NEA-1525: PENELOPE2008.1, A Code System for Monte-Carlo Simulation of Electron and Photon Transport

Program-name Package-ID Status PENELOPE NEA-1525/01 Obsolete PENELOPE NEA-1525/02 Obsolete PENELOPE2000 NEA-1525/03 Obsolete PENELOPE2001 NEA-1525/04 Obsolete PENELOPE2001 NEA-1525/05 Obsolete PENELOPE2003-COURSE NEA-1525/06 Obsolete PENELOPE2003 NEA-1525/07 Obsolete PENELOPE2003 NEA-1525/08 Obsolete PENELOPE2005-COURSE NEA-1525/09 Obsolete PENELOPE2005 NEA-1525/10 Obsolete PENELOPE2006-COURSE NEA-1525/11 Obsolete PENELOPE2006 NEA-1525/12 Obsolete PENELOPE2008-COURSE NEA-1525/13 Obsolete PENELOPE2008 NEA-1525/14 Obsolete PENELOPE2008-COURSE NEA-1525/15 Obsolete PENELOPE2008.1 NEA-1525/16 Tested

Machines used: Package-ID Orig.Computer Test Computer NEA-1525/16 Linux-based PC,PC Windows,UNIX W.S. IBM PC,PC Windows

3. DESCRIPTION OF PROGRAM OR FUNCTION - PENELOPE performs Monte Carlo simulation of coupled electron-photon transport in arbitrary materials and complex quadric geometries. A mixed procedure is used for the simulation of electron and positron interactions (elastic scattering, inelastic scattering and bremsstrahlung emission), in which 'hard' events (i.e. those with deflection angle and/or energy loss larger than pre-selected cutoffs) are simulated in a detailed way, while 'soft' interactions are calculated from multiple scattering approaches. Photon interactions (Rayleigh scattering, Compton scattering, photoelectric effect and electron-positron pair production) and positron annihilation are simulated in a detailed way.

The following features are specific to the 2001 and later versions of the code:

1) The simulation parameters (Eabs, C1, C2, Wcc and Wcr) are defined independently for each material. This allows the user to specify regions of interest where the simulation is performed in greater detail.
2) The argument DSMAX of subroutine JUMP specifies the maximum allowed path length between hard interactions of electrons and positrons. By selecting a suitably small value for this parameter,
the user can control the number of hinges in thin regions (which must be larger that 10 or so, to ensure accuracy). This argument is also used for simulating the transport of charged particles in the presence of static external electric and magnetic fields. DSMAX has no effect when set equal to a very large number (e.g. 10**35).
3) The structure of the common /TRACK/ differs from previous versions. The variable ILB(5), which describes the origin of secondary particles, can be used to study partial contributions from particles originated by a given process.


The following features are specific to the 2003 and later versions of the code:

1) The generation of fluorescent radiation (x rays and Auger electrons) resulting from ionization of inner shells by impact of electrons and positrons is described as an independent process. The adopted ionization cross sections were calculated by using the relativistic Born approximation with a generalized oscillator strength model built from the partial photoelectric cross section of the active electron shell. This gives a more accurate description of the generation of characteristic x rays by electron and positron impact.
2) The energies of characteristic x rays are set equal to their experimental values (in previous versions of the code they were calculated from the ionization energies of the active electron shells).
3) The simulation algorithm for electron and positron inelastic collisions has been re-coded to allow more flexibility in the description of the physics and also to improve the simulation speed. Apart from a certain gain in speed (which is higher for heavy elements) this feature is not "visible" from the user's main program.
4) The program TABLES.F, which produces tables of interaction properties (photon mass attenuation coefficients, electron/positron mean free paths, stopping powers, radiation yields, ranges,...) for arbitrary materials, has been included in the distribution package.


The following features have been added to the 2005 version of the code:

