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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Density of molten oxides measured in an aero-acoustic levitator

Knowing the thermophysical properties of high-temperature melts can aid the design of melt processes and validate atomic structural models, such as those used in studying glass formation. Property measurements on such melts are challenging, however, due to container-related contamination and heterogeneous nucleation. Containerless processing techniques that employ levitation can be used to avoid these obstacles. In that context, we demonstrate here the application of silhouette imaging to measure the density of molten oxides in an aero-acoustic levitation instrument (AAL). The AAL combines gas jet levitation with actively controlled acoustic positioning to enable full optical access to samples ca. 2–4 mm in diameter, which are laser beam heated and melted. The cross sections of molten drops are imaged using a monochromatic light source and narrowband-filtered camera. Melt volume is calculated from the cross sections and used to find density at several temperatures ranging 1530–1920 K, including up to 350 K of supercooling. We report densities for CaAl 2 O 4 , Ca 12 Al 14 O 33 , CaSiO 3 , their Fe 2 O 3 -bearing analogs, and 83TiO 2 -17RE 2 O 3 (RE = La or Nd). These provide important benchmarks of the capabilities, measurement uncertainties, and future outlook for this technique.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Angularly resolved spectral reconstruction of x rays via filter pack attenuation

We have designed a new filter pack array to measure angular variations in x-ray spectra during a single shot. The filter pack was composed of repeating identical columns of aluminum and copper filters of varying thicknesses. These columns were located at different positions to measure the spectrum at each corresponding angle. This array was utilized in an experiment to measure the energy evolution of betatron x rays in a laser wakefield accelerator by curving the wakefield with a transverse density gradient, streaking the x rays across the array in front of an x-ray charge-coupled device (CCD) camera. After subtracting the background and “flattening” the image to remove spatial nonuniformities, a critical energy was calculated for each position that produced the best agreement with the measured signal. There was a clear change in critical energy with angle, shedding light on the dynamics of the electrons that traveled through the accelerator. Furthermore, these angles correspond to distinct emission times, covering a timescale of tens of picoseconds. The filter pack was capable of recovering these angular details without the impact of errors introduced by shot-to-shot variability.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Multiframe X-ray diffraction on the OMEGA EP laser

A method of measuring multiple temporally resolved powder x-ray diffraction measurements during a single dynamic compression laser experiment has been demonstrated on the OMEGA EP laser. Up to four time-gated snapshots of the x-ray diffraction pattern are collected on an ultrafast x-ray framing camera with a 2θ scattering angle coverage of 48°–65° and 400-ps temporal resolution with the potential for 10°–160° and 200-ps resolution. X-ray diffraction snapshots capture the transformation to a high-pressure β phase in ramp-compressed Zr, constraining the atomic structure and pressure–density equation-of-state in a single shot. Here, this platform will be used to constrain transition pressures, understand the role of kinetics, and verify the existence of hysteresis and metastability on phase transformations at the lattice level under single-shot dynamic compression.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

The infrared imaging video bolometer at Wendelstein 7-X

The radiated power distribution is a crucial aspect of heat transport, heat load mitigation, and plasma exhaust performance. An imaging video bolometer camera has been installed to measure the plasma radiated power in the divertor region of the Wendelstein 7-X (W7-X) stellarator. This diagnostic offers a wide-angle (40° × 68°) sampling of the plasma volume in both the poloidal and toroidal directions. The field-of-view is covered with a large number (> 500) of bolometer channels, providing imaging capability. The diagnostic design is introduced here together with its data analysis procedure. A set of laboratory experiments is performed to assess the thermal properties of the gold absorber foil and their spatial uniformity. Following installation, a heat source originating from the inertially cooled front of the diagnostic is identified and filtered out. The discharge data indicate a satisfactory signal-to-noise ratio as well as spatiotemporal resolution. These represent the first toroidally resolved images of the line-integrated radiated power in the W7-X island divertor. The diagnostic was then upgraded with a thinner platinum absorber and adjusted mirrors. Early data from the most recent experimental campaign employing the upgraded design show a considerable improvement in the diagnostic performance with more bolometer channels (> 1400), extended coverage, and increased spatial resolution.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Laser beam pointing stabilization using analog position-sensitive diodes

