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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Simulated impact of fill tube geometry on recent high-yield implosions at the National Ignition Facility

Inertial confinement fusion capsules fielded at the National Ignition Facility are filled with deuterium and tritium fuel by means of a fill tube. The fill tube introduces a low-density pathway into the fuel region of the capsule that allows high Z contaminant to invade the hot spot during the course of the implosion. A recent series of nominally identical high-yield implosions on the NIF has exhibited significant variability in performance. We evaluate the impact of the fill tube in these implosions computationally to determine whether variations in fill tube geometry could have contributed to this variability. The main contrast between the fill tube geometry in the six shots was the outer diameter of the capsule bore hole, a conical hole into which the fill tube is inserted. In our simulations, the geometry of the bore hole can play a significant role in the development of nonlinear flows seeded by the fill tube. Additionally, we find that the amount of space between the bore hole and the fill tube is the primary factor that determines the amount of contaminant jetted into the hot spot by the fill tube and, in turn, the level of yield reduction due to the fill tube in our simulations. As a consequence, some capsules with 5 μm fill tubes are predicted to outperform capsules with 2 μm fill tubes. We also find that micrometer-scale changes to bore hole size can impact fusion yields by up to four times near the ignition threshold. Nevertheless, simulation trends do not reproduce experimental yield trends, suggesting that the fill tube geometry was not the primary factor contributing to the observed variability in performance and that the fill tube could be masking sensitivity to other asymmetries such as other micrometer-scale capsule defects like voids that were not included in our simulations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Low-mass Active Galaxies in the SAMI Galaxy Survey with Spatially Resolved Spectroscopy

The smallest supermassive black holes (BHs), which provide constraints on BH seeds, reside in low-mass galaxies. Here, we present a systematic analysis of 990 low-mass galaxies in the SAMI Galaxy Survey to identify emission from accreting BHs using integral field spectroscopy (IFS). Employing a novel automated scoring algorithm based on spatially resolved narrow emission-line diagnostics, we find signatures of active galactic nuclei (AGNs) in 41 galaxies, as well as an additional 46 (less secure) candidates. The galaxies have stellar masses between 10 9.4 ≲ M ⋆ /M ⊙ ≲ 10 10 (down to 10 8.5 , including less secure candidates), redshifts z ≲ 0.06, and morphologies ranging from early-type ellipticals to late-type spirals. Our AGN fraction of 4% (9% if we include the less secure candidates) is significantly higher than those reported by studies using single-fiber spectroscopy (≲1%–2%). Indeed, our additional analysis of single-fiber spectra of the objects in our sample demonstrates that many of our AGN candidates detected via IFS are missed. This work highlights the advantages of IFS, especially the ability to capture extended or decentralized emission from accreting BHs.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1991

Fiber optic laser Doppler anemometry in swirling jets

Time-averaged and fluctuating quantities are measured in a free turbulent swirling jet. Data from a two-component laser Doppler anemometry (LDA) are compared to the measurements via hot-wire and 5-hole pitot probes. To acquire the proper seeding density near the axis of a swirling jet for LDA measurements proved difficult. This is due to an imbalance of the centrifugal force and radial pressure gradient, which throws the seeding material off the axis. Despite this problem, close agreement between various measurement techniques is obtained.

Taghavi, R.↗
NASA NTRSDate not supplied

3D Printed Materials Characterization for Rapid Prototyping and Plant Growth

Space Biology experimentation but their effects during plant growth and sanitation have not been documented. With further testing we can determine how certain 3D printed materials affect our plants. The way we tested germination included laying two pieces of germination paper down with the printed petri dish insert of the various material and 14 seeds of Outrageous lettuce to fit in the holes of the insert. We kept an even moisture in all parts by wrapping the petri dishes in two layers of parafilm tape. This project tests over 15 different materials to document performance during plant growth scenarios. This research will not only help space biology but also citizens who use these materials to understand the potential of leaching and ill effects. 3D printing is a recent generally accessed technology with new materials coming out every day. It is important to understand how materials could impact the way the plants grow, and the safety of the food grown. As we continue testing these materials, we will also test engineering properties like tension and elasticity. We have a microbiology team working on this project as well to test biofilm formation. From the germination tests we have completed we have seen little impact on germination rate of these seeds. However, some parts absorb moisture. An ideal material is one that doesn’t leach chemicals or microplastics, can withstand high tension and compression, and doesn’t promote microbial growth. This work is funded by NASA. M. Gandhi was funded by MAIANSE.

