Cobalt Radiation Therapy Device

This is a very rough approximation of a radiation therapy device, with a radiation source at the center of a spherical shield material. A conical channel has four rectangular "jaws" which can move in or out of the radiation path.

Geometry

CUBIT view:
Shield (red), collimator (green), source (inside collimator),
jaws (white/cyan/blue/magenta)

VisEd view:
Shield (yellow), collimator (purple), source (inside collimator),
jaws (green)

Results

A 1.4MeV gamma source has interactions at several energies (1.2, .1 MeV). MCNPX/CGM results identical to MCNPX results. Also, when jaws are moved into radiation path, more radiation gets scattered to lower energies (red line in the plot below).