Modeling radial collimators for use in stress and texture measurements with neutron diffraction

Radial collimators have been recently introduced to define the sampling vol ume during neutron diffraction stress and texture mapping experiments. This paper presents both analytical and Monte Carlo numerical models for the ca lculation of the spatial distribution of neutron transmission through a rad ial collimator. It is shown that the effective size of the scattered neutro n beam as seen by detectors behind the collimator is quite sensitive to the collimator length and the number of blades. For a given radius of a collim ator, the effective beam width increases sharply as the length is shortened . Due to the finite blade thickness, the center of gravity of the sampling volume is shifted away from the collimator. In contrast, attenuation of the neutron beam by the sample brings the center of gravity of the sampling vo lume closer to the collimator. (C) 2000 Internatlonat Union of Crystallogra phy Printed in Great Britain - all rights reserved.