Search NASA⌕ Search

SEARCH · Search NASA

Results for “stagnation temperature”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Experimental quantification of vent mechanism flow parameters in 18650 format lithium ion batteries

Lithium ion batteries have a well documented tendency to fail energetically under various abuse conditions. These conditions frequently result in decomposition of the electrochemical components within the battery resulting in gas generation and increased internal pressure which can lead to an explosive case rupture. The 18650 format cell incorporates a vent mechanism located within a crimped cap to relieve pressure and mitigate the risk of case rupture. Cell venting, however, introduces additional safety concerns associated with the flow of flammable gases and liquid electrolyte into the environment. Experiments to quantify key parameters are performed to elucidate the external dynamics of battery venting. A first experiment measures the vent burst pressure. Burst vent caps are then tested with a second experimental fixture to measure vent opening area and discharge coefficient during choked-flow venting, which occurs during battery failure. Vent opening area and discharge coefficient are calculated from stagnation temperature, stagnation pressure, and static pressure measurements along with compressible-isentropic flow equations and conservation of mass. Commercially-sourced vent caps are used with repeated tests run to quantify repeatability and variability. Validation experiments confirmed accuracy of opening area and discharge coefficient measurement. Moreover, trials conducted on vent caps from two sources demonstrate the potential for variation between manufacturers.

25 ENERGY STORAGE↗
DOE OSTI2015

Demonstration of thermonuclear conditions in magnetized liner inertial fusion experiments

The magnetized liner inertial fusion concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)] utilizes a magnetic field and laser heating to relax the pressure requirements of inertial confinement fusion. The first experiments to test the concept [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] were conducted utilizing the 19 MA, 100 ns Z machine, the 2.5 kJ, 1 TW Z Beamlet laser, and the 10 T Applied B-field on Z system. Despite an estimated implosion velocity of only 70 km/s in these experiments, electron and ion temperatures at stagnation were as high as 3 keV, and thermonuclear deuterium-deuterium neutron yields up to 2 × 10{sup 12} have been produced. X-ray emission from the fuel at stagnation had widths ranging from 50 to 110 μm over a roughly 80% of the axial extent of the target (6–8 mm) and lasted approximately 2 ns. X-ray yields from these experiments are consistent with a stagnation density of the hot fuel equal to 0.2–0.4 g/cm{sup 3}. In these experiments, up to 5 × 10{sup 10} secondary deuterium-tritium neutrons were produced. Given that the areal density of the plasma was approximately 1–2 mg/cm{sup 2}, this indicates the stagnation plasma was significantly magnetized, which is consistent with the anisotropy observed in the deuterium-tritium neutron spectra. Control experiments where the laser and/or magnetic field were not utilized failed to produce stagnation temperatures greater than 1 keV and primary deuterium-deuterium yields greater than 10{sup 10}. An additional control experiment where the fuel contained a sufficient dopant fraction to substantially increase radiative losses also failed to produce a relevant stagnation temperature. The results of these experiments are consistent with a thermonuclear neutron source.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

Ion Temperature and Hydrodynamic-Energy Measurements in a Z-Pinch Plasma at Stagnation

The time history of the local ion kinetic energy in a stagnating plasma was determined from Doppler-dominated line shapes. Using independent determination of the plasma properties for the same plasma region, the data allowed for inferring the time-dependent ion temperature, and for discriminating the temperature from the total ion kinetic energy. It is found that throughout most of the stagnation period the ion thermal energy constitutes a small fraction of the total ion kinetic energy; the latter is dominated by hydrodynamic motion. Both the ion hydrodynamic and thermal energies are observed to decrease to the electron thermal energy by the end of the stagnation period. It is confirmed that the total ion kinetic energy available at the stagnating plasma and the total radiation emitted are in balance, as obtained in our previous experiment. The dissipation time of the hydrodynamic energy thus appears to determine the duration (and power) of the K emission.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Semiconductor-based Multilayer Selective Solar Absorber for Unconcentrated Solar Thermal Energy Conversion

Solar thermal energy conversion has attracted substantial renewed interest due to its applications in industrial heating, air conditioning, and electricity generation. Achieving stagnation temperatures exceeding 200 °C, pertinent to these technologies, with unconcentrated sunlight requires spectrally selective absorbers with exceptionally low emissivity in the thermal wavelength range and high visible absorptivity for the solar spectrum. In this Communication, we then report a semiconductor-based multilayer selective absorber that exploits the sharp drop in optical absorption at the bandgap energy to achieve a measured absorptance of 76% at solar wavelengths and a low emittance of approximately 5% at thermal wavelengths. In field tests, we obtain a peak temperature of 225 °C, comparable to that achieved with state-of-the-art selective surfaces. Furthemore, with straightforward optimization to improve solar absorption, our work shows the potential for unconcentrated solar thermal systems to reach stagnation temperatures exceeding 300 °C, thereby eliminating the need for solar concentrators for mid-temperature solar applications such as supplying process heat

