Neutron Radiographic Unsharpness and Dimensional Analysis

Abstract

<p>The neutron image unsharpness which generally limits radiographic resolution to a qualitative assessement has been studied in detail and found to exhibit unique features at object boundaries and material discontinuities. These radiographic features provide intrinsic criteria for accurate dimensional measurements and the determination of material boundaries.</p> <p>As a basis for our investigation, the analysis of the underlying radiation-conversion and transport phenomena of the neutron imaging process was undertaken. The resultant functional image characterizations were found to be dependent on the radiographed object geometry, object dimensions, and material composition. Two avenues for extracting quantitative details from radiographs have thereupon been identified. Firstly, the coordinates bounding an object or regions of material discontinuities were found to be obtainable by an adaptation of the experimental optical density data to the functional representation. Secondly, the optical density variations due to image unsharpness was found to possess functional inflections at object boundaries and material discontinuities.</p> <p>The applications of both methods to the determination of limits of internal material discontinuities and dimensions of objects have been investigated in some detail. Experimental tests of the inflection approach show excellent agreement with theory. A mathematical-theoretical characterization of the neutron imaging phenomenon has thus been established and developed into a practical tool for extracting dimensional information from a neutron radiographic image.</p>