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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Preparation & shipping of ten neutron irradiated Eurofer97 steel variants to HFIR for SANS experiments

At ORNL, ten variants of Eurofer97 steel were irradiated in the high flux isotope reactor (HFIR) to ~2.94 – 3.24 dpa at 300 ± 30 °C, as part of the EUROfusion Lot-IV collaboration. The irradiations were performed in non-instrumented rabbit capsules in the flux trap region, which included SS-J3 type tensile samples and M4-CVN multi-notch bend bars. Their full set of microstructure and mechanical properties were previously reported in multiple previous publications. In this project, half-broken irradiated and nonirradiated SS-J3 tensile samples from ten alloys, code-named H, I, J, K, L, M, N, O, P and E, were prepared and shipped for facilitating small angle neutron scattering (SANS) experiments at the HFIR general purpose (GP)-SANS beam line. This report summarizes the completed tasks which included canister moves at the Irradiated Materials Examination and Testing (IMET) hot-cell facility to retrieve the samples from long-term storage, loading of the ten irradiated samples at IMET inside lead (Pb) piglets that were specifically provided by ORNL for SANS experiments and radiological shipment from IMET facility to the HFIR hot cells for performing SANS experiments. In addition to the irradiated samples, ten nonirradiated half-broken pieces from the Eurofer97 variants were also provided to HFIR for SANS.

36 MATERIALS SCIENCE↗
NASA NTRS2016

SEEDS Direct Imaging of the RV-Detected Companion to V450 Andromedae, and Characterization of the System

We report the direct imaging detection of a low-mass companion to a young, moderately active star V450 And, that was previously identified with the radial velocity (RV) method. The companion was found in high-contrast images obtained with the Subaru Telescope equipped with the HiCIAO camera and AO188 adaptive optics system. From the public ELODIE and SOPHIE archives we extracted available high-resolution spectra and RV measurements, along with RVs from the Lick planet search program. We combined our multi-epoch astrometry with these archival, partially unpublished RVs, and found that the companion is a low-mass star, not a brown dwarf, as previously suggested. We found the best-fitting dynamical masses to be m(sub 1) = 1.141(sup + 0.037, sub - 0.091) and m(sub 2) = 0.279(sup + 0.023, sub - 0.020) solar mass. We also performed spectral analysis of the SOPHIE spectra with the iSpec code. Hipparcos time-series photometry shows a periodicity of P = 5.743 day, which is also seen in the SOPHIE spectra as an RV modulation of the star A. We interpret it as being caused by spots on the stellar surface, and the star to be rotating with the given period. From the rotation and level of activity, we found that the system is 380(sup + 220, sub -100) Myr old, consistent with an isochrone analysis (220 (sup +2120, sub -90) Myr). This work may serve as a test case for future studies of low mass stars, brown dwarfs, and exoplanets by combination of RV and direct imaging data.

direct imaging detection of a low-mass companion↗
DOE OSTI2023

Physics basis for the Wisconsin HTS Axisymmetric Mirror (WHAM)

The Wisconsin high-temperature superconductor axisymmetric mirror experiment (WHAM) will be a high-field platform for prototyping technologies, validating interchange stabilization techniques and benchmarking numerical code performance, enabling the next step up to reactor parameters. A detailed overview of the experimental apparatus and its various subsystems is presented. WHAM will use electron cyclotron heating to ionize and build a dense target plasma for neutral beam injection of fast ions, stabilized by edge-biased sheared flow. At 25 keV injection energies, charge exchange dominates over impact ionization and limits the effectiveness of neutral beam injection fuelling. This paper outlines an iterative technique for self-consistently predicting the neutral beam driven anisotropic ion distribution and its role in the finite beta equilibrium. Beginning with recent work by Egedal et al. ( Nucl. Fusion , vol. 62, no. 12, 2022, p. 126053) on the WHAM geometry, we detail how the FIDASIM code is used to model the charge exchange sources and sinks in the distribution function, and both are combined with an anisotropic magnetohydrodynamic equilibrium solver method to self-consistently reach an equilibrium. We compare this with recent results using the CQL3D code adapted for the mirror geometry, which includes the high-harmonic fast wave heating of fast ions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Impact of moderate pump–Stokes chirp on femtosecond coherent anti-Stokes Raman scattering spectra

