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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 451 records · Page 25

Department of Energy: Office of Scientific and Technical Information

The international acquisitions functions and activities of the Office of Scientific and Technical Information (OSTI) are described. There are four mechanisms for obtaining foreign information related to energy and nuclear science: The Energy Technology Data Exchange consisting of 14 member countries and 2 associate members; the International Nuclear Information System consisting of 86 countries and 17 international organizations; the Nuclear Energy Agency's 19 member countries provide reports for departmental scientists' use; bilateral agreements with countries such as Germany, the Nordic Consortium, and Australia result in records of foreign research in progress.

Grissom, Catherine↗

NASA Tech Briefs, Summer 1978, Volume 3, No. 2

Topics covered include: NASA TU Services: Technology Utilization services that can assist you in learning about and applying NASA technology; New Product Ideas: A summary of selected innovations of value to manufacturers for the development of new products; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Solar Energy; Materials; Life Sciences; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences.

Source record↗

Studies to Improve the Sensitivity to Low Energy Interactions in Dual-Phase Xenon Dark Matter Detectors. Department of Energy Office of Science Graduate Student Research (SCGSR) Program, Final project report

Noble liquid time projection chambers (TPCs) are some of the most sensitive particle detectors ever developed. They see use in searches for new physics with neutrinos, or for new particles like dark matter. They work by sensing light and charge signals left behind by particle interactions in a volume of liquified xenon or argon. TPCs are so sensitive that even a single electron liberated in an interaction can be readily detected. However this sensitivity to signals comes with a sensitivity to background noise, with one example being single electrons that arrive long after the signals from a true particle interaction. This type of noise has been the subject of multiple studies, which have concluded that single electron backgrounds are well correlated with prior events in the TPC, as well as impurities in the detection medium. At Lawrence Livermore National Laboratory (LLNL), the XeNu TPC is a testbed for a novel study of these backgrounds by generating data with new components made of aluminum and Shapal--the latter being an exotic ceramic which can be machined using standard tools. These materials were selected to replace plastic components which introduce impurities in the TPC during operation. Without plastic, the hope is that electron backgrounds will be reduced, leaving new opportunities for studying their origins and dependence on impurities. The SCGSR fellowship served as a springboard to help meet these objectives. Over the course of a year, the new components were designed, fabricated, and installed in XeNu. Following their installation, data was taken for use in a future study that will enable the electron background contributions from plastic components to be studied directly. In the interim, preliminary analysis results indicate that electron backgrounds with the new components are roughly 50% lower. This has established the efficacy of Shapal as a low-background replacement for plastic components where electrical and thermal stability are needed

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Fully Convolutional Spatio-Temporal Models for Representation Learning in Plasma Science

We have trained a fully convolutional spatio-temporal model for fast and accurate representation learning in the challenging exemplar application area of fusion energy plasma science. The onset of major disruptions is a critically important fusion energy science issue that must be resolved for advanced tokamak plasmas such as the $25B burning plasma international thermonuclear experimental reactor (ITER) experiment. While a variety of statistical methods have been used to address the problem of tokamak disruption prediction and control, recent approaches based on deep learning have proven particularly compelling. In the present paper, we introduce further improvements to the fusion recurrent neural network (FRNN) software suite, which delivered cross-machine disruption predictions with unprecedented accuracy using a large database of experimental signals from two major tokamaks. Up to now, FRNN was based on the long short-term memory (LSTM) variant of recurrent neural networks to leverage the temporal information in the data. Here, we implement and apply the "temporal convolutional neural network (TCN)" architecture to the time-dependent input signals. Furthermore, this allows highly optimized convolution operations to carry the majority of the computational load of training, thus enabling a reduction in training time, and the effective use of high-performance computing resources for hyperparameter tuning. At the same time, the TCN-based architecture achieves better predictive performance when compared with the LSTM architecture for various tasks for a representative fusion database.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Electronic Structure of Compressively Strained Bilayer Nickelate Thin Film

