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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 1,567 records · Page 87
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Measuring implosion velocities in experiments and simulations of laser-driven cylindrical implosions on the OMEGA laser

Laser-driven magnetized liner inertial fusion (MagLIF) on OMEGA involves cylindrical implosions, a preheat beam, and an applied magnetic field. Initial experiments excluded the preheat beam and magnetic field to better characterize the implosion. X-ray self-emission as measured by framing cameras was used to determine the shell trajectory. The 1-D code LILAC was used to model the central region of the implosion, and results were compared to 2-D simulations from the HYDRA code. Post-processing of simulation output with SPECT3D and Yorick produced synthetic x-ray images that were used to compare the simulation results with the x-ray framing camera data. Quantitative analysis shows that higher measured neutron yields correlate with higher implosion velocities. The future goal is to further analyze the x-ray images to characterize the uniformity of the implosions and apply these analysis techniques to integrated laser-driven MagLIF shots to better understand the effects of preheat and the magnetic field.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Wire, hybrid, and laser-cut X-pinches as Talbot–Lau backlighters for electron density diagnostics

Talbot–Lau x-ray deflectometry (TXD) enables refraction-based imaging for high-energy-density physics experiments, and thus, it has been studied and developed with the goal of diagnosing plasmas relevant to inertial confinement and magnetic liner inertial fusion. X-pinches, known for reliably generating fast (~1 ns), small (~1 µm) x-ray sources, were driven on the compact current driver generator for ablation structure and implosion studies (~200 kA, 150 ns) as a potential backlighter source for TXD. Considering that different X-pinch configurations have characteristic advantages and drawbacks as x-ray generating loads, three distinct copper X-pinch configurations were studied: the wire X-pinch, the hybrid X-pinch, and the laser-cut X-pinch. Furthermore, the Cu K-shell emission from each configuration was characterized and analyzed regarding the specific backlighter requirements for an 8 keV TXD system: spatial and temporal resolution, number of sources, time of emission, spectrum, and reproducibility. Recommendations for future experimental improvements and applications are presented. The electron density of static objects was retrieved from Moiré images obtained through TXD. This allowed to calculate the mass density of static samples within 4% of the expected value for laser-cut X-pinches, which were found to be the optimal X-pinch configuration for TXD due to their high reproducibility, small source size (≤5 µm), short duration (~1 ns), and up to 106 W peak power near 8 keV photon energy. Plasma loads were imaged through TXD for the first-time using laser-cut X-pinch backlighting. Experimental images were compared with simulations from the x-ray wave-front propagation code, demonstrating that TXD can be a powerful x-ray refraction-based diagnostic for dense Z-pinch loads. Future plans for Talbot–Lau interferometry diagnostics in the pulsed-power environment are described.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

The Higgs Factory muon collider superconducting magnets and their protection against beam decay radiation

We report a low-energy medium-luminosity Muon Collider (MC) is being studied as a possible Higgs Factory (HF). Electrons from muon decays will deposit more than 300 kW in superconducting (SC) magnets of the HF collider ring. This imposes significant challenges to SC magnets used in the HF storage ring (SR) and interaction regions (IR). Conceptual designs of SC dipole and quadrupole magnets are described which provide high operating gradient and field in a large aperture to accommodate the large size of muon beams (due to low β*), as well as a cooling system to intercept the large heat deposition from the showers induced by decay electrons. The distribution of heat deposition in the main elements of HF SR lattice requires large-aperture magnets to accommodate thick high-Z absorbers to protect the SC coils. Based on the developed MARS15 model and intensive simulations, a sophisticated protection system from radiation was designed for the collider SR and IR to bring the peak power density in the SC coils well below the quench limit and reduce the dynamic heat deposition in the cold mass of SC magnets by a factor of 100. The radiation protection system consists of tight tungsten masks in the magnet interconnect regions and elliptical tungsten liners in the magnet aperture optimized for each magnet. Lastly, these elements reduce also the background particle fluxes in the collider detector.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

