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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Design Considerations for Compact High-Average Power Free-Electron Lasers/Masers at Terahertz Frequencies

Interest is increasing in high-power terahertz (THz) sources of radiation. The terminology is fluid, but researchers in the field typically refer to frequencies ranging from about 300 GHz to 10 THz as THz radiation. In this article, we present a description of design considerations for a compact, high-average power free-electron laser. At present, THz radiation is generated by a variety of mechanisms, including laser-based sources and electron-beam-based sources. Here, we provide a short description of current THz source technology to give background against which to compare the present concept; however, this should not be considered a comprehensive discussion of such technologies.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

PET Imaging of Leg Arteries for Determining the Input Function in PET/MRI Brain Studies Using a Compact, MRI-Compatible PET System

In this work, we used a compact, high-resolution, and magnetic resonance imaging (MRI)-compatible positron emission tomography (PET) camera (VersaPET) to assess the feasibility of measuring the image-derived input function (IDIF) from arteries in the leg with the ultimate goal of enabling fully quantitative PET brain imaging without blood sampling. We used this approach in five 18 F-FDG PET/MRI brain studies in which the input function was also acquired using the gold standard of serial arterial blood sampling. After accounting for partial volume, dispersion, and calibration effects, we compared the metabolic rates of glucose (MRglu) quantified from VersaPET IDIFs in 80 brain regions to those using the gold standard and achieved a bias and variability of <5% which is within the range of reported test-retest values for this type of study. We also achieved a strong linear relationship (R 2 >0.97) against the gold standard across regions. The results of this preliminary study are promising and support further studies to optimize methods, validate in a larger cohort, and extend to the modeling of other radiotracers.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Preparing Li-garnet electrodes with engineered structures by phase inversion and high shear compaction processes

We report solid-state lithium batteries are promising for safety and energy density com-pared with traditional lithium-ion batteries. However, the large interfacial resistance between the electrode and electrolyte is a bottleneck to achieving high-performance solid-state batteries. Engineered electrode structures with a porous scaffold of the solid electrolyte material are promising to lower the interfacial resistance and provide a mechanical support for a thin solid electrolyte layer. In this work, two ceramic processing techniques are used to fabricate porous/dense bilayer architectures based on a Li 6.25 Al 0.25 La 3 Zr 2 O 12 (LLZO) Li-garnet material. Finger-like vertically aligned pores are created by the phase inversion (PI) process. A water bath presaturated with Li salt prevents Li loss during the PI solvent exchange step. Pore size and porosity can be optimized by adjusting the bath temperature. The high shear compaction process was used to prepare LLZO tapes with 40, 60, and 80 vol% poreformer. The porosity of the tapes after sintering is 39.5%, 58.4%, and 75.4%, respectively. Microtomography exhibits the porosity, pore shape, and pore distribution of the tapes. A typical cathode material LiNi 0.33 Mn 0.33 Co 0.33 O 2 (NMC) is filled into the pores via vacuum infiltration, and a dense cathode layer is formed within the garnet scaffold.

25 ENERGY STORAGE↗
DOE OSTI2020

Characterization and Scaling of Forced Convective Swirl in Sinusoidal Wavy-Plate-Fin Cores of Compact Heat Exchangers

The characterization and scaling of the thermal-hydraulic performance in wavy plate-fin compact heat exchanger cores, based on the understanding of the physical phenomena and heat transfer enhancement mechanism is delineated. Experimental data are presented for forced convection in air (Pr = 0.71) with flow rates in the range 50 ≤ Re ≤ 4000. A variety of wavy-fin cores that span viable applications, with geometrical attributes described by the cross section aspect ratio α (ratio of fin spacing to height), fin corrugation aspect ratio γ (ratio of 2× corrugation amplitude to wave pitch), and fin spacing ratio ζ (ratio of fin spacing to wave pitch), are considered. To characterize and correlate the vortex-flow mixing in interfin spaces, a Swirl number Sw is introduced from the balance of viscous, inertial and centrifugal forces. It is shown that the laminar, transitional and turbulent flow regimes can be explicitly identified by this Swirl number. Based on the experimental results and extended analysis, new correlations for Fanning friction factor f and Colburn factor j are developed with Sw, α, γ, and ζ as scaling parameters. Requisite expressions are devised by a superposition of both enhancement components due to the corrugated surface area enlargement and induced swirl flow field, and they are combined to cover the laminar, transitional and turbulent regimes by the method of asymptotic matching. The resulting generalized correlations are further shown to predict all available experimental data for f and j factors to within ±20% and ±15%, respectively.

