s. m. gibson, iwaa7 november 2002 1 atlas group, university of oxford, uk s. m. gibson, p. a. coe,...

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


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


Motivation – the alignment of ATLASMotivation – the alignment of ATLAS

Inner detector:Physics

requires shape variations to be measured

to <10m

7m


Solution – FSI geodetic gridsSolution – FSI geodetic grids

Barrel SCT grid

Forward SCT grid

SemiConductor Trackermonitored using a

geodetic grid of 800 length measurements.


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.


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


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


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.


Square GridSquare Grid


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


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


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


-0.0010

0.0000

0.0010

253.998 253.999 254.000 254.001 254.002


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


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


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


253.998

253.999

254.000

254.001

254.002

-0.002 -0.001 0.000 0.001 0.002


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


-0.0010

0.0000

0.0010

253.998 253.999 254.000 254.001 254.002


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


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


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


253.998

253.999

254.000

254.001

254.002

-0.002 -0.001 0.000 0.001 0.002


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


-0.0010

0.0000

0.0010

253.998 253.999 254.000 254.001 254.002


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


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


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


253.998

253.999

254.000

254.001

254.002

-0.002 -0.001 0.000 0.001 0.002


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


-0.0010

0.0000

0.0010

253.998 253.999 254.000 254.001 254.002


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


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


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


253.998

253.999

254.000

254.001

254.002

-0.002 -0.001 0.000 0.001 0.002


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


-0.0010

0.0000

0.0010

253.998 253.999 254.000 254.001 254.002


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


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


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


253.998

253.999

254.000

254.001

254.002

-0.002 -0.001 0.000 0.001 0.002


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


-0.0010

0.0000

0.0010

253.998 253.999 254.000 254.001 254.002


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


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


Y a

xis

(p

erp

en

dic

ula

r to

A->

B)

/ m

m


253.998

253.999

254.000

254.001

254.002

-0.002 -0.001 0.000 0.001 0.002


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


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


Square GridSquare GridTetrahedral GridTetrahedral Grid

Jewel C raised

up by 100mm

Now sensitive to Z coordinate, allowing three dimensional coordinate reconstruction


Node C Three Dimensional Coordinate ReconstructionNode C Three Dimensional Coordinate Reconstruction

(Stationary Stage)(Stationary Stage)

RMS scatter = 640nm


Node C Three Dimensional Coordinate ReconstructionNode C Three Dimensional Coordinate Reconstruction

(Stage translated in X)(Stage translated in X)


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


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.


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 &central jewels constrained in rotation

Z X

Y


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


FEA model of SCT structureFEA model of SCT structure

Barrel SCT is normally supported

at four points


Torsional behaviour:Torsional behaviour:4 point to 3 point support4 point to 3 point support

Loss of contact with

this point


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


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.

s. m. gibson, iwaa7 november 2002 1 atlas group, university of oxford, uk s. m. gibson, p. a. coe,...

Documents

atlas group

atlas grid simulations

fea slide

quasi real time alignment

overview motivation

nickerson geodetic grids

shape variations

university of oxford