THE BRIGHTEST CLUSTER GALAXY IN A85: THE LARGEST CORE KNOWN SO FAR

We have found that the brightest cluster galaxy (BCG) in A85, Holm 15A, displays the largest core known so far. Its cusp radius, r {sub γ} = 4.57 ± 0.06 kpc (4.''26 ± 0.''06), is more than 18 times larger than the mean for BCGs and ≳ 1 kpc larger than A2261-BCG, hitherto the largest-cored BCG. Holm 15A hosts the luminous amorphous radio source 0039-095B and has the optical signature of a LINER. Scaling laws indicate that this core could host a supermassive black hole (SMBH) of mass M {sub •} ∼ (10{sup 9}-10{sup 11}) M {sub ☉}. We suggest that cores this large represent a relatively short phase in the evolution of BCGs, whereas the masses of their associated SBMH might be set by initial conditions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

The TELPERION survey for distant [O iii ] clouds around luminous and hibernating AGN

ABSTRACT We present a narrow-band [O iii] imaging survey of 111 active galactic nucleus (AGN) hosts and 17 merging-galaxy systems, in search of distant extended emission-line regions (EELRs) around AGNs (either extant or faded). Our data reach deeper than detection from the broad-band SDSS data and cover a wider field than some early emission-line surveys used to study extended structure around AGNs. Spectroscopic follow-up confirms two new distant AGN-ionized clouds, in the merging systems NGC 235 and NGC 5514, projected at 26 and 75 kpc from the nuclei (respectively). We also recover the previously known region in NGC 7252. These results strengthen the connection between EELRs and tidal features; kinematically quiescent distant EELRs are virtually always photoionized tidal debris. We see them in ≈10 per cent of the galaxies in our sample with tidal tails. Energy budgets suggest that the AGN in NGC 5514 has faded by >3 times during the extra light traveltime ≈250 000 yr from the nucleus to the cloud and then to the observer; strong shock emission in outflows masks the optical signature of the AGN. For NGC 235 our data are consistent with but do not unequivocally require variation over ≈85 000 yr. In addition to these very distant ionized clouds, we find luminous and extensive line emission within four galaxies – IC 1481, ESO 362-G08, NGC 5514, and NGC 7679. Among these, IC 1481 shows apparent ionization cones, a rare combination with its LINER AGN spectrum. In NGC 5514, we measure a 7-kpc shell expanding at ≈370 km s−1 west of the nucleus.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

On the relation of host properties and environment of AGN galaxies across the standard optical diagnostic diagram

ABSTRACT We study the host properties and environment of active galactic nuclei (AGNs) galaxies, taken from SDSS-DR12, across the [O iii]/H β versus [N ii]/H α diagnostic diagram. We select AGN subsamples defined as parallel and perpendicular to the star-forming locus on the BPT diagram based on the Kauffmann et al. and Schawinski et al. criteria. For parallel subsamples we find that AGN host properties exhibit a morphological evolution as they become more distant to the star-forming sequence. The local density environment shows a more evident morphology–density relationship for subsamples mainly formed by Composite and Spiral galaxies than those containing LINERs and Seyferts, where the AGN emission is the dominant source. We also analyse the properties of the five closest AGN neighbours observing no significant differences in the environment, although the AGN host properties of every subsample have noticeable variations. The AGNs belonging to perpendicular subsamples show clear differences on their host properties from left top to right bottom on the diagram. However, the analysis of the local density environment do not reflect strong dependency with the host AGN properties. This result is reinforced by the characteristics of the AGN neighbouring galaxies. These findings suggest that mixed AGN/star-forming galaxies present environmental features more similar to that of non-active galaxies. However, as AGNs at the centre of the more evolved galaxies become the dominant source, the environment tends to provide suitable conditions for the central black hole feeding with an increasing content of gas and likelihood of a higher merger rate.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Fast and efficient identification of anomalous galaxy spectra with neural density estimation

