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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 OSTI2011

First-principles study of noble gas impurities and defects in UO{sub 2}

We performed a series of density functional theory + U (DFT + U) calculations to explore the energetics of various defects in UO{sub 2}, i.e., noble gases (He, Ne, Ar, Kr, Xe), Schottky defects, and the interaction between these defects. We found the following: (1) collinear antiferromagnetic UO{sub 2} has an energy-lowering distortion of the oxygen sublattice from ideal fluorite positions; (2) DFT + U qualitatively affects the formation volume of Schottky defect clusters in UO{sub 2} (without U the formation volume is negative, but including U the formation volume is positive); (3) the configuration of the Schottky defect cluster is dictated by a competition between electrostatic and surface energy effects; (4) the incorporation energy of inserting noble gas atoms into an interstitial site has a strong dependence on the volume of the noble gas atom, corresponding to the strain it causes in the interstitial site, from He (0.98 eV) to Xe (9.73 eV); (5) the energetics of each of the noble gas atoms incorporated in Schottky defects show strong favorable binding, due to strain relief associated with moving the noble gas atom from the highly strained interstitial position into the vacant space of the Schottky defect; and (6) for argon, krypton, and xenon, the binding energy of a noble gas impurity with the Schottky defect is larger than the formation energy of a Schottky defect, thereby making the formation of Schottky defects thermodynamically favorable in the presence of these large impurities.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2011

Determination of the half-life of the ground state of {sup 229}Th by using {sup 232}U and {sup 233}U decay series

The half-life of the ground state of {sup 229}Th ({sup 229}Th{sup g}) has become an important factor in nuclear technology, for example, in the geological disposal of nuclear spent fuel. However, the values reported in two previous studies are not in agreement. This study reevaluates the half-life of {sup 229}Th{sup g} by using a simple and reliable method. The {sup 232}U/{sup 233}U activity ratio of a {sup 232,233}U sample was measured by high-resolution {alpha}-particle spectrometry. Next, the {sup 228}Th/{sup 229}Th{sup g} activity ratio of the Th sample, which was grown from the {sup 232,233}U sample, was also measured. The half-life of {sup 229}Th{sup g} was calculated from these activity ratios, the growth time, and the half-lives of {sup 232}U, {sup 233}U, and {sup 228}Th. From the results of these five measurements, the half-life of {sup 229}Th{sup g} is determined to be 7932 {+-} 55 yr at a confidence level of 2{sigma}.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Probing Nilsson states in {sup 233}U

The reaction {sup 234}U(d-vector, t){sup 233}U was measured at the Munich Q3D magnetic spectrometer with a polarized deuteron beam. The beam energy was 22 MeV, and a vector polarization of the deuterons of 80% was achieved. Angular distributions of the reaction cross section and analyzing power at seven angles between 5 deg. and 35 deg. were analyzed. Spin and parity assignments for 33 states were determined by comparison with results from distorted wave Born approximation (DWBA) calculations. Based on these assignments and energy systematics, the observed states were sorted into rotational bands. The Nilsson configurations of the bands are identified by examining the population strengths within each band. Two rotational bands with Nilsson configurations 1/2[501] and 3/2[501] could be identified for the first time.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Probing Angular Correlations in Sequential Double Ionization

We study electron correlation in sequential double ionization of noble gas atoms and HCl in intense, femtosecond laser pulses. We measure the photoelectron angular distributions of Ne{sup +} relative to the first electron in a pump-probe experiment with 8 fs, 800 nm, circularly polarized laser pulses at a peak intensity of a few 10{sup 15} W/cm{sup 2}. Using a linear-linear pump-probe setup, we further study He, Ar, and HCl. We find a clear angular correlation between the two ionization steps in the sequential double ionization intensity regime.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Exploring Interatomic Coulombic Decay by Free Electron Lasers

