Monte Carlo Methods to Model Radiation Interactions and Induced Damage - Radiation Damage in Biomolecular Systems - page 209

dominant for low-LET particles such as electrons. Although Geant4 cannot handle
mutual interactions between particles, Geant4-DNA is currently being extended for
the simulation of such physico-chemistry processes.
These developments should become publicly available soon in upcoming re-
leases of the general-purpose Geant4 simulation toolkit. We expect they will offer
users an open-source alternative to already existing advanced codes [ 34 ] usually
designed for specific applications and not easily accessible.

13.3 PENELOPE

PENELOPE is a general-purpose Monte Carlo code system for the simulation of
coupled electron-photon transport in arbitrary materials, which has been developed
at the University of Barcelona over the last 15 years [ 14 , 35 , 36 ]. The name, an
acronym for “PENetration and Energy LOss of Positrons and Electrons”, was
inherited from earlier works of the authors on the transport of low-energy electrons
in solids, where the conventional detailed simulation (i.e., interaction by interaction)
is applicable. This background naturally lead to the adoption of mixed simulation
schemes (class II schemes in the terminology of Berger [ 9 ]) for electrons and
positrons, which is the most characteristic feature of PENELOPE .
PENELOPE allows the simulation of electron-photon showers in material systems
consisting of homogeneous bodies with arbitrary chemical compositions, for an
energy range from 50 eV to 1 GeV (although the interaction database extends down
to 50 eV, results for energies less than about 1 keV should be regarded as semi-
quantitative). The interaction models implemented in the code are based on the most
reliable information currently available, limited only by the required generality of
the code. These models combine results from first-principles calculations, semi-
empirical models and evaluated databases.
The core of the code system is a Fortran subroutine package that generates
electron-photon showers in homogeneous materials. These subroutines are invoked
from a main steering program, to be provided by the user, which controls the
evolution of the tracks and keeps score of the relevant quantities. The code system
also includes a flexible subroutine package for automatic tracking of particles within
quadric geometries (i.e. systems consisting of homogeneous bodies limited by
quadric surfaces) and a geometry viewer and debugger. A generic main program,
called PENMAIN , allows the simulation of a variety of radiation sources in arbitrary
quadric geometries; the user can define impact detectors and energy-deposition
detectors to extract information from the simulation. The operation of PENMAIN
is completely controlled from an input file. The latest public version of PENELOPE ,
released in 2008, is available from the OECD Nuclear Energy Agency Data Bank
( http://www.nea.fr ).
PENELOPE has been applied to a wide variety of problems in dosimetry,
microdosimetry, radiotherapy, radiation protection, nuclear spectroscopy, electron
microscopy, electron probe microanalysis, etc. A comprehensive comparison of