PENELOPE 2003 - OECD Nuclear Energy Agency

166 Chapter 5. Constructive quadric geometry
10 15 cm radius) that is supposed to satisfy this condition. Make sure that the
system does not contain bodies that extend outside the enclosure (this normally
will cause errors).
◦ The rotation and the translation are optional and apply to all elements of the
module. The line filled with 1’s ends the definition of elements and starts that of
transformation parameters (it can be skipped if no transformation parameters are
entered). The I3 value following each parameter has the same meaning as above.
It has to be negative or zero to make the parameter value effective; otherwise, the
parameter must be set from the main program.
A single surface can be used to define several bodies and/or submodules in the same
module; unnecessary duplication of a surface reduces the calculation speed. Notice,
however, that rotation or translation of a module modifies all the surfaces of its descendants
and, therefore, a transformed surface must be redefined to be used again. Thus,
if the system contains two identical modules in different positions (e.g. two detectors
in a coincidence experiment), each of them must be defined explicitly. This does not
require too much editing work; after generating the first of the two modules, we can just
duplicate its definition data sets and change their labels.
The INCLUDE option allows inserting a predefined structure (e.g. a scintillation detector,
an encapsulated nuclear source, . . . ) within the geometry file. The inserted
structure is defined by a complete definition file (i.e. ending with an “END-----” line).
The labels of the objects in the included file must be different from the labels used in
the main file and in any other included file. The format of an INCLUDE block is the
following,
0000000000000000000000000000000000000000000000000000000000000000
INCLUDE
FILE= (filename.ext)
0000000000000000000000000000000000000000000000000000000000000000
The name of the included file must be written between the parentheses. It may be up
to twelve characters long; if it is shorter, the blanks must be left at the right end of
the field. Only one-level INCLUDES are allowed, i.e. an included file cannot contain any
INCLUDE blocks.
The definition of the geometry may seem somewhat more laborious than with combinatorial
methods, where the system is described by combining basic bodies of several
simple shapes [see Jenkins et al. (1988) and references therein]. In practice, however,
defining the various surfaces that limit a body may be more convenient, and intuitive,
than considering all the parameters needed to specify that body. The example of a right
elliptical cylinder, which needs 9 parameters, is quite illustrative. With our method, this
body can be defined as a module by means of two planes perpendicular to the z-axis
(only one parameter if the base is the z = 0 plane) and a scaled cylinder (2 parameters);
the rotation (3 parameters) of the module gives the required orientation and the
translation (3 parameters) puts it in the required position. The definition as a proper
body requires defining the three surfaces that limit the cylinder in its actual position,