Chalk River Laboratories

About: Chalk River Laboratories is a based out in . It is known for research contribution in the topics: Neutron diffraction & Neutron scattering. The organization has 2297 authors who have published 2700 publications receiving 73287 citations.

Radiation damage during heavy ion elastic recoil detection analysis of insulating materials

Abstract: Loss of low-Z elements (H, C, N, O, etc.) during heavy ion Elastic Recoil Detection Analysis (ERDA) has been investigated for various molecular target materials, using beams of 79Br, 127I, 197Au and 209Bi at 1.1 MeV/amu. Ceramic targets such as Nb2O5 and UO2 exhibit negligible oxygen loss even at fluences 100 times larger than that typically required during ERDA to determine the stoichiometry of a given material (1012–1013 ions/cm2). However, silicon oxynitride targets and various organic materials (photoresist, polyethylene and polycarbonate films) exhibit observable losses of hydrogen, nitrogen, oxygen and even carbon in some cases. Thus ERDA of such materials requires small corrections to determine the original target composition. For all beams, the energy loss of the incident ion due to nuclear stopping is far too small to be responsible for the observed elemental depletion; hence the much larger electronic stopping must be the primary cause. In the silicon oxynitride and photoresist targets, the observed loss rates of H, C, N or O, normalised by the corresponding recoil cross section σR, are roughly the same for all four beams. At a constant velocity of 1.1 MeV/amu, σR depends approximately on Z12 and the electronic energy loss is approximately proportional to Z1. We therefore conclude that the depletion rate of low-Z elements also depends roughly on the square of the electronic energy loss.

Selection index: economic weights for maximum simultaneous genetic gain.

Abstract: Selection indices that maximize the correlation between an individual organism's index score and its breeding value frequently require a priori known “economic” weights before the optimum phenotypic weights can be estimated. The long generation intervals and economic uncertainty that surround forest tree breeding can make the choice of weights arbitrary. In this paper an algorithm is introduced for finding “economic” weights that will ensure maximum simultaneous progress in all index traits. At the outset the traits are assumed to be of equal preference. The solutions are functions of the eigenvalues and eigenvectors of a quadratic form of the additive genetic and phenotypic covariance matrices. Examples of applications in tree breeding emphasize the practical aspects of the method.

The influence of martensite on line broadening in neutron diffraction spectra of a DP steel

Abstract: Neutron diffraction experiments were performed on dual-phase steels to determine the feasibility of measuring the martensite volume fraction through ferrite peak broadening. Mechanical properties were also investigated to determine if a correlation exists with ferrite peak broadening. Results indicate that the correlation between martensite volume fraction and ferrite peak broadening is carbon dependent. Furthermore, two mechanisms regarding the nature of the ferrite peak broadening in dual-phase steels are proposed. Tensile testing demonstrated that a correlation between peak broadening and mechanical properties exists for dual-phase steels.

Mott-Kondo insulator behavior in the iron oxychalcogenides

Abstract: We perform a combined experimental-theoretical study of the Fe-oxychalcogenides (FeOCh) series La2O2Fe2OM2 (M=S, Se), which are among the latest Fe-based materials with the potential to show unconventional high-Tc superconductivity (HTSC). A combination of incoherent Hubbard features in x-ray absorption and resonant inelastic x-ray scattering spectra, as well as resistivity data, reveal that the parent FeOCh are correlation-driven insulators. To uncover microscopics underlying these findings, we perform local density approximation-plus-dynamical mean field theory (LDA+DMFT) calculations that reveal a novel Mott-Kondo insulating state. Based upon good agreement between theory and a range of data, we propose that FeOCh may constitute an ideal testing ground to explore HTSC arising from a strange metal proximate to a novel selective-Mott quantum criticality.