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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

NucD-24 Nuclear Diagnostics Development: Time resolved 12 C-rhoR on GCD and NIS technology development for polar LOS and data quality [Slides]

The Neutron Imaging team is readying for the NIS2 polar LOS development and future improvements to data quality on all LOS given consistently higher yields at NIF. Next-gen nano guide scintillators for NIS2 and CMOS cameras to replace outdated CCDs will be studied. Digital image plates will be tested for better data quality on passive imaging systems. The transition into the ignition regime is expected to show a significant signature in the ablator areal density. In the marginal ignition regime, a decrease of 12C-rhoR (ablator areal density) is expected but once the burn propagation produces a shock and compresses the ablator the trend reverses. GCD with the PD-PMT can resolve this effect in the ablator areal density by a temporal shift in the carbon signal. To give quantitative results a calibration of the detector for the Hohlraum/TMP signal is needed. Shots using Al, Si, and Au pucks will yield the needed information to move forward with this project.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Towards Portable Laser Desorption Postionization Mass Spectrometry Utilizing Microchip Laser Pulses

A 355 nm, 1.5 ns, up to 1 kHz microchip laser system has been tested to both yield ablation spots and postionize material within a plasma plume. A 30 µJ pulse energy microchip laser successfully ablated all samples: 6601 aluminum, 316 and 304 stainless steel, and Mo metal. While visible ablation craters were observed on all samples mentioned above, the stainless-steel samples displayed visible color changes in the resolidified iron, indicating ionization with the 355 nm pulses during ablation. Additionally, when used to intercept a plasma plume of Cs 2 CO 3 made with a separate laser system, the microchip laser pulses yielded Cs + emission signal otherwise not observed. With these experiments completed, the microchip laser has been successfully verified for readiness to be integrated into the front end of a mass spectrometer system as the ion source.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Early Experience of Trans-arterial Chemo-Embolisation for Hepatocellular Carcinoma with a Novel Radiopaque Bead

Aims: To evaluate early outcomes of patients with hepatocellular carcinoma (HCC) treated with a novel radiopaque bead, the 75–150 μm DC Bead LUMI™ (Biocompatibles UK Ltd). Materials and Methods: This was a retrospective review of the first 40 consecutive patients at a UK tertiary hepato-biliary centre, treated for HCC with TACE using radiopaque beads, between May 2017 and March 2019. Information regarding complications, mortality, lesion response and subsequent ablation procedures was collected from electronic records and case notes. Intra- and post-operative imaging was reviewed for visibility of the embolised territory. Results: Fifty-five TACE procedures were performed in 40 patients, with a median age of 70 years (range 28–88) and median lesion size of 3.8 cm (range 1.5–7.8). The median follow-up period was 30 weeks (range 6–101). Mean post-procedure hospital stay was 1.2 days. Complications of CIRSE Grade II or above occurred after 4/55 procedures (7.3%). Mortality at 30 days was zero. Objective response rates (mRECIST) at 1, 3 and 6 months were 32/35 (91.4%), 21/24 (87.5%) and 12/15 (80%), respectively. Complete response rates at 1, 3 and 6 months were 16/35 (45.7%), 12/24 (50%) and 9/15 (60%). The embolised territory was visible on intra-operative and follow-up CT imaging in all patients. The radiopaque beads were used as a fiducial marker to guide ablation in 5/40 patients (12.5%). Conclusion: TACE with radiopaque beads shows promising tolerability and efficacy. The radiopaque beads ensure visualisation of the embolised lesion on intra- and post-operative imaging and, in selected cases, can act as a marker for CT-guided ablation.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2024

Use of tritium-rich fuel to improve the yield of layered deuterium/tritium inertial fusion capsules

