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Geant4 for gamma-ray
spectrometry
Andi Hektor
[email protected]
GEANT4 WORKSHOP at HIP
Oct 30-31, 2003
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

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
[email protected]
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
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
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
GM based
dose rate meter
Detector system
Connected to the UAV
NaI(Tl)
Scintillation
detector
Pilot camera
Temp + Rh sensor
Data acquisition
computer w/GPS
CZT detector
Air volume sensor
Sampling unit
Tetra Radio
Secondary data link
to the VIRVE network
Geometry of the detector system
Light weight structure
• Airworthiness above all
• Vibration attenuation
• Temperature control
• Modularity
• Easy installation
Jari Lyytinen, HUT/LLS
Installation of the detector
A gamma-ray spectrometer
Physics in gamma-ray
spectrometer

Photoelectric absorption

Compton scattering

Pair production

Multiple scattering

Electron ionisation

Bremsstrahlung

Positron annihilation
Source
NaI(Tl)
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
Physical properties of NaI(Tl) 2/2
Emission spectra of some materials,
from http://www.scionixusa.com/crystals.html
Detection limits of the detector? 1/2
3D
2D
1D
Different type of sources, long distances between the source
and detector, high speed of the detector, energy resolution
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
Geant4

Supported physics?

Structure of
Geant4?

C++?

Examples?

Support: manuals,
user forums, etc?
3D-model of our detector in
Geant4
3D-model
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
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
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
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
Constructing of our detector in
Geant4
Ideas for physics
and input data
CAD model
Physics List
Geometry
Input parameters
Kernel
Analysis
Visualization
Histograms
Analysis
Visualization files
Tracks
Kernel logs
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
GammaSpecSTUKDetectorConstruction.cc
- detector geometry
GammaSpecSTUKEventAction.cc
GammaSpecSTUKEventActionMessenger.cc
GammaSpecSTUKPhysicsList.cc
GammaSpecSTUKPrimaryGeneratorAction.cc
GammaSpecSTUKRunAction.cc
GammaSpecSTUKSteppingAction.cc
GammaSpecSTUKSteppingVerbose.cc
GammaSpecSTUKVisManager.cc
- physics in detector
For example, air definition in the
detector construction file
…
G4VPhysicalVolume* GammaSpecSTUKDetectorConstruction::Construct() {
G4String name, symbol;
G4double a, z, density;
G4int ncomponents, natoms;
// Air - environment around the detector
G4Element* elN = new G4Element("Nitrogen", "N", z=7., a=14.01*g/mole);
G4Element* elO = new G4Element("Oxygen" , "O", z=8., a=16.00*g/mole);
density=1.29*mg/cm3;
G4Material* Air = new G4Material("Air", density, ncomponents=2);
Air->AddElement(elN, 70*perCent);
Air->AddElement(elO, 30*perCent);
…
A result
0.07
Normalized number of counts
0.06
MC calculation
Experimental result
0.05
0.04
0.03
0.02
0.01
0.00
60
70
80
90
100
110
120
130
140
150
160
170
180
190
Channels (1 channel ~ 5.1 keV)
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
An utopia of a Geant4 user


“Parallel-Geant4”
“Continuous project development”
“Parallel-Geant4”

Monte Carlo methods
1
2





Some projects is running for Geant4

Geant4 and Grid-technology
“Continuous project development”
Initial ideas
Ideas, model
Analysis
Simulations
Final results
“Continuous project development”
Ideas for physics
and input data
CAD model
Physics List
Geometry
Input parameters
Kernel
Analysis
Visualization
Histograms
Analysis
Visualization files
Tracks
Kernel logs
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
Acknowledgements



STUK
HIP
SCIENTIFIC
ADVISORY BOARD
FOR DEFENCE IN
FINLAND for
funding