The Use of X-Rays from Inelastic Scattering Reactions of 2-3 MeV Neutrons for Material Analysis

A method has been established for detecting and analyzing characteristic gamma rays promptly emitted as a result of the inelastic scattering of 3.29 MeV neutrons by nuclei. The experimental set-up designed and built for such a measurement is described. A remote controlled sample changer is used in conjunction with a measuring procedure, whereby during the course of a run, data is added into the analyzer from the sample irradiation, and subtracted from a carbon blank in alternate periods. Such data acquisition procedure is shown to lead to
a satisfactory treatment of the background problem. A data reduction system is described in detail, with a photopeak integration method which is shown to give reliable and precise results in conditions of high count-rate and varying background.
The measurements performed for the differential gamma emission cross-sections of 23 elements are described, and the results obtained are discussed. The excited state gamma energies observed for the elements are presented, and shown to be generally in good agreement with the known nuclear levels of
the elements. A level at 1290 keV observed in Mn, although agreeing with the nuclear level diagram for the element given by some authors, was not observed by these same authors. Another level at 1640 keV observed in Bi, although close to a line at 1615 keV found by one worker, was not observed by another group of workers. The differential cross-sections, although agreeing well with some published data (e.g. Cr, Fe and Mn), are in disagreement with some other. For many elements, no data could be found in the literature for comparison. Analytical sensitivities for the 23 elements are presented in the form of sensitivities (photopeak counts per g) and detection limits (% by weight), for specified conditions of measurement.
Finally, the application of the developed technique to material analysis is demonstrated on the example of some real mineral ores, and conclusions drawn about its potential uses.