High energy collision cascades in tungsten: dislocation loops structure and clustering scaling laws

Recent experiments on in-situ high-energy self-ion irradiation of tungsten (W) show the occurrence of unusual cascade damage effects resulting from single ion impacts, shedding light on the nature of radiation damage expected in the tungsten components of a fusion reactor. In this paper, we investigate the dynamics of defect production in 150 keV collision cascades in W at atomic resolution, using molecular dynamics simulations and comparing predictions with experimental observations. We show that cascades in W exhibit no subcascade break-up even at high energies, producing a massive, unbroken molten area, which facilitates the formation of large defect clusters. Simulations show evidence of the formation of both 1/2 and interstitial-type dislocation loops, as well as the occurrence of cascade collapse resulting in vacancy-type dislocation loops, in excellent agreement with experimental observations. The fractal nature of the cascades gives rise to a scale-less power law type size distribution of defect clusters.Comment: 6 pages, 3 figure

Spill-Overs from Good Jobs

Does attracting or losing jobs in high paying sectors have important spill-over effects on wages in other sectors? The answer to this question is central to a proper assessment of many trade and industrial policies. In this paper, we explore this question by examining how predictable changes in industrial composition in favor of high paying sectors affect wage determination at the industry-city level. In particular, we use US Census data over the years 1970 to 2000 to quantify the relationship between changes in industry-specific city-level wages and changes in industrial composition. Our finding is that the spill-over (i.e., general equilibrium) effects associated with changes in the fraction of jobs in high paying sectors are very substantial and persistent. Our point estimates indicate that the total effect on average wages of a change in industrial composition that favors high paying sectors is about 3.5 times greater than that obtained from a commonly used composition-adjustment approach which neglects general equilibrium effects. We interpret our results as being most likely driven by a variant of the mechanism recently emphasized in the heterogenous firm literature whereby changes in competitive pressure cause a reallocation of employment toward the most efficient firms.

Recoil energy dependence of primary radiation damage in tungsten from cascade overlap with voids

Models of radiation damage accumulation often assume a constant rate of additional primary damage formation during prolonged irradiation. However, molecular dynamics simulations have shown that the presence of pre-existing radiation-induced defects modifies the numbers of additional defects formed from individual cascades. In this work, we study the formation of defects in tungsten for a range of pri-mary recoil energies, for cascades that fully overlap with pre-existing voids of different sizes. We extend a recent model describing defect production in the presence of pre-existing damage to also account for the recoil energy dependence, and parametrize the extension based on our simulation data. We also an-alyze the morphology of the primary damage from cascades overlapping with voids, and show that the in-cascade formation of ( 1 0 0 ) dislocation loops in such events is more dependent on the size of the pre-existing void, than on the energy of the primary recoil. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )Peer reviewe

Summary of data from test cases of seeding thunderstorms with silver iodide in northeastern Colorado, 1962-63-64

CER64RAS35.December 1964.Progress report, NSF GP-2594, research supported by the Atmospheric Science Program, National Science Foundation.Includes bibliographical references.Under NSF Grant GP-2594

The economic value of remote sensing by satellite: An ERTS overview and the value of continuity of service. Volume 2: Source document

The economic value of an ERS system with a technical capability similar to ERTS, allowing for increased coverage obtained through the use of multiple active satellites in orbit is presented. A detailed breakdown of the benefits achievable from an ERS system is given and a methodology for their estimation is established. The ECON case studies in agriculture, water use, and land cover are described along with the current ERTS system. The cost for a projected ERS system is given

Direct observation of size scaling and elastic interaction between nano-scale defects in collision cascades

Using in-situ transmission electron microscopy, we have directly observed nano-scale defects formed in ultra-high purity tungsten by low-dose high energy self-ion irradiation at 30K. At cryogenic temperature lattice defects have reduced mobility, so these microscope observations offer a window on the initial, primary damage caused by individual collision cascade events. Electron microscope images provide direct evidence for a power-law size distribution of nano-scale defects formed in high-energy cascades, with an upper size limit independent of the incident ion energy, as predicted by Sand et al. [Eur. Phys. Lett., 103:46003, (2013)]. Furthermore, the analysis of pair distribution functions of defects observed in the micrographs shows significant intra-cascade spatial correlations consistent with strong elastic interaction between the defects