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At least 595 records · Page 33

NO formation by N 2 /O 2 plasma catalysis: The impact of surface reactions, gas-phase reactions, and mass transport

Pathways and timescales relevant to facilitate plasma-assisted N 2 -O 2 reactions are assessed by measuring the consumption of plasma-derived N and the formation of NO in the gas phase and over Ag catalytic surfaces. These measurements are enabled by a setup that enables N 2 activation in an atmospheric pressure RF plasma jet, enables O 2 addition in the plasma afterglow, facilitates reactions over an Ag wire catalyst, and allows species density quantification by molecular beam mass spectrometry. Gas-phase reactions consume N but do not form NO with high selectivity. The presence of the non-porous Ag wire catalyst increases the rate of N conversion to NO, though mass transfer processes, not surface reactions, dictate the rate of N consumption. When O 2 concentrations and the ratio of the surface area of the catalyst to the void volume of the reactor are high (3–5 mol% O 2 , 10900 m –1 ), N conversion to NO reaches 100 % selectivity. When both N 2 and O 2 are fed through the plasma jet, gas-phase NO production increases 10×, although plasma and gas-phase processes do not exclusively produce NO. Above a threshold NO density, N cannot diffuse to the catalyst surface faster than it is consumed in the gas phase by reactions with NO. Furthermore, the use of heterogeneous catalysts to enhance plasma-driven N x O y formation and control N x O y product selectivity is limited to cases where diffusive transport of N from the gas phase to the catalyst surface is faster than consumption of N from gas-phase reactions with NO.

Engineering↗

Operability thresholds for thermally damaged EBW detonators

Operability thresholds that differentiate between functional RP-87 exploding bridge wire (EBW) detonators and nonfunctional RP-87 EBW detonators (duds) were determined by measuring the time delay between initiation and early wall movement (function time). The detonators were inserted into an externally heated hollow cylinder of aluminum and fired with current flow from a charged capacitor using an exploding bridge wire (EBW initiated). Functioning detonators responded like unheated pristine detonators when the function time was 4 μs or less. The operability thresholds of the detonators were characterized with a simple decomposition cookoff model calibrated using a modified version of the Sandia Instrumented Thermal Ignition (SITI) experiment. These thresholds are based on the calculated state of the PETN when the detonators fire. The operability threshold is proportional to the positive temperature difference (ΔT) between the maximum temperature within the PETN and the onset of decomposition (~406 K). Furthermore, the temperature difference alone was not sufficient to define the operability threshold. The operability threshold was also proportional to the time that the PETN had been at elevated temperatures. That is, failure was proportional to both temperature and reaction rate. The reacted gas fraction is used in the current work for the reaction correlation. Melting of PETN also had a significant effect on the operability threshold. Detonator failure occurred when the maximum temperature exceeded the nominal melting point of PETN (414 K) for 45±5 s or more.

42 ENGINEERING↗

High performance Nb/TiNi nanocomposites produced by packaged accumulative roll bonding

Taking full advantage of intrinsic high strength of nano-reinforcements has been proven difficult in a composite until the concept of strain matching was experimental verified in a nanowire Nb/TiNi in-situ composite, which was obtained via solidifying eutectic Nb/TiNi and subsequent severe wire drawing. However, the volume fraction of the nano-reinforcement was dictated by eutectic reaction, which severely limited the development of high-performance composites. Here, the martensitic transformation nanocomposites were successfully acquired with increased volume fraction and changeable morphology of the nano-reinforcement through hot packaged ARB (PARB) and subsequent wire drawing. The nano-reinforcement with lamellar configuration in the composite could exhibit a large lattice strain of similar to 3.8%, which demonstrated the applicability and effectiveness of the strain matching principle in nano-lamellar composite. The obtained composites show a yield strength over 2.0 GPa and a quasi-linear elastic strain as larger as similar to 6.5% with adjustable apparent elastic modulus from 30 to 50 GPa.