ABSTRACT Current large-scale astrophysical experiments produce unprecedented amounts of rich and diverse data. This creates a growing need for fast and flexible automated data inspection methods. Deep learning algorithms can capture and pick up subtle variations in rich data sets and are fast to apply once trained. Here, we study the applicability of an unsupervised and probabilistic deep learning framework, the probabilistic auto-encoder, to the detection of peculiar objects in galaxy spectra from the SDSS survey. Different to supervised algorithms, this algorithm is not trained to detect a specific feature or type of anomaly, instead it learns the complex and diverse distribution of galaxy spectra from training data and identifies outliers with respect to the learned distribution. We find that the algorithm assigns consistently lower probabilities (higher anomaly score) to spectra that exhibit unusual features. For example, the majority of outliers among quiescent galaxies are E+A galaxies, whose spectra combine features from old and young stellar population. Other identified outliers include LINERs, supernovae, and overlapping objects. Conditional modelling further allows us to incorporate additional information. Namely, we evaluate the probability of an object being anomalous given a certain spectral class, but other information such as metrics of data quality or estimated redshift could be incorporated as well. We make our code publicly available.

Böhm, Vanessa↗
DOE OSTI2024

Stellar populations and merger rates of brightest cluster galaxies a billion years ago: SDSS MaNGA IFU spectroscopy

ABSTRACT We investigate the spectroscopic properties of 85 brightest cluster galaxies (BCGs) and their companions observed with the SDSS MaNGA integral field unit. Galaxy redshifts are between 0.08 < z < 0.15, allowing for a field-of-view up to 80 × 80 kpc. For the main galaxies: the average age of the BCG cores is 7.66$\, \pm \,$1.36 Gyr with no significant gradient out to $2\, R_ {e}$; the average metallicity of the BCG cores is $[Z/H]=0.23\, \pm \, 0.03$ with a negative gradient of Δ[Z/H]/Δ(R/Re) = –0.14$\, \pm \, 0.09$ which flattens beyond $1.2\, R_ {e}$. Velocity dispersion gradients are mostly flat, but a few positive slopes are seen in the most massive galaxies. Emission lines are present in 12 of the BCGs, most often confined to the central $\sim 2\,$ kpc with emission line ratios well-described by a LINER or AGN excitation source. There are 78 companion galaxies identified and 9 have nebular emission lines that indicate recent star formation. The companions with flux ratios of 4:1 and 20:1 within 30 kpc of their BCG’s core are studied. The companion galaxies have a median age of 7.65$\, \pm \,$1.55 Gyr and are high-metallicity systems, with a median [Z/H] = 0.17 ± 0.07. Close spectroscopic companions with higher merging probabilities have an average merging time of 0.5 ± 0.2 Gyr. The average merger rate is 0.08$\, \pm \, 0.12 \,$ Gyr−1 for 4:1 companions and 0.26$\, \pm \, 0.22 \,$ Gyr−1 for 20:1 companions, allowing for an increase in mass of 2.3$\, \pm \,$3.4 per cent Gyr−1 and 3.5$\, \pm \,$3.2 per cent Gyr−1, respectively.

Edwards, Louise O. V. (ORCID:000000029135997X)↗
DOE OSTI2019

H i galaxies with little star formation: an abundance of LIERs

Abstract We present a sample of 91 H i galaxies with little or no star formation, and discuss the analysis of the integral field unit (IFU) spectra of 28 of these galaxies. We identified H i galaxies from the H i Parkes All-Sky Survey Catalog (HICAT) with Wide-field Infrared Survey Explorer (WISE) colours consistent with low specific star formation (<10−10.4 yr−1), and obtained optical IFU spectra with the Wide-Field Spectrograph (WiFeS). Visual inspection of the PanSTARRS, Dark Energy Survey, and Carnegie-Irvine imaging of 62 galaxies reveals that at least 32 galaxies in the sample have low levels of star formation, primarily in arms/rings. New IFU spectra of 28 of these galaxies reveals 3 galaxies with central star formation, 1 galaxy with low-ionization nuclear emission-line regions (LINERs), 20 with extended low-ionization emission-line regions (LIERs), and 4 with high excitation Seyfert (Sy) emission. From the spectroscopic analysis of H i selected galaxies with little star formation, we conclude that 75 per cent of this population are LINERs/LIERs.

