Monte Carlo simulation of pulsed neutron experiments on samples of variable mass density

A method is presented to facilitate the interpretation of a pulsed neutron experiment (the variable geometric buckling experiment) when the mass densi ties of individual samples differ. A generalisation of the classic expressi on, which connects the fundamental mode decay constant to the thermal neutr on diffusion parameters and to the geometrical buckling, is presented. The method has been tested (on polyethylene) by means of a computer simulation of the experiments. The simulation has been based on a Monte Carlo method, using the MCNP code. The described generalised buckling method is especiall y recommended for experiments with bulk materials. (C) 2000 Elsevier Scienc e B.V. All rights reserved.