Thermal Neutron Scattering Studies in Metals

Abstract

The interaction of slow or C neutrons can be modified by changes in the physical parameters of the material which the neutrons are traversing. Measurements of the effect of grain size on total C neutron cross section were made on randomly-oriented poly-crystalline iron and copper. In the case of copper it was found that the total cross section decreased in an exponential manner with increase in grain size. For iron it was simply established that the total cross section was substantially smaller for the larger grain size.T HE work of Nix, Beyer, and Dunning 1 has shown that the presence of order in binary iron-nickel alloys, in which the grain size was maintained constant and free of preferred orientation, decreased the cross section below that obtained from random alloys: the greater the degree of order, the lower the total cross section obtained. The establishment of such an effect 1,2 illustrates that thermal neutrons may be used as a tool to study the structure of the solid state. In order to render this tool more useful for our systematic studies of order-disorder transformations in alloys, it was necessary to establish the influence of other physical parameters on the neutron scattering. As our first problem in this series of studies, we selected the effect of grain size. Grain growth frequently takes place in the thermal treatments necessary to produce orderdisorder transformation. As metals we selected copper as a non-ferromagnetic face-centered cubic metal free from polymorphic transformations, and iron as a ferromagnetic body-centered cubic metal subject to polymorphic transformations.

Study of Reaction Cross Section of Light Mass Nuclei Using Glauber Formalisms

“…The total reaction cross-section measurements at intermediate energy have been used extensively by the nuclear physics community to investigate the nuclear size and distribution of nucleons [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The advancement in radioactive ion beams (RIB) at intermediate energy made it possible to explore the nuclear chart, and it opened up new opportunities to investigate numerous exotic phenomena.…”

The Thermal Neutron Scattering by Ammonium Chloride

“…6 * 7 If this is the case, however, the scattering cross section must depend on the grain size of the powdered scatterer of NH 4 C1 of the same temperature as in the case of a polycrystalline metal scatterer. 8,9 We measured the variation using scatterers of various grain size ranging from 2X10~4 to 4X10" 1 cm, and found no change within the limits of error of ±2 percent. This result implies that, contrary to perfect crystals such as Si0 2 , the crystal of NH4CI belongs to an imperfect type such as those of sulfur and lead 10 -11 and cannot show any variation in scattering cross section by internal distortion.…”

“…On the other hand, several investigators using counter arrangements obtained more or less divergent results. [7][8][9] We have started fresh experiments with a counter arrangement much more effective than the original one (Fig. 1).…”

Упругое Рассеяние Нейтронов Атомными Ядрами

“…Систематическое изучение взаимодействия нейтронов с атомными яд-рами начинается обширной работой Даннинга и его сотрудников по из-мерению σ «поглощения» нейтронов, имеющих тепловую энергию 18 .…”