To exploit the high intensity of laser radiation, we propose to select frequencies at which single-photon absorption is of too low energy and two or more photons are needed to produce states of an atom that can undergo interatomic Coulombic decay (ICD) with its neighbors. For Ne{sub 2} it is explicitly demonstrated that the proposed multiphoton absorption scheme is much more efficient than schemes used until now, which rely on single-photon absorption. Extensive calculations on Ne{sub 2} show how the low-energy ICD electrons and Ne{sup +} pairs are produced for different laser intensities and pulse durations. At higher intensities the production of Ne{sup +} pairs by successive ionization of the two atoms becomes competitive and the respective emitted electrons interfere with the ICD electrons. It is also shown that a measurement after a time delay can be used to determine the contribution of ICD even at high laser intensity.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2011

The NA62 RICH detector

The NA62 experiment is designed to measure the very rare kaon decay K{sup +} {yields} {pi}{sup +} at the CERN SPS with a 10% accuracy. The Standard Model prediction for the Branching Ratio is (8.5 {+-} 0.7) x 10{sup -11}. One of the challenging aspect of the experiment is the suppression of the K{sup +} {yields} {mu}{sup +} v{sub {mu}} background at the 10{sup -12} level. To satisfy this requirement a Ring Imaging Cherenkov Detector (RICH), able to separate {pi}{sup {+-}} from {mu}{sup {+-}} in the momentum range between 15 and 35 GeV/c, with a {mu}, rejection factor better than 10{sup -2}, is needed. The RICH must also have a time resolution of about 100 ps to disentangle accidental time associations of beam particles with pions. The RICH will have a very long focal length (17 m) and will be filled with Ne gas at atmospheric pressure. Two test beams were held at CERN in 2007 and 2009 with a RICH prototype. The results of the two test beams will be presented: the {mu}, mis-identification probability is found to be about 0.7% and the time resolution better than 100 ps in the whole momentum range. (authors)

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Recent developments in support of the shattered pellet technique for disruption mitigation

The technology for producing, accelerating, and shattering large pellets (before injection into plasmas) for disruption mitigation has been under development at the Oak Ridge National Laboratory for several years, including a system on DIII-D that has been used to provide some significant experimental results. The original proof-of-principle testing was carried out using a pipe gun injector cooled by a cryogenic refrigerator (temperatures ~8 to 20 K) and equipped with a stainless steel tube to produce 16.5 mm pellets composed of either pure D2, pure Ne, or a dual layer with a thin outer shell of D2 and core of Ne. Recently, significant progress has been made in the laboratory using that same pipe gun and a new injector that is an ITER test apparatus cooled with liquid helium. The new injector operates at ~5 to 8 K, which is similar to temperatures expected with cooling provided by the flow of supercritical helium on ITER. An alternative technique for producing/solidifying large pellets directly from a pre-mixed gas has now been successfully tested in the laboratory. Also, two additional pellet sizes have been tested recently (nominal 24.4 and 34.0 mm diameters). With larger pellets, the number of injectors required for ITER disruption mitigation can be reduced, resulting in less cost and a smaller footprint for the hardware. An attractive option is longer pellets, and 24.4 mm pellets with a length/diameter ratio of ~3 have been successfully tested. Since pellet speed is the key parameter in determining the response time of a shattered pellet system to a plasma disruption event, recent tests have concentrated on documenting the speeds with different hardware configurations and operating parameters; speeds of ~100 to 800 m/s have been recorded. The data and results from laboratory testing are presented and discussed.

neon↗
DOE OSTI2016

Solidification and Acceleration of Large Cryogenic Pellets Relevant for Plasma Disruption Mitigation