42 ENGINEERING↗
DOE OSTI2024

High Power Density Thermal Energy Storage With Phase Change Material in Enhanced Compact Heat Exchangers

Abstract Performance of a novel ultracompact thermal energy storage (TES) heat exchanger, designed as a microchannel finned-tube exchanger is presented. With water as the heating–cooling fluid in the microchannels, a salt hydrate phase change material (PCM), lithium nitrate trihydrate (LiNO3 · 3H2O), was encased on the fin side. To establish the hypothesis that small-length-scale encasement (<3 mm) of PCM substantially enhances heat transfer to yield very high power-density energy storage, heat exchanger designs with 10 and 24 fins/inch were considered. They were subjected to thermal cycling, or repeated heating (melting) and cooling (freezing), with inlet fluid flow mimicking diurnal variation between 42 °C and 25 °C (representing typical arid-region conditions) over an accelerated time period. By employing salt self-seeding to obviate subcooling during cooling or recrystallization, the TES was found to exhibit stable long-term (100 heating–cooling cycles) operation with very high PCM-side heat transfer coefficients (∼100–500 W/m2 K) and storage power density (∼160–175 kW/m3). In fact, with optimization of heating–cooling fluid flowrate for given charging–discharging time period and exchanger size, power density >300 kW/m3 can be achieved. The results clearly establish that highly compact heat exchangers used as TES units can provide very high-performance alternatives to conventional ones.

Engineering↗
DOE OSTI2022

Diffusion bonded compact heat exchanger in Inconel 740H for high temperature and high-pressure applications

It is desired to develop heat exchangers able to be operated at high temperatures (750°C) and pressures (3636 psi) for use in advanced Brayton power cycle. Conventional materials have not had the high strength at temperature required for these applications previously, however a fairly new material Inconel 740H developed by Special Metals for the ultra-supercritical water fossil industry has shown good performance under these conditions. In further efforts to capitalize on these new high strength high temperature alloys CompRex has developed a diffusion bonding procedure capable of alloying compact high effectiveness heat exchangers that can perform under these high temperature and high-pressure conditions. Initial tests of the heat exchanger are being conducted at the University of Wisconsin using supercritical CO2 working fluid. The bonding process has been adjusted such that the strength of the bonded block has achieved over 90% yield and tensile strength of the 740H base material values. Grain size before and after bonding were measured to determine the extent of grain growth and grain diffusion across the interface. A discussion of the heat exchanger design, etching and initial tensile tests on sample bonds will be discussed.

14 SOLAR ENERGY↗
DOE OSTI2022

Low energy neutrino detection with a compact water-based liquid scintillator detector

In this study, the conceptual design and physics simulations of a near-field Water-based Liquid Scintillator (WbLS) detector placed 100 m from the Akkuyu Nuclear Power Plant (ANPP), currently under construction and aiming at being Turkey’s first nuclear power plant, is presented. The ANPP is an excellent opportunity for neutrino studies and the development of an R &D program for neutrino detectors in Turkey. The Reactor Neutrino Experiments of Turkey (RNET) program includes a compact detector with a 2.5-ton volume of WbLS and a ~ 30% photo-coverage, and the program is planned to be expanded with a medium-size 30-ton detector that will be an international testbed for WbLS and new detector technologies through low energy neutrino studies. In the following, the focus will be on the smaller ~2.5 ton detector, instrumented with 8-in. high quantum efficiency PMTs and two layers of cosmic veto paddles, covering all sides of the detector, to track and veto cosmic particles. Inverse Beta Decay (IBD) events from electron anti-neutrinos generated in the reactor core are simulated using the RAT-PAC simulation package and several liquids with different percentages of Liquid Scintillator (LS) and Gadolinium (Gd) are investigated.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Ultra-compact hybrid silicon:chalcogenide waveguide temperature sensor

We demonstrate a real-time, reusable, and reversible integrated optical sensor for temperature monitoring within harsh environments. The sensor architecture combines the phase change property of chalcogenide glasses (ChG) with the high-density integration advantages of high index silicon waveguides. To demonstrate sensor feasibility, ChG composition Ge 40 S 60 , which is characterized by a sharp phase transition from amorphous to crystalline phase around 415 °C, is deposited over a 50 µ m section of a single mode optical waveguide. The phase transition changes the behavior of Ge 40 S 60 from a low loss to high loss material, thus significantly affecting the hybrid waveguide loss around the phase transition temperature. A transmission power drop of over 40dB in the crystalline phase compared to the amorphous phase is experimentally measured. Moreover, we recover the amorphous phase through the application of an electrical pulse, thus showing the reversible nature of our compact temperature sensor. Through integrating multiple compositions of ChG with well-defined phases transition temperatures over a silicon waveguide array, it is possible to determine, in real-time, the temperature evolution within a harsh environment, such as within a nuclear reactor cladding.

