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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Beam Diagnostic Challenges for FACET-II

FACET-II, the Facility for Advanced Accelerator Experimental Tests II, is a new accelerator R&D test facility to be constructed at SLAC. It will provide high-energy, high-density electron and positron beams to advance the development of beam driven plasma wakefield acceleration and support a broad range of experiments. The FACET-II beams are expected to have 10 GeV energy, contain 2 nC of charge, have a transverse normalized emittance of 7 microns, be compressed to about 1 micron long and focused to about 6 micron wide at the interaction point. Additionally, the nominal peak current is 20 kA and is expected to fluctuate up to 200 kA. Most experiments desire complete knowledge of the incoming beam parameters on a pulse-to-pulse basis. However, the extreme beam densities and strong fields of the beam current will destroy any diagnostics intercepting the beam in a single shot and impose unique challenges for beam diagnostics. Moreover, non-intercepting diagnostics are desirable to provide feedback for machine setup and characterization. Finally, we need to look beyond conventional diagnostics to seek new solutions for measurements of the high charge, small beam size, short bunch length, and low emittance.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Physics Goals of DWA Experiments at FACET-II

The dielectric wakefield acceleration (DWA) program at FACET produced a multitude of new physics results that range from GeV/m acceleration to the discovery of high field-induced conductivity in THz waves, and beyond, to a demonstration of positron-driven wakes. Here we review the rich program now developing in the DWA experiments at FACET-II. With increases in beam quality, a key feature of this program is extended interaction lengths, near 0.5 m, permitting GeV-class acceleration. Detailed physics studies in this context include beam breakup and its control through the exploitation of DWA structure symmetry. The next step in understanding DWA limits requires the exploration of new materials with low loss tangent, large bandgap, and improved thermal characteristics. Advanced structures with photonic features for mode confinement and exclusion of the field from the dielectric, as well as quasi-optical handling of coherent Cerenkov signals is discussed. Use of DWA for laser-based injection and advanced temporal diagnostics is examined.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Analysis on linac quadrupole misalignment in FACET commissioning 2012

In this note, the analysis on linac quadrupole misalignment is presented for the FACET linac section LI05-09 plus LI11-19. The effectiveness of the beam-based alignment technique is preliminarily confirmed by the measurement. Beam-based alignment technique was adopted at SLAC linac since SLC time. Here the beam-based alignment algorithms are further developed and applied in the FACET commissioning during 2012 run.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

2016 FACET-II Science Workshop Summary Report

The second in a series of FACET-II Science Workshops was held at SLAC National Accelerator Laboratory on October 17-19, 2016 [1]. The workshop drew thirty-five participants from eighteen different institutions including CERN, DESY, Ecole Polytechnique, FNAL, JAI, LBNL, LLNL, Radiabeam, Radiasoft, SLAC, Stony Brook, Strathclyde, Tech-X, Tsinghua, UC Boulder, UCLA and UT Austin. The 2015 workshop [2, 3] helped prioritize research directions for FACET-II. The 2016 workshop was focused on understanding what improvements are needed at the facility to support the next generation of experiments. All presentations are linked to the workshop website as a permanent record.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Descriptors for Cu facets for CO2 reduction reaction activity

Computation screening is crucial for designing efficient electrochemical catalysts for carbon dioxide (CO2R) reduction to valuable hydrocarbons and oxygenates. Herein, leveraging density functional theory calculations of the CO adsorption energy ΔE_CO on seventeen Cu terminations, we discover a strong linear correlation between ΔE_CO and the recently experimentally measured CO2R electrochemical currents (ACS Catal. 2022, 12, 11, 6578–6588). Examining the ab initio thermodynamics of the early critical intermediates CO*, COH*, and CHO*, we find that CO* → CHO* is the thermodynamically preferred step, and notably shows a volcano trend with the experimental currents where the maximum CO2R current corresponds to the moderate CHO* formation energy. Importantly, we show that increasing the step and kink density of the Cu termination not only enhances CO adsorption strength but also modulates the CO* → CHO* pathway, as respectively exemplified in the (941) and (741) facets. We also explain why (741) is exceptional with high CO2R activity as measured experimentally due to its relatively low activity toward the hydrogen evolution reaction compared with the other Cu surfaces. Beyond the general CO adsorption energy that only shows a linear trend with CO2R activity, we show that the reaction CO* → CHO* free energy is a descriptor that displays a volcano relationship with the overall CO2R activity on Cu facets.

machine learning↗
DOE OSTI2019

Controlled Two-Step Formation of Faceted Perovskite Rare-Earth Scandate Nanoparticles

A general approach to the formation of well-faceted nanoparticles is discussed and successfully applied to the production of several rare-earth scandates. Two steps were used, with higher temperatures first to nucleate the perovskite phase, followed by lower temperatures to smooth the particle surfaces. Exploiting these two different regimes led to smaller nanoparticles with more faceting. This general approach may be tailored to other material systems as a step towards producing shape-controlled nanoparticles for a desired application.