42 ENGINEERING↗

Graphite crystals in catalytically-graphitized glass-like carbon

Catalytic graphitization of glass-like carbon leads to enhanced growth of micro-sized graphitic crystals with unusual shapes of wires, filaments, tubes, rods, whiskers, and spirals. Similar particles with axial symmetry are also found in pure glass-like carbon heat-treated at high temperatures. Nonetheless, the presence of a graphitization catalyst, Si in this case, in the heat-treatment process supports the transformation of porous, disordered carbon structure towards the graphitic atomic order and the formation of manifold peculiar polyhedral wires and particles of geometry distinct from the plate-like shape typical for conventional graphite. In contrast to conventional carbon nanotubes and fibers, the graphene layers are stacked perpendicular to the tube axis, while the size of the most common tube fibers can reach up to 10 μm in diameter and 100 μm in length. X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, small-angle X-ray scattering combined with complementary techniques have been used to characterize the structure of the glass-like carbon derived from furfuryl alcohol catalytically-graphitized using Si particles at 3000 °C. Finally, since control of graphite shape is vital to achieving the level of performance required in contemporary applications, the obtained results demonstrate that the catalytic graphitization method may be employed to produce filamentous graphite crystals.

36 MATERIALS SCIENCE↗

A new tubular ironless linear induction motor using non-interrupted winding method

The ironless linear induction motor device can be used for any application which requires a large motion span or rotation restrictedly by the ironless feature due to the strong magnetic field environment. One of the possible applications is ITER diagnostics shutters. The tokamak reactor systems have a severe radiation issue during the operation. The traditional Kapton-insulated wires have significantly lower radiation resistance than an expected large radiation dose at ITER Motion Stark Effect (MSE) shutter location. Furthermore, the traditional single-sided linear induction motor winds the wire to make the N-turn pitch coils independently and then connect them in series to make a one-phase winding. Therefore, it is a big challenge to make so many radiation-protection connectors in such a limited space as inside the vacuum vessel of fusion reactors. The approved mineral-insulated kinds of cables need a large bend radius for the end turns, so the traditional single-sided linear motor with two-layer three-phase windings need to be upgraded to the tubular linear motors. The new proposed tubular ironless linear induction motor can not only overcome the large bend radius issue with the mineral-insulated cables but also allow the motor coils wound continuously around the tubular-shaped stator, forward and backward N times to make a N-turn winding for each phase, in order to resolve the radiation protection issue with the winding connection. The 3D transient Maxwell electromagnetic model with a tubular three-phase linear induction motor has been analyzed. Furthermore, this paper will present the detailed design and winding method of ironless linear induction motor actuators, and results of the 3D transient numerical simulation of the actuator performance.

Ironless↗

Strength-conductivity synergy via lean alloy design: A study on novel solid stir extrusion of an Al-2Cu-0.1 Nb-0.15Zr (~wt.%) alloy

Aluminum alloys find wide applications in power and transmission cables, and electrical conductors due to their advantageous properties of high electrical conductivity, and lower cost per unit. However, the lower tensile strength compared to copper poses a challenge for the mechanical stability of aluminum-based cables. In this study, we addressed this issue by adopting a process-based alloy design approach, creating a lean alloy with a dilute composition of Al-2Cu-0.1 Nb-0.15Zr (~wt.%). Here, the alloy was processed using a friction stir based novel SolidStir® (SSE) technique, followed by low-temperature aging. The resulting aluminum wire exhibited improved strength (240 MPa) while simultaneously enhancing electrical conductivity (64%IACS). The study employed computational simulations (Thermocalc) and experimental techniques (differential scanning calorimetry and transmission electron microscopy) to thoroughly investigate the microstructure. Microstructural examinations revealed that the precipitation kinetics in SSE and SSE+aged conditions played a significant role in enhancing strength and electrical conductivity. These findings demonstrate the successful achievement of high strength and high electrical conductivity in aluminum wire through a lean alloy design approach.

36 MATERIALS SCIENCE↗

Process-level cost analysis of hybrid manufacturing pathways for aerospace structural components

