MATERIAL

Summary

Defines a single-element material or (coupled to a COMPOUND card) a compound ​​

​ See also COMPOUND, LOW–MAT, MAT–PROP
​
WHAT(1) =

atomic number​ (meaningful only when not coupled to a COMPOUND card; otherwise WHAT(1) must be = 0.0)

No default

WHAT(2) =

NOT to be filled. It allows to overwrite the default value of atomic weight​ (in g/mole)

Default

:  computed according to the natural composition of an element with atomic number WHAT(1) or to the identity of its isotope specified by WHAT(6). Meaningless if coupled to a COMPOUND card.

WHAT(3) =

density​ in g/cm\(^3\). Note that if the density is lower than 0.01, the material is considered to be a gas​ at atmospheric pressure​ unless set otherwise by MAT–PROP

No default

WHAT(4) =

number (index) of the material. NOT to be filled in case of name-based input.

Default

= NMAT+1, where NMAT is the greatest number of current defined materials. The number sequence of the defined materials must be uninterrupted. Its value is = 25 before any MATERIAL card is given, and doesn’t change if WHAT(4) overrides a number which has already been assigned.

WHAT(5) > 2.0:

alternate material number (or name, in name-based input) for ionisation processes​ (this material will be used instead of WHAT(1) for dE/dx etc.)

≥ 0.0

and ≤ 2.0: ignored

< 0.0:

reset to default

Default

:  no alternate material

WHAT(6) =

mass number of the material. Only integer values (still in real format) make sense.

Default

= 0 i.e. natural isotopic composition of the WHAT(1) element (but see Note 8). For isotopic composition​ other than natural or single isotope​​, see COMPOUND.

SDUM

= name of the material

No default

Default

(option MATERIAL not given): standard pre-defined material numbers are used (see list in Table 5.3).

Notes

  1. MATERIAL cards can be used in couple with COMPOUND cards in order to define compounds​, mixtures​ or isotopic compositions. See COMPOUND​ for input instructions.

  2. Material number 1.0 is always Black Hole​ (called also External Vacuum​) and it cannot be redefined. (All particles vanish when they reach the Black Hole, which has an infinite absorption cross section)

  3. Material number 2.0 is always Vacuum​ (of zero absorption cross section) and it cannot be redefined.

  4. In name-based inputs it is recommended to omit the number of the material​ (and use its name in COMPOUND​ and ASSIGNMAt ​ commands). On the contrary, if the input is number-based, it is not recommended to omit it.

  5. In an explicitely number-based input (declared as such by WHAT(4)= 4.0 in command GLOBAL​) it is allowed to redefine a material name overriding a number already assigned (either by default, see list in Table 5.3, or by a previous MATERIAL card), or by using a new number.

    If the number has not been assigned before, it must be the next number available (26.0, 27.0…for successive MATERIAL cards). In a number-based input, it is dangerous to leave empty gaps in the number sequence​, although the program takes care of redefining the number: in fact, the incorrect number is likely to be still used in other commands such as ASSIGNMAt and COMPOUND, leading to crashes or to undetected errors.

    If the input is name-based and the number is not given explicitly, the program automatically assigns it and the number sequence is automatically respected. The assigned number can be read from standard output, but the user only needs to refer to that material by its name in other input cards.

  6. Materials having a different density at the macroscopic and at the microscopic​ level (e.g. spongy matter or approximations for not entirely empty vacuum) need a special treatment regarding stopping power​ (density effect​). In such cases, see MAT–PROP.

  7. If low-energy neutron transport is desired, the material name must coincide with that of one of the low-energy neutron cross section materials in the FLUKA library (see The FLUKA neutron cross section library), or a correspondence must be set using option LOW–MAT.

  8. If the card concerns an element that does not exist in nature, setting WHAT(6) = 0.0 cannot provide the natural isotopic composition. Therefore a single isotope will be selected (usually the one with the longest half-life). To avoid confusion, it is suggested to declare explicitly instead the isotope desired.

  9. The largest atomic number that can be handled by FLUKA is 100.

Example:

*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
MATERIAL          1.            8.988E-5                 0.0       1. HYDROGEN
LOW-MAT     HYDROGEN        1.       11.      296.       0.0       0. HYDROGEN
MATERIAL          6.               2.265                 0.0       0. CARBON
MATERIAL          6.                 2.0                 0.0       0. GRAPHITE
LOW-MAT       CARBON        6.       -3.      296.       0.0       0. GRAPHITE
MATERIAL         41.                8.57                 0.0       0. NIOBIUM
MATERIAL         48.               8.650                 0.0       0. CADMIUM
MATERIAL         24.                7.19                 0.0       0. CHROMIUM
MATERIAL         27.                8.90                 0.0       0. COBALT
* Several (name-based) cases are illustrated:
* Hydrogen, pre-defined as material 3, is re-defined as monoisotopic 1-H.
* Command LOW-MAT has been added to force this material to be mapped to
* CH2-bound 1-H for what concerns low energy neutron transport.
* Carbon, pre-defined as material 6.0, is re-defined with a different density,
* and is also redefined with a different name (GRAPHITE), mapped to
* graphite-bound carbon.
* Niobium, Cadmium, Chromium and Cobalt are added to the list.