Use of Discrete-Ordinates Methods for Solution of Photon Transport Problems

To permit numerical solution of photon transport problems by the method of discrete ordinates, an anisotropic scattering approximation and a multigroup cross-section preparation recipe are selected. The incorporation of the anisotropic scattering approximation in a discrete-ordinates transport-theory code is described. Results of discrete-ordinates calculations are compared to Monte Carlo and moments-methods computations in three test problems. Flux values and leakage percentages in the different methods of solution are found to be in excellent agreement, even when a relatively low-order (four or six terms of a Legendre polynomial expansion) anisotropic scattering approximation is used in the discrete-ordinates method. In the test problems considered, the discrete-ordinates method is (computationally) nearly an order of magnitude faster than the other methods.