10 254.15 254.20
X axis (defined by direction A->B) /mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel D Coordinate
253.998
253.999
254.000
254.001
254.002
-0.002 -0.001 0.000 0.001 0.002
X axis (defined by direction A->B) /mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel B Coordinate
-0.0010
0.0000
0.0010
253.998 253.999 254.000 254.001 254.002
X axis (defined by direction A->B) / mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel C Coordinate
253.998
253.999
254.000
254.001
254.002
253.80 253.85 253.90 253.95 254.00 254.05 254.10 254.15 254.20
X axis (defined by direction A->B) /mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel D Coordinate
253.998
253.999
254.000
254.001
254.002
-0.002 -0.001 0.000 0.001 0.002
X axis (defined by direction A->B) /mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel B Coordinate
-0.0010
0.0000
0.0010
253.998 253.999 254.000 254.001 254.002
X axis (defined by direction A->B) / mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel C Coordinate
253.998
253.999
254.000
254.001
254.002
253.80 253.85 253.90 253.95 254.00 254.05 254.10 254.15 254.20
X axis (defined by direction A->B) /mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel D Coordinate
253.998
253.999
254.000
254.001
254.002
-0.002 -0.001 0.000 0.001 0.002
X axis (defined by direction A->B) /mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel B Coordinate
-0.0010
0.0000
0.0010
253.998 253.999 254.000 254.001 254.002
X axis (defined by direction A->B) / mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel C Coordinate
253.998
253.999
254.000
254.001
254.002
253.80 253.85 253.90 253.95 254.00 254.05 254.10 254.15 254.20
X axis (defined by direction A->B) /mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel D Coordinate
253.998
253.999
254.000
254.001
254.002
-0.002 -0.001 0.000 0.001 0.002
X axis (defined by direction A->B) /mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel B Coordinate
-0.0010
0.0000
0.0010
253.998 253.999 254.000 254.001 254.002
X axis (defined by direction A->B) / mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel C Coordinate
253.998
253.999
254.000
254.001
254.002
253.80 253.85 253.90 253.95 254.00 254.05 254.10 254.15 254.20
X axis (defined by direction A->B) /mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel D Coordinate
253.998
253.999
254.000
254.001
254.002
-0.002 -0.001 0.000 0.001 0.002
X axis (defined by direction A->B) /mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel B Coordinate
-0.0010
0.0000
0.0010
253.998 253.999 254.000 254.001 254.002
X axis (defined by direction A->B) / mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel C Coordinate
253.998
253.999
254.000
254.001
254.002
253.80 253.85 253.90 253.95 254.00 254.05 254.10 254.15 254.20
X axis (defined by direction A->B) /mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
Reconstructed Jewel D Coordinate
253.998
253.999
254.000
254.001
254.002
-0.002 -0.001 0.000 0.001 0.002
X axis (defined by direction A->B) /mm
Y a
xis
(p
erp
en
dic
ula
r to
A->
B)
/ m
m
A B
CD1m
1m50m1m
Node A Node B
Node D Node C
S. M. Gibson, IWAA7 November 200212
Reconstruction of Jewel C TranslationReconstruction of Jewel C Translation(Square Grid)(Square Grid)
Std Dev = 400 nm
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
0 50 100 150 200 250 300
X stage / micron
Rec
on
stru
cted
X s
tag
e,re
sid
ual
s /
mic
ron
S. M. Gibson, IWAA7 November 200213
Square GridSquare GridTetrahedral GridTetrahedral Grid
Jewel C raised
up by 100mm
Now sensitive to Z coordinate, allowing three dimensional coordinate reconstruction
S. M. Gibson, IWAA7 November 200214
Node C Three Dimensional Coordinate ReconstructionNode C Three Dimensional Coordinate Reconstruction
(Stationary Stage)(Stationary Stage)
RMS scatter = 640nm
S. M. Gibson, IWAA7 November 200215
Node C Three Dimensional Coordinate ReconstructionNode C Three Dimensional Coordinate Reconstruction
(Stage translated in X)(Stage translated in X)
S. M. Gibson, IWAA7 November 200216
Reconstruction of Jewel C TranslationReconstruction of Jewel C Translation(Tetra Grid)(Tetra Grid)
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
0 50 100 150 200 250 300
X stage position / micron
Re
co
ns
tru
cte
d X
sta
ge
re
sid
ua
ls/
mic
ron
Sdt Dev = 460 nm
S. M. Gibson, IWAA7 November 200217
Grids for ATLASGrids for ATLAS
• The grid for ATLAS will contain eight hundred lines of sight in a complex geometry.
• A quarter of the Barrel grid:
• One of the two Endcap grids:
• The error propagation through these grids has been simulated.
S. M. Gibson, IWAA7 November 200218
Barrel Grid SimulationsBarrel Grid SimulationsLines of sight for one quadrant of Alignment Grid
FEA model of carbon fibre FEA model of carbon fibre support structuresupport structure
7035m0m
Simulgeoref1 model of Alignment Grid nodes
(jewels)ASSUME: end flanges are rigid rings ¢ral jewels constrained in rotation
Z X
Y
S. M. Gibson, IWAA7 November 200219
Single Barrel Grid Simulation ResultsSingle Barrel Grid Simulation Results
Measured object
Degree of Freedom
Calculated Error
End Flange
Translation in X Translation in Y Translation in Z
Rotation about X Rotation about Y Rotation about Z
0.29 m 0.29 m 0.34 m 1.31 rad 1.31 rad 0.61 rad
Each Central Jewel
Translation in R Translation in R Translation in Z
Rotation about R Rotation about R Rotation about Z
2.19 m 13.54 m 0.90 m
97.07 rad 9.91 rad
99.47 rad
• NB: rigid end flanges assumed – currently repeating with increased number of degrees of freedom.
• 1 micron precision assumed throughout.
• Fixed inner barrel.
Central jewels constrained in
rotation
Result without radial lines
S. M. Gibson, IWAA7 November 200220
FEA model of SCT structureFEA model of SCT structure
Barrel SCT is normally supported
at four points
S. M. Gibson, IWAA7 November 200221
Torsional behaviour:Torsional behaviour:4 point to 3 point support4 point to 3 point support
Loss of contact with
this point
S. M. Gibson, IWAA7 November 200222
Future work: Cross-check of Grid SimulationsFuture work: Cross-check of Grid Simulations
• Take FEA model of perfect barrel Extract lengths from geodetic grid (add random errors to lengths) Pass to reconstruction software for calibration of model
• Distort FEA model eg, twist and/or multipole distortions Extract new lengths (add random errors to lengths) Pass to reconstruction software Reconstruct nodes co-ordinates and compare with those in FEA model
• Compare with predicted errors
S. M. Gibson, IWAA7 November 200223
ConclusionsConclusions
• A novel alignment system, based on FSI, is under construction for the ATLAS SCT.
• Prototype geodetic grid nodes can be reconstructed to well within the ATLAS requirements (<1ppm).
• Error propagation through the final SCT grid has been simulated.
• Future work: cross-check simulations using distorted FEA models.
• Referencesref1 used with kind permission of the author:
• L. Brunel, ‘SIMULGEO: Simulation and reconstruction software for opto-geometrical systems’, CERN CMS Note 1998/079.