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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Magnetic-Nozzle Studies for Fusion Propulsion Applications: Gigawatt Plasma Source Operation and Magnetic Nozzle Analysis

This project has been a multiyear effort to assess the feasibility of a key process inherent to virtually all fusion propulsion concepts: the expansion of a fusion-grade plasma through a diverging magnetic field. Current fusion energy research touches on this process only indirectly through studies of plasma divertors designed to remove the fusion products from a reactor. This project was aimed at directly addressing propulsion system issues, without the expense of constructing a fusion reactor. Instead, the program designed, constructed, and operated a facility suitable for simulating fusion reactor grade edge plasmas, and to examine their expansion in an expanding magnetic nozzle. The approach was to create and accelerate a dense (up to l0(exp 20)/m) plasma, stagnate it in a converging magnetic field to convert kinetic energy to thermal energy, and examine the subsequent expansion of the hot (100's eV) plasma in a subsequent magnetic nozzle. Throughout the project, there has been a parallel effort between theoretical and numerical design and modelling of the experiment and the experiment itself. In particular, the MACH2 code was used to design and predict the performance of the magnetoplasmadynamic (MPD) plasma accelerator, and to design and predict the design and expected behavior for the magnetic field coils that could be added later. Progress to date includes the theoretical accelerator design and construction, development of the power and vacuum systems to accommodate the powers and mass flow rates of interest to out research, operation of the accelerator and comparison to theoretical predictions, and computational analysis of future magnetic field coils and the expected performance of an integrated source-nozzle experiment.

Gilland, James H.↗
DOE OSTI2018

Electron-cyclotron-resonance heating in Wendelstein 7-X: A versatile heating and current-drive method and a tool for in-depth physics studies

For stellarators, which need no or only small amounts of current drive, electron-cyclotron-resonance heating (ECRH) is a promising heating method even for the envisaged application in a fusion power plant. Wendelstein 7-X (W7-X) is equipped with a steady-state capable ECRH system, operating at 140 GHz, which corresponds to the 2nd cyclotron harmonic of the electrons at a magnetic field of 2.5 T. Ten gyrotrons are operational and already delivered 7 MW to W7-X plasmas. Combined with pellet injection, the highest triple product (0.68 × 10 20 keV m –3 s), observed up to now in stellarators, was achieved. For the first time, W7-X plasmas were sustained by 2nd harmonic O-mode heating, approaching the collisionality regime for which W7-X was optimized. Power deposition scans did not show any indication of electron temperature profile resilience. In low-density, low-power plasmas a compensation of the bootstrap current with electron-cyclotron current drive (ECCD) was demonstrated. Furthermore, sufficiently strong ECCD close to the plasma centre produced periodic internal plasma-crash events, which coincide with the appearance of low order rationals of the rotational transform.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Direct comparison of gyrokinetic and fluid scrape-off layer simulations

Typically, fluid simulations are used for tokamak divertor design. However, fluid models are only valid if the scrape-off layer (SOL) is highly collisional. This assumption is valid in many present-day experiments but is questionable in the upstream SOL of some high-power scenarios envisioned for burning plasmas and fusion pilot plants. This paper reports on comparisons between fluid and kinetic simulations of the SOL for upstream parameters and geometry representative of the Spherical Tokamak for Energy Production fusion pilot plant. The SOLPS-ITER (fluid) and Gkeyll (gyrokinetic) codes are operated in a two-dimensional axisymmetric mode, which replaces turbulence with ad-hoc diffusivities. In kinetic simulations, we observe that the ions in the upstream SOL experience significant mirror trapping. This substantially increases the upstream temperature and has important implications for impurity dynamics. We show that the mirror force, which is excluded in SOLPS’s fluid equations, enhances the electrostatic potential drop along the field line in the SOL. We also show that the assumption of equal main ion and impurity temperatures, which is made in commonly used fluid codes, is invalid for the regimes explored here. The combination of these effects results in superior confinement of impurities to the divertor region in kinetic simulations, consistent with our earlier predictions [Kotschenreuther et al., in 29th IAEA 29 Fusion Energy Conference (IAEA, London, UK, 2023)]. This effect can be dramatic, reducing the midplane impurity density by orders of magnitude. These results indicate that in lower collisionality SOL’s the tolerable downstream impurity densities may be higher than would be predicted by fluid simulations, allowing for higher radiated power while avoiding unacceptable core contamination. Our results highlight the importance of kinetic simulations for divertor design and optimization for fusion pilot plants.