1) Version 2005 includes the new program PENMAIN, that works like a blackbox for solving a large variety of problems with quadric geometries. With PENMAIN occasional (and normal) users can solve problems without having to write a single program line.
2) The program TABLES gives access to additional details of the interactions physics, both in a numeric and graphical way, e.g. the energy loss of electrons, or the photon attenuation coefficients in a material.
3) TIMER subroutines have been modified, according to a suggestion from a user from the NEA Data Bank, and are portable now (so far these work correctly with all compilers, under Windows or Linux).
4) Also following a suggestion from a NEA Data Bank user, unit 6 is no longer the standard output unit, except when the program makes a fatal error and stops. Now it is possible to write messages on the screen (like number of simulated showers) at predefined intervals, and consequently, it is possible to follow the program execution.
5) The electron elastic differential cross-sections are now obtained through partial wave analysis (PWA). Before only the total cross-section and the two first momenta of the differential cross-sections were considered..
6) The atomic disexcitation process following the vacancies in the M layer is now described. Before only the X rays and Auger electrons resulting from the vacancies in the K and L layers were described.
7) Some improvements have introduced in the geometry subroutine (PENGEOM). For instance, now it is possible to clone objects.
8) Consequently, some changes had to be made in the geometry viewers. For instance GVIEW allows to visualise materials and shapes (before only materials).


Improvements in the 2006 version compared to version 2005.
1) The correction for the energy dependence of the stopping power and the energy straggling parameter for soft interactions of electrons and positrons has been improved.
2) The sampling algorithm for Rayleigh scattering (which caused the g77 compiler to issue multiple warning messages) has been reformulated and improved.
3) Numerical interpolations, particularly those of elastic-scattering differential cross sections, are more accurate.
4) The structure of several common blocks has been modified to make interaction properties accessible from the program TABLES, and to facilitate future extensions of the interaction database. The names of interaction physics routines have been modified to allow the use of multiple models for each interaction mechanism.
5) The geometry package PENGEOM has been expanded. The present version can handle complex quadric geometries with up to 9,999 surfaces and 5,000 bodies. This extension required slight changes in the FORMAT of the geometry definition files (old files can be adapted with little editing work).
The geometry enclosure is defined as a sphere of 1.0e7 cm radius. This corrects a bug in the 2005 version (which caused inconsistencies when the whole material system was enclosed in a single module and this module was not simply connected).
6) The manual (penelope-2006-NEA.pdf) has been expanded and adapted to the present structure of the code.


Improvements in the 2008 version compared to version 2006.
This new version incorporates substantial changes and additions to the previous versions (1996, 2000, 01, 03, 05 and 06), which aim at improving both reliability and generality of the code system. As for the physics, the ionisation of inner shells by electron and positron impact is now described by using a numerical database of total cross sections for K, L and M shells, which was calculated from the theory described by Bote and Salvat (2008). Also included are photon polarisation effects in Rayleigh and Compton scattering, as well as refinements in the modelling of Rayleigh photon scattering and of inelastic collisions of electrons and positrons. The distribution package includes two examples of main programs: pencyl (for transport in cylindrical geometries), and penmain (for generic quadric geometries). In the present version, these codes are more flexible and allow a number of new options (e.g., extended sources, photon polarisation, and calculation of energy distributions of average fluence in selected bodies). The geometry viewers have also been improved to allow the easy identification of body labels.


Changes in the 2008.1 version:
1) The implementation of Bielajew's random hinge method has been modified. Soft angular deflections are sampled by assuming that the energy of the particle along the step decreases at a constant rate.
2) In the source file 'penelope.f', the RITA subroutines have been modified to allow a more accurate calculation of moments from the interpolating rational function.
3) In PENGEOM, surfaces defined as SURFACE* are never altered. That is, these surfaces are effectively fixed in space. In previous versions, when a SURFACE* was used in the definition of a module, possible translations or rotations of that module affected the surface.
4) A bug in PENGEOM (version 2008 only), which caused inconsistencies for geometries with infinite bodies, has been corrected. Note that now the enclosure is assumed to have a finite volume.
5) A (short) list of errata of the 2008 manual has been included in the .\doc directory.

4. METHOD OF SOLUTION - The Monte Carlo method is used. A sufficiently large number of particle histories is simulated, and relevant quantities are obtained as averages.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM - Electron and positron kinetic energies must be in the range from 100 eV to 1 GeV and plural or multiple scattering conditions have to be fulfilled, i.e. the number of both elastic and inelastic interactions in the material must be larger than about 10. Photon energies should be in the range from 100 eV (or the M-shell absorption edge, whichever is the largest) to 1 GeV. Photo-nuclear reactions are disregarded.

6. TYPICAL RUNNING TIME - The running time largely depends on the number of histories to be simulated, the kind of incident particle, its initial energy and the considered geometry. The adopted simulation parameters (energy cutoffs, etc.) also influence the computing time. As an example, a broad-beam depth-dose distribution of 10 MeV electrons incident on a water phantom, obtained by simulating 100.000 histories, can be obtained with a running time of some 320 s on an Intel Pentium III at 733 MHz with 128 MB RAM.

