2.2.1. Introduction to Cross Sections

OpenSn does not provide a cross-section library. Users must supply cross-section data or generate it with a tool such as NJOY, Dragon, or OpenMC. In Python, multigroup cross-section data is represented by MultiGroupXS.

The tutorials in this section demonstrate three creation and input paths:

• CreateSimpleOneGroup() constructs an isotropic one-group cross section from a total cross section, scattering ratio, and optional group velocity.

• LoadFromOpenSn() reads OpenSn’s ASCII cross-section format for one-group or multigroup data.

• LoadFromOpenMC() reads a named dataset and temperature from an OpenMC-generated HDF5 cross-section library.

The Python API also provides LoadFromCEPXS() for CEPXS files. Once loaded, cross sections can be combined with Combine() or modified in place with Scale().

See the Python API reference for constructor arguments, available data properties, and method behavior.