Badamchi, Bahareh (ORCID:0000000193105300)↗
DOE OSTI2024

Compact, ultrastable, high repetition-rate 2 μm and 3 μm fiber laser for seeding mid-IR OPCPA

We report a compact and reliable ultrafast fiber laser system optimized for seeding a high energy, 2 μ m pumped, 3 μ m wavelength optical parametric chirped pulse amplification to drive soft X-ray high harmonics. The system delivers 100 MHz narrowband 2 μ m pulses with >1 nJ energy, synchronized with ultra-broadband optical pulses with a ∼1 μ m FWHM spectrum centered at 3 μ m with 39 pJ pulse energy. The 2 μ m and 3 μ m pulses are derived from a single 1.5 μ m fiber oscillator, fully fiber integrated with free-space downconversion for the 3 μ m. The system operates hands-off with power instabilities <0.2% over extended periods of time.

Optics↗
DOE OSTI2025

Amplification of 10 μm picosecond pulses in a compact optically pumped multiatmosphere CO 2 laser

Picosecond pulses, generated by a commercial mid-IR optical parametric source (∼0.5 ps, 1-5 μJ), have been regeneratively amplified to an energy of ≤2 mJ in a palm-size high-pressure CO 2 amplifier optically pumped by a Q-switched 2.8 μm Cr:Er:YSGG laser. The characteristics of the amplified pulses have been studied as a function of seed wavelength centered around 10.3 or 10.6 μm, and the pressure in the gain medium. The measured amplified pulse length is ∼5 ps. Numerical modeling suggests that pulses as short as ∼0.5 ps with multi-GW peak power can be generated in a mixture of CO 2 isotopes. Robustness of the output of a compact CO 2 regenerative amplifier to the seed and pump fluctuations measured at 3 Hz and a perfect Gaussian beam profile indicates the potential of such laser technology for producing high-power ultrashort long-wave infrared pulses at high repetition rates.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Ultra compact Bragg grating devices with broadband selectivity

Current silicon waveguide Bragg gratings typically introduce perturbation to the optical mode in the form of modulation of the waveguide width or cladding. However, since such a perturbation approach is limited to weak perturbations to avoid intolerable scattering loss and higher-order modal coupling, it is difficult to produce ultra-wide stopbands. In this Letter, we report an ultra-compact Bragg grating device with strong perturbations by etching nanoholes in the waveguide core to enable an ultra-large stopband with apodization achieved by proper location of the nanoholes. With this approach, a 15 µm long device can generate a stopband as wide as 110 nm that covers the entire C + L band with a 40 dB extinction ratio and over a 10 dB sidelobe suppression ratio (SSR). Similar structures can be further optimized to achieve higher SSR of > <#comment/> 17 d B for a stopband of about 80 nm.

Li, Ang (ORCID:0000000232251280)↗
DOE OSTI2021

Demonstration of a compact, multi-joule, diode-pumped Tm:YLF laser

We report the demonstration of a diode-pumped Tm:YLF laser operating at 1.88 µm that produces pulse energies up to 3.88 J in 20 ns. The compact system consists of a Q-switched cavity-dumped oscillator generating 18 mJ pulses, which are then amplified in a 4-pass power amplifier. Energies up to 38.1 J were obtained with long-pulse amplifier operation. These results illustrate the high energy storage and extraction capabilities of diode-pumped Tm:YLF, opening the path to high peak and average power mid-infrared solid-state lasers

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

Robust, automated sleep scoring by a compact neural network with distributional shift correction

Studying the biology of sleep requires the accurate assessment of the state of experimental subjects, and manual analysis of relevant data is a major bottleneck. Recently, deep learning applied to electroencephalogram and electromyogram data has shown great promise as a sleep scoring method, approaching the limits of inter-rater reliability. As with any machine learning algorithm, the inputs to a sleep scoring classifier are typically standardized in order to remove distributional shift caused by variability in the signal collection process. However, in scientific data, experimental manipulations introduce variability that should not be removed. For example, in sleep scoring, the fraction of time spent in each arousal state can vary between control and experimental subjects. We introduce a standardization method, mixture z-scoring, that preserves this crucial form of distributional shift. Using both a simulated experiment and mouse in vivo data, we demonstrate that a common standardization method used by state-of-the-art sleep scoring algorithms introduces systematic bias, but that mixture z-scoring does not. We present a free, open-source user interface that uses a compact neural network and mixture z-scoring to allow for rapid sleep scoring with accuracy that compares well to contemporary methods. This work provides a set of computational tools for the robust automation of sleep scoring.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Diagonally implicit Runge–Kutta schemes: Discrete energy-balance laws and compactness properties