The effects of inducing moderate chirp in the pump and Stokes beams in chirped-probe-pulse femtosecond coherent anti-Stokes Raman scattering (CARS) spectroscopy are discussed. This is an important issue for measurements in high-pressure systems where the CARS beams must be transmitted through glass of significant thickness to reach the probe volume of interest. The effects were investigated both experimentally, by inserting disks of SF-11 glass into the pump and Stokes beam paths, and theoretically, by incorporating pulse chirp into our time-dependent density matrix (TDDM) simulations. Experimentally, we found that inducing moderate pump and Stokes chirp produced significant spectral narrowing of the nonresonant four-wave mixing contribution to the CARS signal, and this allowed us to control the resonant excitation bandwidth to eliminate interferences from neighboring species. The temperature measurement accuracy and precision were essentially unchanged with respect to the unchirped pump and Stokes case. The effect of moderate pump and Stokes chirp on the narrowing of the Raman excitation efficiency envelope was investigated by solving the full set of TDDM through direct numerical integration. The numerical efficiency of the solutions was enhanced dramatically by developing a parallel version of the TDDM code. The calculated Raman excitation efficiency profile was incorporated in our phenomenological spectral fitting codes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Feasibility study of a high spatial and time resolution beam emission spectroscopy diagnostic for localized density fluctuation measurements in Lithium Tokamak eXperiment-β (LTX-β)

Trapped electron mode (TEM) is the main source of turbulence predicted for the unique operation regime of a flat temperature profile under low-recycling conditions in the LTX-β tokamak, while ion temperature gradient driven turbulence may also occur with gas fueling from the edge. To investigate mainly TEM scale density fluctuations, a high spatial and time resolution 2D beam emission spectroscopy (BES) diagnostic is being developed. Apart from spatially localized density turbulence measurement, BES can provide turbulence flow and flow shear dynamics. This BES system will be realized using an avalanche photodiode-based camera and narrow band interference filter. The system can acquire data at 2 MHz. Simulations with the Simulation of Spectra (SOS) code indicate that a high signal to noise ratio can be achieved with the proposed system. This will enable sampling the density fluctuations at this high time resolution. Finally, the design considerations and system optimization using the SOS code are presented.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

A Multifidelity and Multimodal Machine Learning Approach for Extracting Bonding Environments of Impurities and Dopants from X-ray Spectroscopies

Extended X-ray absorption fine structure (EXAFS) spectroscopy is crucial for determining the coordination environment of impurities and dopants; however, it requires difficult measurements. X-ray absorption near edge structure (XANES) spectroscopy and X-ray emission spectroscopy (XES) can be obtained easily but cannot be converted to determine structures. In this work we develop tools to map measured XANES to the EXAFS signal through machine learning, thereby facilitating the use of EXAFS structural-determination analyses on XANES data. Through the use of Deep Operator Networks (DeepONets), we are able to accurately predict the EXAFS spectrum between 6 and 14 Å -1 from the first 6 Å -1 (~100 eV) of the absorption spectrum of Cu 2+ substitutional defects in the Fe 3+ mineral hematite (a-Fe 2 O 3 ). This surprising finding implies that theoretical analyses of X-ray absorption spectra could be implemented that extract the same conclusions as high-quality EXAFS studies from spectra collected over a much smaller range of photon energies. To encourage similar efforts, the simulated x-ray spectra, machine learning, and fitting code is made publicly available.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1982

Comparison between computations and experimental data in unsteady three-dimensional transonic aerodynamics, including aeroelastic applications

Comparisons were made of computed and experimental data in three-dimensional unsteady transonic aerodynamics, including aeroelastic applications. The computer code LTRAN3, which is based on small-disturbance aerodynamic theory, was used to obtain the aerodynamic data. A procedure based on the U-g method was developed to compute flutter boundaries by using the unsteady aerodynamic coefficients obtained from LTRAN3. The experimental data were obtained from available NASA publications. All the studies were conducted for thin, unswept, rectangular wings with circular-arc cross sections. Numerical and experimental steady and unsteady aerodynamic data were compared for a wing with an aspect ratio of 3 and a thickness ratio of 5% at Mach numbers of 0.7 and 0.9. Flutter data were compared for a wing with an aspect ratio of 5. Two thickness ratios, 6% at Mach numbers of 0.715, 0.851, and 0.913, and 4% at Mach number of 0.904, were considered. Based on the unsteady aerodynamic data obtained from LTRAN3, flutter boundaries were computed; they were compared with those obtained from experiments and the code NASTRAN, which uses linear aerodynamics.

Guruswamy, P.↗
NASA NTRS1984

Analysis of a Coded, M-ary Orthogonal Input Optical Channel with Random-gain Photomultiplier Detection

Performance of two coding systems is analyzed for a noisy optical channel with M(=2(L)-ary orthogonal signaling and random gain photomultiplier detection. The considered coding systems are the Reed Solomon (RS) coding with error only correction decoding and the interleaved binary convolutional system with soft decision Viterbi decoding. The required average number of received signal photons per information bit, N sub b, for a desired bit error of 0.000001 is found for a set of commonly used parameters and with a high background noise level. We find that the interleaved binary convolutional coding system is preferable to the RS coding system in performance complexity tradeoffs.

Lee, P. J.↗
NASA NTRS1986

Integrated Composite Analyzer (ICAN): Users and programmers manual

The use of and relevant equations programmed in a computer code designed to carry out a comprehensive linear analysis of multilayered fiber composites is described. The analysis contains the essential features required to effectively design structural components made from fiber composites. The inputs to the code are constituent material properties, factors reflecting the fabrication process, and composite geometry. The code performs micromechanics, macromechanics, and laminate analysis, including the hygrothermal response of fiber composites. The code outputs are the various ply and composite properties, composite structural response, and composite stress analysis results with details on failure. The code is in Fortran IV and can be used efficiently as a package in complex structural analysis programs. The input-output format is described extensively through the use of a sample problem. The program listing is also included. The code manual consists of two parts.

Murthy, P. L. N.↗
NASA NTRS1988

A user's manual for the Loaded Microstrip Antenna Code (LMAC)

The use of the Loaded Microstrip Antenna Code is described. The geometry of this antenna is shown and its dimensions are described in terms of the program outputs. The READ statements for the inputs are detailed and typical values are given where applicable. The inputs of four example problems are displayed with the corresponding output of the code given in the appendices.

Forrai, D. P.↗
NASA NTRS1993

On the performance of Trellis coded modulation with octal phase shift keying over the TDRSS channel