Mily Gandhi↗
DOE OSTI2022

The development of a high-resolution Eulerian radiation-hydrodynamics simulation capability for laser-driven Hohlraums

Hohlraums are hollow cylindrical cavities with high-Z material walls used to convert laser energy into uniform x-ray radiation drives for inertial confinement fusion capsule implosions and high energy density physics experiments. Credible computational modeling of hohlraums requires detailed modeling and coupling of laser physics, hydrodynamics, radiation transport, heat transport, and atomic physics. We report on improvements to Los Alamos National Laboratory's xRAGE radiation-hydrodynamics code in order to enable hohlraum modeling. xRAGE's Eulerian hydrodynamics and adaptive mesh refinement make it uniquely well suited to study the impacts of multiscale features in hohlraums. In order to provide confidence in this new modeling capability, we demonstrate xRAGE's ability to produce reasonable agreement with data from several benchmark hohlraum experiments. We also use xRAGE to perform integrated simulations of a recent layered high density carbon capsule implosion on the National Ignition Facility in order to evaluate the potential impacts of the capsule support tent, mixed cell conductivity methodologies, plasma transport, and cross-beam energy transfer (XBT). We find that XBT, seeded by plasma flows in the laser entrance hole (LEH), causes a slight decrease in energy coupling to the capsule and that all of these impact the symmetry of the x-ray drive such that they have an appreciable impact on the capsule implosion shape.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Comptonization by reconnection plasmoids in black hole coronae I: Magnetically dominated pair plasma

We perform 2D particle-in-cell simulations of reconnection in magnetically dominated electron–positron plasmas subject to strong Compton cooling. We vary the magnetization σ $\gg$ 1, defined as the ratio of magnetic tension to plasma inertia, and the strength of cooling losses. Magnetic reconnection under such conditions can operate in magnetically dominated coronae around accreting black holes, which produce hard X-rays through Comptonization of seed soft photons. We find that the particle energy spectrum is dominated by a peak at mildly relativistic energies, which results from bulk motions of cooled plasmoids. The peak has a quasi-Maxwellian shape with an effective temperature of ~100 keV, which depends only weakly on the flow magnetization and the strength of radiative cooling. The mean bulk energy of the reconnected plasma is roughly independent of σ, whereas the variance is larger for higher magnetizations. The spectra also display a high-energy tail, which receives ~25 percent of the dissipated reconnection power for σ = 10 and ~40 percent for σ = 40. We complement our particle-in-cell studies with a Monte Carlo simulation of the transfer of seed soft photons through the reconnection layer, and find the escaping X-ray spectrum. The simulation demonstrates that Comptonization is dominated by the bulk motions in the chain of Compton-cooled plasmoids and, for σ ~ 10, yields a spectrum consistent with the typical hard state of accreting black holes.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2019