14 SOLAR ENERGY↗
DOE OSTI2013

Determination of hydrogen cluster velocities and comparison with numerical calculations

The use of powerful hydrogen cluster jet targets in storage ring experiments led to the need of precise data on the mean cluster velocity as function of the stagnation temperature and pressure for the determination of the volume density of the target beams. For this purpose a large data set of hydrogen cluster velocity distributions and mean velocities was measured at a high density hydrogen cluster jet target using a trumpet shaped nozzle. The measurements have been performed at pressures above and below the critical pressure and for a broad range of temperatures relevant for target operation, e.g., at storage ring experiments. The used experimental method is described which allows for the velocity measurement of single clusters using a time-of-flight technique. Since this method is rather time-consuming and these measurements are typically interfering negatively with storage ring experiments, a method for a precise calculation of these mean velocities was needed. For this, the determined mean cluster velocities are compared with model calculations based on an isentropic one-dimensional van der Waals gas. Based on the obtained data and the presented numerical calculations, a new method has been developed which allows to predict the mean cluster velocities with an accuracy of about 5%. For this two cut-off parameters defining positions inside the nozzle are introduced, which can be determined for a given nozzle by only two velocity measurements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Controlling morphology and improving reproducibility of magnetized liner inertial fusion experiments

X-ray imaging indicates magnetized liner inertial fusion (MagLIF) stagnation columns have a complicated quasi-helical structure with significant variations in x-ray brightness along the column. In this work, we describe MagLIF experiments aimed at controlling these stagnation structures by varying the initial liner geometry and composition. First, by varying the initial aspect ratio of the liner, we demonstrate a change in the stagnation structures that is consistent with helical magneto Rayleigh–Taylor (MRT) instabilities feedthrough from the outer-to-inner surfaces of the liner. Second, to minimize the seed for such instabilities, we incorporate a dielectric coating on the outer surface of the beryllium liner, which has previously been shown to reduce the growth of the electrothermal instability, a likely seed for MRT growth. Using this coating, we achieve a stagnation column with significantly reduced helical structure and axial variation in x-ray brightness. We discuss how this coating changes the evolution of structures through stagnation along with the spatial uniformity of neutron production. Finally, we show that these more uniform stagnations also result in improved reproducibility in stagnation temperatures and primary DD neutron yield.

Ampleford, D. J. (ORCID:0000000237422421)↗
DOE OSTI2014

Experimental demonstration of fusion-relevant conditions in magnetized liner inertial fusion

This Letter presents results from the first fully integrated experiments testing the magnetized liner inertial fusion concept [S.A. Slutz et al., Phys. Plasmas 17, 056303 (2010)], in which a cylinder of deuterium gas with a preimposed axial magnetic field of 10 T is heated by Z beamlet, a 2.5 kJ, 1 TW laser, and magnetically imploded by a 19 MA current with 100 ns rise time on the Z facility. Despite a predicted peak implosion velocity of only 70 km/s, the fuel reaches a stagnation temperature of approximately 3 keV, with T e ≈ T i , and produces up to 2e12 thermonuclear DD neutrons. In this study, X-ray emission indicates a hot fuel region with full width at half maximum ranging from 60 to 120 μm over a 6 mm height and lasting approximately 2 ns. The number of secondary deuterium-tritium neutrons observed was greater than 10 10 , indicating significant fuel magnetization given that the estimated radial areal density of the plasma is only 2 mg/cm 2 .

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Estimation of stagnation performance metrics in magnetized liner inertial fusion experiments using Bayesian data assimilation

Here we present a new analysis methodology that allows for the self-consistent integration of multiple diagnostics including nuclear measurements, x-ray imaging, and x-ray power detectors to determine the primary stagnation parameters, such as temperature, pressure, stagnation volume, and mix fraction in magnetized liner inertial fusion (MagLIF) experiments. The analysis uses a simplified model of the stagnation plasma in conjunction with a Bayesian inference framework to determine the most probable configuration that describes the experimental observations while simultaneously revealing the principal uncertainties in the analysis. We validate the approach by using a range of tests including analytic and three-dimensional MHD models. An ensemble of MagLIF experiments is analyzed, and the generalized Lawson criterion χ is estimated for all experiments.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Target geometrical effects on the stagnation layer formed by colliding a pair of laser produced copper plasmas

We present the results of a time and space resolved optical-spectroscopic study of colliding plasmas formed at the front surfaces of flat and inclined Cu slab targets as a function of both the distance and the wedge angle between them for angles ranging from 100° to 180° (laterally colliding plasmas). The key parameters studied are stagnation layer density, temperature, duration, and kinetics of atomic/ionic spatial distributions and all have been found to vary significantly with wedge angle. It is found that the density and temperature of the stagnation layer decrease with increasing wedge angle. It is also found that the larger the wedge angle, the tighter and more well defined the stagnation layer formed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Development of a krypton-doped gas symmetry capsule platform for x-ray spectroscopy of implosion cores on the NIF

