A generalized interpretation of buckling experiments for thermal neutrons

The buckling experiment is a well-known pulsed measurement method used to determine the thermal neutron diffusion parameters of a medium. In the classic form of the method, a dependence between the geometric buckling B2 (in cm−2) and the thermal neutron time decay constant λ (in s−1) are involved. In the present paper, dimensionless values for the decay constant and for the buckling are introduced. This unification offers a method to generalize the description of the buckling experiment and makes it possible to compare experiments made for different media. The application of this procedure is exemplified on results for polyethylene of two different densities (from a Monte-Carlo-simulated experiment) and for Plexiglas (from a real laboratory experiment). The conclusion is that the buckling experiment is relatively easy for interpretation in the dimensionless buckling range which does not exceed 0.2. It corresponds, for example, to the geometric buckling B2=1.1 cm−2 for polyethylene of density 0.57 g cm−3 or to B2=3.0 cm−2 for polyethylene of density 0.95 g cm−3.