Component Manual for the Neutron Ray-Tracing Package McStas, version 3.8.6

12.13  The Union_make_material McStas Component

Component that takes a number of Union processes and constructs a Union material

Identification

Description

Part of the Union components, a set of components that work together and thus separates geometry and physics within McStas. The use of this component requires other components to be used.

1) One specifies a number of processes using process components 2) These are gathered into material definitions using this component 3) Geometries are placed using Union_box/cylinder/sphere, assigned a material 4) A Union_master component placed after all of the above

Only in step 4 will any simulation happen, and per default all geometries defined before the master, but after the previous will be simulated here.

There is a dedicated manual available for the Union_components

Algorithm: Described elsewhere

Input parameters

Parameters in boldface are required; the others are optional.

Name

Unit

Description

Default

process_string

string

Comma seperated names of physical processes

"NULL"

my_absorption

1/m

Inverse penetration depth from absorption at standard energy

absorber

0/1

Control parameter, if set to 1 the material will have no scattering processes

0

refraction_density

g/cm\(^{3}\)

Density of the refracting material. density < 0 means the material is outside/before the shape.

0

refraction_sigma_coh

barn

Coherent cross section of refracting material. Use negative value to indicate a negative coherent scattering length

0

refraction_weight

g/mol

Molar mass of the refracting material

0

refraction_SLD

Å\(^{-2}\)

Scattering length density of material (overwrites sigma_coh, density and weight)

-1500

init

string

Name of Union_init component (typically "init", default)

"init"

Links