Laser wire scanners have been used for ion beam profile and emittance measurements at the Spallation Neutron Source linear accelerator. Due to propagation distances exceeding 100 m, reliable measurements require laser beam stabilization, previously accomplished with a feedback control loop using a digital camera as a position sensor [Hardin et al., Opt. Express 19, 2874 (2011)]. Here, this paper presents an upgraded pointing stabilization system utilizing analog position-sensitive diodes (PSDs) as the position detector, optimized with an optical diffuser. The new system significantly surpasses the previous system by offering an order-of-magnitude improvement in radiation tolerance and a bandwidth limited only by the burst repetition rate of the laser beam. Operating with a 60-Hz burst mode laser, the new system effectively suppresses laser beam drifts up to 30 Hz, compared to the previous system’s 4 Hz limit. In addition, the amplitude of spectral components below 0.1 Hz was reduced by a factor of more than 100, which is over seven times greater than was achieved by the previous system.

Data acquisition↗
DOE OSTI2025

Automated imaging of the annihilation of a transverse domain wall in patterned magnetic thin films

Imaging the magnetic domain wall behavior in patterned thin films under external stimuli can enable understanding the underlying energy landscape and the role of local microstructure and defects. We present an automated workflow for in situ Lorentz transmission electron microscopy to image magnetic domain walls at the nanometer length scale and at a time resolution in the sub-millisecond regime—the latter of which is limited by the speed of the available camera. Our workflow is modular and can be broadly applied to various types of in situ experiments, taking us a step closer to the future of autonomous imaging of nanomagnetic films with electron microscopy. Using our workflow, we show the transformation of a transverse domain wall with sub-millisecond time resolution under the application of an in situ transverse magnetic field, a study of whose dynamics are essential in the design of future domain wall mediated spintronic device applications.

Algebraic topology↗
DOE OSTI2025

Experimental study of high-energy single-pulse nanosecond discharges in pin-to-pin configuration

Single-pulse pin-to-pin nanosecond pulsed discharges in ambient air (gap distances of 3–7 mm) were investigated at high pulse energies (∼20–30 mJ deposited energy per 11 ns full width at half maximum pulse). A Michelson interferometry setup (532 nm continuous-wave laser) was employed to record time-resolved interferograms of the discharge, enabling spatially resolved calculation of the electron number density. An intensified charge-coupled device camera was used to capture the spatiotemporal evolution of the discharge (streamer formation and spark channel development), and Coherent Anti-Stokes Raman Spectroscopy (CARS) was used to measure post-discharge N 2 vibrational temperatures. Discharge current and voltage were monitored with a back-current shunt. The discharge was initiated with simultaneous cathode-directed and anode-directed streamers that bridge the gap within ∼1 ns and form a luminous, filamentary plasma channel immediately after breakdown. Laser interferometry measurements showed peak electron number densities of the order of 10 1 7–10 18 cm −3 , occurring about 15–20 ns after pulse arrival at the discharge gap. Shorter gap discharges yielded higher peak electron densities, consistent with the higher energy density in the smaller gaps. Spatially, the electron density was highest near the electrodes and decreased toward the midgap region, with 5 and 7 mm gaps exhibiting a pronounced drop in the central channel. CARS indicated initial vibrational temperatures of approximately 4000–6000 K in the spark core of ∼50 ns after the discharge onset, decaying on a ∼500 ns timescale as the plasma cooled and recombined.

Coherent anti-Stokes Raman spectroscopy↗
DOE OSTI2026

Reduced fast-ion transport calculations of m = n = 1 fishbone-like instabilities in MAST-U

Fast-ion transport associated with an m = n = 1 fishbone-like burst in MAST-U discharge 47128 is investigated using a reduced guiding-center-based transport model (ORBIT-Kick) constrained by multi-diagnostic measurements. The two-dimensional beam-emission spectroscopy system provides measurements of the core poloidal mode structure and fluctuation amplitude, while EFIT++ reconstructions constrained by the motional Stark effect diagnostic indicate a flat q-profile with q 0 > 1⁠, indicating the absence of a resonant q = 1 surface and supporting a pressure-driven infernal-mode interpretation. Analytic m = n = 1 displacement profiles consistent with the measured core mode structure and equilibrium constraints are used as the mode structure inputs to ORBIT-Kick. The calculations show that the dominant resonances occur between the mode and co-passing fast ions, producing redistribution localized near the magnetic axis. Synthetic neutron camera signals from TRANSP-Kick recover up to 90% of the experimentally observed neutron deficit at the time of peak mode amplitude, indicating that the measured m = n = 1 mode is a dominant contributor to core fast-ion transport. However, the synthetic neutron signals recover rapidly, whereas the measured neutron emission continues to decrease after the peak amplitude. In conclusion, the remaining discrepancy may arise from contributions not included in the present single-harmonic model, including higher-m and higher-n harmonics, multi-harmonic interactions, and additional transport mechanisms, motivating future diagnostic development and modeling efforts to resolve and incorporate these additional contributions.

