PENELOPE 2003 - OECD Nuclear Energy Agency

6.1. penelope 179
and/or numbers indicating the kind of calculation (TX for total x-section, DX for differential
x-section) or action (W for write data on a file, R for read data from a file, I for
initialization of simulation algorithm).
Thus, for instance, subroutine EEL simulates elastic collisions of electrons while subroutine
EINTX computes total (integrated) cross sections for inelastic scattering of electrons.
6.1.1 Database and input material data file
Penelope reads the required physical information about each material (which includes
tables of physical properties, interaction cross sections, relaxation data, etc.) from the
input material data file (identified as UNIT=IRD in the code source listing). The material
data file is created by means of the auxiliary program material, which extracts
atomic interaction data from the database. This program runs interactively and is selfexplanatory.
Basic information about the considered material is supplied by the user
from the keyboard, in response to prompts from the program. The required information
is: 1) chemical composition (i.e. elements present and stoichiometric index of each element),
2) mass density, 3) mean excitation energy and 4) energy and oscillator strength
of plasmon excitations. Alternatively, for a set of 279 prepared materials, the program
material can read data directly from the PDCOMPOS.TAB file (see below).
For compounds and mixtures, the additivity approximation is adopted to define the
material’s cross sections, i.e. the corresponding “molecular” cross section is set equal to
the sum of atomic cross sections weighted with the stoichiometric index of the element.
Alloys and mixtures are treated as compounds, with stoichiometric indices equal, or
proportional, to the percent number of atoms of the elements.
The penelope database consists of the following 465 ASCII files,
PDATCONF.TAB . . . Atomic ground-state configurations, ionization energies (Lederer
and Shirley, 1978) and central values, J i (p z = 0), of the one-electron shell Compton
profiles (Biggs et al., 1975) for the elements, from hydrogen to uranium.
PDCOMPOS.TAB . . . This file contains composition data, densities and mean excitation
energies for 279 materials, adapted from the database of the estar program
of Berger (1992). The first 98 entries are the elements Z = 1 − 98, ordered by
atomic number Z. Materials 99 to 279 are compounds and mixtures, in alphabetical
order. Notice that penelope does not work for elements with atomic number
Z > 92.
PDEFLIST.TAB . . . List of materials predefined in file PDCOMPOS.TAB, with their identification
numbers.
PDRELAX.TAB . . . Data on atomic relaxation, extracted from the LLNL Evaluated
Atomic Data Library (Perkins et al., 1991). Each line in the file PDRELAX.TAB
describes an atomic transition. The quantities listed are the atomic number of