Parkash, Vaishali↗
DOE OSTI2018

Dissecting the main sequence: AGN activity and bulge growth in the local Universe

ABSTRACT Local galaxies from the Sloan Digital Sky Survey (SDSS) are used to provide additional support for an evolutionary pathway in which active galactic nucleus activity is associated with star formation quenching. Composite, Seyfert 2, and LINER galaxies account for ∼60 per cent of all star formation in massive galaxies (M⋆ > 1010.5 M⊙). Inclusion of these galaxies results in a ‘turnover’ in the star formation rate and stellar mass (SFR−M⋆) relation for massive galaxies. Our analysis shows that bulge growth has already occurred in the most massive galaxies (M⋆ > 1010.5 M⊙), and bulges continue to grow as galaxies quench and redden, (g − r) = 0.5 → 0.75. Significant bulge growth is also occurring in low mass starburst galaxies (M⋆ < 1010.5 M⊙) at 0.5 dex above the ‘main sequence’ (MS), where we find an increase in B/T from 0.1 → 0.3 and bluer colours, (g − r) < 0.25 compared to low-mass galaxies on the MS.

McPartland, C. (ORCID:000000030639025X)↗
DOE OSTI2015

Performance and Mix Measurements of Indirect Drive Cu-Doped Be Implosions

The ablator couples energy between the driver and fusion fuel in inertial confinement fusion (ICF). Because of its low opacity, high solid density, and material properties, beryllium has long been considered an ideal ablator for ICF ignition experiments at the National Ignition Facility. We report here the first indirect drive Be implosions driven with shaped laser pulses and diagnosed with fusion yield at the OMEGA laser. The results show good performance with an average DD neutron yield of ~2 × 10⁹ at a convergence ratio of R₀/R ~ 10 and little impact due to the growth of hydrodynamic instabilities and mix. In addition, the effect of adding an inner liner of W between the Be and DD is demonstrated.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Favorable Collisional Demixing of Ash and Fuel in Magnetized Inertial Fusion

Magnetized inertial fusion experiments are approaching regimes where the radial transport is dominated by collisions between magnetized ions, providing an opportunity to exploit effects usually associated with steady-state magnetic fusion. Here, the low-density hotspot characteristic of magnetized liner inertial fusion results in diamagnetic and thermal frictions, which can demix thermalized ash from fuel, accelerating the fusion reaction. For reactor regimes in which there is a substantial burnup of the fuel, increases in the fusion energy yield on the order of 5% are possible.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Effects of an axial magnetic field on the current distribution in a Z-pinch implosion with preembedded magnetic field

In this study, the fundamental physics of the magnetic field distribution in a plasma implosion with a pre-embedded magnetic field is investigated within a gas puff Z-pinch. Time and space resolved spectroscopy of the polarized Zeeman effect, applied for the first time, reveals the impact of a pre-embedded axial field on the evolution of the current distribution driven by a pulsed-power generator. The measurements show that the azimuthal magnetic field in the imploding plasma, even in the presence of a weak axial magnetic field, is substantially smaller than expected from the ratio of the driving current to the plasma radius. Much of the current flows at large radii through a slowly-imploding, low-density plasma. The development of a force-free current configuration is suggested to explain this phenomenon. Finally, previously unpredicted observations in higher-power imploding-magnetized-plasma experiments, including recent unexplained structures observed in the Magnetized Liner Inertial Fusion experiment, may be explained by the present discovery.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Harmonic Generation and Inverse Cascade in the z-Pinch Driven, Preseeded Multimode, Magneto-Rayleigh-Taylor Instability

