Structured mesh source

This example shows users how to make a mesh source using a cylindrical mesh and a source term for each voxel.

This is a minimal example but a more realistic example could use the voxel location to look up properties of the plasma at each coordinate and customize the source energy and strength at each mesh voxel location

from pathlib import Path
import numpy as np
import openmc
from openmc_source_plotter import plot_source_position
# Setting the cross section path to the correct location in the docker image.
# If you are running this outside the docker image you will have to change this path to your local cross section path.
openmc.config['cross_sections'] = Path.home() / 'nuclear_data' / 'cross_sections.xml'

# allows notebook rendering of plotly plots in the HTML made by jupyter-book
import plotly.offline as pyo
pyo.init_notebook_mode(connected=True)

/opt/hostedtoolcache/Python/3.12.11/x64/lib/python3.12/site-packages/openmc_source_plotter/core.py:12: UserWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html. The pkg_resources package is slated for removal as early as 2025-11-30. Refrain from using this package or pin to Setuptools<81.
  import pkg_resources

Making a minimal geometry

sphere_surf_1 = openmc.Sphere(r=2000)
sphere_cell_1 = openmc.Cell(region=-sphere_surf_1)

my_geometry = openmc.Geometry([sphere_cell_1])

# creating the mesh used for the mesh source
cylindrical_mesh = openmc.CylindricalMesh.from_domain(
    my_geometry, # the corners of the mesh are being set automatically to surround the geometry
    dimension=[10,10,10]
)

# empty list that will contain one source for each mesh voxel
all_sources = []
for i in cylindrical_mesh.indices:

    mesh_index = (i[0]-1, i[1]-1, i[2]-1)
    # this minimal example sets the same source for each voxel
    # to create a realistic plasma source the mesh centroid could be used to
    # find source strength, temperature and make a location specific source
    # a function could be called that returns the temperature and relative source
    # strength for each x,y,z or r, phi, z location
    # voxel centroid can be obtained like this
    # centroid = cylindrical_mesh.centroids[mesh_index]
    # voxel cylindrical_coords (z, phi, r) can be obtained like this
    cylindrical_coords = cylindrical_mesh.vertices_cylindrical[mesh_index]
    volume = cylindrical_mesh.volumes[mesh_index]
 
    # making a source for each voxel
    my_source = openmc.IndependentSource()
    my_source.energy = openmc.stats.Discrete([14.1e6], [1])
    my_source.angle = openmc.stats.Isotropic()
    if cylindrical_coords[2] > 1000: # filtering out sources below radius of 1000
        my_source.strength = volume # uniform source
    else:
        my_source.strength = 0
    all_sources.append(my_source)

# creating the mesh source from the mesh and the list of sources
# the main difference between MeshSpatial (previous example) and MeshSource is that in
# MeshSpatial each mesh element has the same source with potentially a different
# strength while in MeshSource the elements can have a different source.
# Having a different source would allow a different energy distribution and therefore
# MeshSources are useful for shut down dose rate simulations where each active element
# results in a different photon emission
mesh_source = openmc.MeshSource(
    mesh=cylindrical_mesh,
    sources=np.array(all_sources).reshape(cylindrical_mesh.dimension)
)

# Update all element source strengths such that they sum to 1.0.
# this makes post processing the results easier if the total source strength is 1
mesh_source.normalize_source_strengths()

plotting the mesh source

plot = plot_source_position([mesh_source], n_samples=10000)
plot.show()