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8.7} LATTICE card


 This is an optional card for modular geometries. Its use needs some
 more effort and preparation:

* The basic unit of the geometry, composed by an arbitrary number of
regions, must be described in full detail in the body and region data.
* Additional body and region data must also be provided to describe
"container" regions representing the "boxes", or lattice cells, wherein the basic unit has to be replicated. No material assignment is needed for these lattice-cell regions.
* A roto-translation must be defined (option ROT-DEFI) and
associated with each lattice to provide the transformation bringing from any point and direction inside each lattice cell to the corresponding point and direction in the basic unit. Alternatively, a user routine (LATTIC, see 13}) can be written for the same purpose.
* The LATTICE card itself identifies the lattice cells and establishes the
correspondence between region number and lattice cell number, where the region number is the sequential number in the region table, and the lattice cell number is that used in the tracking to address the transformation routine, and is chosen by the user. Contiguous numbering is recommended for memory management reasons, but is not mandatory. Non-contiguous numbering can be done using several LATTICE cards. In the LATTICE card, the meanings of the WHAT parameters are:
WHAT(1)
= "Container-region" number of the first lattice cell ("From region
WHAT(1)
...") No default
WHAT(2)
= "Container-region" number of the last lattice cell ("...to region
WHAT(2)
...")
Default
=
WHAT(1)
WHAT(3)
= step length in assigning "Container-region" numbers ("...in steps of
WHAT(3)
").
Default
= 1.
WHAT(4)
= lattice number of the first lattice cell (or corresponding name), assigned to region
WHAT(1)
No default
WHAT(5)
= lattice number of the last lattice cell (or corresponding name), assigned to region
WHAT(2)
WHAT(6)
= step length in assigning cell numbers/names ("...in steps of
WHAT(6)
").
Default
= 1.
SDUM
= possible index of transformation associated with this lattice. Exceptionally, here
SDUM
can contain an integer number, in free format, following any of the strings "ROT#", "Rot#", "rot#", "RO#", "Ro#", "ro#. If any one of such strings is present, an integer identifying the associated roto-translation is read in the following characters. If no such string is found, the LATTIC user routine will be called whenever a transformation is required. A single geometry can be a mixture of modular areas, described by lattices, and "normal" areas, described by standard regions. Many different LATTICE cards may be issued in the same geometry, when different symmetries are present in different areas. In principle, any analytical symmetry transformation can be implemented (rotation, translation, reflection, or combination of these). Care must be taken to ensure that any region in the basic unit is fully contained (after coordinate transformation) in any lattice cell belonging to its symmetry transformation. Regions falling across two different lattice cells would lead to unpredictable behaviour. The basic unit does not need necessarily to describe a "real" geometry region, but can as well be used only as a prototype to reproduce in any number of "copies". NOTE: The lattice cell regions do not need to be included in the other input option cards. Materials, thresholds, etc, must be assigned ONLY to the regions contained in the basic unit. Of course, this implies that all copies of a same basic unit share the same material, setting and biasing properties.

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