Transport analysis of measured neutron energy spectra in a graphite stack with a collimated deuterium-tritium neutron beam

The Ben-Gurion University measurements of neutron energy spectra in a graphite stack, resulting from the scattering of 14.7-MeV neutrons streaming through a 6-cm-diam collimator in a 121-cm-thick paraffin wall, have been used as a benchmark for the compatibility and accuracy of discrete ordinates P_n, and transport calculations and as a tool for fusion reactor neutronics. The transport analysis has been carried out with the DOT 4.2 discrete ordinates code and with cross sections processed with the NJOY code. Most of the parameters affecting the accuracy of the calculations have been investigated: the density of the spatial mesh, the order of expansion of the flux and L system scattering cross sections in the P_n approximation, the quadrature set employed, and the energy multigroup structure.