In deuterium–tritium (DT) ice layered implosions, nearly all hot spot mass at peak burn comes from the dense fuel. Accurate prediction of the fuel mass ablation, including the enthalpy associated with mass inflow into the hot spot from the dense fuel, is essential to understanding the energetics and ignition of the hot spot in layered implosions. A recently published boundary layer analysis (Daughton et al., 2023) indicates a faster mass ablation rate than in previous analyses of layered implosions. Inclusion of this effect provides a better match to simulations and leads to a new ignition threshold where the temperature of the dense fuel plays a critical role. This analysis motivates possible new directions for improved capsule performance. Here, the authors present evidence in support of one such approach: the use of tritium-rich ice to decrease 14 MeV neutron scattering and heating of the dense fuel, resulting in less mass ablation and more robust burn of the hot spot. It is found from numerical simulations that despite a less favorable D:T ratio in the ice, the use of a 40:60 D:T ratio leads to an increase in capsule yield of 17% percent compared with that of a 50:50 D:T ratio fuel for capsules resembling those of the recent N210808 ignition experiment on the NIF (Abu-Shawareb et al., 2022) and an increase of 74% compared with that of a 60:40 D:T ratio fuel capsule. Finally, these results are potentially important for modeling all layered implosions, since some degree of DT fractionization may arise naturally during the beta layering process. In addition, this physics is important for the feasibility of high-gain capsule designs that seek to minimize tritium usage, as in some inertial fusion energy concepts.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Targeting HSPA8 inhibits proliferation via downregulating BCR-ABL and enhances chemosensitivity in imatinib-resistant chronic myeloid leukemia cells

The resistance to tyrosine kinase inhibitors is currently a major problem for chronic myeloid leukemia (CML) treatment and HSPA8 is highly expressed and a hallmark of poor prognosis in several human cancers. However, its role in imatinib-resistant CML (IR-CML) cells remains undetermined. Here, we determined HSPA8 was overexpressed in IR-CML cells and associated with imatinib resistance. HSPA8 ablation could downregulate BCR-ABL/STAT5 and BCR-ABL/AKT signaling pathways, dramatically induce proliferation inhibition, autophagy, G0/G1 phase cell cycle arrest but not apoptosis in IR-CML cells. Significantly, HSPA8 ablation enhanced the antitumor activity of imatinib via promoting apoptosis in vitro and vivo. These findings unraveled that HSPA8 ablation inhibits proliferation via downregulating BCR-ABL and enhances chemosensitivity of imatinib in IR-CML cells, which investigate the role and molecular mechanism of HSPA8 in IR-CML cells and suggest that HSPA8 may be a potential target for IR-CML treatment.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Femtosecond Laser Desorption Postionization MS vs ToF-SIMS Imaging for Uncovering Biomarkers Buried in Geological Samples

The study of lipid molecular fossils by traditional biomarker analysis requires bulk sample crushing, followed by solvent extraction, and then the analysis of the extract by gas chromatography-mass spectrometry (GC–MS). This traditional analysis mixes all organic compounds in the sample regardless of their origins, with a loss of information on the spatial distribution of organic molecules within the sample. These shortcomings can be overcome using the chemical mapping of intact samples. Spectroscopic techniques such as UV fluorescence or Raman spectroscopy, laser ablation inductively coupled plasma mass spectrometry, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) are among those elemental and molecular mapping techniques. This study employed femtosecond (fs) laser ablation combined with single-photon ionization, a method called fs-laser desorption postionization mass spectrometry (fs-LDPI-MS). In this work, a pulsed ~75 fs, 800 nm laser was used to ablate the geological sample, which was then photoionized after a few microseconds by a pulsed 7.9 eV vacuum ultraviolet laser. An organic carbon-rich geological sample was used for this study to map hydrocarbon biomarkers in sediments that were previously studied by GC–MS. The petrography of this sample was examined by optical and fluorescence microscopy. It is demonstrated here that fs-LDPI-MS combined with petrography for multimodal imaging can expose buried compounds within the sample via in situ layer removal. When used in conjunction with traditional organic geochemical analysis, this method has the potential to determine the spatial distribution of organic biomarkers in geological material. Finally, fs-LDPI-MS imaging data are compared with ToF-SIMS imaging that is commonly used for such studies.

