SRNA-2K5: Proton Transport Simulation by Monte Carlo Techniques.

Institute of Nuclear Sciences VINCA Physics Laboratory (010), Beograd, Serbia, through the OECD Nuclear Energy Agency Data Bank, Issy-les-Moulineaux, France.

Fortran 77 and C, PC and Mac (C00789PCX8600).

SRNA-2K5 performs a Monte Carlo transport simulation of protons in 3D source and 3D geometry of arbitrary materials. The proton transport is based on a condensed history model and on a compound nuclei decay model created in non-elastic nuclear interaction by proton absorption.

The SRNA-2K5 package is developed for time independent simulation of proton transport by Monte Carlo techniques for numerical experiments in complex geometry using PENGEOM from PENELOPE with different material compositions and arbitrary spectrum of proton generated from the 3D source. This package, developed for 3D proton dose distribution in proton therapy and dosimetry, is based on the theory of multiple scattering. The compound nuclei decay was simulated by our model and Russian MSDM models using ICRU 49 and ICRU 63 data. If protons trajectory are divided on a great number of steps, proton passage can be simulated according to Berger’s Condensed Random Walk model. Conditions of angular distribution and fluctuation of energy loss determines the step length.

A physical picture of these processes is described by stopping power, Moliere’s angular distribution, Vavilov’s distribution with Sulek’s correction per all electron orbits, and Chadwick’s cross sections for non-elastic nuclear interactions, obtained by the GNASH code. According to physical pictures of protons passage (and with probabilities of protons transition from previous to next stage)

simulation of proton transport in all SRNA codes runs according to the usual Monte Carlo scheme:(i) protons from the spectrum prepared for random choice of energy, position and space angle is emitted from the source;

(ii) protons loose the average energy on the step;

(iii) on that step, protons experience a great number of collisions, and it changes direction of movement randomly chosen from angular distribution;

(iv) random fluctuation is added to average energy loss;

(v) proton step is corrected with data about the proton’s position before and after scattering;

(vi) there is final probability on step for non-elastic nuclear interactions to happen, and for the proton to be absorbed. Compound nuclei decays with the emission of protons, neutrons, deuterons, tritons, alpha particles or photons. Particular decay particles are sampled from a Poisson’s distribution with appropriate average values of multiplication factor of each particle. Energy and angle of particle emission and factors of multiplication are determined from the cross section obtained by the integration of differential cross section for non-elastic nuclear interaction. Energy and angle of secondary neutron are sampled from emission spectrum. Neutron and photon transport are not included in the current model. They are registered in the data file and can be used by other codes to simulate their transport. Emitted deuteron, triton and alpha particles are absorbed at creation.

Proton kinetic energies have to be in the range of 100 keV to 250 MeV. No more than 128 geometry zones and less than 32 materials with no more than 15 elements are permitted. In these conditions the user can obtain a geometrical image with gview2d.exe.

The adopted parameters (energy cutoffs, geometry zones, etc.) have an influence on the computing time.

PC compatible or Mac.

Executables are provided for Windows operating systems. Fortran and C compilers are required for Linux and Mac Operating Systems.

Radovan D. Ilic, “SRNA-2K5 - Protons Transport Simulation by Monte Carlo Techniques Version 2K5,” March, 2005 (User’s Guide).

Radovan D. Ilic, *et al*, SRNA - Monte Carlo
Codes for Proton Transport Simulation in Combined and Voxelized Geometries,” *NT&RP
2002 XVII 1-2* pp. 27-36.

Radovan D. Ilic, *et al*, “The Monte Carlo
SRNA-VOX Code for 3D Proton Dose Distribution in Voxelized Geometry Using CT
Data,” *Phys. Med. Biol*. 50 (2005) 1011–1017 (February 2005).

The package includes the referenced documents, source, data, executables for Windows OS and sample input and output files.

November 2011.

**KEYWORDS**: MONTE CARLO, PROTON, PROTON DOSE