Wong, Henry H. [University of California, Los Ange↗
DOE OSTI2020

Adaptive system for wavefront correction of the PEARL laser facility

The results of the operation of a wavefront correction system based on a deformable bimorph mirror of the PEARL subpetawatt laser facility are presented. An improvement in the quality of focusing of laser radiation, which led to an increase in the Strehl ratio from 0.3 to 0.6, is demonstrated. The features of the compensation for phase distortions of the wavefront in the case of a low pulse repetition rate, as well as the correct allowance for the noise of the CCD camera when calculating the Strehl ratio are investigated. (paper)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

A population of free-living highland wild dogs in Indonesian Papua

A 10-day rapid assessment has confirmed a small population of indigenous wild-living dogs in the highlands of Papua Province, Indonesia. The goal of the assessment was to observe, census, assess health and reproductive status, and collect biological samples or other data for this understudied canid. Trail cameras and DNA hair traps were deployed and baited with scent attractants, and game calls were used to elicit vocal responses or lure the dogs within observation range. Adults and pups of both sexes as well as a den were documented in 149 photographs. DNA testing of scat samples confirmed a canid origin with a close relationship to other oceanic canids including NGSD (New Guinea Singing Dog) and dingoes.

Zoology↗
DOE OSTI2019

Investigating Powder Spreading Dynamics in Additive Manufacturing Processes by In-situ High-speed X-ray Imaging

The quality of the powder bed is known to be one of the main factors that influence the quality of the part being manufactured by powderbed- based additive manufacturing processes. For example, in the laser powder bed fusion process, it has been demonstrated that improving the powder bed density and homogeneity improves the final quality of the part. Understanding powder spreading dynamics in the powder-bed-based additive manufacturing processes is critical for designing spreading structures and spreading parameters, identifying defect formation mechanisms in the powder bed, and guiding the design of optimized feedstock powders. Extensive efforts have been devoted to understand the fundamental mechanism of the powder flow and spreading process. Various powder flow testers were used to study the flow behavior of powders used in additive manufacturing. However, the powder flow conditions in flow meters are different from those in real additive manufacturing conditions. Models have also been developed to simulate and study the spreading process. The discrete element method (DEM) is currently the main tool for computationally simulating the spreading process. However, these models are based on many physical assumptions. Visible light cameras have been used recently to conduct in-situ study of powder spreading in additive manufacturing. Due to the limited resolution and penetration depth of visible light, it is extremely difficulty to study the particle-scale powder spreading dynamics. Here, to overcome the challenges of studying powder spreading dynamics under real additive manufacturing conditions, we developed an experimental approach to study the particle-scale powder spreading process with high spatial and temporal resolution using the high-speed high-energy X-ray imaging facility at beamline 32-ID-B of the APS. Figure 1 shows an overview of the research setup. It is composed of a vacuum chamber (building environment), an automatic powder spreading system, a laser system, an X-ray source (X-ray outlet), and an X-ray detection/imaging system.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Surface Erosion of Plasma-Facing Materials Using an Electrothermal Plasma Source and Ion Beam Micro-Trenches