The technology for producing, accelerating, and shattering large pellets (before injection into plasmas) for disruption mitigation has been under development at the Oak Ridge National Laboratory for several years, including a system on DIII-D that has been used to provide some significant experimental results. The original proof-of-principle testing was carried out using a pipe gun injector cooled by a cryogenic refrig- erator (temperatures ~8-20 K) and equipped with a stainless steel tube to produce 16.5-mm pellets composed of either pure D 2 , pure Ne, or a dual layer with a thin outer shell of D 2 and core of Ne. Recently, significant progress has been made in the laboratory using that same pipe gun and a new injector that is an ITER test apparatus cooled with liquid helium. The new injector operates at ~5-8 K, which is similar to temperatures expected with cooling provided by the flow of supercritical helium on ITER. An alternative technique for producing/solidifying large pellets directly from a premixed gas has now been successfully tested in the laboratory. Also, two additional pellet sizes have been tested recently (nominal 24.4 and 34.0 mm diameters). With larger pellets, the number of injectors required for ITER disruption mitigation can be reduced, resulting in less cost and a smaller footprint for the hardware. An attractive option is longer pellets, and 24.4-mm pellets with a length/diameter ratio of ~3 have been successfully tested. Since pellet speed is the key parameter in determining the response time of a shattered pellet system to a plasma disruption event, recent tests have concentrated on documenting the speeds with different hardware configurations and operating parameters; speeds of ~100-800 m/s have been recorded. The data and results from laboratory testing are presented and discussed, and a simple model for the pellet solidification process is described.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Simulation of Liquid Lithium Divertor Geometry Using SOLPS-ITER

Here, plasma-facing component (PFC) geometries are evaluated for a Fusion Nuclear Science Facility (FNSF) design to find solutions that are compatible with flowing liquid lithium components while satisfying requirements from the perspective of plasma and neutral particle transport. Flowing liquid metal (LM) divertor systems offer important advantages due to continual regeneration of the surface material, but may require modifications from standard optimized tokamak divertor designs. Scrape Off Layer Plasma Simulator for the International Thermonuclear Experimental Reactor (SOLPS-ITER) simulations are used to compare standard vertical target, open, and balanced baffled geometries. It is found that the open geometry offers little control of neutral particles and has narrow operating windows where the divertor fluxes can be lowered to acceptable levels, while maintaining the required upstream density. The addition of neutral baffles allows greater control over the divertor conditions with less impact on the upstream density. The divertor neutral pressure in the baffled geometry is slightly higher than the open divertor, but not as large with a vertical target. A first-pass coupling of the SOLPS solution with sheath and implantation/erosion models to compute the lithium emission shows that the lithium is largely confined to the near-surface region due to the small ionization mean free path and large main ion flow toward the surface. The lithium source was varied by three orders of magnitude. At the highest rate, when the sourced lithium approaches the level of the main ion recycling flux, a high core lithium concentration (~10%) is observed with only moderate power dissipation to affect the divertor plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Exploring the role of biotic factors in regulating the spatial variability in land surface phenology across four temperate forest sites

Here, land surface phenology (LSP), the characterization of plant phenology with satellite data, is essential for understanding the effects of climate change on ecosystem functions. Considerable LSP variation is observed within local landscapes, and the role of biotic factors in regulating such variation remains underexplored. In this study, we selected four National Ecological Observatory Network terrestrial sites with minor topographic relief to investigate how biotic factors regulate intra-site LSP variability. We utilized plant functional type (PFT) maps, functional traits, and LSP data to assess the explanatory power of biotic factors for the start and end of season (SOS and EOS) variability. Our results indicate that PFTs alone explain only 0.8–23.4% of intra-site SOS and EOS variation, whereas including functional traits significantly improves explanatory power, with cross-validation correlations ranging from 0.50 to 0.85. While functional traits exhibited diverse effects on SOS and EOS across different sites, traits related to competitive ability and productivity were important for explaining both SOS and EOS variation at these sites. These findings reveal that plants exhibit diverse phenological responses to comparable environmental conditions, and functional traits significantly contribute to intra-site LSP variability, highlighting the importance of intrinsic biotic properties in regulating plant phenology.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Sputtering yields and surface chemical modification of tin-doped indium oxide in hydrocarbon-based plasma etching