A 10,000-solar-mass black hole in the nucleus of a bulgeless dwarf galaxy

The motions of gas and stars in the nuclei of nearby galaxies have demonstrated that massive black holes are common1 and that their masses correlate with the stellar velocity dispersion σ⁎ of the bulge. This correlation suggests that massive black holes and galaxies influence each other’s growth. Dynamical measurements are less reliable when the sphere of influence is unresolved; thus, it remains unknown whether this correlation exists in galaxies much smaller than the Milky Way. Light echoes from photoionized clouds around accreting black holes, in combination with the velocity of these clouds, yield a direct mass measurement that circumvents this difficulty. Here we report an exceptionally low reverberation delay of 83 ± 14 min between variability in the accretion disk and Hα emission from the nucleus of the dwarf galaxy NGC 4395. Combined with the Hα velocity dispersion σline = 426 ± 1 km/s, this lag determines a mass of about 10,000 M⊙ for the black hole (M(BH)). This mass is among the smallest central black hole masses reported, near the low end of expected masses for heavy ‘seeds’, and the best direct mass measurement for a galaxy of this size. Despite the lack of a bulge, NGC 4395 is consistent with the M(BH–σ⁎) relation, indicating that the relation need not originate from hierarchical galaxy assembly nor from black hole feedback.

Jong-Hak Woo↗
NASA NTRS1988

Automated seed manipulation and planting

Activities for the Fall Semester, 1987 focused on investigating the mechanical/electrical properties of wheat seeds and forming various Seed Planting System (SPS) concepts based on those properties. The Electrical Division of the design group was formed to devise an SPS using electrostatic charge fields for seeding operations. Experiments concerning seed separation using electrical induction (rearranging of the charges within the seed) were conducted with promising results. The seeds, when exposed to the high voltage and low current field produced by a Van de Graff generator, were observed to move back and forth between two electrodes. An SPS concept has been developed based on this phenomena, and will be developed throughout the Spring Semester, 1988. The Mechanical Division centered on SPS concepts involving valves, pumps, and fluids to separate and deliver seeds. An SPS idea utilizing the pressure difference caused by air as it rushes out of holes drilled in the wall of a closed container has been formulated and will be considered for future development. Also, a system of seed separation and delivery employing a combination of centrifugal force, friction, and air flow was considered.

Garcia, Ray↗
NASA NTRS1990

A porous stainless steel membrane system for extraterrestrial crop production

A system was developed in which nutrient flow to plant roots is controlled by a thin (0.98 or 1.18 mm) porous (0.2 or 0.5 microns) stainless steel sheet membrane. The flow of nutrient solution through the membrane is controlled by adjusting the relative negative pressure on the nutrient solution side of the membrane. Thus, the nutrient solution is contained by the membrane and cannot escape from the compartment even under microgravity conditions if the appropriate pressure gradient across the membrane is maintained. Plant roots grow directly on the top surface of the membrane and pull the nutrient solution through this membrane interface. The volume of nutrient solution required by this system for plant growth is relatively small, since the plenum, which contains the nutrient solution in contact with the membrane, needs only to be of sufficient size to provide for uniform flow to all parts of the membrane. Solution not passing through the membrane to the root zone is recirculated through a reservoir where pH and nutrient levels are controlled. The size of the solution reservoir depends on the sophistication of the replenishment system. The roots on the surface of the membrane are covered with a polyethylene film (white on top, black on bottom) to maintain a high relative humidity and also limit light to prevent algal growth. Seeds are sown directly on the stainless steel membrane under the holes in the polyethylene film that allow a pathway for the shoots.

NASA Discipline Number 61-20↗
DOE OSTI2020

Observation of Seeded Mn K β Stimulated X-Ray Emission Using Two-Color X-Ray Free-Electron Laser Pulses

Kβ x-ray emission spectroscopy is a powerful probe for electronic structure analysis of 3d transition metal systems and their ultrafast dynamics. Selectively enhancing specific spectral regions would increase this sensitivity and provide fundamentally new insights. Recently we reported the observation and analysis of Kα amplified spontaneous x-ray emission from Mn solutions using an x-ray free-electron laser to create the 1s core-hole population inversion [Kroll et al., Phys. Rev. Lett. 120, 133203 (2018)]. To apply this new approach to the chemically more sensitive but much weaker Kβ x-ray emission lines requires a mechanism to outcompete the dominant amplification of the Kα emission. Here we report the observation of seeded amplified Kβ x-ray emission from a NaMnO 4 solution using two colors of x-ray free-electron laser pulses, one to create the 1s core-hole population inversion and the other to seed the amplified Kβ emission. Comparing the observed seeded amplified Kβ emission signal with that from conventional Kβ emission into the same solid angle, we obtain a signal enhancement of more than 10 5 . Finally, our findings are the first important step of enhancing and controlling the emission of selected final states of the Kβ spectrum with applications in chemical and materials science.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

