PENELOPE 2003 - OECD Nuclear Energy Agency

The present version of PENELOPE is the result of continued evolution from the first version,
which was released in 1996. The idea of developing a general-purpose Monte Carlo code, with better
modelling than those available at that time, arose during a short course on radiation transport simulation
given by F. Salvat at the Radiation Metrology Unit, CIEMAT (Madrid), in 1988. The present version
2003 contains substantial changes/improvements to the previous versions 1996, 2000 and 2001. As for
the physics, the model for electron/positron elastic scattering has been revised, bremsstrahlung
emission is now simulated using partial-wave data instead of analytical approximate formulae,
photoelectric absorption in K and L shells is described from the corresponding partial cross sections,
and fluorescence radiation from vacancies in K and L shells is now followed. Refinements have also
been introduced in the electron/positron transport mechanics, mostly to account for the energy
dependence of the mean free paths for hard events. Inner-shell ionisation by electron and positron
impact is described as an independent mechanism by means of total cross sections obtained from an
optical-data model. The simulation routines have been re-programmed in a more structured (and
readable) way and new example MAIN programs have been written, with a more flexible input and
expanded output.
We have recently published a set of benchmark comparisons of simulation results with
experimental data (Sempau, et al., 2003), which involves radiation transport in multiple materials and
for a wide energy range. Overall, the agreement between PENELOPE results and experiment was
found to be excellent. These calculations can be easily reproduced by using the example MAIN
programs included in the distribution package.
This report is intended not only to serve as a manual of the simulation package, but also to
provide the user with the necessary information to understand the details of the Monte Carlo algorithm.
In Chapter 1 we give a brief survey of random sampling methods and an elementary introduction to
Monte Carlo simulation of radiation transport. The cross sections adopted in PENELOPE to describe
particle interactions, and the associated sampling techniques, are presented in Chapters 2 and 3. 2
Chapter 4 is devoted to mixed simulation methods for electron and positron transport. In Chapter 5, a
relatively simple, but effective, method to handle simulation in quadric geometries is presented.
The FORTRAN77 simulation package PENELOPE and other complementary programs, are described
in Chapter 6, which also provides instructions to operate them. Information on relativistic kinematics
and numerical methods is given in Appendices A and B. Finally, Appendix C is devoted to simulation
of electron/positron transport under external, static electric and magnetic fields. The source files of
PENELOPE, the auxiliary programs and the database are supplied on a ZIP-compressed file, which is
distributed by the NEA Data Bank. 3 The code is also available from the authors, but we would
appreciate it if users did try to get the code from this institution.
In the course of our Monte Carlo research, we have had the fortune of getting much help from
numerous friends and colleagues. Since the mid 1980s, we have benefited from discussions with
D. Liljequist, which gave shape to our first algorithm for simulation of electrons and positrons. We are
particularly grateful to A. Riveros for his enthusiastic and friendly support over the years, and for
guiding us into the field of microanalysis and X-ray simulation. A. Sánchez-Reyes and E. García-Toraño
were the first external users of the code system; they suffered the inconveniences of using continuously
changing preliminary versions of the code without complaining too much. More recently, stimulating
collaboration with A.F. Bielajew has led to substantial improvements in the electron transport
mechanics and in the code organisation. We are deeply indebted to J.H. Hubbell and D.E. Cullen for
kindly providing us with updated information on photon interaction and atomic relaxation data.
2 In these chapters, and in other parts of the text, the CGS Gaussian system of units is adopted.
3 OECD Nuclear Energy Agency Data Bank. Le Seine St. Germain, 12 Bd. des Iles. 92130 Issy-les-Moulineaux,
France. E-mail: nea@nea.fr; http://www.nea.fr
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