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

Hot-tail electrons’ impact on assimilation and injection penetration of D2 shattered pellet injections

The assimilation and the penetration of injected materials play significant roles in the mitigation efficiency of shattered pellet injection (SPI) as a disruption mitigation system (DMS), hence an accurate description of the fragment ablation rate is desirable. Current mainstream 3D MHD codes modelling SPIs mostly assume instantaneous thermalization between the previously hot ambient electrons and the newly released cold electrons. This could result in underestimation of the ablation rate if the hot electron thermalization time is comparable or even longer than the fragment flying time across flux tubes, putting the validity of these 3D SPI simulations into question. To resolve this doubt, we, in this study, investigate the thermalization dynamics and the overall hot-electron impact. The finite-time collisional thermalization of hot-tail electrons in a rapidly cooling plasma, as well as the so-called ‘self-limiting’ effect are considered. The former effect tends to deplete the colder population within a hot-tail species, while the latter is found to preferentially deplete the higher energy population. The combined result is found to cause an almost self-similar decay of the hot electron distribution function, while its shape does not deviate much from that of Maxwellian distribution and the mean energy does not change much during the thermalization process. Based on this observation, axisymmetric JOREK D2 SPI simulations were carried out with additional hot-tail contribution to evaluate their overall impact onto the injection assimilation and penetration. It is found that the hot-tail effect indeed causes enhanced assimilation and shallower penetration, although the overall effect depends on the exact injection configuration, with the slow injection showing negligible hot-tail effect while the fast single non-shattered pellet case shows drastic hot-tail ablation enhancement. For ITER-like SPI parameters, there is no significant deviation in the total assimilation, but some deviation in the injection penetration is observed for the fast injection velocity cases.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Tungsten doped diamond shells for record neutron yield inertial confinement fusion experiments at the National Ignition Facility

We report on fabrication and characterization of layered, tungsten doped, spherical about 2 mm diameter microcrystalline diamond ablator shells for inertial confinement fusion (ICF) experiments at the National Ignition Facility. As previously reported, diamond ICF ablator shells can be fabricated by chemical vapor deposition (CVD) on solid spherical silicon mandrels using an ellipsoidal microwave plasma reactor. In the present work, we further developed these ablator shells by embedding a W -doped diamond layer sandwiched between two undoped diamond regions. W incorporation in diamond was achieved by adding tungsten hexacarbonyl to the CH 4 /H 2 CVD feed gas. We observe that the W doping concentration decreases with increasing deposition rate which, in turn, is controlled by adjusting the total gas pressure. Cross sectional microstructural analysis reveals sharp interfaces between doped and undoped regions of the diamond shell and uniform W distribution with concentrations up to about 0.3 at.%. At higher W concentrations (>0.3 at.%) formation of tungsten carbide precipitates is observed. Using a 3-shock 1.6 MJ laser pulse, the targets described in this work produced the first laser driven implosion to break the 1 × 10 16 neutron yield barrier, followed by experiments (described in future publications) with similar targets and slightly more laser energy producing yields as high as 4 × 10 17 .

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Generation of shock trains in free liquid jets with a nanosecond green laser

Shock wave trains in liquid jets were previously generated only by ablation with femtosecond x-ray lasers. Here we show that shock trains in water microjets can be also generated using nanosecond green laser pulses with 1- to 10-mJ energy. Furthermore, the ablation of 15-, 20-, 30-, and 70-μm water microjets opened a gap in the jets and launched an initial shock wave. Fully developed shock trains were observed in the 30- and 70-μm jets up to 250-ns delays, and these trains were also transmitted inside the nozzles. A few tens of nanoseconds after the pulse, the shock dynamics and its pressure became similar to the ones generated by x-ray lasers, with a more rapid pressure decay in thinner jets. At time delays exceeding 100 ns in the 30-μm jets, the leading shock pressure stabilized to an approximately constant pressure of 40 MPa. The energy density deposited in the jets was estimated at 30 MJ/cm 3 by comparing the jet gaps in the green and x-ray laser experiments, and matched previous estimates for optical ablation in water. Here, the pressure decay in the 30-μm jets was modeled based on the pressure decay observed in x-ray laser experiments.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2023

