An exponential discontinuous scheme for discrete-ordinate calculations in Cartesian geometries

We describe a new nonlinear spatial differencing scheme for solving the discrete-ordinate transport equations, called the exponential discontinuous (ED) scheme in one, two and three dimensional Cartesian geometries. The ED scheme is much easier to derive and less computationally expensive than the recently developed nonlinear characteristic (NC) scheme and is nearly as accurate for deep penetration shielding problems. Like the nonlinear characteristic scheme, the exponential discontinuous scheme produces strictly positive angular fluxes given positive discrete-ordinate sources. However, the ED scheme can be less accurate than even the linear discontinuous (LD) scheme for certain types of problems. Numerical results are provided to show the accuracy and positivity of the ED scheme.