36 MATERIALS SCIENCE↗
NASA NTRS1974

Rough surface scattering based on facet model

A model for the radar return from bare ground was developed to calculate the radar cross section of bare ground and the effect of the frequency averaging on the reduction of the variance of the return. It is shown that, by assuming that the distribution of the slope to be Gaussian and that the distribution of the length of the facet to be in the form of the positive side of a Gaussian distribution, the results are in good agreement with experimental data collected by an 8- to 18-GHz radar spectrometer system. It is also shown that information on the exact correlation length of the small structure on the ground is not necessary; an effective correlation length may be calculated based on the facet model and the wavelength of the incident wave.

Khamsi, H. R.↗
NASA NTRS1987

Faceting and roughening in quasicrystals

The question whether quasi-crystal shapes should be faceted is studied in a simple model of quasi-crystalline order. At T = 0, the model is proved to yield a completely faceted equilibrium shape in both two and three dimensions. At T greater than 0, an interface model is derived for a two-dimensional Penrose tiling. By mapping it onto a one-dimensional quasi-periodic Schroedinger equation, it is shown that the roughness exponent varies continuously with T at low T.

Garg, Anupam↗
NASA NTRS1991

Development of an improved mirror facet for space applications

A fabrication technique was successfully developed for a metallic aluminum honeycomb, high-accuracy, lightweight, and long-life solar concentrator (mirror) for Advanced Solar Dynamic Space Power Systems. The program scope was limited to the development, fabrication, evaluation, and delivery of a solar concentrator facet (petal) that was sized for a 2-meter deployable solar concentrator. A surface accuracy of 1.0 mrad was achieved. The development incorporated tooling design, material selection, facet forming, adhesive selection, testing, and analysis. Techniques for applying levelizing, reflective, and protective optical coatings were also developed.

Schertz, Paul↗
DOE OSTI2012

Intensity Effects of the FACET Beam in the SLAC Linac

The beam for FACET (Facility for Advanced aCcelerator Experimental Tests) at SLAC requires an energy-time correlation ('chirp') along the linac, so it can be compressed in two chicanes, one at the midpoint in sector 10 and one W-shaped chicane just before the FACET experimental area. The induced correlation has the opposite sign to the typical used for BNS damping, and therefore any orbit variations away from the center kick the tail of the beam more than the head, causing a shear in the beam and emittance growth. Any dispersion created along the linac has similar effects due to the high (>1.2% rms) energy spread necessary for compression. The initial huge emittances could be reduced by a factor of 10, but were still bigger than expected by a factor of 2-3. Normalized emittance of 3 {micro}m-rad in Sector 2 blew up to 150 {micro}m-rad in Sector 11 but could be reduced to about 6-12 {micro}m-rad, for the vertical plane although the results were not very stable. Investigating possible root causes for this, we found locations where up to 10 mm dispersion was created along the linac, which were finally verified with strong steering and up to 7 mm settling of the linac accelerator at these locations.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

TENDL-2017: the making of multi-faceted technological nuclear data library - 25340

Multi-purpose methodical nuclear data libraries generated by TALYS/T6 as Evaluated Nuclear Data Library TENDL have been released regularly since 2008. Considerable experience has been acquired during those early production of such unique, truly multi-faceted, multi-particle nuclear data libraries based on the feedback from the developers, evaluators, processing experts and, most importantly, users. The backbone of this achievement is simple and robust: completeness, quality, upgradability and, most of all, reproducibility and methodology. Since TENDL has been seamlessly adopted by many different applications (accelerator, astrophysics, fusion, fission, medical) that require multi-faceted nuclear reaction data forms for shielding, radio-protection, transmutation, materials or earth sciences, it is felt necessary to understand its strengths and remaining weaknesses. The essential knowledge is not the TENDL library itself, but rather the necessary methods, processes, codes, tools and know-how that go into the making of every evaluations of such a library. Current efforts are focused on a proper evaluation of the underlying physics and incorporation of information and metrics into the scientific TALYS/T6 system. (authors)

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2022

Acetone to isobutene conversion on Zn x Ti y O z : Effects of TiO 2 facet

In this study, liquid-phase chemical grafting method was used to graft Zn onto TiO 2 with preferentially exposed (1 0 1) or (0 0 1) facet. The obtained Zn x Ti y O z materials were characterized using various techniques (e.g., XRD, Raman, DRIFTS etc.) and evaluated for the acetone-to-isobutene reaction. It was found that over TiO 2 (0 0 1), both terminal and bridging hydroxyls were readily titrated by Zn deposition, whereas a substantial amount of bridging hydroxyls on TiO 2 (1 0 1) remained. Although dominant Zn-O-terminated surface was obtained on two Zn x Ti y O z samples, bridging hydroxyls with high H-D exchange reactivity were observed on Zn x Ti y O z (1 0 1) compared with Zn x Ti y O z (0 0 1). The bridging hydroxyls showing rapid proton transfer efficiently stabilizes a transition state of diacetone alcohol intramolecular rearrangement for isobutene production as opposed to the diacetone alcohol dehydration.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Ostwald ripening of faceted Si particles in an Al-Si-Cu melt