Computational fluid dynamics↗
DOE OSTI2021

Microscopic ejecta measurements from hypervelocity impacts on aluminum and powdered regolith targets

Meteoroids and space debris pose a two-fold threat to spacecraft due to the risk of both mechanical damage from the impact and electrical damage from the impact-generated plasma, which produces electromagnetic emissions. Analysis of impact products, however, has the potential to provide useful information about planetary rings and small solar system bodies, such as asteroids and comets. Understanding the plasma dynamics and radiation mechanism is essential to addressing the impact threat and extracting science data from impacts. Charge attachment to condensed-phase debris may lead to a dusty plasma under certain conditions, so interpreting hypervelocity impacts requires knowledge of both the nature of the plasma and of the ejecta. We address the latter with measurements of the microscopic ejecta distribution produced by light gas gun impacts on solid aluminum and powdered regolith simulant targets. We examine both the size and shape of the ejecta using thin-film witness plates and find that the size distributions of microscopic ejecta follow power laws. Observations from the powdered regolith simulant match well with disruption experiments of solid basalt, while measurements from the aluminum impacts diverge from extrapolations based on studies of macroscopic debris. Analysis of the ejecta shape shows a transition from smooth to irregularly shaped ejecta at the material grain size, and the shape of debris may provide insight on the phase of the ejected material. Finally, based on our results, we predict a significant number of secondary impacts on plasma sensors due to ejecta, even at considerable distance from the target, supporting the hypothesis that charged dust affects plasma measurements in the ejecta curtain.

42 ENGINEERING↗
DOE OSTI2023

Interfacial bond characterization of epoxy adhesives to aluminum alloy and carbon fiber-reinforced polyamide by vibrational spectroscopy

Vibrational spectroscopic technique has been utilized to investigate interfacial bonding chemistry of two epoxy adhesive products, XP0012 and XP5005F, on plasma-treated AA6061 and carbon fiber-reinforced polyamide 66 (CFRP-PA66) surfaces. The change in vibrational peak ratios was measured by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy to deduce bonding mechanisms. Both adhesives showed strong crosslinking polymerization of hydroxyl- and amine-initiated epoxy ring opening on AA6061 surface, but on CFRP surface XP0012 formed a simple amide linkage by the reaction of surface hydroxyl groups and nitrile groups of curing agent, and XP5005F formed a crosslinked network by hydroxyl-initiated epoxy ring opening polymerization. The different interfacial bonding formation of two adhesives on CFRP-PA66 surface is attributed to additive effect. Addition of additives to epoxy adhesives (XP5005F) changed the interfacial bonding mechanism on CFRP-PA66 surface, rather forming hydroxyl-initiated epoxy opening crosslinking polymerization than a simple amide bond formation (XP0012). The interfacial bonding chemistry was also proved by addition of bisphenol A (BA) to a simplified model diglycidyl ether of bisphenol A/dicyandiamide (DGEBA/DICY) epoxy system. When BA was added to the model DGEBA/DICY system, epoxy ring gradually decreased on CFRP-PA66 surface, while without BA, DGEBA/DICY showed only decrease in a nitrile peak intensity in ATR-FTIR. In conclusion, the foregoing different types of interfacial chemical bonds at the adhesive/CFRP-PA66 interfaces can affect the lap shear behavior of the joint.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Benznidazole, the trypanocidal drug used for Chagas disease, induces hepatic NRF2 activation and attenuates the inflammatory response in a murine model of sepsis

Molecular mechanisms on sepsis progression are linked to the imbalance between reactive oxygen species (ROS) production and cellular antioxidant capacity. Previous studies demonstrated that benznidazole (BZL), known for its antiparasitic action on Trypanosoma cruzi, has immunomodulatory effects, increasing survival in C57BL/6 mice in a model of polymicrobial sepsis induced by cecal ligation and puncture (CLP). The mechanism by which BZL inhibits inflammatory response in sepsis is poorly understood. Also, our group recently reported that BZL is able to activate the nuclear factor erytroide-derived 2-Like 2 (NRF2) in vitro. The aim of the present work was to delineate the beneficial role of BZL during sepsis, analyzing its effects on the cellular redox status and the possible link to the innate immunity receptor TLR4. Specifically, we analyzed the effect of BZL on Nrf2 regulation and TLR4 expression in liver of mice 24 hours post-CLP. BZL was able to induce NRF2 nuclear protein localization in CLP mice. Also, we found that protein kinase C (PKC) is involved in the NRF2 nuclear accumulation and induction of its target genes. In addition, BZL prompted a reduction in hepatic CLP-induced TLR4 protein membrane localization, evidencing its immunomodulatory effects. Together, our results demonstrate that BZL induces hepatic NRF2 activation with the concomitant increase in the antioxidant defenses, and the attenuation of inflammatory response, in part, by inhibiting TLR4 expression in a murine model of sepsis. - Highlights: • BZL improves survival rate after polymicrobial sepsis • BZL enhances hepatic NRF2 nuclear accumulation in a model of sepsis, in part, by a mechanism dependent on PKC activation • BZL-enhanced NRF2 induction regulates antioxidant enzymes and increases antioxidant cellular defenses in sepsis • BZL blocks liver ROS production and ROS-induced TLR4 plasma membrane expression in septic mice.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2011