On the Effect of Beating during Nonlinear Frequency Chirping

Spectroscopic analyses of energetic particle (EP) driven bursts of MHD fluctuations in magnetically confined plasmas often exhibit chirps that occur simultaneously in groups of two or more. While the superposition of oscillations at multiple frequencies necessarily causes beating in the signal acquired by a localized external probe, self-consistent hybrid simulations of chirping EP modes in a JT-60U tokamak plasma have demonstrated the possibility of global beating, where the mode's electromagnetic field vanishes globally between beats and reappears with opposite phase [Bierwage et al., Nucl. Fusion 57, 016036 (2017)]. This implies that there can be a single coherent field mode that oscillates at multiple frequencies simultaneously when it is resonantly driven by multiple density waves in EP phase space. Conversely, this means that the EP density waves are mutually coupled and interfere with each other via the jointly driven field, a mechanism ignored in some theories of chirping. In this thesis-style treatise, we study the role of field pulsations in general and beating in particular using the Hamiltonian guiding center orbit-following code ORBIT with a reduced wave-particle interaction model in realistic geometry. Beating is found to drive the evolution of EP phase space structures. Additionally, a key mechanism is the pulsation of effective phase space islands combined with the alternation of their effective O- and X-points due to phase jumps between each beat. Observations: (1) Beating causes density wave fronts to advance radially in a pulsed manner and the resulting chirps become staircase-like. (2) The pulsations facilitate convective transfer of material between neighboring layers of phase space density waves. On the one hand, this may inhibit the early detachment of solitary phase space vortices. On the other hand, it facilitates the accumulation of hole and clump fragments into larger structures. (3) Long-range chirping is observed when massive holes or clumps detach and drift away from the turbulent belt around the seed resonance. It is remarkable that the detached vortices remain robust and,on average, maintain their concentric nested layers while being visibly perturbed by the field's continued beating.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Formation and Redshift Evolution of Dark Matter Spikes

Dark matter density spikes forming around adiabatically growing black holes can dramatically enhance indirect and direct detection signals. Canonical predictions, however, assume a zero-mass seed in a purely dark matter environment and do not track the long-term dynamical impact of surrounding stars. We present a semi-analytic framework that first generalizes adiabatic spike formation to include finite seed masses, stellar cusps, and non-circular orbits, and then studies the subsequent cosmic evolution by solving coupled Fokker-Planck equations for the dark matter and stellar phase-space distributions, with a heating rate modulated by the cosmic star formation rate. Starting conservatively from canonical Gondolo-Silk spikes and marginalizing over astrophysical uncertainties, we find that stellar gravitational heating drives the inner slope towards $γ_χ\simeq 1.5$ within a few Gyrs (e.g by $z \lesssim 2$ for spikes formed at $z\simeq 10$), yielding overdensities two to four orders of magnitude below canonical expectations but still well above an NFW-like cusp. We provide redshift-dependent benchmarks for the column density and $J$-factor relevant to scattering, decay and annihilation signatures. Any robust interpretation of indirect dark matter signals from galactic nuclei must account for this evolution.