Hybrid manufacturing is a promising route for producing complex aerospace components, yet systematic cost benchmarking across multiple additive-subtractive pathways remains limited. This study presents a comprehensive process-based cost analysis of seven hybrid manufacturing routes, including laser powder bed fusion (L-PBF), powder- and wire-directed energy deposition (DED), wire arc additive manufacturing (WAAM), additive friction stir deposition (AFSD), metal binder jetting (MBJ), and agility forging, followed by scanning and finish machining. Parametric cost models incorporating direct material, labor, and energy costs were developed. L-PBF results are discussed in detail for a pickle fork component and directly compared with commercial pricing. Across all hybrid routes, labor emerged as the dominant cost driver, contributing more than 70% of total manufacturing cost in some cases. AFSD exhibited the lowest cost for aluminum components, with MBJ being its 316 L stainless steel counterpart, after accounting for geometric scaling. Benchmarking against industrial quotes suggests that hybrid manufacturing can achieve cost levels comparable to those of commercial services, although labor-intensive processes exhibit greater deviation. The analysis highlights automation of material handling, setup, and supervision as key opportunities for improving economic competitiveness. Overall, the proposed framework provides a quantitative basis for evaluating and optimizing hybrid manufacturing pathways for aerospace applications.

Baruah, Sweta [ORNL] (ORCID:0009000174256207)↗

The CLAS12 drift chamber system

The CEBAF Large Acceptance Spectrometer at 12~GeV (CLAS12) is located in Hall~B, one of the experimental halls at Jefferson Lab. The forward part of CLAS12 is built around a superconducting toroidal magnet. The six coils of the toroid divide the detector azimuthally into six sectors. Each sector contains three multi-layer drift chambers for reconstructing the trajectories of charged particles originating from a fixed target. Each of the 18 planar chambers has two ``superlayers'' of six layers each, with the wires in the two adjacent superlayers oriented at ± 6° stereo angles. Each layer has 112 hexagonal cells spanning a range from about 5° to 40° in polar angle. The six-layer structure provides redundancy in track segment finding and good tracking efficiency even in the presence of some individual wire inefficiency. The design, construction, operation, and calibration methods are described, and estimates of the efficiency and resolution are presented from in-beam measurements.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

The GlueX beamline and detector

The GlueX experiment at Jefferson Lab has been designed to study photoproduction reactions with a 9-GeV linearly polarized photon beam. The energy and arrival time of beam photons are tagged using a scintillator hodoscope and a scintillating fiber array. The photon flux is determined using a pair spectrometer, while the linear polarization of the photon beam is determined using a polarimeter based on triplet photoproduction. Charged-particle tracks from interactions in the central target are analyzed in a solenoidal field using a central straw-tube drift chamber and six packages of planar chambers with cathode strips and drift wires. Electromagnetic showers are reconstructed in a cylindrical scintillating fiber calorimeter inside the magnet and a lead-glass array downstream. Charged particle identification is achieved by measuring energy loss in the wire chambers and using the flight time of particles between the target and detectors outside the magnet. The signals from all detectors are recorded with flash ADCs and/or pipeline TDCs into memories allowing trigger decisions with a latency of 3.3 $μs$. The detector operates routinely at trigger rates of 40 kHz and data rates of 600 megabytes per second. Here, we describe the photon beam, the GlueX detector components, electronics, data-acquisition and monitoring systems, and the performance of the experiment during the first three years of operation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Advanced focusing system for secondary electrons in a bunch shape monitor

Non-destructive measurements of longitudinal beam profile in non-relativistic hadron accelerators are usually performed with Bunch Shape Monitors that utilize secondary electron emission to reproduce the shape of a primary ion beam. The existing devices, however, have poor electron collection efficiency from the wire and are limited to one dimensional measurements of the phase coordinate. Here, we present the development of a bunch shape monitor with improved performance for proton beams to be used in the Spallation Neutron Source accelerator. This improvement was achieved by adding focusing optics between the wire and the entrance slit, which will also allow measurements over a much higher dynamic range. Here we present the design, simulation and experimental test results of the developed new electron beam guidance system for the existing SNS bunch shape monitor that allowed significant improvement in the collection efficiency.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Tidal energy resource characterization measurements at Cook Inlet’s East Foreland: Velocity and turbulence

To characterize tidal current and turbulence at a top tidal energy site off the East Foreland in Cook Inlet, Alaska, United States, three moorings were deployed for two months between July and August 2021, and a transect survey was conducted over the course of two tidal cycles at the end of the deployment period. Measurements of velocity and turbulence were then analyzed to better understand the site's hydrodynamics and power potential. Analysis reveals that swift, north-flowing flood currents peak at 4~m/s, while south-flowing ebb currents reach just over 3~m/s. Turbulence intensity ranges from 23\% at the seafloor to 8\% near the surface, and the presence of the foreland creates more intense turbulence near-shore during ebb tide than flood. Power availability at the site could be as high as 720~MW, or 13~kW/m$^2$, though the energy available to a marine energy device will be smaller than this estimate because of water-to-wire efficiency and wake losses. The results from this measurement campaign will inform the validation of a high-resolution tidal hydrodynamic model, as well as early tidal energy projects that are beginning to move beyond the prototyping and demonstration stages to full-scale deployments.

