1. Packages for Monte Carlo simulation of radiation interaction with matter
Sergey Ananko
Saint-Petersburg State University
Department of Physics
Division of Computational Physics
JASS-06

2. Outline Actuality Short description of physical model
Monte Carlo method
Geant4
Fluka
Comparison of packages
Conclusions
Future plans
JASS-06

3. Actuality Particular General Nuclear physics
Necessity to have several ways of the solution of the same problem
General
Nuclear physics
High-energy physics
Cosmic rays
Neutrino physics
Medicine
JASS-06

4. Gamma-rays
Physics review
Gamma-rays – high-frequency electromagnetic oscillations: and above
Gamma-particles characteristics:
velocity:
energy:
momentum:
wave length:
Gamma photons energy range:
Effects: photoelectrical absorption, Compton effect and pair production
JASS-06

5. Scattering cross-section
Physics review
- number of photons through unit square per unit of time
- number of scattered photons
- cross-section
- number of scattered gamma photons
- probability
of photons scattering
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6. Photoelectrical effect
Physics review
Photoelectrical effect is a process of gamma photon absorption by atom of substance
- photoelectron energy
- photon energy
- binding energy
JASS-06

7. Compton effect
Physics review
Compton effect is a process of gamma photon scattering on electron of atom
- scattered photon energy incident photon energy
- electron rest-energy
- wave length after interaction - wave length before interaction
- Compton electron energy
JASS-06

8. Compton effect - minimal value of scattered photon energy
Physics review
- minimal value of scattered photon energy
- maximum photoelectron energy
- gamma-quantum
scattering angle
- Compton electron
scattering angle
JASS-06

9. Pair production
Physics review
Pair production is a process of generation electron-positron pair in nucleus or atom field
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10. Total interaction coefficient
Physics review
Number of photons lost by the beam:
where
- cross-sections of Compton effect, photo effect, pair production
- atom number per unit of volume
- flux density
- beam cross-section
- total interaction cross-section per one atom of matter
Quantum energy loss per unit of time:
JASS-06

11. Total interaction coefficient
Physics review
mass absorption coefficient for air
- linear absorption coefficient
- mass absorption coefficient
- matter density
JASS-06

12. Energy and angular distribution of secondary particles
Model
Physics review
Air-filled
cubic volume:
Detecting plane
Gamma energy range:
Point-like source
Energy and angular distribution of secondary particles
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13. Deterministic methods
Two approaches
The Monte Carlo Method
Deterministic methods
Finite difference method
Finite element method
The Monte Carlo method
JASS-06

14. Model: probability estimation
The Monte Carlo Method
Source – anisotropic point-like monoenergetic gamma photon source
Shield – relatively thick spherical shell, only one sort of atom
Effects:
Elastic scattering
Absorption
Effects are characterized by:
Cross-section
Probability density function for path length
JASS-06

15. Simulation steps First step: free path length
The Monte Carlo Method
First step: free path length
Second step: scattering or absorption
Third step: scattering angle
Further steps: repeating
- number of generated trajectories
- number of escaped gamma photons
- score
Estimated probability of escape:
Variance of the :
Relative error z
JASS-06

16. Variance reduction Brute-force approach Truncation Population control:
The Monte Carlo Method
Brute-force approach
Truncation
Population control:
Splitting
Russian roulette
Probability modification
Pseudodeterministic methods
JASS-06

17. Geometry description Combinatorial object Surface-sense object
The Monte Carlo Method
Combinatorial object
Surface-sense object
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18. Monte Carlo packages Main aspirations: Examples:
The Monte Carlo Method
Main components:
Data base of cross-sections and other parameters
Theoretical base
Random number generator
Tool for geometry description
Main aspirations:
Extended range of ability
Flexibility
Examples:
MNCP, Fluka, Geant, Geant4, Vulcanu, PYTHIA, ARIADNE and so on
JASS-06

19. Geant4: status Geant4 is a detector description and simulation tool
Application areas:
High-energy physics, nuclear experiment, medical, accelerator and space physics studies
History:
1974 – GEANT first version
1982 – the appearance of GEANT3
1998 December – first release of GEANT4
Geant4 is a free software
It can be downloaded from URL:
Operating systems:
Unix, Linux, Windows
JASS-06

20. Main features GEANT4 is written in C++
GEANT4 is based on an object-oriented technology
Experiment stages:
Detector description
Source description
Physics description
Detector reaction description
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21. Fluka: status Fluka JASS-06
Fluka is a general purpose tool for calculations of particle transport and interactions with matter, covering an extended range of applications spanning from proton and electron accelerator shielding to target design, calorimetry, activation, dosimetry, detector design, Accelerator Driven Systems, cosmic rays, neutrino physics, radiotherapy etc.
Fluka is distributed under the licence as a tar file
It can be downloaded from its web-site:
Supported platforms:
- Hewlett-Packard 9000 Series 700/800 running HP-UX
- Sun running SunOS
- Intel PCs running LINUX:
- RedHat 7.3
- RedHat 9.0
- Scientific Linux 4.1 `
- Fedora Core
History:
First generation – the Fluka of the 70th
Second generation – the Fluka of the 80th
Third generation – the Fluka of today
JASS-06

22. Main features Fluka is written in Fortran
Package consists of compiled libraries, user routing in source form, INCLUDE files, various unformatted and formatted data and a number of scripts for compiling, linking and running the program.
Structure of input file: particle source, geometry, transport options, detectors
Example: source (kind of particle, energy, location in space, distribution)
BEAM 50.E PROTON
BEAMPOS
JASS-06

23. Comparison: main features
Geant4
Fluka
photoelectric effect:
Compton effect:
- recommended value for threshold for Fluka
pair production:
multiple scattering:
threshold energy

24. Conclusion
Both Fluka and Geant4 provide with ability of simulation particles transport in a very extended energy range.
JASS-06

25. Future plans To receive results from Fluka To process them
To compare them with Geant4
To parallel both Fluka and Geant4
JASS-06

26. Thank you for attention