Events at ORNL

A Low-Energy Component in the Magnetic Excitation Spectrum of Pr2Zr2O7

A possible realization of quantum spin ice, Pr2Zr2O7, was recently shown to feature a low-temperature regime of thermal transport consistent with artificial photons in a U(1) Coulomb spin liquid. In this seminar, the speaker will provide spectroscopic evidence for the corresponding low-energy excitations through ultrahigh-resolution magnetic neutron scattering. The momentum-averaged spectrum can be described as relaxational with a rate Γ´ = 10.(4) µeV.

Presenter

  • Huiyuan Man, Johns Hopkins University, Baltimore, Maryland

Scrum Approach in a National Lab Environment: Lessons Learned from an ORNL LDRD Scrum Project

Scrum is an organizational framework that can be applied to difficult projects to do twice the work in half the time. The principles of Scrum are simple to understand but difficult to master. This presentation will address the unique challenges that are specific to applying this work method to R&D efforts in a national lab environment. Lessons learned from an ongoing ORNL LDRD project that employed the Scrum approach also will be presented.

Presenter

  • Joe Justice, Scrum Inc., Cambridge, Massachusetts

Chemistry Beyond Plutonium: How Relativity Alters Electronic Structure in Heavy Elements

Elements beyond plutonium are rich test beds for probing how relativistic effects alter electronic structure as well as molecular structure and reactivity. Curium, berkelium, californium, and einsteinium are the final elements for which bulk properties such as x-ray diffraction, optical spectroscopy, and magnetism can be measured, albeit with great difficulty.

Presenter

  • Thomas E. Albrecht-Schmitt, Florida State University, Tallahassee

Dual-Ion Irradiation of Commercial and Advanced Alloys Relevant to LWR Core Internals at High Dose

The design of next-generation fission reactors and the lifetime extension of current reactors require in-core structural components and fasteners with extreme radiation resistance. At high displacement damage, irradiation defects and transmuted He interact to cause critical damage, hardening, and swelling. While such effects have been partially simulated using proton or heavy-ion irradiations, this study uses simultaneous He implantation and self-ion irradiation to capture the coevolution more faithfully.

Presenter

  • Calvin Lear, The University of Michigan, Ann Arbor

Exploring Anisotropic Vortex Lattices of Unconventional Superconductors using Small-Angle Neutron Scattering

By characterizing the intrinsic anisotropy of the superconducting state deep within the phase, many open questions on the nature of superconductivity can be addressed. In this talk, the intrinsic superconducting anisotropies of KFe2As2 and Sr2RuO4 are studied using small-angle neutron scattering to image the vortex lattice as the applied magnetic field is rotated toward the basal planes. In KFe2As2, the anisotropy is found to be strongly field dependent, indicating multiband superconductivity.

Presenter

  • Stephen Kuhn

What Is Machine Learning and Why Should You Care?

With the very quick rise of machine learning, an enormous amount of hype and confusion clouds the reality of what machine learning is and what it can do for you. This presentation will provide a very basic foundation of machine learning, a broad overview of the field and progress toward discussing state of the art techniques with practical, real world examples.

Presenter

  • Robert Patton, Computational Data Analytics Group

Utilizing Operando Characterization Techniques to Investigate Ion-Induced Nanopatterning of the GaSb System

This seminar describes research to characterize the topographical and compositional evolution of the GaSb surface from the as-is surface to the early stages of ion-induced nanopattern formation utilizing operando techniques. For the topographical study, operando grazing-incidence small-angle x-ray scattering experiments conducted at Brookhaven National Laboratory revealed a nonlinear topographical evolution of GaSb under all ion conditions and showed that a threshold fluence must be reached before ion-induced nanopatterning begins.

Presenter

  • Brandon Holybee, The University of Illinois, Urbana-Champaign

Cartography in a General Purpose Risk Analysis System Supporting Black Swan Theory

This presentation will explore cartographic research under development to visualize the quantification of geographic data uncertainty and the propagation of that uncertainty through multiple computational models, whether the uncertainty is from simple GIS commands or complex social and infrastructural models. We will discuss how the Uncertain Geographic Context Problem is reduced in our multiverse data model while reducing cognitive load, both intrinsic and extraneous, for complex geotemporal analyses.

Presenter

  • Dr. Charles R. Ehlschlaeger, U.S. Army Engineer Research and Development Center (ERDC), Urbana–Champaign

Key Feature Article Testing of Structural Components for Elevated Temperature Design

In support of the development and verification of high-temperature design rules in Section III (the nuclear section) of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, testing capabilities have been fully developed using laboratory-scale test articles with key features of representative high-temperature structures and components. This talk describes two types of key feature article testing methods, that is, simplified model test creep-fatigue evaluation and two-bar thermal ratchet for strain limits evaluation.

Presenter

  • Yanli Wang, Mechanical Properties and Mechanics group, MSTD, Oak Ridge

Synthesis, Physical Properties of β-V2PO5, BAs, and Iron-Based Superconductors

β-V2PO5 was a semiconductor with a band gap of 0.48 eV, undergoing a charge ordering (unusual V2+ and V3+) phase transition accompanied by a tetragonal-to-monoclinic structural distortion at 610 K and a paramagnetic-to-ferrimagnetic phase transition at 128 K with a propagation vector of k = 0. The easy axis is in the monoclinic ac plane pointing 47(9)◦ away from the monoclinic a axis. This collinear ferrimagnetic structure and anisotropic isothermal magnetization measurements suggest weak magnetic anisotropy in this compound.

Presenter

  • Jie Xing, University of California, Los Angeles