Material Definition

Material directive allows to fine-tune an already defined material (e.g. water or PMMA), or to define a completely new material. A new material is described by a set of mandatory parameters:

ID = materialID

Name identifying the material

rho = (float)

Density of the material [g/cm³]

Ipot = (float)

Mean ionization potential [eV]

Lrad = (float)

Radiation length (g/cm²)

composition = [element_1,element_2,…]

Elemental composition of the material given as a list the short names of the elements. For instance, for water it would be [H,O].

fractions = [frac_1,frac_2,…]

Relative number fraction of elements given in the composition. Values are in percentage. For instance for water it would be [66.7,33.3].

weights = [frac_1,frac_2,…]

Relative weight fraction of elements given in the composition. Values are in percentage. For instance for water it would be [11.2,88.8].

To define a material based on other material, simply define:

basedOn = materialName

Clause used to import parameters from a predefined material.

In this case, the mandatory parameters are becoming optional and can be used to change properties with respect to predefined material. Note that the chemical composition cannot be changed when defining a material based on the other material.

Currently, the predefined materials in FRED are Vacuum, BlackHole, Water, Air, PMMA, Al, Ti, Cu, Ni, Si and LEXAN.

Tip

Run the command fred -materials to get detailed information on the predefined materials.

Example of material definition

Multi-line definition of modified PMMA material for a range shifter:

material<
    ID=pmmaRS
    basedOn=pmma
    rho=1.16
    Ipot=74
    Lrad=45.822
material>

Single line definition of modified water:

material:  myWater ; basedOn = water ; rho=0.97 ; Ipot = 76.2

Single line definition of graphite:

material:  Graphite ; basedOn = C ; rho=1.644 ; Ipot = 78 ; Lrad =42.7

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