Understanding non-stochiometric deposition of multi-principal elemental NiCoCr thin films

Multi-principal elemental NiCoCr thin films with compositional flexibility have potential applications as a thermal barrier, corrosion-resistant coatings, and functional energy materials. In this study, the non-stochiometric multi-principal element alloy thin film formation behavior from an equiatomic ablation target of NiCoCr using pulsed laser deposition has been reported. Here, the effect of varying laser fluence on compositions of constituent elements in the NiCoCr thin films is systematically investigated. The increase in laser fluence typically increases the likelihood of acquiring undesirable particulates in thin films. Therefore, to maintain the film quality the laser fluences are adjusted within the range of 1.3–3.3 J·cm -2 , while the film thicknesses are kept constant at ~30 nm. Results show that the constituent elements are well-distributed in the formed NiCoCr thin films, however, having average atomic percentages of Ni and Cr twice as high as Co irrespective of the equiatomic composition of individual elements in the ablation target. This stochiometric alteration in the as-deposited thin films is governed by the rate of ablation and subsequent evaporation of each element, which is facilitated by the optical properties and vapor pressure of individual constituent elements. Additionally, electron energy-loss spectroscopy and x-ray absorption spectroscopy analysis reveal that the thin films have partially oxidized, with the Cr oxidation contributing the most to the O-K edge in comparison to Ni and Co. Finally, this study presents a laser-assisted pathway for fabricating compositionally flexible NiCoCr thin films and develops an understanding of the non-equilibrium laser-material interactions and how the intrinsic properties of constituent elements affect the stoichiometric flow of materials from the target to the final film deposition.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Recent and planned hydrodynamic instability experiments on indirect-drive implosions on the National Ignition Facility

At National Ignition Facility (NIF), yield amplification due to alpha particle heating approached ~3 in the highest performing inertial confinement fusion (ICF) implosions, while yield amplification of ~15-30 is needed for ignition. Hydrodynamic instabilities are a major factor in degradation of implosions while understanding and mitigation of the instabilities are critical to achieving ignition. This article describes recent and planned hydrodynamic instability experiments with several focused platforms that have been developed to directly measure these instabilities in all phases of ICF implosions. Measurements of ripple-shock generation at OMEGA laser have indicated initial seeds for the instabilities in three ablators - plastic (CH), beryllium, and high-density carbon (HDC). Hydrodynamic Growth Radiography (HGR) platform was used to measure instability growth at the ablation front in the acceleration phase of implosions. This platform used pre-imposed 2-D perturbations for growth factor measurements at different perturbation wavelengths and was also used to measure growth of “native roughness” modulations, fill tubes, and capsule support membranes or “tents”. Also, in the acceleration phase several new experimental platforms have been or are being developed to measure instability growth at the ablator-ice interface. In the deceleration phase of implosions, “self-emission” and “self-backlighting” platforms were developed to measure perturbations near peak compression. This article reviews recent progress and results.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Reducing Direct Drive Preheat with Dopants

Preheat in laser-driven experiments can have negative impacts on inertial confinement fusion (ICF) and hydrodynamic experiments. While many groups employ the use of dopants to reduce or block preheat, direct quantification has not previously been explored. We developed a planar platform and a series of ablator targets to measure the electron and x-ray spectra generated by laser-plasma interactions with a direct drive using OMEGA-60. By comparing both thin ablators (75 μm) and thick ablators (270 μm) that were either pure CH, 3% Si doped or 3% I doped, we were able to measure differences in electron and x-ray spectra. In addition, we observed the preheat growth of tracer layers and observed reductions in the growth with different materials. We find that iodine or a thin gold layer is the best at tamping the direct-drive preheat at OMEGA, but that the growth is still significant.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Plasma and X-ray radiation-induced damage mechanisms in a tungsten heavy alloy

