Radiation Transport Setup

Radiation transport is performed using one of the following:

• A multi-group, flux-limited diffusion model
• A multi-group, multi-angle long characteristics model.

At present, the multi-angle model can be utilized only in planar geometry. When selecting the multi-angle model, the number of angles must be specified.

The binning, or distribution, of frequency (i.e., photon energy) groups is set up using one of the following approaches:

• Typical: Using the specified number of frequency groups, a grid is set up with approximately 85% of the groups having photon energies between 0.1 eV and 3 KeV, while the remaining 15% lie between 3 KeV and 1 MeV.
• Tabulated Group Boundaries: The boundaries of the frequency groups are entered into a table or the table values can be imported from a file. The table is accessed by clicking the Setup button. See Entering Table Data for information about entering or importing data.
• Specify Frequency Groups in Sections: The spectrum is divided into "sections" (or spectral ranges), the number of which is given by the number of filled table rows. For each section, the number of groups and the upper bound of each section of groups is specified. This allows the user to specify high frequency resolution in one spectral range, and a coarser frequency resolution in another range.

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