Geant4 for gamma-ray spectrometry

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Geant4 for gamma-ray spectrometry

• Andi Hektor
• andi_at_ut.ee
• GEANT4 WORKSHOP at HIP
• Oct 30-31, 2003

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Outline

• Introduction our detector system
• Gamma-ray spectrometry
• Detection limits
• Why Geant4?
• Model and some examples
• Results
• An utopia of a Geant4 user
• Summary and some acknowledgements

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REAL TIME RADIATION SURVEILLANCE EQUIPMENT FOR
THE UNMANNED AERIAL VEHICLE RANGER
A. Hektor, K. Kurvinen, R. Pöllänen and P.
Smolander STUK - Radiation and Nuclear Safety
Authority P.O.Box 14, FIN-00881 HELSINKI,
Finland petri.smolander_at_stuk.fi
M. Kettunen Finnish Defence Forces Technical
Research Centre P.O.Box 5, FIN-34111 LAKIALA,
Finland
J. Lyytinen Helsinki University of Technology,
Laboratory of Lightweight Structures P.O.Box
4100, FIN-02015 HUT, Finland
Funded by SCIENTIFIC ADVISORY BOARD FOR DEFENCE
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Mobile gamma-ray detector

• Tracking of a release plume
• Time critical, decision aid for initial response,
  radiation safety of the air crew
• Fallout mapping
• After the initial emergency, long term risk
  management
• Locating of a point source
• Lost sources, smuggling and terrorism

Unmanned aerial vehicle (UAV) is an excellent
choice from the radiation safety stand point
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Unmanned aerial vehicle

• Ranger Tactical UAV
• Operated by FDF
• Range 150 km
• Endurance 5 hrs
• Payload 40 kg
• Catapult take-off
• Landing on skids
• Fully autonomous or remotely piloted

Photo Lauri Ahonen, FDF
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Detector system
Connected to the UAV
NaI(Tl)Scintillationdetector
GM baseddose rate meter
Pilot camera
Temp Rh sensor
CZT detector
Data acquisition computer w/GPS
Air volume sensor
Sampling unit
Tetra Radio
Secondary data link to the VIRVE network
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Geometry of the detector system
Light weight structure

• Airworthiness above all
• Vibration attenuation
• Temperature control
• Modularity
• Easy installation

Jari Lyytinen, HUT/LLS
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Installation of the detector
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A gamma-ray spectrometer
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Physics in gamma-ray spectrometer

• Photoelectric absorption
• Compton scattering
• Pair production
• Multiple scattering
• Electron ionisation
• Bremsstrahlung
• Positron annihilation

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Physical properties of NaI(Tl) 1/2
MATERIAL DENSITY g/cm3 EMISSION MAX nm DECAY CONSTANT REFRACTIVE INDEX CONVERSION EFFICIENCY
CsI(Tl) 4.51 550 0.6/3.4 µs 1.79 45
CsI(Na) 4.51 420 0.63 µs 1.84 85
CsI 4.51 315 16 µs 1.95 4-6
NaI(Tl) 3.67 415 0.23 µs 1.85 100
CaF2(Eu) 3.18 435 0.84 µs 1.47 50
6LiI(Eu) 4.08 470 1.4 µs 1.96 35
6Li-glass 2.6 390-430 60 ns 1.56 4-6
CsF 4.64 390 3 - 5 ns 1.48 5-7
BaF2 4.88 315/220 0.6/0.8 ns 1.50/1.54 16/5
YAP (Ce) 5.55 350 27 ns 1.94 35-40
GSO (Ce) 6.71 440 30-60 ns 1.85 20-25
BGO 7.13 480 0.3 µs 2.15 15-20
CdWO4 7.90 470/540 20/5 µs 2.3 25-30
Plastics 1.03 375-600 1-3 µs 1.58 25-30
From http//www.scionixusa.com/crystals.html
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Physical properties of NaI(Tl) 2/2
Emission spectra of some materials, from
http//www.scionixusa.com/crystals.html
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Detection limits of the detector? 1/2
3D
1D
2D
Different type of sources, long distances between
the source and detector, high speed of the
detector, energy resolution
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Detection limits of the detector? 2/2