Study of Heating and Fusion Power Production in ITER Discharges

ITER simulations, in which the temperatures, toroidal angular frequency and currents are evolved, are carried out using the PTRANSP code starting with initial profiles and boundary conditions obtained from TSC code studies. The dependence of heat deposition and current drive on ICRF frequency, number of poloidal modes, beam orientation, number of Monte Carlo particles and ECRH launch angles is studied in order to examine various possibilities and contingencies for ITER steady state and hybrid discharges. For the hybrid discharges, the fusion power production and fusion Q, computed using the Multi-Mode MMM v7.1 anomalous transport model, are compared with those predicted using the GLF23 model. The simulations of the hybrid scenario indicate that the fusion power production at 1000 sec will be approximately 500 MW corresponding to a fusion Q = 10.0. The discharge scenarios simulated aid in understanding the conditions for optimizing fusion power production and in examining measures of plasma performance.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Advanced geometries and regimes

We review and discuss different schemes of laser ion acceleration as well as advanced target geometries in connection with the development of the laser-driven proton source for hadron therapy of oncological diseases, which is a part of the ELIMED project.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Ternary SiGeSn alloy nanocrystals via nonthermal plasma synthesis

We report on the synthesis of ternary SiGeSn nanocrystals (NCs) produced via nonthermal plasma synthesis from silane (SiH 4 ), germane (GeH 4 ), and tetramethylstannane (Sn(CH 3 ) 4 ) precursor sources. Detailed structural, chemical, and vibrational analyses show that all three elements are incorporated both on the NC surface and within the NC core. Incorporation of Sn into the NC core is realized using a secondary injection of SiH 4 and GeH 4 precursor gases in the after-glow region of the plasma, which kinetically traps Sn in the core. We demonstrate compositional tunability of the SiGeSn NCs in which the Si and Ge ratios can be varied broadly at low Sn concentrations. We also show tunability of the Sn content up to ~2 atomic percent as revealed by ICP-MS analysis. More generally, this report demonstrates how nonthermal plasma synthesis can be used to produce metastable ternary nanostructured alloys involving thermodynamically insoluble constituents.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Laser cutting apparatus for high energy density and diamond anvil cell science

In this paper, we present a low-cost, high-resolution laser cutting system designed for use in the fabrication of samples for high energy density physics. Such samples are necessarily small but require precision and repeatability, particularly with the recently available high repetition rates possible at modern facilities. The system allows simultaneous laser cutting, using nanosecond near-infrared laser pulses, and optical microscopy so that the cut can be monitored in real time. The capabilities of the system are demonstrated on a range of materials for both laser-matter interaction targets and components for high pressure diamond anvil cell experiment.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

New oxygen radical source using selective sputtering of oxygen atoms for high rate deposition of TiO{sub 2} films

We have developed a new oxygen radical source based on the reactive sputtering phenomena of a titanium target for high rate deposition of TiO{sub 2} films. In this oxygen radical source, oxygen radicals are mainly produced by two mechanisms: selective sputter-emission of oxygen atoms from the target surface covered with a titanium oxide layer, and production of high-density oxygen plasma in the space near the magnetron-sputtering cathode. Compared with molecular oxygen ions, the amount of atomic oxygen radicals increased significantly with an increase in discharge current so that atomic oxygen radicals were mainly produced by this radical source. It should be noted that oxygen atoms were selectively sputtered from the target surface, and titanium atoms sputter-emitted from the target cathode were negligibly small. The amount of oxygen radicals supplied from this radical source increased linearly with increasing discharge current, and oxygen radicals of 1 Multiplication-Sign 10{sup 15} atoms/s/cm{sup 2} were supplied to the substrate surface at a discharge current of 1.2 A. We conclude that our newly developed oxygen radical source can be a good tool to achieve high rate deposition and to control the structure of TiO{sub 2} films for many industrial design applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Orientation-dependent etching of silicon by fluorine molecules: A quantum chemistry computational study

