Searching for Systematic Error in X
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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
Largest barrel chamber, NIKHEF
2.2 m
5 m
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
“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
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
X-ray sources
2.2 m
C. Hayward 7/30/2003 UM-CERN 2003 Summer REU
X-ray beams
Scintillators
Measurement Principle
One corridor
Scintillator counts/20mm
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
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
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
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
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
Silvia Schuh
Professor Jean Krisch,
Professor Tom Dershem,
Professor Steve Goldfarb,
and Professor Homer Neal
CERN
The ROOT Team
ROOTTalk subscribers
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