Tungsten-based materials are among the main candidate plasma-facing materials for future fusion reactors where extreme conditions of thermomechanical stresses, radiation, and energetic particles must be withstood. Here a hybrid X-pinch platform combined with a pulsed power machine was used to study damage mechanisms in 90W–4Cu–6Ni tungsten heavy alloy as a result of exposure to high energy density plasma, X-ray radiation, and the resulting thermal shock. It was found that the plasma-facing surface of the material undergoes severe melting and ablation with the extent of ablation being higher in the Cu–Ni phase than the W particles. Rapid melting and solidification transform the W particles into fine dendrite morphologies embedded in the Cu–Ni solid solution. Cracking was also observed in the subsurface layers at the interfaces between the W particles and the Cu-rich phase of the Cu–Ni matrix. X-ray radiation, on the other hand, cause slight melting on the surface without significant ablation and no cracking.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Full-torus impurity transport simulation in boron powder injection experiments in the Large Helical Device

The toroidal distribution of boron deposition on plasma-facing components (PFCs) in boron powder injection using an impurity power dropper (IPD) was investigated by full-torus simulation and observations in a systematic plasma density-scan experiment. The images of the ablation of dropped boron powders observed with a visible CCD camera were consistently explained by the simulations of the ablation positions of the boron powders considering the size distribution. Simulations assuming full-torus boron deposition on the PFCs did not reproduce the observed intensity profile of boron emission lines for higher plasma densities. It indicated that the density of boron deposited on PFCs installed toroidally far from the IPD was low for higher plasma densities due to the change in the ablation positions of the boron powders toward the outboard side. The experimental results verified the previous full-torus simulation of the toroidal distribution of the boron deposition in both lower and higher plasma densities.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Measurement of neutral gadolinium oscillator strengths using dual-comb absorption spectroscopy in laser-produced plasmas

The oscillator strengths of 43 transitions of neutral gadolinium from 530 to 535 nm were determined based on high-resolution absorption spectra measured by probing a laser-produced plasma (LPP) using time-resolved dual-comb spectroscopy (DCS). Absorption spectra were measured at various time delays, ranging from 33 to 252 µs after the onset of the plasma formation, over which the temperature and number density varied as the ablation plume evolved. A Boltzmann analysis was used to determine the excitation temperature and column density of Gd in the ablation plume, based on measured absorption from 20 Gd I spectral lines with known oscillator strengths. Oscillator strengths were then determined for additional dipole-allowed Gd I transitions identified in the absorption spectra, 19 of which were previously unreported. Oscillator strengths of all measured transitions were compared with literature values when available and show good agreement in most cases. Time-resolved measurement of atomic absorption in the cooling plasma provides access to a range of excitation temperatures and optical densities for the atoms in the ablation plume, allowing repeated measurements under different conditions, thereby improving confidence in the results. The high spectral bandwidth and resolution capabilities of DCS make it well-suited to measuring the dense optical spectrum of Gd, and the technique is applicable to other elements, especially lanthanides and actinides.

(280.4788) Optical Sensing, (280.5395) Plasma Diag↗
DOE OSTI2024

The Effect of Physically Based Ice Radiative Processes on Greenland Ice Sheet Albedo and Surface Mass Balance in E3SM

