  As more and more numerical and analytical solutions to the linear neutron
transport equation become available, verification of numerical results is
increasingly important. This presentation concerns the development of another
benchmark for the linear neutron transport equation. There are numerous ways of
solving the transport equation, such as the Wiener-Hopf method based on
analyticity, method of singular eigenfunctions, Laplace and Fourier transforms
and ana-lytical discrete ordinates, which is arguably one of the most
straightforward, to name a few. Another potential method is the PN method,
where the solution is expanded in terms of full range orthogonal Legendre
polynomials and with orthogonality and truncation, the moments form a set of
second order ODEs. Because of the half-range boundary conditions for incoming
particles however, full range Legendre expansions are inaccurate near material
discontinuities. For this reason, a double PN (DPN) expansion is more
appropriate, where the incoming and exiting flux distributions are expanded
separately to preserve the discontinuity at material interfaces. Here, a new
method of solution for the DPN equations is proposed and demonstrated for an
isotropically scattering medium.