• Analytical methods
• Quite complicated
• Numerical calculations
• Monte Carlo simulations
• Many packages are available DPM, EA-MC EGS4,
  EGS5, EGSnrc, FLUKA Geant3, Geant4 GEM
  HER-MES LAHET MARS MCBEND MCNP, MCNPX,
  A3MCNP, MCNP-DSP, MCNP4B MF3D MVP, MVP -BURN
  MONK, MORSE NMTC, etc.
• Easy to use (!)
• Why Geant4?
• Object-oriented and fast (C)
• Many integrated modules
• Some nice memories and experiences from high
  energy physics

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Geant4

• Supported physics?
• Structure of Geant4?
• C?
• Examples?
• Support manuals, user forums, etc?

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3D-model of our detector in Geant4
3D-model
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Some examples of the Monte Carlo simulations in
Geant4 1/4
Example 1
Example 1
Energy of the gammas 662 keV (Cs-137) Number of
the gammas 15
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Some examples of the Monte Carlo simulations in
Geant4 2/4
Example 2
Energy of the gammas 662 keV (Cs-137) Number of
the gammas 15
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Some examples of the Monte Carlo simulations in
Geant4 3/4
Example 3
Energy of the gammas 662 keV (Cs-137) Number of
the gammas 15
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Some examples of the Monte Carlo simulations in
Geant4 4/4
Example 3
Energy of the gammas 662 keV (Cs-137) Number of
the gammas 15
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Constructing of our detector in Geant4
Ideas for physics and input data
CAD model
Physics List
Geometry
Input parameters
Kernel
Analysis
Visualization
Histograms
Visualization files
Kernel logs
Tracks
Analysis
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Files for our Geant4 silmulations
GammaSpecSTUK.cc - main source of our
detector GNUmakefile - make file for
compilation include/ - include
files README - informative README
file vis.mac - default input
parameters src/ - source files GammaSpecSTUKDe
tectorConstruction.cc - detector
geometry GammaSpecSTUKEventAction.cc GammaSpecST
UKEventActionMessenger.cc GammaSpecSTUKPhysicsLis
t.cc - physics in detector GammaSpecSTUKPrimary
GeneratorAction.cc GammaSpecSTUKRunAction.cc Gam
maSpecSTUKSteppingAction.cc GammaSpecSTUKStepping
Verbose.cc GammaSpecSTUKVisManager.cc
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For example, air definition in the detector
construction file
G4VPhysicalVolume GammaSpecSTUKDetectorConstruc
tionConstruct() G4String name, symbol
G4double a, z, density G4int ncomponents,
natoms // Air - environment around the
detector G4Element elN new
G4Element("Nitrogen", "N", z7.,
a14.01g/mole) G4Element elO new
G4Element("Oxygen" , "O", z8.,
a16.00g/mole) density1.29mg/cm3
G4Material Air new G4Material("Air", density,
ncomponents2) Air-gtAddElement(elN,
70perCent) Air-gtAddElement(elO, 30perCent)
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A result
The peak of Cs-137 (662 keV) the location of the
source 10 cm in the x-direction number of the
events in the detector 200 000
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An utopia of a Geant4 user

• Parallel-Geant4
• Continuous project development

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Parallel-Geant4

• Monte Carlo methods

• Some projects is running for Geant4
• Geant4 and Grid-technology

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Continuous project development
Initial ideas
Ideas, model
Simulations
Analysis
Final results
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Continuous project development
Ideas for physics and input data
CAD model
Physics List
Geometry
Input parameters
Kernel
Analysis
Visualization
Histograms
Visualization files
Kernel logs
Tracks
Analysis
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Summary

• Geant4 is a great MC package
• You do not have to be an expert of C
• Most of needed physics is there (in our case)
• Some nice results for our project
• Graphical interface?
• Parallel version?
• Development of models in CAD (XML, VRML, etc) and
  Geant4 together

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Acknowledgements

• STUK
• HIP
• SCIENTIFIC ADVISORY BOARD FOR DEFENCE IN FINLAND
  for funding