We report the magneto-Rayleigh-Taylor instability (MRTI) plays an essential role in astrophysical systems and in magneto-inertial fusion, where it is known to be an important degradation mechanism of confinement and target performance. In this Letter, we show for the first time experimental evidence of mode mixing and the onset of an inverse-cascade process resulting from the nonlinear coupling of two discrete preseeded axial modes (400- and 550 - μm wavelengths) on an Al liner that is magnetically imploded using the 20-MA, 100-ns rise-time Z Machine at Sandia National Laboratories. Four radiographs captured the temporal evolution of the MRTI. We introduce a novel unfold technique to analyze the experimental radiographs and compare the results to simulations and to a weakly nonlinear model. We find good quantitative agreement with simulations using the radiation magnetohydrodynamics code hydra. Spectral analysis of the MRTI time evolution obtained from the simulations shows evidence of harmonic generation, mode coupling, and the onset of an inverse-cascade process. The experiments provide a benchmark for future work on the MRTI and motivate the development of new analytical theories to better understand this instability.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Greybox Thermal Parameter Identification of Electric Machine Stators

The parameters of electric machine thermal equivalent circuit networks are difficult to predict due to material and manufacturing uncertainties. In this paper, a Greybox system identification approach is used to identify parameters of electric machine stator lumped parameter thermal networks (LPTNs). LPTNs provide a low order, computationally efficient, dynamic model of temperatures at specific locations. Second and third order LPTN model structures are defined as state space equations with stator thermal parameters to be identified. To test the Greybox electric machine stator thermal system identification, five stator motorette prototypes were constructed with controlled variations in slot fill and slot liner thickness. The variation in the motorette thermal parameters and thermal time constants are detected using the Greybox identification. Special attention is given to the impact of sampling rate and Greybox data record length on parameter estimation accuracy.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2019

Unscented Kalman Filter-based Unbiased Minimum-Variance Estimation for Nonlinear Systems with Unknown Inputs

This paper proposes an unscented Kalman filter (UKF)-based unbiased minimum-variance estimation (UMV) method for the nonlinear system with unknown inputs. By utilizing the statistical linerization, the nonlinear system and measurement functions are transformed into a “linear-like” regression form. The latter preserves the nonlinearity of the system and the measurement models. To this end, the unknown inputs can be estimated by the weighted least-squares. This “linear-like” regression form also allows us to resort to the UMV state estimation framework for the development of new nonlinear filter to handle unknown inputs. Specifically, two approaches have been developed: 1) given the estimated inputs, we derive a filter by minimizing the trace of the state error covariance matrix; 2) without input estimation, we derive the filter by minimizing the trace of the state error covariance matrix subject to a constraint imposed on the gain matrix. We prove that these two approaches provide the same results. Numerical results validate the effectiveness of the proposed method.

Unscented Kalman filter, unbiased minimumvariance ↗
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↗
DOE OSTI2025

A new method for measuring refractory corrosion of ceramics in glass

Abstract Nuclear waste glass vitrification furnaces are lined with refractory ceramic blocks to contain the molten glass. The refractory liner is susceptible to corrosion and has a finite service lifetime. For this reason, predicting the refractory corrosion in contact with molten glass is integral to estimating melter service lifetime. Standardized laboratory tests varying time and temperature are commonly performed to estimate refractory material loss as a function of glass composition. These data are time and resource‐intensive to collect and are susceptible to considerable measurement error. In order to accelerate glass formulation and design for nuclear waste vitrification, methods are needed to increase laboratory‐scale throughput while maintaining data quality. In this work, a method to remove the residual glass from a corroded coupon using hydrofluoric acid is presented that accelerates the throughput of sample analysis while simultaneously facilitating more accurate measurements.

Amoroso, Jake W. [Savannah River National Laborato↗