Erosion characteristics of tungsten-alternative plasma-facing materials (PFMs) were tested under high heat flux conditions in the electrothermal plasma source facility at Oak Ridge National Laboratory. The PFMs of interest are high-purity β-3C chemical vapor deposition silicon carbide (SiC) and the MAX phases Ti 3 SiC 2 and Ti 2 AlC [MAX = chemical formula M n+1 AX n , where M is an early transition metal (such as Ti or Ta), A is an A-group element (such as Si or Al), and X is carbon or nitrogen]. Additionally, an erosion analysis method was developed using a combination of focused ion beam microscopy and scanning electron microscopy, carving micro-trench geometries into polished sample surfaces. Samples of SiC, Ti 3 SiC 2 , and Ti 2 AlC were exposed to the electrothermal plasma source alongside tungsten and monocrystalline silicon. Samples were exposed to a Lexan polycarbonate (C 16 H 14 O 3 ) electrothermal plasma stream in a He environment, at a specified impact angle, with infrared camera diagnostics. Edge localized mode–relevant heat fluxes of 0.9 to 1 GW/m 2 over 1-ms discharges were generated on the target surfaces. Tungsten samples exhibited pronounced melt-layer formation and deformation, with measured molten pits 2 to 10 μm in diameter and melt-layer depths of up to 7 μm deep. Surface erosion rates for Ti 3 SiC 2 and Ti 2 AlC ranged from 80 to 775 μm/s and 85 to 470 μm/s, respectively. Both MAX phases exhibited extreme surface fracture and material ejection, with damage depths past 4 μm for Ti 2 AlC and 11 μm for Ti 3 SiC 2 . Lastly, SiC displayed the best performance, in one case surviving 15 consecutive electrothermal plasma exposures with an average erosion rate of about 29 μm/s and no surface fracturing. SiC erosion rates ranged from 23 to 128 μm/s.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Analysis of the Shattered Pellet Injection Fragment Plumes Generated by Machine Specific Shatter Tube Designs

Shattered pellet injector systems have been installed on DIII-D, JET, and KSTAR and used to experimentally determine the effectiveness of the shattered pellet injection (SPI) process in mitigating the deleterious effects of a tokamak plasma disruption. Pellets are fired, and before entering the plasma, strike a bent tube known as a shatter tube causing the pellet to shatter. The process of pellet fragmentation is a chaotic process that can be described in terms of fragment size distribution through a statistical model that incorporates the effects of the pellet material and impact characteristics. In addition to the fragment size distribution, the shatter plume has other characteristics of interest, such as a fragment velocity distribution and temporal mass evolution. The fragment velocity distribution is important because it is needed to accurately model the spread and location of the ablation and the deposition of impurities in the plasma over time. The temporal mass evolution is necessary to determine the time-resolved delivery of mass to the plasma.Due to installation constraints, the shatter tube currently installed on JET has a unique geometry with a modest S-bend followed by a 20-deg bend at the end of the tube. The DIII-D and KSTAR shatter tube design is a simple tube bent through an angle of 20 deg followed by a straight section. The resulting shatter sprays from the JET shatter tube and a 20-deg miter bend shatter tube were experimentally characterized for various pellet materials and speeds. Laboratory testing of these shatter tubes allows for the use of fast cameras to capture the fragment spray traveling through a large vacuum chamber. These high-speed videos of the shatter plumes allow the fragment size distribution, temporal mass evolution, and velocity distribution of the fragments within the plume to be determined. Overall, this paper presents a comparison of the unique geometry of the JET shatter tube to the miter bend geometries used for shattering and some insight into the variables that may be adjusted to produce the optimal shatter spray. The impact of entrained propellant gas on the resulting shatter spray was examined during testing.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Analysis of Design Alternatives of Actively Cooled RF Window for MPEX

The Materials Plasma Exposure eXperiment (MPEX) has been designed as a linear plasma divertor simulator in order to address plasma material interaction (PMI) science for next-generation fusion devices. It will have the capability to test neutron irradiated samples with plasma fluxes of greater than 10 24 m -2 s -1 . It is expected to operate steady state for up to 10 6 s to consider PMI affects through reactor end of life. The conceptual design of MPEX was completed in 2019, with preliminary design having begun in 2020. The plasma source for MPEX is a helicon antenna, where the energized helical antenna sits outside of the vacuum in order to minimize impurities in the plasma. It is expected to receive up to 200 kW of continuous power, and so the antenna and the window must be actively cooled. The water-cooled copper antenna has been operated at full power on the Proto-MPEX device (which is a test facility to demonstrate the plasma source and heating systems). The water-cooled window, however, is a novel component that must meet numerous competing requirements. It requires a low dielectric loss to allow the Radio Frequency (RF) power to create the plasma within the vacuum boundary. It must be structurally robust to handle the significant heat flux from the plasma and any heat from dielectric coupling. It must be compatible with the coolant (preferably water). It requires a vacuum seal that minimizes impurities into the plasma and does not compromise the structural integrity of the window. Two window designs have been tested. Results from these tests, where temperatures are measured and heat fluxes inferred from infrared camera data, have been correlated with thermal-structural simulations. When these simulations are extrapolated to the full power steady-state heat fluxes that are expected in MPEX, the designs do not appear to have the necessary structural robustness. This study explores design alternatives for the MPEX helicon antenna window, presents analysis results for several of the alternatives, and shows a viable solution that satisfies the requirements for MPEX operation.

