EXPERIMENTAL DEMONSTRATION OF THE FINITE MEASUREMENT TIME EFFECT ON THE FEYNMAN-ALPHA TECHNIQUE

The reactivity of a subcritical system is determined by fitting two di fferent theoretical models to a measured Feynman-cr curve. The first m odel is the expression usually found in the literature which can be sh own to be the epectation value of the experimental quality if the meas urement time is infinite. The second model is a new expression which i s the expectation value of the experimental quantity for a finite meas urement time. The reactivity inferred with the new model is seen to be independent of the length of the fitting interval, whereas the reacti vity inferred with the conventional model is seen to vary. This differ ence demonstrates the effect of the finite measurement time. As a refe rence, the reactivity is also measured with the pulsed-neutron source method. It is seen to be in good agreement with the reactivity obtaine d with the Feynman-alpha technique when the new expression is applied. (C) 1998 Elsevier Science Ltd. All rights reserved.