McVey, James R.↗

The structure of 3-D collisional magnetized bow shocks in pulsed-power-driven plasma flows

Here we investigate three-dimensional (3-D) bow shocks in a highly collisional magnetized aluminium plasma, generated during the ablation phase of an exploding wire array on the MAGPIE facility (1.4 MA, 240 ns). Ablation of plasma from the wire array generates radially diverging, supersonic ($M_S$ $\sim 7$), super-Alfvénic ($M_A>1$) magnetized flows with frozen-in magnetic flux $(R_M\gg1)$. These flows collide with an inductive probe placed in the flow, which serves both as the obstacle that generates the magnetized bow shock, and as a diagnostic of the advected magnetic field. Laser interferometry along two orthogonal lines of sight is used to measure the line-integrated electron density. A detached bow shock forms ahead of the probe, with a larger opening angle in the plane parallel to the magnetic field than in the plane normal to it. Since the resistive diffusion length of the plasma is comparable to the probe size, the magnetic field decouples from the ion fluid at the shock front and generates a hydrodynamic shock, whose structure is determined by the sonic Mach number, rather than the magnetosonic Mach number of the flow. The 3-D simulations performed using the resistive magnetohydrodynamic (MHD) code Gorgon confirm this picture, but under-predict the anisotropy observed in the shape of the experimental bow shock, suggesting that non-MHD mechanisms may be important for modifying the shock structure.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Stacking Fault Induced Symmetry Breaking in van der Waals Nanowires

While traditional ferroelectrics are based on polar crystals in bulk or thin film form, two-dimensional and layered materials can support mechanisms for symmetry breaking between centrosymmetric building blocks, e.g., by creating low-symmetry interfaces in van der Waals stacks. Here, we introduce an approach toward symmetry breaking in van der Waals crystals that relies on the spontaneous incorporation of stacking faults in a nonpolar bulk layer sequence. The concept is realized in nanowires consisting of Se-rich group IV monochalcogenide (GeSe 1–x S x ) alloys, obtained by vapor–liquid–solid growth. The single crystalline wires adopt a layered structure in which the nonpolar A-B bulk stacking along the nanowire axis is interrupted by single-layer stacking faults with local A-A' stacking. Density functional theory explains this behavior by a reduced stacking fault formation energy in GeSe (or Se-rich GeSe 1–x S x alloys). Computations demonstrate that, similar to monochalcogenide monolayers, the inserted A-layers should show a spontaneous electric polarization with a switching barrier consistent with a Curie temperature above room temperature. Second-harmonic generation signals are consistent with a variable density of stacking faults along the wires. Here, our results point to possible routes for designing ferroelectrics via the layer stacking in van der Waals crystals.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Time-resolved nanosecond optical pyrometry of the vapor to plasma transitions in exploding bridgewires

Electrically exploded wires find uses throughout high-energy physics. For example, they are commonly used as high-temperature sources, X-ray generators, and in precision timing detonators. However, the detailed and complete physics that occurs is complex and still poorly understood. A full mechanistic description of these complex phenomena is beyond the scope of a single paper. Instead, we focus on the formation of metal vapor and its transition to plasma. This single transition is commonly assumed to comprise “bridge-burst”. We use a suite of diagnostics including a novel, fiber-based, high-speed, optical pyrometer to better characterize this transition. The primary finding from this project is that peak light output from an exploding wire does not temporally match the peak temperature. Additionally, it is found that peak light does not align with peak bridge-burst voltage and that the peak temperature is not voltage-dependent. These findings are non-intuitive and will allow for the correction of false assumptions previously made about this topic.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Chirality and dislocation effects in single nanostructures probed by whispering gallery modes

