Transcript Searching for Systematic Error in X

Analyzing Praxial Platform
Positions on MDT Barrel
Chambers Using X-Ray
Tomograph Measurements
Chris Hayward
Advisor: Silvia Schuh
August 14, 2003
UM CERN 2003 Summer REU
Outline

ATLAS
 Muon Spectrometer
 MDT Chambers
 RASNIK system
 X-Ray Tomograph

My Project
 ROOT
 Current
Status/Results
 Acknowledgements
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU
ATLAS – A Toroidal LHC
Apparatus
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU
Muon Spectrometer

Outer layer of ATLAS.
 Uses magnetic field to
deflect muons and
measure their momentum.
 High momentum
resolution (order 10% for
pt ~1 TeV) necessary to
detect SUSY, Higgs, and
other physics.
 MDT wire positions must
be know with high
precision.
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU
Monitored Drift Tube (MDT)
Chambers
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Largest barrel chamber, NIKHEF
2.2 m
5 m
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MDTs: Al tubes, W wires.
Filled with Ar/CO2.
~2000 V applied.
Detect charged particles.
Used to reconstruct muon
tracks.
Chambers: 2 multi-layers
with 3 or 4 monolayers glued
on either side of support
structure (spacer frame).
Barrel and endcap types.
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU
RASNIK System
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“Monitored”: RASNIK system provides dynamic
alignment information; goal: ~30 microns.
RASNIK: LED & CCD system used to monitor
deformations.
Inplane (mounted on spacer frame): deformations due to
magnetic field, varying chamber sags, temperature, etc.
Station-to-station (praxial, projective): RASNIK system
mounted on platforms glued to chambers; platform
position relative to wire grid must be well-known.
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU
X-Ray Tomograph
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Central quality
control of MDT
chamber mechanical
construction.
MDT wire placement
precision goal: RMS
< 20 micrometers for
whole chamber.
Samples 15% of
MDTs from 13 sites
around the world.
Calibrated rulers
0.6 m
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X-ray sources
2.2 m
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU
X-ray beams
Scintillators
Measurement Principle
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One corridor
Scintillator counts/20mm
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W absorbs more x-rays than
Al.
Yields a shadowgram from
which wire positions can be
extracted.
Calibration rulers provide
vertical scale & orthogonality
information.
Scintillator counts/20 mm
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Tube walls
X-ray carrier position (mm)
Full Scan
Small barrel chamber
20000
10000
0
Support frame
Peak
position
m = 1.7mm
Long beams
1000
X-ray carrier position (mm)
2900
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU
162
0
Measurement Results
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU
My Project
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Praxial platform positions relative to wire grid are measured by xtomo.
These measurements must be analyzed for systematic errors (due to
construction and/or measurement process).
I wrote a program using ROOT that reads in barrel chamber data, stores the
data in a TTree, and plots default histograms which we developed.
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU
Program Components
1.
2.
3.
4.
5.
Search data directories for barrel chambers scanned
since last run.
Read in data from new chambers and store in a
ROOT TTree.
Calculate mean parameters per tool/platform and
side.
Plot a set of standard histograms and allow the user
to plot others.
Store data in a ROOT TFile which can be easily
accessed and analyzed through the ROOT
interactive interface.
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU
ROOT
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TTrees are ROOT TObjects that
are used to store many different
kinds of data.
I created a class “Chamber”.
Each TBranch of my TTree
stores one Chamber object.
Useful to inherit from TObject
because it enables use of ROOT’s
powerful I/O.
TTrees also offer very effective
compression and organization;
members of a class can be read
without reading the whole object.
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU
A Chamber Branch
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU
Current Status/Results
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The program is ready
to do analysis, but we
must update old
HTML data files
before we can
analyze all the
chambers we plan to.
I am staying an extra
week to go a bit
further in the
analysis.
Our goal is to
analyze ~50
chambers (over half
of those measured).
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU
Acknowledgements
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Silvia Schuh
Professor Jean Krisch,
Professor Tom Dershem,
Professor Steve Goldfarb,
and Professor Homer Neal
CERN
The ROOT Team
ROOTTalk subscribers
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University of Michigan
CERN REU program
UM Physics Department
Michigan Center for
Theoretical Physics
UM Global Intercultural
Experience for
Undergraduates
Ford Motor Co.
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU