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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 1,477 records · Page 82
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Application of molecular convergent close-coupling cross sections in a collisional radiative model for the triplet system of molecular hydrogen

Collisional radiative (CR) models for molecular hydrogen are of high relevance for performing qualitative and quantitative analysis of excited-state population densities measured in plasmas or predicting the dependence of plasma emission on parameter variations. Although the development of such models for H 2 started decades ago, major uncertainties still exist regarding the most important set of input parameters, namely the cross sections for electron-impact excitation. The deviations between cross sections from different datasets are particularly pronounced in the energy region close to the threshold energy, strongly increasing the uncertainty of CR models applied to low-temperature plasmas. This paper presents experimental validation of a set of newly calculated non ro-vibrationally resolved electron-impact cross sections calculated for the triplet system of H 2 using the molecular convergent close-coupling method in the adiabatic-nuclei formulation. These cross sections are implemented into a CR model based on the flexible solver Yacora. A first comparison of CR calculations with the different datasets to experimentally-determined population densities is performed at a planar ICP discharge for varying pressure (between 1 and 10 Pa) and RF power (between 700 and 1100 W). For the experimentally-accessible electron temperature and density range (2.5–10 eV and 1.8–3.3 × 10 16 m –3 , respectively), very good agreement between the model and experiment is obtained using the new data set, in contrast to previously used cross sections.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Development of a neural network model for peeling–ballooning stability analysis in the KSTAR tokamak pedestals

The neural network model, MISHKA-NN is developed to mitigate the computational burden associated with the linear ideal magnetohydrodynamic (MHD) stability analysis of the pedestal based on the peeling–ballooning (P–B) model. By utilizing both 1D plasma profiles (current density, pressure gradient, and safety factor) and 0D parameters (plasma geometry, total current, and toroidal mode number), the model predicts linear growth rate of edge-localized ideal MHD instability in a given equilibrium state. By enabling the prediction of each instability within a second, the model reduces the time required for plotting a pedestal P–B stability diagram (j - α diagram) from approximately 100 CPU hours to a few CPU minutes. Notably, even with the utilization of parametric pressure and current profiles and plasma boundary shapes for the training dataset, the model shows a satisfactory level of performance in benchmarking the j - α diagram for the reconstructed equilibrium from a KSTAR tokamak experiment. We anticipate the model to serve as a versatile alternative to 2D linear MHD stability codes, alleviating numerical costs.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

On the Development of Compact HTS Coil Modules for Large Bore High Field Superconducting Magnets

Lower cost, high current density superconducting coil modules producing higher magnetic fields and cooled affordably are crucial for obtaining cost-effective, compact commercial fusion reactors. Accessibility to low cost, higher field magnets (>30 T) is also critical for the discovery of new quantum phenomena in materials, cosmic frontier and other topics in basic science research. The Princeton Plasma Physics Laboratory (PPPL) is working with Princeton University to develop unique large bore, compact superconducting magnets to support science experiments including the development of new instrumentation for condensed matter physics and Axion dark matter search in the cosmic frontier. Core elements of these experiments are unique for access to lower cost, simple fabrication of compact superconducting magnets that can be cooled affordably, while integrated with dedicated science instruments. Conductor qualification and coil design concepts are discussed in support of needs for these experiments. PPPL has the unique expertise and experimental facilities to design, construct and test subscale coil modules for these projects. Compact high field coil modules were fabricated and tested to validate coil design concepts and coil performance. Finally, the design and model coil integration challenges are discussed to identify performance risks and demonstrate feasibility for deploying full scale large bore compact superconducting magnets for cost effective operations of multiple laboratory experiments.

axion dark matter↗
DOE OSTI2022

Modeling Molten Salt Spreading and Heat Transfer using MELTSPREAD – Model Development Updates

This report summarizes spreading and heat transfer results calculated using MELTSPREAD for a scenario of molten FLiNaK spilling onto a flat stainless steel substrate that was inspired by the “maximum credible accident” scenario of the Molten Salt Reactor Experiment (MSRE). MELTSPREAD was developed at Argonne to model the one-dimensional flowing and freezing of molten corium and was applied to model molten salts for the first time during FY21. The molten salt MELTSPREAD model that was developed during FY21 was updated as part of this work using a corrected heat of fusion value of FLiNaK and to accommodate a larger salt spill volume. The model was run with and without the inclusion of contributions from decay heat and a sensitivity analysis of initial spill conditions was performed to determine the importance of those factors on model outcome. The results provide insight into the expected spreading and heat transfer behavior of simulated and irradiated fuel salt that has been spilled and indicate aspects of the model to be revised in future versions of the MELTSPREAD model for applications to molten salt.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2025

