S. Gibson FSI Offline Analysis 9 th October 2003 1 FSI Alignment: Offline Analysis Overview ATLAS...

S. Gibson FSI Offline Analysis 9th October 20031

FSI Alignment:FSI Alignment: Offline Analysis Offline Analysis

Overview

ATLAS Group, University of OxfordStephen Gibson, Danny Hindson, Pawel Bruckman de Renstrom,

Paul Coe, Tony Weidberg

• Reminder of FSI

• What FSI provides

• Node reconstruction

• Analysis approaches:

• Reverse FEA

• Eigenmode decomposition

http://www-pnp.physics.ox.ac.uk/~atlas/index.html


SCT monitored with FSI geodetic gridsSCT monitored with FSI geodetic grids

SemiConductor Trackermonitored using a

geodetic grid of 842 length measurements.

Forward SCT grid

Barrel SCT grid


FSI System Installed on Barrel 3FSI System Installed on Barrel 3

FSI grid

nodes


Barrel FSI grid node: “Scorpion”Barrel FSI grid node: “Scorpion”

Pre-alignment jig Installed on barrel


Endcap FSI Grid Node: “Viking”Endcap FSI Grid Node: “Viking”


Endcap FSI Grid Node: “Viking”Endcap FSI Grid Node: “Viking”

Now in pre-alignment jig – see hardware tour


Endcap FSI: Pre-alignment jigEndcap FSI: Pre-alignment jig


What does FSI provide?What does FSI provide?

• One FSI scan provides a set of precise length measurements between grid nodes (<1micron).

• Not absolute but relative measurements – interested in differences between scans.

Timescale:

• Each laser scan will take a few minutes (to generate the raw data).

• Rate of scans will depend on: Available processor resources. Data storage:

• Interferometer data ~ 1 GB per scan.• Length data ~ only 10 kB per scan.

Demand for FSI data (during a fill/ between fills/ shutdowns).

• Frequent measurements allow short time scale distortions to be followed and corrected.

• Access to low spatial frequency modes of tracker distortion (sagitta).


Alignment System CalibrationAlignment System Calibration

scanning head

Initial ModuleCo-ordinates

Initial Node Positions

X-ray survey

FSI scan

FSI System Calibrationsimultaneous


Analysis of FSI dataAnalysis of FSI data

Interferometer data analysis:

• This data consists of sinusoidal fringes from each grid line interferometer (for both lasers) + gas measurements. Total ~ 1GB per scan.

• PC farm will process data in quasi-real-time to determine the set of lengths for each scan.

• Time to process each scan?

• Result is 842 lengths kept on record.

How to use these 842 lengths?


Analysis of FSI dataAnalysis of FSI data

FSI Grid Lengths

Reconstruction

ModuleCo-ordinates

Interpolation

Node DoF

Want to determine parameters of a model.

Model to bedefined

Reconstruction software.

Node reconstruction already shown for simple prototype grids.

ATLAS grid simulations: see next slide.

Interpolation process:

Shape parameterisation

FEA: barrel and disc eigenmodes

Check with ESPI studies

Calibration from initial X-ray survey


Reconstruction Software StatusReconstruction Software Status

• Preliminary investigations: A. Fox-Murphy Thesis

Final grid designs:• Barrel grid error propagations:

Inner barrel grid quadrant Single barrel grid End-flange grid Full Barrel SCT grid

• Endcap grid error propagations: Initial simulation: ATL-IS-AP-0054. Improved final design described in ATL-IS-ES-0081.

• Node reconstruction already shown for simple prototype grids.

• Will extend simulations of ATLAS grids to allow node reconstruction. (PPARC fellowship)

Simulated: ATL-IS-ES-0026

In progress: S. Gibson Thesis(to be published)

Simulated: S. Gibson Thesis


Precise Grid MeasurementsPrecise Grid Measurements

Precise three dimensional

node reconstruction

1m

Well within ATLAS 10m requirement


Endcap Grid Reconstruction SimulationEndcap Grid Reconstruction Simulation

• Error in reconstructing the translational DoF of each disc with respect to the first disc.