As the National Aeronautics and Space Administration moves into the 21st century with programs like Space Station Freedom, a manned mission to Mars, and the new Landsat mission, transmission demands on the Tracking and Data Relay Satellite System (TDRSS) will very likely exceed the available bandwidth. The Manual Lujan, Jr. Center for Space Telemetering and Telecommunications Systems (CSTTS) at New Mexico State University (NMSU) is studying techniques for increasing the data rate capabilities of TDRSS. These techniques include the use of advanced bandwidth efficient modulation formats to increase the data rate that can be sustained in a TDRSS transponder and the use of lossless bandwidth compression of the data to be transmitted to lower the data rate required from the user spacecraft. Based upon current technology the most promising bandwidth efficient modulation technique is Trellis Coded Modulation (TCM) operating with Octal Phase shift Keying (8PSK). Trellis Coded Modulation coding with 8PSK carrier modulation has the capability to increase the data rate which can be transmitted through the TDRSS spacecraft by a factor of 2 to 2.5 times that available with todays coded QPSK systems with only a small penalty in link performance relative to the existing systems. However, before NASA can safely employ TCM coding it is necessary to prove that this complex format can perform on the real TDRSS link as it does in labs and simulation studies. This proof-of-concept test over a live satellite channel was the objective of the construction and testing performed under this task of the NMSU NASA grant referenced above. In conjunction with NASA, NMSU's CSTTS has constructed a system to test a new candidate TDRSS modulation scheme, TCM 8PSK, that can enhance the information throughput of the TDRSS spacecraft. The test system for this project which was constructed over a period of 18 months by NMSU consisted of two racks of commercial and univeristy-designed and -built equipment. This project has included modifications of an existing White Sands Ground Terminal (WSGT) High Rate QPSK Demodulator to demodulate 8PSK as well as the construction of other support hardware. Also, two TCM codecs (coder/decoders) have been constructed to implement two levels of bandwidth efficiency. One was designed and built by the research team at NMSU while the other was created by the University of Notre Dame with the University of South Australia. The NMSU codec achieves a 2-to-1 increase in data rate per unit bandwidth with a coding gain relative to QPSK of about 3dB. The Notre Dame/South Australia codec achieves a 2.5-to-1 increase in data rate per unit of occupied bandwidth and a coding gain of about 2dB.

Osborne, William P.↗
NASA NTRS1994

Uncertainties in radiation effect predictions for the natural radiation environments of space

Future manned missions beyond low earth orbit require accurate predictions of the risk to astronauts and to critical systems from exposure to ionizing radiation. For low-level exposures, the hazards are dominated by rare single-event phenomena where individual cosmic-ray particles or spallation reactions result in potentially catastrophic changes in critical components. Examples might be a biological lesion leading to cancer in an astronaut or a memory upset leading to an undesired rocket firing. The risks of such events appears to depend on the amount of energy deposited within critical sensitive volumes of biological cells and microelectronic components. The critical environmental information needed to estimate the risks posed by the natural space environments, including solar flares, is the number of times more than a threshold amount of energy for an event will be deposited in the critical microvolumes. These predictions are complicated by uncertainties in the natural environments, particularly the composition of flares, and by the effects of shielding. Microdosimetric data for large numbers of orbits are needed to improve the environmental models and to test the transport codes used to predict event rates.

Mcnulty, P. J.↗
DOE OSTI2023

On the relationship between the multi-region relaxed variational principle and resistive inner-layer theory

We show that the variational energy principle of the multi-region relaxed magnetohydrodynamic (MRxMHD) model can be used to predict finite-pressure linear tearing instabilities. In this model, the plasma volume is sliced into sub-volumes separated by 'ideal interfaces', and in each volume the magnetic field relaxes to a Taylor state, where the pressure gradient $\nabla p = 0$. The MRxMHD model is implemented in the Stepped-Pressure Equilibrium Code (SPEC) so that the equilibrium solution in each region is computed while preserving the force balance across the interfaces. As SPEC computes the Hessian matrix (a discretized stability matrix), the stability of an MRxMHD equilibrium can also be computed with SPEC. In this article, using SPEC, we investigate the effect of local pressure gradients and the $\nabla p = 0$ in the vicinity of the resonant surface of a tearing mode. For low-beta plasma, we have been able to illustrate a relationship between the resistive singular-layer theory (Coppi et al 1966 Nucl. Fusion6 101; Glasser et al 1975 Phys. Fluids18 875–88) and the MRxMHD model. Within the singular layer, the volume-averaged magnetic helicity and the flux-averaged toroidal flux are shown to be the invariants for the linear tearing modes in SPEC simulations. Our technique to compute MRxMHD stability is first tested numerically in a cylindrical tokamak and its application in toroidal geometry is demonstrated. We demonstrate an agreement between the stability boundary obtained with SPEC simulation and the resistive inner-layer theories.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