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.

Charge and magnetic ordering in the electron-doped magnetoresistive materials CaMnO 3 − δ ( δ = 0.06 , 0.11 )

Abstract: The magnetoresistive ``electron''-doped materials ${\mathrm{CaMnO}}_{3\ensuremath{-}\ensuremath{\delta}}$ $(\ensuremath{\delta}=006,011)$ have been investigated using powder neutron diffraction The two materials are n-type semiconductors which exhibit antiferromagnetic ordering at ${T}_{N}\ensuremath{\sim}125\mathrm{K},$ but they have different magnetic structures The ${\mathrm{CaMnO}}_{294}$ sample orders in a simple G-type antiferromagnetic structure, which is also observed in ${\mathrm{CaMnO}}_{3}$ The ${\mathrm{CaMnO}}_{289}$ sample, on the other hand, exhibits two magnetic features: the G-type reflections as noted above, and a set of reflections that can be indexed on a $k=(0,0,\frac{1}{4})$ ordering wave vector A model for the magnetic structure is proposed which involves ${\mathrm{Mn}}^{3+}{/\mathrm{M}\mathrm{n}}^{4+}$ charge ordering concomitant with the magnetic ordering The presence of a set of weak, temperature independent structural reflections which can also be indexed on a $k=(0,0,\frac{1}{4})$ supercell suggests an oxygen vacancy ordering which may play a role in the charge ordering

An accelerator based system for in vivo neutron activation analysis measurements of manganese in human hand bones.

Abstract: Manganese (Mn) is an essential nutrient for growth and development. Unfortunately, overexposure can lead to neurological damage, which is manifested as a movement disorder marked by tremors. Preclinical symptoms have been found in populations occupationally exposed to the element, and it is suggested that in late stages of the disorder, removing the Mn exposure will not prevent symptoms from progressing. Hence, it is desirable to have a means of monitoring Mn body burden. In vivoneutronactivation analysis (IVNAA) is a technique which allows the concentration of some elements to be determined within sites of the body without invasive procedures. Data in the literature suggests that the Mn concentration in bone is greater than other tissues, and that it may be a long term storage site following exposure. Therefore, using the McMaster KN-accelerator to produce neutrons through the 7 Li (p,n) 7 Be reaction, the feasibility of IVNAA for measuring Mn levels in the human hand bone was investigated. Mn is activated through the 55 Mn (n,γ) 56 Mn reaction, and the 847 keV gamma rays emitted when 56 Mn decays are measured outside the body using NaI(Tl) detectors. An optimal incident proton energy of 2.00 MeV was determined from indium foil and microdosimetry measurements. Hand phantom data suggest a minimum detectable limit of approximately 1.8 ppm could be achieved with a reasonably low dose of 50 mSv to the hand (normal manganese levels in the human hand are approximately 1 ppm). It is recommended the technique be developed further to make human in vivo measurements.

Residual stress analysis in linear friction welded in-service Inconel 718 superalloy via neutron diffraction and contour method approaches

Abstract: In this study, an analysis of elastic residual stress in Inconel ® 718 (IN 718) linear friction welds (LFWs) was carried out. In particular, the suitability of LFW for manufacturing and repair of aero engine components was emulated by joining virgin and in-service (extracted from a turbine disk) materials. The evolution in the residual strains and stresses in the heat-affected zone (HAZ), thermomechanically affected zone (TMAZ) and dynamically recrystallized zone (DRX) of the weld was characterized using the neutron diffraction and contour methods. The results provided insight into diverse challenges in quantitative analysis of residual stresses in welded IN 718 using diffraction techniques. Specifically, judicious selection of the beam width, height and stress-free lattice spacing were seen to be crucial to minimize measurement error and increase accuracy. Further, the contour method – a destructive technique relying on capturing the stress relaxation after electrical discharge machining – was used to characterize the residual stress distribution on two-dimensional plane sections of the welds. Both techniques suggested an increasing magnitude of residual stress originating from the base metal that reached a peak at the weld interface. Both methods indicated that the peak magnitude of residual stresses were below the yield stress of IN 718.