PENGEOM: tools for handling complex quadric geometries in Monte Carlo simulations of radiation transport

Servicio de Radiofísica y P.R., Hosp. Univ. Virgen de las Nieves, Granada, Spain; Institut für Theoretische Physik, Goethe-Universität Frankfurt, Frankfurt am Main, Germany; Departamento de Ciencias Físicas, Universidad de La Frontera, Temuco, Chile; Facultat de Física, Universitat de Barcelona, Barcelona, Spain and Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, Granada, Spain, through the OECD NEA Data Bank, Boulogne-Billancourt, France.

Fortran, C and Java source code (C840MNYCP00).

The Fortran subroutine package PENGEOM and the associated graphical user interface PenGeomJar constitute a complete set of tools for handling complex quadric geometries in Monte Carlo simulations of radiation transport. The material structure where radiation propagates is assumed to consist of homogeneous bodies limited by quadric surfaces. The PENGEOM subroutines (a subset of the PENELOPE code) automatically track particles through the material structure, independently of the details of the physics models adopted to describe the interactions. These subroutines are designed for detailed simulation schemes, where all individual interactions of the transported particles are simulated sequentially. They also work with mixed (class II) schemes for high-energy charged particles, where the effect of soft interactions is described by the random-hinge method. The tracking algorithm and the definition of the geometry are tailored to optimize simulation speed. The Java graphical user interface allows editing and debugging the geometry definition file, as well as visualizing the material structure.

Particle trajectories are generated following a detailed or class II simulation scheme. Intersections of rays with limiting quadric surfaces are calculated analytically. Because of round-off errors, the effective resolution worsens when the distance to the origin of coordinates increases. The impact of these errors is reduced by considering that limiting surfaces are fuzzy. The PENGEOM subroutines are capable of resolving a sphere of unit radius located at a distance of 107 length units from the origin.

The connection between the steering main program and the tracking routines is through a Fortran module, which contains the state variables of the transported particle. The generation of a particle trajectory reduces to a call to subroutine LOCATE, which initializes the track, and a sequence of calls to subroutine STEP, which moves the particle across the material structure.

**6. RESTRICTIONS
OR LIMITATIONS**

By default PENGEOM can handle systems with up to 5,000 bodies and 10,000 surfaces. These numbers can be increased by editing the Fortran source file.

The running time much depends on the complexity of the geometrical structure. The most complex example provided is an anthropomorphic phantom with 264 surfaces and 169 bodies. The rendering of 2D images of that phantom is almost instantaneous, while the generation of 3D images with 1680 × 1050 pixels takes about 25 seconds on an Intel Core I7-3520M CPU with Windows 7

Minimal

Fortran, C, and JAVA compliant
compilers.

**Documentation
included in package:**

PENGEOM - A
general-purpose geometry package for Monte Carlo simulation of radiation
transport in complex material structures: Almansaa, Julio; Salvat-Pujolb,
Francesc; Diaz-Londo~noc, Gloria;
Carnicerd, Artur; Lallenae, Antonio M.;
Salvat, June 9^{th} 2015

Included in CD distribution are documents, Fortran, C source, Linux and Windows GUI interfaces and data files. (C840MNYCP00) (NEA-DB ID: NEA-1886/02)

October 2016

**KEYWORDS:**MONTE CARLO, RAY-TRACING