The electron temperature at stagnation of an ICF implosion can be measured from the emission spectrum of high-energy x-rays that pass through the cold material surrounding the hot stagnating core. Here we describe a platform developed on the National Ignition Facility where trace levels of a mid-Z dopant (krypton) are added to the fuel gas of a symcap (symmetry surrogate) implosion to allow for the use of x-ray spectroscopy of the krypton line emission.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Merging of high speed argon plasma jets

Formation of an imploding plasma liner for the plasma liner experiment (PLX) requires individual plasma jets to merge into a quasi-spherical shell of plasma converging on the origin. Understanding dynamics of the merging process requires knowledge of the plasma phenomena involved. We present results from the study of the merging of three plasma jets in three dimensional geometry. The experiments were performed using HyperV Technologies Corp. 1 cm Minirailguns with a preionized argon plasma armature. The vacuum chamber partially reproduces the port geometry of the PLX chamber. Diagnostics include fast imaging, spectroscopy, interferometry, fast pressure probes, B-dot probes, and high speed spatially resolved photodiodes, permitting measurements of plasma density, temperature, velocity, stagnation pressure, magnetic field, and density gradients. These experimental results are compared with simulation results from the LSP 3D hybrid PIC code.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Investigating Laser Preheat and Applied Magnetic Fields Relevant to the MagLIF Fusion Scheme

The MAGnetized Liner Inertial Fusion (MagLIF) scheme has achieved thermonuclear fusion yields on the Z Facility by imploding a cylindrical liner filled with D 2 fuel that is preheated with a multi-kJ laser and pre-magnetized with an axial Bz=10 T magnetic field. Preheating (T e = 100-200 eV) and pre-magnetizing (10-30 T) the fuel serves to reduce the implosion velocity required to achieve multi-keV fusion-relevant temperatures at stagnation with a modest radial convergence. The challenge of fuel preheat in MagLIF is to deposit multiple-kJ of energy into the underdense (n e /n c <0.1) fuel over ~10 mm target length efficiently and without introducing contaminants. Once the fuel is heated the applied axial magnetic field (ω ce τ e ~ 10) needs to suppress electron thermal conduction sufficiently to prevent unacceptable heat losses to the liner walls. In this LDRD we investigated laser energy deposition at two facilities: The OMEGA-EP laser at the Laboratory for Laser Energetics and the Z-beamlet laser at Sandia National Labs utilizing the PECOS chamber. Multiple experiments were carried out investigating laser transmission through LEH foils, laser heating of underdense gasses and the effects of magnetization on laser preheat. The studies find that magneto-hydrodynamic simulations are able to reproduce energy deposition at MagLIF-like conditions but that at the intensities currently used to preheat MagLIF significant laser plasma instabilities (LPI) occur which partly explain the inability of codes to reproduce previous MagLIF preheat studies. The experiments find that reducing the intensity and smoothing the beam dramatically reduces the amount of stimulated Brillouin backscatter and produces deposition profiles more similar to those produced in simulations. The experiments have provided a large and varied dataset that can be compared to simulations. As part of the LDRD new experimental capabilities have also been developed that will be used to design future MagLIF integrated experiments and investigate fuel magnetization.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

A simple counter-flow cooling system for a supersonic free-jet beam source assembly

A simple design for an inexpensive, cooled, free-jet beam source is described. The source assembly features an integrated cooling system as supplied by a counter-flow of chilled nitrogen, and is composed primarily of off-the-shelf tube fittings. The design facilitates rapid implementation and eases subsequent alignment with respect to any downstream beamline aperture. The source assembly outlined cools the full length of the stagnation volume, offering temperature control down to 100 K and long-term temperature stability better than ±1 K.

42 ENGINEERING↗
DOE OSTI2014

Effective versus ion thermal temperatures in the Weizmann Ne Z-pinch: Modeling and stagnation physics

