Packages for Monte Carlo simulation of radiation interaction

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

Outline n n n n Actuality Short description of physical model Monte Carlo method Geant 4 Fluka Comparison of packages Conclusions Future plans JASS-06

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

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

Physics review Scattering cross-section - 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 JASS-06

Physics review Photoelectrical effect is a process of gamma photon absorption by atom of substance - photoelectron energy - photon energy - binding energy JASS-06

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

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

Physics review Pair production is a process of generation electron-positron pair in nucleus or atom field JASS-06

Physics review Total interaction coefficient 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

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

Physics review Model Air-filled cubic volume: Detecting plane Gamma energy range: Point-like source Energy and angular distribution of secondary particles JASS-06

The Monte Carlo Method Two approaches Deterministic methods n n The Monte Carlo method Finite difference method Finite element method JASS-06

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

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

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

The Monte Carlo Method Geometry description Combinatorial object Surface-sense object JASS-06

The Monte Carlo Method Monte Carlo packages n Ш Ш Main components: Data base of cross-sections and other parameters Theoretical base Random number generator Tool for geometry description § Main aspirations: Ш Extended range of ability Ш Flexibility § Examples: MNCP, Fluka, Geant 4, Vulcanu, PYTHIA, ARIADNE and so on JASS-06

GEANT 4 Geant 4: status Geant 4 is a detector description and simulation tool Application areas: High-energy physics, nuclear experiment, medical, accelerator and space physics studies Geant 4 is a free software It can be downloaded from URL: http: //geant 4. cern. ch History: 1974 – GEANT first version 1982 – the appearance of GEANT 3 1998 December – first release of GEANT 4 Operating systems: Unix, Linux, Windows JASS-06

GEANT 4 Main features GEANT 4 is written in C++ GEANT 4 is based on an object-oriented technology Experiment stages: n Detector description n Source description n Physics description n Detector reaction description JASS-06

Fluka: status 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: n n n n - Hewlett-Packard 9000 Series 700/800 running HP-UX - Sun running Sun. OS - Intel PCs running LINUX: - Red. Hat 7. 3 History: - Red. Hat 9. 0 First generation – the Fluka of the 70 th - Scientific Linux 4. 1 ` Second generation – the Fluka of the 80 th - Fedora Core Third generation – the Fluka of today JASS-06

Fluka 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+00 BEAMPOS 0. 0 PROTON 0. 0 -50. 0 JASS-06

Comparison: main features Geant 4 Fluka photoelectric effect: Compton effect: - recommended value for threshold for Fluka pair production: multiple scattering: threshold energy

Conclusion Both Fluka and Geant 4 provide with ability of simulation particles transport in a very extended energy range. JASS-06

Future plans To receive results from Fluka n To process them n To compare them with Geant 4 n To parallel both Fluka and Geant 4 n JASS-06

Thank you for attention