LOW–MAT

Summary

Sets the correspondence between FLUKA materials and low-energy neutron cross sections ​​ ​

​ See also LOW–NEUT

WHAT(1) =

number or name of the FLUKA material, either taken from the list of standard FLUKA materials (see Tables 260 neutron, 42 gamma group library and 5.3, or defined via a MATERIAL option.

Default

:  No default!

WHAT(2) =
first numerical identifier of the corresponding low-energy neutron material.​
Not used if = 0.0
WHAT(3) =
second numerical identifier of the corresponding low-energy neutron material.
Not used if = 0.0
WHAT(4) =
third numerical identifier of the corresponding low-energy neutron material.
Not used if = 0.0
WHAT(5) =

Not used.

WHAT(6) =

Not used.

SDUM

= name of the low-energy neutron material

Default

: same name as the FLUKA material

Default

(option LOW-MAT not given): correspondence between FLUKA and low-energy neutron materials is by name. In case of ambiguity, the first material in the relevant list is chosen.


Notes

  1. Each material in the FLUKA low-energy neutron libraries​ (see Low-energy neutrons in FLUKA) is identified by an alphanumeric​ name (a string of ≤ 8 characters, all in upper case), and by three integer numbers. Correspondence with FLUKA materials (standard or user-defined) is based on any combination of name and zero or more identifiers. In case of ambiguity, the first material in the list fulfilling the combination is selected.​

  2. Option LOW–MAT should be avoided if it is not really necessary (experience has shown that it is often misinterpreted by beginner users). The option is not required if the following 3 conditions are all true:

    • the low-energy neutron material desired is unique or is listed before any other material with the same name in Table 10.3
      and
    • that name is the same as one in the FLUKA list (Table 10.3) or as given by a MATERIAL option
      and

    • there is only one FLUKA material associated with that low-energy neutron material

  3. On the other hand, the option is required in any one of the following cases:

    • there is more than one low-energy neutron material with that name (this can happen because of data sets coming from different sources, or corresponding to different neutron temperatures, or concerning different isotopes, or weighted on different spectra, etc), and the one desired is not coming first in the list. In this case it is sufficient to provide just as many identifiers as required to remove ambiguity
      or
    • The FLUKA name is different from the name of the low-energy neutron material
      or

    • There is more than one FLUKA material associated with the given low-energy neutron material. This can happen for instance when the same material is present with different densities in different regions. In reality this is a special case of ii) above, since to distinguish between the different densities, different names must be used and one at least will not be equal to the name of the low-energy neutron material.

Example (number based):

*...+....1....+....2....+....3....+....4....+....5....+....6....+....7...+...8
MATERIAL          6.       0.0     2.000        6.       0.0       0. CARBON
MATERIAL          6.       0.0     1.700       15.       0.0       0. GRAPHITE
MATERIAL          6.       0.0     3.520       16.       0.0       0. DIAMOND
LOW-MAT         15.0        6.       -3.      296.       0.0       0. CARBON
LOW-MAT         16.0        6.       -2.      296.       0.0       0. CARBON
*  We have three materials with the same atomic composition, but different
*  density (amorphous carbon, graphite and diamond). Graphite is declared as
*  having the cross section of Graphite bound natural Carbon, while diamond
*  is declared as having the same low-energy neutron cross section as Free Gas
*  Carbon.

The same example, name based:

*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
MATERIAL          6.       0.0     2.000       0.0       0.0       0. CARBON
MATERIAL          6.       0.0     1.700       0.0       0.0       0. GRAPHITE
MATERIAL          6.       0.0     3.520       0.0       0.0       0. DIAMOND
LOW-MAT     GRAPHITE        6.       -3.      296.       0.0       0. CARBON
LOW-MAT      DIAMOND        6.       -2.      296.       0.0       0. CARBON