The difference between the ion thermal and effective temperatures is investigated through simulations of the Ne gas puff z-pinch reported by Kroupp et al. [Phys. Rev. Lett. 107, 105001 (2011)]. Calculations are performed using a 2D, radiation-magnetohydrodynamic code with Tabular Collisional-Radiative Equilibrium, namely Mach2-TCRE [Thornhill et al., Phys. Plasmas 8, 3480 (2001)]. The extensive data set of imaging and K-shell spectroscopy from the experiments provides a challenging validation test for z-pinch simulations. Synthetic visible images of the implosion phase match the observed large scale structure if the breakdown occurs at the density corresponding to the Paschen minimum. At the beginning of stagnation (−4 ns), computed plasma conditions change rapidly showing a rising electron density and a peak in the ion thermal temperature of ∼1.8 keV. This is larger than the ion thermal temperature (<400 eV) inferred from the experiment. By the time of peak K-shell power (0 ns), the calculated electron density is similar to the data and the electron and ion thermal temperatures are equilibrated, as is observed. Effective ion temperatures are obtained from calculated emission line widths accounting for thermal broadening and Doppler velocity shifts. The observed, large effective ion temperatures (∼4 keV) early in the stagnation of this Ne pinch can be explained solely as a combination of compressional ion heating and steep radial velocity gradients near the axis. Approximations in the modeling are discussed in regard to the higher ion thermal temperature and lower electron density early in the stagnation compared to the experimental results.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

A 3D dynamic model to assess the impacts of low-mode asymmetry, aneurysms and mix-induced radiative loss on capsule performance across inertial confinement fusion platforms

A simple 3D dynamic model for inertial confinement fusion (ICF) implosions has been developed and used to assess the impacts of low-mode asymmetry, aneurysms and mix-induced radiative loss on capsule performance across ICF platforms. While benchmarked against radiation hydrodynamics simulations, this model benefits from simplicity and speed to allow rapid assessment of possible sources of degradation as well as to help build intuition about the relative importance of different effects. Degradations in the model result from 3D pr areal density perturbations that grow under deceleration from a radial stagnation flow, resulting in reduced convergence, stagnation pressure and temperature. When available, experimental data are used as input to seed 3D perturbations in the model so that the actual observed hotspot and shell areal density asymmetry at stagnation, as well as the radiation loss increase from mix impurities, are accurately reproduced. This model is applied to a broad set of implosion data from the NIF and Omega, including examples from both indirect drive and direct drive. The model matches most experimental observables and explains major performance degradation mechanisms which can result in 30–100-fold reductions in yield. We investigate a modified ignition criterion that accounts for the increase in expansion pdV work, due to the presence of 3D pr perturbations and loss-of-confinement in thin regions of the shell.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Thermal conductance of interfaces between titanium nitride and group IV semiconductors at high temperatures

Measuring the temperature dependence of material properties is a standard method for better understanding the microscopic origins for that property. Surprisingly, only a few experimental studies of thermal boundary conductance at high temperatures exist. This lack of high temperature data makes it difficult to evaluate competing theories for how inelastic processes contribute to thermal conductance. To address this, we report time domain thermoreflectance measurements of the thermal boundary conductance for TiN on diamond, silicon-carbide, silicon, and germanium between 120 and 1000 K. In all systems, the interface conductance increases monotonically without stagnating at higher temperatures. For TiN/SiC interfaces, G ranges from 330 to 1000 MW/m2-K, with a room temperature conductance of 750 MW/m2-K. The interface conductance for TiN/diamond ranges from 140 to 950 MW/m2-K. Notably, for all four interfacial systems, the conductance continues to increase with temperature even after all phonon modes in the vibrationally soft material are thermally excited. This observation suggests that inelastic processes are significant contributors to the thermal conductance in all four interfacial systems, regardless of whether the materials forming the interface are vibrationally similar or dissimilar. Our study fills a notable gap in the literature for how interfacial conductance evolves at high temperatures and tests burgeoning theories for the role of inelastic processes in interfacial thermal transport.

Physics↗
DOE OSTI2018

Time-Resolved Thomson Scattering on Gas-Puff Z-Pinch Plasmas at Pinch Time

The conditions and dynamics of neon gas puff Z-pinch plasmas at pinch time are studied on a pulsed power generator with a current rise time of approximately 200-ns and 0.9-mA peak current. Radial tailoring of the gas puff massdensity profile using a triple-nozzle coaxial valve (two annular gas liners and a central jet) allows production of both more stable and less stable (with regard to the magneto-Rayleigh– Taylor instability) Z-pinch implosions. A 526.5-nm, 10-J Thomson scattering diagnostic laser enables probing of the flow dynamics and plasma conditions of these implosions with both spatial and temporal resolutions. The 2.2-ns laser pulse scatters from the plasma electrons and is carried by one optical fiber to a visible light streak camera, and by a bundle of optical fibers to a time-gated camera, both after spectral dispersion by 750-mm spectrometers. The streak camera, with a 10-ns full streak time, provides subnanosecond resolution of the evolution of the pinch plasma parameters through stagnation. The timegated camera provides spatially resolved spectra (across a field of view of 6.1 mm) at the same time as the streak. Scattering spectra suggest that temperatures are high at stagnation, with the ion temperature as much as three times higher than the electron temperature. Furthermore, we consider the possibility of nonthermal explanations for the broad scattering spectra and high effective ion temperature, including collisionality, implosion velocity distributions (velocity gradients), and small-scale hydrodynamic motion.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