External Radiation Sources Setup

An external radiation sources can be applied to the hydro grid boundaries during a HELIOS simulation. For planar geometries an external source can be applied at the inner boundary (R(min)) and/or the outer boundary (R(max)). For cylindrical and spherical geometries, an external source can only be applied at the outer boundary.

Models used to specify the flux incident at the boundary are:

• 1-T Table: A two-column table of times and radiation temperatures. The time-dependence of the flux is based on interpolated radiation temperatures from the table. The photon energy-dependence is determined assuming a Planckian source with a temperature given by the radiation temperature.
• Flux table: A multi-column table of photon-energy- and time-dependent fluxes. Photon energies from the table are automatically remapped to radiation group structure of the simulation. The time-dependence of the flux is based on interpolated radiation fluxes from the table. These tabulated data contain information similar to what was previously available only from VisRad files. The first cell (row 1, column 1) is a header -- your input ascii file must have an entry in this location. The first column (row 2 through Npe+1) contains photon energies in eV. The first row (columns 2 through Nt+1) contains time in seconds. Fluxes for each time and photon energy are in W/cm^2/eV.
• VISRAD Incident Flux File: A file generated by VisRad containing the time- and frequency-dependent incident flux onto a surface.

To specify that an external radiation source is to be applied at one of the boundaries, check the appropriate box at the top of the Radiation Source parameters widget.

Clicking on the Advanced button allows a flux multiplier to be specified for the radiation source values:

There is also an option to specify that the radiation be treated as if it were incident normal to the surface instead of the usual Lambertian angular dependence. The normal incidence option is the default when a laser source is used as an external radiation source. The spectral distribution of the radiation source can also be treated as being angle dependent (only if the radiation source is specified using a VISRAD flux file).

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