Herrera, Gonzalo [MIT, LNS; MIT, MKI; Harvard U.]↗
NASA NTRS2008

Stereoscopic Imaging in Hypersonics Boundary Layers using Planar Laser-Induced Fluorescence

Stereoscopic time-resolved visualization of three-dimensional structures in a hypersonic flow has been performed for the first time. Nitric Oxide (NO) was seeded into hypersonic boundary layer flows that were designed to transition from laminar to turbulent. A thick laser sheet illuminated and excited the NO, causing spatially-varying fluorescence. Two cameras in a stereoscopic configuration were used to image the fluorescence. The images were processed in a computer visualization environment to provide stereoscopic image pairs. Two methods were used to display these image pairs: a cross-eyed viewing method which can be viewed by naked eyes, and red/blue anaglyphs, which require viewing through red/blue glasses. The images visualized three-dimensional information that would be lost if conventional planar laser-induced fluorescence imaging had been used. Two model configurations were studied in NASA Langley Research Center's 31-Inch Mach 10 Air Wind tunnel. One model was a 10 degree half-angle wedge containing a small protuberance to force the flow to transition. The other model was a 1/3-scale, truncated Hyper-X forebody model with blowing through a series of holes to force the boundary layer flow to transition to turbulence. In the former case, low flowrates of pure NO seeded and marked the boundary layer fluid. In the latter, a trace concentration of NO was seeded into the injected N2 gas. The three-dimensional visualizations have an effective time resolution of about 500 ns, which is fast enough to freeze this hypersonic flow. The 512x512 resolution of the resulting images is much higher than high-speed laser-sheet scanning systems with similar time response, which typically measure 10-20 planes.

Danehy, Paul M.↗
NASA NTRS2002

Using Multiwavelength Observations to Determine the Black Hole Mass and Accretion Rate in the Type 1 Seyfert Galaxy NGC 5548

We model the spectral energy distribution of the type 1 Seyfert galaxy NGC 5548, fitting data from simultaneous optical, UV, and X-ray monitoring observations. We assume a geometry consisting of a hot central Comptonizing region surrounded by a thin accretion disk. The properties of the disk and the hot central region are determined by the feedback occurring between the hot Comptonizing region and thermal reprocessing in the disk that, along with viscous dissipation, provides the seed photons for the Comptonization process. The constraints imposed upon this model by the multiwavelength data allow us to derive limits on the central black hole mass, Mu is approximately or less than 2x10(exp 7) solar mass, the accretion rate, Mu is approximately or less than 2.5x10(exp 5) sq solar mass per year/Mu, and the radius of the transition region between the thin outer disk and the geometrically thick, hot inner region, is approximately 2-5x10(exp 14) cm.

Chiang, James↗
DOE OSTI2021

A Sample of Massive Black Holes in Dwarf Galaxies Detected via [Fe x] Coronal Line Emission: Active Galactic Nuclei and/or Tidal Disruption Events

The massive black hole (BH) population in dwarf galaxies ( M BH ≲ 10 5 M ⊙ ) can provide strong constraints on the origin of BH seeds. However, traditional optical searches for active galactic nuclei (AGNs) only reliably detect high-accretion, relatively high-mass BHs in dwarf galaxies with low amounts of star formation, leaving a large portion of the overall BH population in dwarf galaxies relatively unexplored. Here, we present a sample of 81 dwarf galaxies ( M $\star$ ≤ 3 × 10 9 M ⊙ ) with detectable [Fe x]λ6374 coronal line emission indicative of accretion onto massive BHs, only two of which were previously identified as optical AGNs. Here, we analyze optical spectroscopy from the Sloan Digital Sky Survey and find [Fe x]λ6374 luminosities in the range L [Fe x] ≈ 10 36 –10 39 erg s –1 , with a median value of 1.6 × 10 38 erg s –1 . The [Fe x]λ6374 luminosities are generally much too high to be produced by stellar sources, including luminous Type IIn supernovae (SNe). Moreover, based on known SNe rates, we expect at most eight Type IIn SNe in our sample. That said, the [Fe x]λ6374 luminosities are consistent with accretion onto massive BHs from AGNs or tidal disruption events (TDEs). We find additional indicators of BH accretion in some cases using other emission line diagnostics, optical variability, and X-ray and radio emission (or some combination of these). However, many of the galaxies in our sample only have evidence for a massive BH based on their [Fe x]λ6374 luminosities. This work highlights the power of coronal line emission to find BHs in dwarf galaxies missed by other selection techniques and to probe the BH population in bluer, lower-mass dwarf galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Predictions for a Low-mass Cutoff for the Primordial Black Hole Mass Spectrum

