Packages for Monte Carlo simulation of radiation interaction with matter

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

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Actuality

• Particular
• Necessity to have several ways of the solution of
  the same problem

• General
• Nuclear physics
• High-energy physics
• Cosmic rays
• Neutrino physics
• Medicine

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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

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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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Photoelectrical effect
Physics review

• Photoelectrical effect is a process of gamma
  photon absorption by atom of substance
• - photoelectron energy
• - photon energy
• - binding energy

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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

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Compton effect
Physics review

• - minimal value of scattered
  photon energy
• - maximum
  photoelectron energy

- gamma-quantum scattering angle
- Compton electron scattering angle
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Pair production
Physics review

• Pair production is a process of generation
  electron-positron pair in nucleus or atom
  field

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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

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Total interaction coefficient
Physics review
mass absorption coefficient for air

- linear absorption coefficient
- mass absorption coefficient
- matter density
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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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Two approaches
The Monte Carlo Method

• Deterministic methods
• Finite difference method
• Finite element method

• The Monte Carlo method

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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

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Simulation steps
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
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Variance reduction
The Monte Carlo Method

• Brute-force approach
• Truncation
• Population control
• Splitting
• Russian roulette
• Probability modification
• Pseudodeterministic methods

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Geometry description
The Monte Carlo Method

• Combinatorial object

• Surface-sense object

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Monte Carlo packages
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

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Geant4 status
GEANT4

• 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 http//geant4.cern.ch Operating
systems Unix, Linux, Windows
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Main features
GEANT4

• 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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Fluka status
Fluka

• 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
• www.fluka.org
• 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
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Main features
Fluka

• 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.E00

PROTON BEAMPOS 0.0 0.0
-50.0
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Comparison main features
Geant4
Fluka
photoelectric effect
Compton effect
- recommended value for threshold for Fluka
pair production
multiple scattering
threshold energy
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Conclusion

• Both Fluka and Geant4 provide with ability of
  simulation particles transport in a very extended
  energy range.

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Future plans

• To receive results from Fluka
• To process them
• To compare them with Geant4
• To parallel both Fluka and Geant4

JASS-06
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• Thank you for attention