Transformational Opacity Platforms on the Z Facility: A Design Study

The goal of this one-year LDRD is to study novel experimental approaches to provide benchmark spectral opacity measurements at the most extreme conditions beyond existing measurements (i.e. 2x temperature, ~5x density). These conditions correspond to those at half the solar radius and would provide a unique and novel test for stellar physics. These conditions are also relevant to advance stockpile stewardship research. The basic idea is to embed a sample inside the z-pinch dynamic hohlraum on the Z facility and obtain its opacity from either 1) its self-emission or 2) its absorption from using a capsule backlighter. This study evaluates the feasibility, limitations to these two approaches from a design approach. We found that emission-based perspective gives, at best, an opacity accuracy of about 20% for the current studied pinch conditions due to the limit of LTE approximation and radiation transport effects. The capsule-backlighter-based approach overcomes this limitation although some specific design questions remain to be answered. Promising designs are proposed for follow-on Z experiments. Future designs would help maintain Z relevancy in relation to ignition-enabled platforms at NIF.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

First application of a digital mirror Langmuir probe for real-time plasma diagnosis

For the first time, a digital Mirror Langmuir probe (MLP) has successfully sampled plasma temperature, ion saturation current, and floating potential together on a single probe tip in real time in a radio-frequency driven helicon linear plasma device. This is accomplished by feedback control of the bias sweep to ensure a good fit to I-V characteristics with a high frequency, high power digital amplifier and field-programmable gate array (FPGA) controller. Measurements taken by the MLP were validated by a low speed I-V characteristic manually collected during static plasma conditions. Plasma fluctuations, induced by varying the axial magnetic field (f̃ = 10 Hz), were also successfully monitored with the MLP. Further refinement of the digital MLP pushes it towards a turn-key system that minimizes the time to deployment and lessens the learning curve, positioning the digital MLP as a capable diagnostic for the study of low radio-frequency plasma physics. These demonstrations bolster confidence in fielding such digital MLP diagnostics in magnetic confinement experiments with high spatial and adequate temporal resolution such as edge plasma, scrape-off layer, and divertor probes.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1993

Growth of binary organic NLO crystals: m.NA-p.NA and m.NA-CNA system

Experiments were carried out to grow 3.Nitroaniline (m.NA) crystals doped with 4.Nitroaniline (p.NA) and 2.chloro 4.Nitroaniline (CNA). The measured undercooling for m.NA, p.NA, and CNA were 0.21 tm K, 0.23 tm K, and 0.35 tm K respectively, where tm represents the melting temperature of the pure component. Because of the crystals' large heat of fusion and large undercooling, it was not possible to grow good quality crystals with low thermal gradients. In the conventional two-zone Bridgman furnace we had to raise the temperature of the hot zone above the decomposition temperature of CNA, p.NA, and m.NA to achieve the desired thermal gradient. To avoid decomposition, we used an unconventional Bridgman furnace. Two immiscible liquids, silicone oil and ethylene glycol, were used to build a special two-zone Bridgman furnace. A temperature gradient of 18 K/cm was achieved without exceeding the decomposition temperature of the crystal. The binary crystals, m.NA-p.NA and m.NA-CNA, were grown in centimeter size in this furnace. X-ray and optical characterization showed good optical quality.

Singh, N. B.↗
DOE OSTI2023

Attosecond light-field control of high-density plasmas (Final Scientific/Technical Report)

Sub-optical-cycle dynamics of dense electron bunches in relativistic-intensity laser—solid interactions (relativistic plasma mirrors) lead to the emission of high-order harmonics and attosecond light pulses. The aim of this project was to advance our understanding of the fundamental principles underlying high-energy-density physics behind this phenomenon. We achieved this goal by conducting experiments and a comprehensive theoretical analysis of harmonics driven by specially tailored light waveforms providing precise control over the sub-laser-cycle trajectories of the emitting electron bunches. The multi-color laser waveforms, generated in our experiments in a cascaded plasma mirror configuration, allowed us to manipulate (enhance and suppress) harmonic generation in relativistic laser-solid interactions by adjusting the relative phase between the colors.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Results and lessons learned from accelerating radio frequency modeling using machine learning [slides]