Anisotropic etching is a widely used process in semiconductor manufacturing, in particular, for micro- and nanoscale texturing of silicon surfaces for black silicon production. The typical process of plasma-assisted etching uses energetic ions to remove materials in the vertical direction, creating anisotropic etch profiles. Plasmaless anisotropic etching, considered here, is a less common process that does not use ions and plasma. The anisotropy is caused by the unequal etching rates of different crystal planes; the etching process, thus, proceeds in a preferred direction. In this paper, we have performed quantum chemistry modeling of gas-surface reactions involved in the etching of silicon surfaces by molecular fluorine. The results confirm that orientation-dependent etch rates are the reason for anisotropy. The modeling of F 2 dissociative chemisorption on F-terminated silicon surfaces shows that Si–Si bond breaking is slow for the Si(111) surface, while it is fast for Si(100) and Si(110) surfaces. Both Si(100) and Si(110) surfaces incorporate a larger number of fluorine atoms resulting in Si–Si bonds having a larger amount of positive charge, which lowers the reaction barrier of F 2 dissociative chemisorption, yielding a higher etch rate for Si(100) and Si(110) surfaces compared to Si(111) surfaces. Molecular dynamics modeling of the same reactions has shown that the chosen reactive bond order potential does not accurately reproduce the lower reaction barriers for F 2 dissociative chemisorption on Si(100) and Si(100) surfaces. Furthermore, reparameterization is necessary to model the anisotropic etching process that occurs at lower temperatures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Review of bottomonium measurements from CMS

We review the results on the bottomonium system from the CMS experiment at the Large Hadron Collider. Measurements have been carried out at different center-of-mass energies in proton collisions and in collisions involving heavy ions. These include precision measurements of cross sections and polarizations, shedding light on hadroproduction mechanisms, and the observation of quarkonium sequential suppression, a notable indication of quark–gluon plasma formation. The observation of the production of bottomonium pairs is also reported along with searches for new states. We close with a brief outlook of the future physics program.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Characterization of Ceramic Material Produced From a Cold Crucible Induction Melter Test

This report summarizes the results from characterization of samples from a melt processed surrogate ceramic waste form. Completed in October of 2014, the first scaled proof of principle cold crucible induction melter (CCIM) test was conducted to process a Fe-hollandite-rich titanate ceramic for treatment of high level nuclear waste. X-ray diffraction, electron microscopy, inductively coupled plasma-atomic emission spectroscopy (and inductively coupled plasma-mass spectroscopy for Cs), and product consistency tests were used to characterize the CCIM material produced. Core samples at various radial locations from the center of the CCIM were taken. These samples were also sectioned and analyzed vertically. Together, the various samples were intended to provide an indication of the homogeneity throughout the CCIM with respect to phase assemblage, chemical composition, and chemical durability. Characterization analyses confirmed that a crystalline ceramic with desirable phase assemblage was produced from a melt using a CCIM. Hollandite and zirconolite were identified in addition to possible highly-substituted pyrochlore and perovskite. Minor phases rich in Fe, Al, or Cs were also identified. Remarkably only minor differences were observed vertically or radially in the CCIM material with respect to chemical composition, phase assemblage, and durability. This recent CCIM test and the resulting characterization in conjunction with demonstrated compositional improvements support continuation of CCIM testing with an improved feed composition and improved melter system.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Experimental Investigations of Fundamental Processes in Dusty Plasmas

This is the final technical report for DOE Grant #DE-FG02-04ER54795-Experimental Investigations of Fundamental Processes in Dusty Plasmas. A plasma is an ionized gas, and a dusty plasmas is a plasma that contains, in addition to electrons and ions, micron-sized dust particles. The dust particles acquire and electric charge in the plasma by collecting electrons and ions. The electrons move more rapidly than the ions, so the dust charge is negative. A 1 micron dust particle in a typical low temperature plasma has a charge corresponding to approximately 2000 electrons. Dusty plasmas are naturally found in astrophysical plasmas, planetary rings, technological plasmas, and magnetic fusion plasmas. The goal of this project was to study in the laboratory, the basic physical processes that occur in dusty plasmas. This report provides a summary of the major scientific products and activities of this award.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Develop On-Demand nanoplasmonic Device Concepts in a Semiconductor Compatible Hybrid System. Final Report

This report summarizes the research activities supported by the U.S. Department of Energy grant DE-SC-0010399. The goal of this project is to is to develop an on-demand nanoplasmonic platform that combines emerging oxide nanoelectronics with a low-loss semiconductor-friendly plasmonic materials. Toward this goal, several unique heterostructures formed between complex oxides and 2D layered materials have been developed. Based on these material systems, a set of atomic force microscope (AFM) based techniques have been developed that can allow long-living and reversible material phase transitions to be manipulated in nanoscale at room temperature. Using such technique and through interface coupling, we can effectively tune the plasmon propagations in unconventional plasmonic materials such as graphene and VO 2 . In addition, we also discovered a plethora of novel interface enabled electro-optic effects, including the spatial modulation of light using 2DEG, a giant programmable photothermoelectric effects at room temperature, a light induced superconducting transition, and a tunable giant third order optical nonlinearities. These major results are outlined in this report, along with lists of project participants and products.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