Abstract A significant portion of surface melt on the Greenland Ice Sheet (GrIS) is due to dark ice regions in the ablation zone, where solar absorption is influenced by the physical properties of the ice, light absorbing constituents (LACs), and the overlying crustal surface or melt ponds. Earth system models (ESMs) typically prescribe the albedo of ice surfaces as a constant value in the visible and near‐infrared spectral regions. This work advances ESM ice radiative transfer modeling by (a) incorporating a physically based radiative transfer model (SNow, ICe and Aerosol Radiation model Adding‐Doubling Version 4; SNICAR‐ADv4) into the Energy Exascale Earth System Model (E3SM), (b) determining spatially and temporally varying bare ice physical properties over the GrIS ablation zone from satellite observations to inform SNICAR‐ADv4, and (c) assessing the impacts on simulated GrIS albedo and surface mass balance associated with modeling of more realistic bare ice albedo. GrIS‐wide bare ice albedo in E3SMv2 is overestimated by ∼4% in the visible and ∼7% in the near‐infrared wavelengths compared to the Moderate Resolution Imaging Spectroradiometer. Our bare ice physical property retrieval method found that LACs, ice crustal surfaces, and melt ponds reduce visible albedo by 30% in the bare ice region of the GrIS ablation zone. The realistic bare ice albedo reduces surface mass balance by ∼145 Gt, or 0.4 mm of sea‐level equivalent between 2000 and 2021 compared to the default E3SM. This work highlights the importance of simulating bare ice albedo accurately and realistically to improve our ability to quantify changes in the GrIS surface mass and radiative energy budgets.

58 GEOSCIENCES↗
DOE OSTI2020

Development of a directly driven multi-shell platform: Laser drive energetics

Simulations predict that directly driven multi-shell targets can provide a robust alternative to conventional high-convergence implosion concepts by coupling two to three times more energy into the final igniting thermonuclear fuel assembly than indirect-drive concepts. The three-shell directly driven Revolver concept [K. Molvig, M. J. Schmitt, B. J. Albright, E.S. Dodd, N.M. Hoffman, G.H. McCall, and S.D. Ramsey, Phys. Rev. Lett. 116, 255003 (2016)] utilizes a design that maximizes laser energy conversion into inward kinetic energy of the outermost ablator shell (~9%) while minimizing the DT fuel convergence (~9) to reduce the mixing of material from the innermost shell into the fuel. Inherent in this design concept is the use of 192 narrow beams (with a 1/e laser beam-to-capsule diameter ratio of 0.33) from the National Ignition Facility laser pointed in a polar direct drive laser configuration. In this paper, we demonstrate that low average laser intensity at the capsule surface (≤300 TW/cm 2 ) limits the measured laser backscatter, indicating that a greater amount of laser energy is coupled into the target. Omega experiments have been performed to determine the coupling of laser energy to the outermost shell of a scaled Revolver target (i.e., the ablator shell) by measuring capsule implosion trajectories and scattered-light fractions for two different drive configurations. Comparisons of simulated shell trajectory and velocity profiles with experimental data obtained from self-emission images show good agreement and are consistent with measured scattered light data. Furthermore, the low levels of scattered light measured are consistent with post-shot simulation results that show high hydro-coupling efficiency. These results strengthen the case for using narrow beams at low intensity to drive large ablator capsules for future direct-drive, multi-shell ignition concepts.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Mixing in ICF implosions on the National Ignition Facility caused by the fill-tube

The micrometer-scale tube that fills capsules with thermonuclear fuel in inertial confinement fusion experiments at the National Ignition Facility is also one of the implosion's main degradation sources. It seeds a perturbation that injects the ablator material into the center, radiating away some of the hot-spot energy. This paper discusses how the perturbation arises in experiments using high-density carbon ablators and how the ablator mix interacts once it enters the hot-spot. Both modeling and experiments show an in-flight areal-density perturbation and localized x-ray emission at stagnation from the fill-tube. Simulations suggest that the fill-tube is degrading an otherwise 1D implosion by ~2×, but when other degradation sources are present, the yield reduction is closer to 20%. Characteristics of the fill-tube assembly, such as the through-hole size and the glue mass, alter the dynamics and magnitude of the degradation. Overall, these aspects point the way toward improvements in the design, some of which (smaller diameter fill-tube) have already shown improvements.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