Abstract We study diagonally implicit Runge–Kutta (DIRK) schemes when applied to abstract evolution problems that fit into the Gelfand-triple framework. We introduce novel stability notions that are well-suited to this setting and provide simple, necessary and sufficient, conditions to verify that a DIRK scheme is stable in our sense and in Bochner-type norms. We use several popular DIRK schemes in order to illustrate cases that satisfy the required structural stability properties and cases that do not. In addition, under some mild structural conditions on the problem we can guarantee compactness of families of discrete solutions with respect to time discretization.

Mathematics↗
DOE OSTI2024

Development of a compact electron cyclotron resonance accelerator for industrial and security applications

We describe the development of a novel accelerator, an electron Cyclotron Resonance Accelerator (eCRA) [1], to produce high power electron beams and X-ray beams for medical, research, sterilization, and national security applications. The several attractive features of eCRA include: a compact robust room-temperature single-cell RF cavity as the accelerating structure; continuous ampere-level high current output; and production of a self-rastering electron beam, thus eliminating the need for a separate beam scanner. Progress on the eCRA development, including numerical simulation, engineering design, and on-going experimental efforts will be reported here.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Compact, High-Power Superconducting Electron Linear Accelerators for MW Industrial Applications

Fermilab has developed a novel concept for an industrial electron linac using Nb₃Sn coating technology and conduction cooling. We will show the range of multi-cavity linac designs targeted toward various applications. We will also discuss technology development status with results on conduction cooling of SRF cavities based on cryocoolers, which removes the need for liquid Helium, thus making SRF technology accessible to industrial applications. These conduction-cooled linacs can generate electron beam energies up to 10 MeV in continuous-wave operation and can reach higher power (>=1 MW) by combing several modules. Compact and light enough to mount on mobile platforms, our machine is anticipated to enable new in-situ environmental remediation applications such as waste-water treatment for urban areas, X-ray medical device sterilization, and innovative pavement applications. We also show cost-economics and key R&D areas that much be addressed for a practical machine.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

ON THE WAY TO A 10MEV, CONDUCTION-COOLED COMPACT SRF ACCELERATOR

After the success of designing a compact 1MeV, 1MW accelerator based on conduction-cooled SRF, Jefferson Lab is now pursuing a concept to provide a tenfold increase of the beam energy. The obvious challenge for SRF is to move from a single-cell to a multicell cavity while maintaining high efficiency and the ability to operate the machine without a complex cryogenic plant. This paper summarizes the current state of this effort with respect to the design of a Nb3Sn coated five-cell cavity and the corresponding RF components, especially the fundamental power coupler (FPC), as well as first thermal analysis of the cryocooler-based cooling setup.

Ciovati, G.↗
DOE OSTI2019

Measurement of accreted helium ion velocity using Doppler spectroscopy in the CTIX compact-toroid plasma accelerator

A compact-toroid (CT) accelerator is a device for the production of plasma bodies which contain a relatively strong internal magnetic field, which permits the plasma body to withstand large forces of acceleration while retaining its magnetic field structure. Typically, the CT occupies an annular region between inner and outer radii, defined by coaxial inner and outer electrodes, across which a large electric potential is applied. The internal magnetic fields of the CT contain both a toroidal and poloidal component, as shown in Fig. 1(a). These fields are typically of comparable magnitude. Because of the effective rigidity provided by internal magnetic fields, the CT can be accelerated to high velocities in short distances. Since internal fields increase in proportion to accelerating magnetic field, there is no strength at which the accelerating magnetic fields overcome the internal field (blow-by). Because of this, the kinetic energy density of CTs can be made to exceed the energy density of magnetic fields typical of plasma containment devices such as tokamaks. CTs have the potential to be launched into the interior of such devices for either delivering fuel (typically deuterium or hydrogen), or to deliver particles of high atomic number (high-Z). An important application of high-Z CT injection into tokamaks is to aid in plasma quenching by radiation, to mitigate the effects of plasma disruptions and prevent damage to the plasma confinement device. In addition, high-Z CTs may be used as sources of kinetic energy density for plasma-compression experiments. In this case, the use of plasma species of high atomic number is also desirable, since kinetic energy density is proportional to atomic number for given CT velocity and electron density gas puffing.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