Nanostructures such as nanoribbons and -wires are of interest as components for building integrated photonic systems, especially if their basic functionality as dielectric waveguides can be extended by chiroptical phenomena or modifications of their optoelectronic properties by extended defects, such as dislocations. However, conventional optical measurements typically require monodisperse (and chiral) ensembles, and identifying emerging chiral optical activity or dislocation effects in single nanostructures has remained an unmet challenge. Here we show that whispering gallery modes can probe chirality and dislocation effects in single nanowires. Wires of the van der Waals semiconductor germanium(II) sulfide (GeS), obtained by vapor–liquid–solid growth, invariably form as growth spirals around a single screw dislocation that gives rise to a chiral structure and can modify the electronic properties. Cathodoluminescence spectroscopy on single tapered GeS nanowires containing joined dislocated and defect-free segments, augmented by numerical simulations and ab-initio calculations, identifies chiral whispering gallery modes as well as a pronounced modulation of the electronic structure attributed to the screw dislocation. Further, our results establish chiral light-matter interactions and dislocation-induced electronic modifications in single nanostructures, paving the way for their application in multifunctional photonic architectures.

36 MATERIALS SCIENCE↗

Evaluation of Low Dose Silicon Carbide Temperature Monitors

Thermocouples are generally used to provide real-time temperature indications in instrumented tests performed at materials and test reactors. Melt wires or paint spots are often included in such tests as an independent technique of detecting peak temperatures incurred during irradiation. In addition, less expensive static capsule tests, which have no leads attached for real-time data transmission, often rely on melt wires and paint spots as a post-irradiation technique for peak temperature indication. Unfortunately, these techniques are limited in that they can only detect whether a single temperature is or is not exceeded. Silicon carbide (SiC) monitors are advantageous because a single monitor can be used to determine the peak temperature reached within a relatively broad range (200 – 800°C). Although the use of SiC monitors was proposed more than five decades ago, the ultimate performance limits of this technique are not fully understood. The Nuclear Science User Facilities (NSUF) is the United States Department of Energy Office of Nuclear Energy's only designated nuclear energy user facility. Its mission is to provide nuclear energy researchers access to world-class capabilities and to facilitate the advancement of nuclear science and technology. This mission is supported by providing access to state-of-the-art experimental irradiation testing, post irradiation examination facilities, and high performance computing capabilities as well as technical and scientific assistance for the design and execution of projects. As part of an NSUF project, low dose silicon carbide monitors were irradiated in the Belgian Reactor 2 and were then evaluated both at the SCK•CEN and at Idaho National Laboratory's High Temperature Test Laboratory to determine their peak temperature achieved during irradiation. The technical significance of this work was that the monitors were irradiated to a dose that was significantly less than recommended in published literature. This paper will discuss the evaluation process, the irradiation test, and the performance of the low dose silicon carbide temperature monitors.

36 MATERIALS SCIENCE↗

Features of explosion of thin aluminum foils on an 8 kA, 350 ns pulse generator

This paper presents the results of a study of the explosion of Al foils with a thickness of 4 μm on an 8 kA, 350 ns pulsed-power generator. The features of the energy deposition process in the explosion of foils in comparison with wires of similar mass and cross section, as well as with thin wires, are studied. In the experiments presented here, the dependence of the energy deposition in the foil on its initial structure was found. In conclusion, two types of exploded foil structure were recorded using point-projection radiography

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Microparticle cloud imaging and tracking for data-driven plasma science

Oceans of image and particle track data encountered in plasma interactions with microparticle clouds motivate development and applications of machine-learning (ML) algorithms. A local-constant-velocity tracker, a Kohonen neural network or self-organizing map, the feature tracking kit, and U-Net are described and compared with each other for microparticle cloud datasets generated from exploding wires, dusty plasmas, and atmospheric plasmas. Particle density and the signal-to-noise ratio have been identified as two important factors that affect the tracking accuracy. Fast Fourier transform is used to reveal how U-Net, a deep convolutional neural network developed for non-plasma applications, achieves the improvements for noisy scenes. Viscous effects are revealed in the ballistic motions of the particles from the exploding wires and atmospheric plasmas. Subdiffusion of microparticles satisfying Δr 2 ∝t k (k=0.84±0.02) is obtained from the dusty plasma datasets. Microparticle cloud imaging and tracking, when enhanced with data and ML models, present new possibilities for plasma physics.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