The microstructural evolution of an Al-Si-Cu alloy during Ostwald ripening is imaged via synchrotron-based, four-dimensional (i.e., space and time resolved) X-ray tomography. Samples of composition Al-32 wt%Si-15 wt%Cu were annealed isothermally at 650 °C, in the two-phase solid-liquid regime, while tomographic projections were collected in situ over the course of five hours. Advances in experimental methods and computational approaches enable us to characterize the local interfacial curvatures and velocities during ripening. The sequence of three-dimensional reconstructions and interfacial shape distributions shows highly faceted Si particles in a copper-enriched liquid, that become increasingly isotropic or rounded over time. In addition, we find that the coarsening rate constant is approximately the same in the binary and ternary systems. By coupling these experimental measurements with CALPHAD modeling and ab initio molecular dynamics simulation, we assess the influence of Cu on the coarsening process. Lastly, we find the unusual “pinning” of microstructure at the junction between rough and smooth interfaces and suggest a mechanism for this behavior.

36 MATERIALS SCIENCE↗
NASA NTRS2008

A Faceted Shape Model Approach to Altimetry and Velocimetry for Irregularly Shaped Bodies

Range and velocity sensors based on lidar or radar with multiple beams are often used to measure the altitude and velocity, respectively, of a spacecraft above a targetbody. A difficulty that arises when navigating about small bodies such as asteroids or comets, is that the notion of altitude is largely obscured by the irregular shape of the target surface. This paper develops a method to incorporate the multibeam altimeter and Doppler velocimeter measurements into the on-board spacecraft state estimator by using information from a faceted shape model representation of the target body surface.

state estimation↗
DOE OSTI2017

Kinetically Controlled Fabrication of Single‐Crystalline TiO 2 Nanobrush Architectures with High Energy {001} Facets

This study demonstrates that precise control of nonequilibrium growth conditions during pulsed laser deposition (PLD) can be exploited to produce single‐crystalline anatase TiO 2 nanobrush architectures with large surface areas terminated with high energy {001} facets. The data indicate that the key to nanobrush formation is controlling the atomic surface transport processes to balance defect aggregation and surface‐smoothing processes. High‐resolution scanning transmission electron microscopy data reveal that defect‐mediated aggregation is the key to TiO 2 nanobrush formation. The large concentration of defects present at the intersection of domain boundaries promotes aggregation of PLD growth species, resulting in the growth of the single‐crystalline nanobrush architecture. This study proposes a model for the relationship between defect creation and growth mode in nonequilibrium environments, which enables application of this growth method to novel nanostructure design in a broad range of materials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

FACET: a new long-lived particle detector in the very forward region of the CMS experiment

We describe a proposal to add a set of very forward detectors to the CMS experiment for the high-luminosity era of the Large Hadron Collider to search for beyond the standard model long-lived particles, such as dark photons, heavy neutral leptons, axion-like particles, and dark Higgs bosons. The proposed subsystem is called FACET for Forward-Aperture CMS ExTension, and will be sensitive to any particles that can penetrate at least 50 m of magnetized iron and decay in an 18 m long, 1 m diameter vacuum pipe. The decay products will be measured in detectors using identical technology to the planned CMS Phase-2 upgrade.

Particle and Resonance Production↗
DOE OSTI2016

Effects of Facet Joint Injection Reducing the Need for Percutaneous Vertebroplasty in Vertebral Compression Fractures

ObjectiveTo evaluate the effects of facet joint injection (FJI) reducing the need for percutaneous vertebroplasty (PVP) in cases of vertebral compression fracture (VCF).Materials and MethodsA total of 169 patients who were referred to the radiology department of our institution for PVP between January 2011 and December 2014 were retrospectively evaluated. The effectiveness of FJI was evaluated by the proportion of patients who cancelled PVP and who experienced reduced pain. In addition, by means of medical chart and MRI review, those clinical factors (age, sex, history of trauma, amount of injected steroids and interval days elapsed between VCF and FJI) and MR image factors (kyphosis angle, height loss, single or multiple level of VCF, burst fracture, central canal compromise, posterior element injury) that were believed to be significant for the effectiveness of FJI were statistically analysed.ResultsIn the 26 patients with FJI prior to PVP, six (23 %) patients cancelled PVP with considerable improvement in reported pain. In the 20 patients with PVP after FJI, improvement in pain after FJI was reported by six patients, resulting in a total of 12 patients (46 %) who experienced reduced pain after FJI. Clinical factors and MR image factors did not show any statistically significant difference between those groups, divided by PVP cancellation and by improvement of pain.ConclusionAfter FJI prior to PVP, about one quarter of patients cancelled PVP due to reduced pain and overall about half of the patients experienced reduced pain.

62 RADIOLOGY AND NUCLEAR MEDICINE↗