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GEOBEGIN


    Starts the geometry description

    See also GEOEND, PLOTGEOM

     
WHAT(1)
: not used
WHAT(2)
> 0.0 : absolute accuracy parameter (Aa) in units of 1.E-6 cm. It is used for tracking and boundary identification. Aa should be larger than Ar*L , where L is the largest coordinate value in the geometry description (excluding the outer blackhole shell containing it) and Ar is the relative accuracy achievable in double precision (of the order of 1.E-14 - 1.E-15).
Default
= 0.0001
WHAT(3)
> 0.0 : logical unit for geometry input. The name of the corresponding file must be input on the next card if
WHAT(3)
is different from 5. Note that values of
WHAT(3)
/= 5.0 and < 21.0 must be avoided because of possible conflicts with FLUKA pre-defined units.
Default
= 5.0 (i.e. geometry input follows)
WHAT(4)
> 0.0 : logical unit for geometry output. If different from 11, the name of the corresponding file must be input on the next card if
WHAT(3)
= 0 or 5, otherwise on the card following the next one. Values of
WHAT(3)
/= 11.0 and < 21.0 must be avoided because of possible conflicts with FLUKA pre-defined units.
Default
= 11.0 (i.e. geometry output is printed on the standard output)
WHAT(5)
: parentheses optimisation level = i0 + i1 x 1000 i0 = 1: logical optimisation only activated 2: logical + "plane" optimisation activated 3: logical + "plane" + "bounding box" optimisation activated (
Default
: 3) i1 > 0 forces optimisation even if no parentheses are found in the region under scrutiny (
Default
: 0) * Start_Devel_seq
WHAT(6)
: if > 0 it indicates the number of geometry output lines to be skipped before starting writing debugging lines. Please note that the output can rapidly become huge * End_Devel_seq * Start_Prod_seq *
WHAT(6)
: not used * End_Prod_seq
SDUM
= COMBINAT : Combinatorial geometry is used. See section on Combinatorial Geometry for input description Other geometries, available in older versions of FLUKA, are no longer supported.
Default
: COMBINAT
SDUM
= COMBNAME : Combinatorial geometry is used in free format, and names can be used instead of body and region numbers
SDUM
= FLUGG : The FluGG interface to the Geant4 geometry is used. In this case, the GEOEND card must immediately follow the GEOBEGIN card. The FluGG interface is available and described on the fluka web site
Default
: COMBINAT
Default
(option GEOBEGIN not given): not allowed! GEOBEGIN and GEOEND must always be present.
Notes:
1) Geometry input and output: i) If
WHAT(3)
and
WHAT(4)
are both =< 0, the geometry input and output are part of the standard I/O streams: the GEOBEGIN card must be immediately followed by the Combinatorial Geometry input, and then by GEOEND. (See Example 1 below). ii) If
WHAT(3)
is > 0 (and not = 5) and
WHAT(4)
is =< 0, GEOBEGIN must be followed by one card with the name of the CG input file, and then by GEOEND. (See Example 2 below). iii) If
WHAT(4)
is > 0 (and not = 11) and
WHAT(3)
is =< 0, GEOBEGIN must be followed by one card with the name of the CG output file, then by the CG input, and then by GEOEND. (See Example 3 below). iv) Otherwise, if
WHAT(3)
is > 0 (and not = 5), and
WHAT(4)
is > 0 (and not = 11), GEOBEGIN must be followed, in the order, by a line with the name of the CG input file, another line with the name of the CG output file and the GEOEND card. (See Example 4 below). The first part of the CG output (9}) is essentially an echo of the input, and gives in addition some information on storage allocation of body and region data. Then follow an "Interpreted body echo" and an "Interpreted region echo", useful in the case where free geometry input format has been requested. It is recommended to check on this output that the geometry description has been correctly reproduced, especially if fixed input format has been chosen, since column alignment errors are critical due to the CG strict input format. In case of severe error ("next region not found", or similar) the CG output will also contain all error and debugging messages. Minor tracking problems, however, are reported on the error message file (logical unit 15, see Chap. 3} and Sec. 9.4}, unless reporting has been de-activated by setting
WHAT(1)
<= 0.0. 2) Special algorithms have been implemented in the Combinatorial Geometry package of FLUKA in order to minimise tracking errors due to rounding, to improve tracking speed and to handle charged particle transport near boundaries and in magnetic fields. 3) A voxel geometry is also available in FLUKA 8.2.11}. It is fully integrated into the FLUKA CG and it is even possible to describe a geometry partly as made of voxels and partly of conventional CG regions. 4) Information on how to set up Combinatorial Geometry input is given in Chap. 8} 5) End of geometry information must end with a GEOEND card. The same card can also be used to activate a geometry debugger. 6) Option PLOTGEOM allows to draw sections of the geometry on planes specified by the user. 7) Only one GEOBEGIN card is allowed. 8) The
WHAT(2)
parameter might need to be increased in case of very large geometries (i.e. L> 100 m).
Example 1:
* CG Input follows, output is printed as part om Main Output *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+... GEOBEGIN 0. 0. 0. 0. 0. 0.COMBINAT
Example 2:
* CG Input read from file BigHall.geo, output printed as part om Main Output *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+... GEOBEGIN 0. 0. 25. 0. 0. 0.COMBINAT BigHall.geo
Example 3:
* CG Input follows, output is printed on file geo2.out *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+... GEOBEGIN 0. 0. 0. 26. 0. 0.COMBINAT geo2.out
Example 4:
* CG Input read from file BigHall.geo, output printed on file geo2.out *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+... GEOBEGIN 0. 0. 25. 26. 0. 0.COMBINAT BigHall.geo geo2.out

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