Endcap grid: reconstruction errorsEndcap grid: reconstruction errors

• Error in reconstructing the translational DoF of each disc with respect to a reference disc.

• ‘Pinch’ effect: on redefining the reference disc, the errors change as shown.

• Smallest errors when ‘held’ at centre (disc 6).

• Reconstructed endcap shape should be model independent – effect is simply a global coordinate transformation.


Interpolation ProcessInterpolation Process

• Output from reconstruction doesn’t have to be x,y,z of each FSI node. (Rather fitted DoF defined in model).

• Must provide node DoF in format compatible with interpolation process.

• Some possible formats: FSI node x,y,z (for 3 independent frames A,B,C). 6 DoF of objects that contain nodes, with further internal

DoF. (barrel SCT: contains 4 barrels: barrel distortion; endcap: contains 9 discs: disc distortion).

• Need to incorporate track data.• Two approaches so far considered for offline

analysis: Reverse FEA Eigenmode decomposition (shape parameterisation)


Interpolation processInterpolation process

• Shape parameterisation Fit eigenmodes of SCT support

structure to FSI grid node positions to determine barrel shape.

• Reverse FEA Insert FSI node positions to FEA

model and solve directly for module coordinates. ESPI

Test process experimentally with independent structural monitoring using:

Electronic Speckle Pattern Interferometry.


Reverse FEAReverse FEA

1. Apply realistic force to barrel eg gravity with missing support

3. Run reverse FEA to interpolate positions of other FEA nodes

2. Retain positions of FSI nodes only. Fix the positions of these nodes

Interpolated positionsActual positions


Reverse FEA: residualsReverse FEA: residuals

This assumes elastic properties of barrel are known perfectly

If rerun with wrong Young’s modulus, wrong Poissons ratio (10% out), mean difference is still <1 micron


• Reconstruction and interpolation process must be checked experimentally.

• Measure lengths of an FSI grid.• Reconstruct nodes and interpolate dummy module positions.• Monitor dummy module positions independently with Electronic

Speckle Pattern Interferometry.

Possible Check with ESPIPossible Check with ESPI

ESPIFSI grid

Distorted barrel


Offline Analysis Method 1Offline Analysis Method 1

ModuleCoords

X24 (assume scanper hour)

Base line Modulecoords


X-ray survey

Reverse FEA

Adjust hit positions

Corrections to module coords

Run track alignment 24 hrs FSI corrected data

A,B,C

FSI Node DoF

TracksDatabase

Inte

rpo

late

in

tim

e?

Timeadjust

modules

Time dep.modules

X24

Time dep.modules

time


Eigenmode DecompositionEigenmode Decomposition

SCT shape (or sub components of it) can be expressed as a sum of eigenmodes. (see next slide)

Spatial frequencyeigenmode

FSI

Time

seconds

minutes

hours

days

months

Tracks

X-ray survey

FEA Module metrology

Module temperature


Offline Analysis Method 2Offline Analysis Method 2


X-ray survey

Global Fit to for eigenmodes

A,B,C

FSI Node DoF

Tracks

DatabaseInterpolate in time?

Time dep.modules

Time dep.modules

time

FEA informatio

n

metrology


Comments/ConclusionsComments/Conclusions

Reconstruction software: Endcap grid fully simulated Barrel grid partially simulated – rest should be done by end

March 2004. Will extend simulations to full reconstruction.

Interpolation• Some initial thoughts, but much to be decided:• Reverse FEA:

Relatively simple. Modular approach. Mechnical constraints added after fit for nodes. Reliability of result?

• Eigenmode decomposition Ideal way to proceed. More difficult to combine all information. Ease of inclusion of mechanical properties? We can improve the model with time.

S. Gibson FSI Offline Analysis 9 th October 2003 1 FSI Alignment: Offline Analysis Overview ATLAS...

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