7. UNUSUAL FEATURES OF THE PROGRAM - The mixed simulation algorithm for electrons and positrons implemented in PENELOPE reproduces the actual transport process to a high degree of accuracy and is very stable even at low energies. This is partly due to the use of a sophisticated transport mechanics model based on the so-called random hinge method, with energy-loss corrections for soft events. Other differentiating features of the simulation are a consistent description of angular deflections in inelastic collisions and of energy-loss straggling in soft stopping events. Binding effects and Doppler broadening in Compton scattering are also taken into account.

9. STATUS
NEA-1525/01: 19-JUN-1998 Obsolete
NEA-1525/02: 16-MAY-2001 Obsolete
NEA-1525/03: 10-JAN-2002 Obsolete
NEA-1525/04: 10-JAN-2002 Obsolete
NEA-1525/05: 21-JUL-2003 Obsolete
NEA-1525/06: 21-JUL-2003 Obsolete
NEA-1525/07: 21-AUG-2003 Obsolete
NEA-1525/08: 02-SEP-2005 Obsolete
NEA-1525/09: 05-SEP-2005 Obsolete
NEA-1525/10: 30-JUN-2006 Obsolete
NEA-1525/11: 08-JUN-2006 Obsolete
NEA-1525/12: 09-DEC-2008 Obsolete
NEA-1525/13: 30-JUN-2008 Obsolete
NEA-1525/14: 02-OCT-2009 Obsolete
NEA-1525/15: 04-SEP-2009 Obsolete
NEA-1525/16: 02-OCT-2009 Tested at NEADB

10. REFERENCES  -
- F.Salvat, J.M. Fernandez-Varea, E.Acosta and J.Sempau:
  "PENELOPE, A Code System for Monte Carlo Simulation of Electron
  and Photon Transport",
  Proceedings of a Workshop/Training Course,
  OECD/NEA 5-7 November 2001
  NEA/NSC/DOC(2001)19.  ISBN:92-64-18475-9
- J. Sempau, E. Acosta, J. Baro, J.M. Fernandez-Varea and F.Salvat:
  An algorithm for Monte Carlo simulation of the coupled
  electron-photon transport.
  Nuclear Instruments and Methods B 132 (1997) 377-390.
- J. Sempau, J.M. Fernandez-Varea, E. Acosta and F. Salvat:
  Experimental benchmarks of the Monte Carlo code PENELOPE.
  Nuclear Instruments and Methods B 207 (2003) 107-123.
NEA-1525/16:
- F.Salvat, J.M. Fernandez-Varea, and J.Sempau:
PENELOPE-2008, A Code System for Monte Carlo Simulation of Electron and
Photon Transport, OECD ISBN 978-92-64-99066-1
- Tutorial for PENELOPE (version 2008)

11. MACHINE REQUIREMENTS - There are no specific requirements for the PENELOPE kernel. However the time subroutine, which is used in the example programs, must be adapted to the user''s operating system. The included time routines are those standard of Fortran 90.

NEA-1525/16:

Tested at the NEA Databank on PC DOS, under Windows XP Pro

12. PROGRAMMING LANGUAGE(S) USED -
NEA-1525/16: FORTRAN

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED - Any operating system supporting a FORTRAN 77 compiler. Fortran 90 compatible.

NEA-1525/16:

Tested at the NEA Databank using compiler Compaq Visual Fortran Professional Edition 6.6a

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS - None.

15. NAME AND ESTABLISHMENT OF AUTHORS -
Francesc Salvat and Jose Maria Fernandez-Varea
Facultat de Fisica (ECM), Universitat de Barcelona
Diagonal 647, 08028 Barcelona, Spain

Josep Sempau
Institut de Tecniques Energetiques,
Universitat Politecnica de Catalunya
Diagonal 647, 08028 Barcelona, Spain

16. MATERIAL AVAILABLE -
NEA-1525/16:
tutorial.pdf Tutorial
manual.pdf Brief description of the PENELOPE system and its use
Official release of the PENELOPE documentation
\fsource \ FORTRAN 77 source files of the PENELOPE code system
\pendbase\ Files necessary for creating material data files
\other\ Additional software
\mains\ pencyl, penmain, and penslab modules of PENELOPE

17. CATEGORIES -

- J. Gamma Heating and Shield Design

Keywords: Monte Carlo method, bremsstrahlung, high-energy reactions, photon transport, positrons