A generalized interpretation of buckling experiments for thermal neutrons

The buckling experiment is a well-known pulsed measurement method used to d etermine the thermal neutron diffusion parameters of a medium. In the class ic form of the method, a dependence between the geometric buckling B-2 (in cm(-2)) and the thermal neutron time decay constant lambda (in s(-1))are in volved. In the present paper, dimensionless values for the decay constant a nd for the buckling are introduced. This unification offers a method to gen eralize the description of the buckling experiment and makes it possible to compare experiments made for different media. The application of this proc edure is exemplified on results for polyethylene of two different densities (from a Monte-Carlo-simulated experiment) and for Plexiglas (from a real l aboratory experiment). The conclusion is that the buckling experiment is re latively easy for interpretation in the dimensionless buckling range which does not exceed 0.2. It corresponds, for example, to the geometric buckling B-2 = 1.1 cm(-2) for polyethylene of density 0.57 g cm(-3) or to B-2 = 3.0 cm(-2) for polyethylene of density 0.95 g cm(-3). (C) 2000 Elsevier Scienc e B.V. All rights reserved.