The “advanced tokamak” reactor concept is a leading candidate for a steady state fusion pilot plant. An advanced tokamak (AT) sustains a majority of the required plasma current with effects resulting from maintenance of the peaked pressure at the device center. This current is augmented by auxiliary current drive sources. These auxiliary actuators may consist of neutral particle beams and/or radio frequency (RF) systems such as lower hybrid current drive (LHCD) and high harmonic fast wave (HHFW) current drive using radio and microwaves from antennas. The primary focus of this work is to develop models of RF current profile control suitable for use in integrated modeling frameworks and for real-time control in experiments. Direct physics models of RF current drive can be computationally intensive. In order to achieve predictive times appropriate for the thousands of calls needed in real-time control of experiments and for use in integrated models, we will apply modern machine learning (ML) techniques to accelerate these models and interpolate their results. To generate the fast and accurate models for use in control level algorithms and integrated modeling we need to replace present models with high dimensional interpolation of their results. We will perform additional simulations across a broader parameter range for EAST and other tokamaks in different physics regimes (Alcator C-Mod, DIII-D, WEST, CFETR, ARC, ITER) and combine them into a larger database for training and testing of the ML models. Further testing of the control level models with experimental current profile data from EAST and C-Mod tokamaks will provide additional confirmation of the control level model before integration in a tokamak control system or integrated modeling suite. ML will be used to optimize the selection of training data consisting of RF current driven at different values of density profile, temperature profile, plasma current, and wavenumber. ML will also be used to facilitate classification of current drive from these input data. The output of this effort will be a validated classifier capable of determining the current drive profiles for HHFW CD and LHCD on a mille-second timescale. This will provide a breakthrough capability enabling real-time control of RF driven current profiles in experiments including ITER ICRF and use integrated modeling frameworks requiring thousands of current profile calculations in discharge simulations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Impact of strong magnetization in cylindrical plasma implosions with applied B-field measured via x-ray emission spectroscopy

Magnetization is a key strategy for enhancing inertial fusion performance, though accurate characterization of magnetized dense plasmas is needed for a better comprehension of the underlying physics. Measured spectra from imploding Ar-doped D 2 -filled cylinders at the OMEGA laser show distinctive features with and without an imposed magnetic field. A multizone spectroscopic diagnosis leads to quantitative estimates of the plasma conditions, namely revealing a 50% core temperature rise at half mass density when a 30-T seed field is applied. Concurrently, experimental spectra align well with predictions from extended-magnetohydrodynamics simulations, providing strong evidence that the attained core conditions at peak compression are consistent with the impact of a 10-kT compressed field. These results pave the way for the validation of magnetized transport models in dense plasmas and for future magnetized laser implosion experiments at a larger scale. Published by the American Physical Society 2024

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Search for heavy neutral Higgs bosons A and H in the $t\bar{t}$Z channel in proton-proton collisions at 13 TeV

A direct search for new heavy neutral Higgs bosons A and H in the $t\bar{t}$Z channel is presented, targeting the process pp → A → ZH with H → $t\bar{t}$. For the first time, the channel with decays of the Z boson to muons or electrons in association with all-hadronic decays of the $t\bar{t}$ system is targeted. The analysis uses proton-proton collision data collected at the CERN LHC with the CMS experiment at $\sqrt{𝑠}$ = 13 TeV, which correspond to an integrated luminosity of 138 fb −1 . No signal is observed. Upper limits on the product of the cross section and branching fractions are derived for narrow resonances A and H with masses up to 2100 and 2000 GeV, respectively, assuming A boson production through gluon fusion. The results are also interpreted within two-Higgs-doublet models, where A and H are CP-odd and CP-even states, respectively, complementing and substantially extending the reach of previous searches.

2HDM↗
DOE OSTI2021

Formation of transient high-β plasmas in a magnetized, weakly collisional regime

We present experimental data providing evidence for the formation of transient (~20 μs) plasmas that are simultaneously weakly magnetized (i.e. Hall magnetization parameter ωτ > 1) and dominated by thermal pressure (i.e. ratio of thermal-to-magnetic pressure β > 1). Particle collisional mean free paths are an appreciable fraction of the overall system size. These plasmas are formed via the head-on merging of two plasmas launched by magnetized coaxial guns. The ratio λ gun = μ 0 I gun /ψ gun of gun current I gun to applied magnetic flux ψ gun is an experimental knob for exploring the parameter space of β and ωτ. These experiments were conducted on the Big Red Ball at the Wisconsin Plasma Physics Laboratory. The transient formation of such plasmas can potentially open up new regimes for the laboratory study of weakly collisional, magnetized, high-β plasma physics; processes relevant to astrophysical objects and phenomena; and novel magnetized plasma targets for magneto-inertial fusion.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

L–H transition threshold studies in helium plasmas at JET

We present a study of the power threshold for L–H transitions (P LH ) in almost pure helium plasmas, obtained in recent experiments at JET with an ITER-like wall (Be wall and W divertor). The most notable new result is that the density at which P LH is minimum, $\bar{n}_{c,min}$, is considerably higher for helium than for deuterium and hydrogen plasmas. We discuss the possible implications for ITER in its pre-fusion operating power phase.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