In this note, we outline how a modest violation in the conservation of mass during the merger of two PBHs affects the PBH mass spectrum that we previously obtained using a Boltzmann equation model for the evolution of the mass spectrum with no mass loss. We find that if the initial cosmological redshift is of the order of 10 12 , then the fraction of primordial holes with masses greater than 10 3 solar masses appears to be close to what is required to provide the seeds for galaxies. In addition, we note that as a result of rapid collisions and strong coupling to electromagnetic radiation for temperatures > GeV, there will be an effective low-mass cutoff in the mass spectrum for PBH masses less than a certain PBH mass less than 0.1M ⊙ . We also point out that this cutoff in the mass spectrum below ~ 0.1M ⊙ can be confirmed by combining future microlensing observations from the Roman Space Telescope and the Vera C. Rubin Observatory with astrometric observations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Limits on X-Ray Polarization at the Core of Centaurus A as Observed with the Imaging X-Ray Polarimetry Explorer

We present measurements of the polarization of X-rays in the 2–8 keV band from the nucleus of the radio galaxy Centaurus A (Cen A), using a 100 ks observation from the Imaging X-ray Polarimetry Explorer (IXPE). Nearly simultaneous observations of Cen A were also taken with the Swift, NuSTAR, and INTEGRAL observatories. No statistically significant degree of polarization is detected with IXPE. These observations have a minimum detectable polarization at 99% confidence (MDP 99 ) of 6.5% using a weighted, spectral model-independent calculation in the 2–8 keV band. The polarization angle ψ is consequently unconstrained. Spectral fitting across three orders of magnitude in X-ray energy (0.3–400 keV) demonstrates that the SED of Cen A is well described by a simple power law with moderate intrinsic absorption (N H ~ 10 23 cm -2 ) and a Fe Kα emission line, although a second unabsorbed power law is required to account for the observed spectrum at energies below 2 keV. This spectrum suggests that the reprocessing material responsible for this emission line is optically thin and distant from the central black hole. Our upper limits on the X-ray polarization are consistent with the predictions of Compton scattering, although the specific seed photon population responsible for the production of the X-rays cannot be identified. The low polarization degree, variability in the core emission, and the relative lack of variability in the Fe Kα emission line support a picture where electrons are accelerated in a region of highly disordered magnetic fields surrounding the innermost jet.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1987

Nondestructive evaluation of structural ceramics by photoacoustic microscopy

A photoacoustic microscopy (PAM) digital imaging system was developed and utilized to characterize silicon nitride material at the various stages of the ceramic fabrication process. Correlation studies revealed that photoacoustic microscopy detected failure initiating defects in substantially more specimens than microradiography and ultrasonic techniques. Photoacoustic microscopy detected 10 to 100 micron size surface and subsurface pores and inclusions, respectively, up to 80 microns below the interrogating surface in machined sintered silicon nitride. Microradiography detected 50 micron diameter fracture controlling pores and inclusions. Subsurface holes were detected up to a depth of 570 microns and 1.00 mm in sintered silicon nitride and silicon carbide, respectively. Seeded voids of 20 to 30 micron diameters at the surface and 50 microns below the interrogating surface were detected by photoacoustic microscopy and microradiography with 1 percent X-ray thickness sensitivity. Tight surface cracks of 96 micron length x 48 micron depth were detected by photoacoustic microscopy. PAM volatilized and removed material in the green state which resulted in linear shallow microcracks after sintering. This significantly limits the use of PAM as an in-process NDE technique.

Khandelwal, Pramod K.↗