Tipton Jr, Joseph↗
DOE OSTI2025

In-Field Testing of Components for Feedback and Control of the ITER Disruption Mitigation System

Here, the shattered pellet injection (SPI) method has been chosen as the disruption mitigation system (DMS) for ITER. To protect the device from plasma disruptions that cause damaging heat and electromagnetic loads, SPI is used to inject high-Z material into the plasma. The process of SPI utilizes cryogenic cooling to form solid pellets. Pellets are accelerated down a barrel and into an angled surface, causing the pellet to shatter prior to entering the tokamak chamber. For the DMS to function reliably, the 27 separate shattered pellet injectors planned for ITER must rely on many components to provide accurate feedback data and for control functions. Each component in the DMS is exposed to an elevated background magnetic field depending on its placement and proximity to the plasma chamber. A Helmholtz coil test stand that is operated at Oak Ridge National Laboratory was utilized to test the components in relevant background field levels to assess component performance. This paper details the test design and results for in-field component operation for a variety of components. This list includes the following components: two different network switches for camera connectivity, a VAT fast shutter valve intended to reduce the flow of SPI propellant gas into the torus, a solenoid control valve intended for use in the pellet formation process, pressure/vacuum switches to be used for feedback and control, a printed circuit board piezo pressure sensor to be used to measure breech pressure, and various relays for the high-voltage pulsed power supply used to drive the SPI propellant valve.

Disruption mitigation↗
DOE OSTI2024

Statistical modelling and Bayesian inversion for a Compton imaging system: application to radioactive source localization

Abstract This paper presents a statistical forward model for a Compton imaging system, called Compton imager. This system, under development at the University of Illinois Urbana Champaign, is a variant of Compton cameras with a single type of sensors which can simultaneously act as scatterers and absorbers. This imager is convenient for imaging situations requiring a wide field of view. The proposed statistical forward model is then used to solve the inverse problem of estimating the location and energy of point-like sources from observed data. This inverse problem is formulated and solved in a Bayesian framework by using a Metropolis within Gibbs algorithm for the estimation of the location, and an expectation-maximization algorithm for the estimation of the energy. This approach leads to more accurate estimation when compared with the deterministic standard back-projection approach, with the additional benefit of uncertainty quantification in the low photon imaging setting.

Tarpau, Cécilia (ORCID:0000000286539490)↗
DOE OSTI2020

Time-resolved site-selective imaging of predissociation and charge transfer dynamics: the CH 3 I B-band

The predissociation dynamics of the 6s (B 2 E) Rydberg state of gas-phase CH 3 I were investigated by time-resolved Coulomb-explosion imaging using extreme ultraviolet (XUV) free-electron laser pulses. Inner-shell ionization at the iodine 4d edge was utilized to provide a site-specific probe of the ensuing dynamics. The combination of a velocity-map imaging (VMI) spectrometer coupled with the pixel imaging mass spectrometry (PImMS) camera permitted three-dimensional ionic fragment momenta to be recorded simultaneously for a wide range of iodine charge states. In accord with previous studies, initial excitation at 201.2 nm results in internal conversion and subsequent dissociation on the lower-lying A-state surface on a picosecond time scale. Examination of the time-dependent yield of low kinetic energy iodine fragments yields mechanistic insights into the predissociation and subsequent charge transfer following multiple ionization of the iodine products. The effect of charge transfer was observed through differing delay-dependencies of the various iodine charge states, from which critical internuclear distances for charge transfer could be inferred and compared to a classical over-the-barrier model. Time-dependent photofragment angular anisotropy parameters were extracted from the central slice of the Newton sphere, without Abel inversion, and highlight the effect of rotation of the parent molecule before dissociation, as observed in previous works. Our results demonstrate the ability to perform three-dimensional ion imaging at high event rates and showcase the potential benefits of this approach, particularly in relation to further time-resolved studies at free-electron laser facilities.

74 ATOMIC AND MOLECULAR PHYSICS↗