The discovery of superconductivity in bulk bilayer nickelates under high pressure, and its subsequent stabilization in compressively strained thin films at ambient pressure, has established a new platform for exploring high-𝑇 c superconductivity beyond the cuprates. Central to this development is the prominent role of the 3⁢𝑑$^2_𝑧$ orbital in shaping the low-energy electronic structure, imposing constraints on microscopic theories and fueling debate over the superconducting mechanism. Here we report a systematic in situ angle-resolved photoemission spectroscopy study of compressively strained bilayer nickelate thin films spanning Ca doping, oxygen stoichiometry and film thickness. Despite variations in oxygen-vacancy disorder and surface termination, the electronic structure remains robust and exhibits a systematic strain-driven evolution consistent with an intermediate-correlation regime. In particular, we demonstrate a Ca-doping-induced electronic structure evolution that is consistent with Fermi-level crossing of the 𝛾 band and is decoupled from the presence of superconductivity, suggesting that, while important for the 𝛾 band to be near the Fermi level, the debated 𝛾 crossing and the resulting Fermi pocket may not be a prerequisite for superconductivity. Together, our results establish key spectroscopic constraints on the minimal fermiology and correlation strength relevant to superconductivity in bilayer nickelates, providing an experimental foundation for microscopic theories of their pairing mechanism.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Reducing the Strain Required for Ambient‐Pressure Superconductivity in Ruddlesden‐Popper Bilayer Nickelates

ABSTRACT The discovery of high‐temperature superconductivity in pressurized bulk Ruddlesden‐Popper (RP) bilayer nickelates has prompted the conjecture that epitaxial compressive strain might mimic essential aspects of hydrostatic pressure. The realization of superconductivity in films on SrLaAlO 4 (001) (SLAO) supports this correspondence, yet it remains unclear whether the pressure–temperature phase diagram of RP bilayer nickelates can be systematically mapped (and studied at ambient pressure) as a function of epitaxial strain. To this end, experimental access near the elusive edge of the superconducting phase boundary would provide invaluable insight into the nature of the superconducting state and the ground state from which it emerges. Here we report superconducting RP bilayer nickelates grown on LaAlO 3 (001) (LAO), where the compressive strain required for ambient‐pressure superconductivity is nearly halved to −1.2%. These films exhibit a superconducting onset above 10 K and reach zero resistance at 3 K, with normal‐state transport properties differing from those of films grown on SLAO. Our comparative study shows that strain–rather than interfacial structure is the primary factor governing the superconductivity and normal‐state properties. This work offers a new opportunity to probe emergent phenomena near the superconducting phase boundary in the strain–temperature phase diagram of RP bilayer nickelates.

Tarn, Yaoju [Department of Applied Physics Stanfor↗

High-Energy X-Ray Diffraction Microscopy in Materials Science

High-energy diffraction microscopy (HEDM) is an implementation of three-dimensional X-ray diffraction microscopy. HEDM yields maps of internal crystal orientation fields, strain states, grain shapes and locations as well as intragranular orientation distributions, and grain boundary character. Because it is nondestructive in hard materials, notably metals and ceramics, HEDM has been used to study responses of these materials to external fields including high temperature and mechanical loading. Currently available sources and detectors lead to a spatial resolution of ~1 μm and an orientation resolution of <0.1°. With the penetration characteristic of high energies ( E ≥ 50 keV), sample cross-section dimensions of ~1 mm can be studied in materials containing elements across much of the Periodic Table. This review describes hardware and software associated with HEDM as well as examples of applications. Overall, these applications include studies of grain growth, recrystallization, texture development, orientation gradients, deformation twinning, annealing twinning, plastic deformation, and additive manufacturing. We also describe relationships to other X-ray-based methods as well as prospects for further development.

36 MATERIALS SCIENCE↗

Synthesis of superconducting freestanding infinite-layer nickelate heterostructures on the millimetre scale

The development of superconductivity in infinite-layer nickelates through hole-doping relies on the controlled synthesis of Ni in a high oxidation state, followed by topotactic reduction to a very low oxidation state. So far, superconductivity has been realized only in epitaxial thin films. Here, in this work, we integrate these techniques with heterostructures that include an epitaxial soluble buffer layer, enabling the release of freestanding (Nd,Sr)NiO 2 heterostructures. The released heterostructures exhibit comparable structural and electronic properties to those of optimized thin films, with lateral dimensions ranging from millimetres to ~100 μm, depending on the degree of strain released with respect to the initial substrate. The changes in the superconducting transition temperature upon release of the heterostructure mirror those reported for variations in substrate and pressure, suggesting a common underlying response to strain in the infinite-layer nickelate superconductivity. These freestanding structures will facilitate a range of experimental studies without the constraints of substrates.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