Egsinp syntax

The basic EGS_Mesh input file syntax is:

:start geometry definition:
    :start geometry:
        library = egs_mesh
        name = my_mesh
        file = model.msh # your mesh here
    :stop geometry:

    simulation geometry = my_mesh
:stop geometry definition:

However, most meshes should be simulated in an envelope, otherwise particles exiting the mesh are discarded immediately, even if they would have reentered the mesh later on.

In an envelope

This example embeds a mesh inside an air box.

:start geometry definition: 
    :start geometry:        
        library = egs_mesh
        name = my_mesh    
        file = model.msh 
    :stop geometry:

    # define a 50cm air cube at the origin
    :start geometry:
        library = egs_box
        name = my_box
        box size = 50 50 50
        :start media input:
            media = air
        :stop media input:
    :stop geometry:
    
    # embed the mesh in the air box
    :start geometry:
        library = egs_genvelope
        name = my_envelope
        base geometry = my_box
        inscribed geometries = my_mesh
    :stop geometry:

    simulation geometry = my_envelope
:stop geometry definition:

Scaling the mesh

Mesh files are assumed to be in cm. The scale key can be used to scale the mesh if the file uses different units.

:start geometry definition:
    :start geometry:
        library = egs_mesh
        name = my_mesh
        file = model.msh
        scale = 0.1 # multiply all node coordinates by 0.1 (e.g. mm to cm)
    :stop geometry:

    simulation geometry = my_mesh
:stop geometry definition: