Exposure Angular Distributions in Air Above Disk Isotropic Cobalt-60 Sources

Exposure angular distributions of scattered gamma rays at points along the axis of plane-disk isotropic ⁶⁰Co sources, imbedded in an infinite air medium (air density = 1.293 g/liter), have been calculated using the moments method solution to the gamma-ray transport equation. The method is based on the Legendre-moments transformation of the transport equation for scattered energy flux density at a height z above an infinite-plane isotropic source. Coefficients of the Legendre expansions were reconstructed using standard biorthogonal polynomial techniques. An extrapolation technique is developed to extend the number of Legendre coefficients to smooth resulting distributions. Results are given for disks of radius 100 ft to infinity at detector heights of 3 to 1000 ft above the source plane.