BeyondFingerprinting: AI-guided discovery of robust materials & processes

BeyondFingerprinting was a 2021-2024 Sandia Grand Challenge LDRD exploring the potential to develop new resilient materials and manufacturing processes by taking an artificial-intelligence (AI)-guided approach that integrates human-subject-matter expertise with algorithms enriched with physics-based constraints to unearth process-structure-property correlations. Such algorithms, trained on high-throughput experiments and simulations, are shown to serve as surrogate models that efficiently detect key “fingerprints” in materials data, prognose material performance, and guide effective process improvements. To accelerate broader adoption across mission areas, this AI-guided approach was demonstrated with three complex process-centric exemplars: electroplating, physical vapor deposition, and laser powder bed fusion. Together, these exemplars impact nearly every hardware component relevant to DOE and NNSA national security missions.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Tailored design of protein nanoparticle scaffolds for multivalent presentation of viral glycoprotein antigens

Multivalent presentation of viral glycoproteins can substantially increase the elicitation of antigen-specific antibodies. To enable a new generation of anti-viral vaccines, we designed self-assembling protein nanoparticles with geometries tailored to present the ectodomains of influenza, HIV, and RSV viral glycoprotein trimers. We first de novo designed trimers tailored for antigen fusion, featuring N-terminal helices positioned to match the C termini of the viral glycoproteins. Trimers that experimentally adopted their designed configurations were incorporated as components of tetrahedral, octahedral, and icosahedral nanoparticles, which were characterized by cryo-electron microscopy and assessed for their ability to present viral glycoproteins. Electron microscopy and antibody binding experiments demonstrated that the designed nanoparticles presented antigenically intact prefusion HIV-1 Env, influenza hemagglutinin, and RSV F trimers in the predicted geometries. This work demonstrates that antigen-displaying protein nanoparticles can be designed from scratch, and provides a systematic way to investigate the influence of antigen presentation geometry on the immune response to vaccination.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Delivering laser performance conditions to enable fusion ignition, and beyond at the National Ignition Facility

On December 5th, 2022, controlled fusion ignition was demonstrated for the first time at the National Ignition Facility (NIF), a major achievement in the field of Inertial Confinement Fusion (ICF) requiring a multi-decadal effort involving broad national and international collaborations. To drive the fusion ignition reaction with the compressed fuel capsule, that yielded 3.15 MJ of nuclear energy [1], the NIF laser delivered a high-precision pulse shape with 2.05 MJ of ultra-violet (UV) laser energy and a peak power of 440 TW. This laser energy was an increase of ~8 % compared to that delivered on the previous “threshold of ignition” record yield experiment (1.37 MJ of yield for 1.89 MJ of laser energy) on August 8th, 2021. Here we explain how the results of our extensive research in laser technology and UV optics damage mitigation led to major improvements in the NIF laser, enabling this energy increase along with additional accuracy, precision, and power balance enhancements. Furthermore, we will discuss on-going efforts that have enabled operations at 2.2 MJ of UV energy as well as potential new initiatives to push the laser performance –accuracy and delivered energy– to even higher levels in the future as previously demonstrated on a small subset of NIF beams.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Electromagnetic full-$f$ gyrokinetics in the tokamak edge with discontinuous Galerkin methods

Here, we present an energy-conserving discontinuous Galerkin scheme for the full-f electromagnetic gyrokinetic system in the long-wavelength limit. We use the symplectic formulation and solve directly for ∂A II /∂t, the inductive component of the parallel electric field, using a generalized Ohm’s law derived directly from the gyrokinetic equation. Linear benchmarks are performed to verify the implementation and show that the scheme avoids the Amp`ere cancellation problem. We perform a nonlinear electromagnetic simulation in a helical open-field-line system as a rough model of the tokamak scrape-off layer using parameters from the National Spherical Torus Experiment (NSTX). This is the first published nonlinear electromagnetic gyrokinetic simulation on open field lines. Comparisons are made to a corresponding electrostatic simulation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Design and construction of the MUSE permanent magnet stellarator

This paper documents the design and construction of MUSE, the world's first permanent magnet (PM) stellarator and the first quasi-axisymmetric experiment. The purpose of MUSE is to develop and assess a new way of building optimised stellarators that uses simple planar coils PMs. Our PM optimisation algorithm consists of initialising a geometry to pack dipoles densely, running the FAMUS code to minimise surface field error subject to PM constraints and applying discrete jumps to reach a physically realisable solution. FAMUS treats the PM system as a set of ideal point dipoles. From there we construct finite-volume magnet towers to be housed in 3D-printed PM holders. We describe the design of the PM holders, which were validated by laser metrology. We analyse the effects of finite permeability, sensitivity to perturbations and magnetostatic forces. An exact analytic formula for the magnetic field from a finite-volume PM tower is presented to compute PM–PM forces and stress on the PM holder. Stellarator construction is complete and experiments are underway.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