Sputtering yields and surface chemical compositions of tin-doped indium oxide (or indium tin oxide, ITO) by CH{sup +}, CH{sub 3}{sup +}, and inert-gas ion (He{sup +}, Ne{sup +}, and Ar{sup +}) incidence have been obtained experimentally with the use of a mass-selected ion beam system and in-situ x-ray photoelectron spectroscopy. It has been found that etching of ITO is chemically enhanced by energetic incidence of hydrocarbon (CH{sub x}{sup +}) ions. At high incident energy incidence, it appears that carbon of incident ions predominantly reduce indium (In) of ITO and the ITO sputtering yields by CH{sup +} and CH{sub 3}{sup +} ions are found to be essentially equal. At lower incident energy (less than 500 eV or so), however, a hydrogen effect on ITO reduction is more pronounced and the ITO surface is more reduced by CH{sub 3}{sup +} ions than CH{sup +} ions. Although the surface is covered more with metallic In by low-energy incident CH{sub 3}{sup +} ions than CH{sup +} ions and metallic In is in general less resistant against physical sputtering than its oxide, the ITO sputtering yield by incident CH{sub 3}{sup +} ions is found to be lower than that by incident CH{sup +} ions in this energy range. A postulation to account for the relation between the observed sputtering yield and reduction of the ITO surface is also presented. The results presented here offer a better understanding of elementary surface reactions observed in reactive ion etching processes of ITO by hydrocarbon plasmas.

36 MATERIALS SCIENCE↗
DOE OSTI2014

SU-E-T-410: Fringe Stability and Phase Shift Measurements in a Michelson Interferometer for Optical Calorimetry

Purpose: To identify the variables limiting the resolution of a Michelson interferometer used to measure phase shifts (PS) in water as part of a radiometric calorimeter. Methods: We investigated the output stability of a He-Ne laser and a laser diode. The short and long term stability of the fringe pattern in a Michelson interferometer was tested with different types of lasers, thermal insulation arrangements, damping systems and optical mounts to optimize system performance. PS were induced by electrically heating water in a 1 cm quartz cuvette located in one of the interferometer arms. The PS was calculated from fringe intensity changes and compared to a calculated PS using thermocouple-measured temperature changes in the water. Results: The intensity of the laser diode is more stable, but the gas laser’s profile is more suitable for fringe analysis and has better temporal coherence. The laser requires a warm-up time of 4 hours before its output is stabilized (SNR>95). The fringe’s stability strongly depends on the thermal insulation. When the interferometer is exposed to ambient temperature swings of 0.7 K, it is not possible to stabilize the fringe pattern. Enclosing the system in a 2.5 cm-thick Styrofoam box improves the SNR, but further insulation will be needed to increase the SNR above 50. High frequency noise is significantly reduced by damping the system.Inducing a temperature rise in water, starting at 299 K, the average temperature increase for a 2π PS is 0.29 ± 0.02 K and the proportionality constant is -21.1 ± 0.8 radians/K. This is 5.8% lower than the calculated value using the thermocouple. Conclusion: Interferometric PS measurements of temperature may provide an alternative to thermistors for water calorimetry. The resolution of the current prototype is limited by ambient temperature stability. Calculated and measured thermally-induced PS in water agreed to within 5.8%.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

SU-E-T-476: Improving KCl:Eu2+ Dosimeter Sensitivity: The Role of Oxygen

Purpose: Recent research has shown that KCl:Eu2+ has great potential for use in megavoltage radiation therapy dosimetry because this material exhibits excellent storage performance and is reusable due to strong radiation hardness. The purpose of this work is to determine if increased signal could be realized in KCl:Eu2+ by incorporating oxygen in the material fabrication process. Methods: The prototype KCl:Eu2+ dosimeters have a physical makeup similar to thermoluminescent dosimeter chips. The photostimulation light source consists of either a He-Ne laser or a UV enhanced Xe arc lamp with wavelength selection provided by a motorized monochromator. X-ray diffraction is used to determine the phase composition of the dosimeters. Photoluminescence (PL) and photostimulated luminescence (PSL) emission spectra are obtained using a Nanolog Spectrofluoremeter. Results: Europium activator is completely incorporated into the KCl parent-matrix without the formation of a noticeable secondary phase. Regardless of synthesis atmosphere, air or pure nitrogen, PSL amplitude shows a maximum at 1.0 mol % Eu. Depending on europium concentration, dosimeters fabricated in air exhibit stronger PSL by a factor of 2 to 4 compared to those made in N2. There is no change in PSL stimulation spectrum while noticeable shifts in both PL and PSL emission spectra are observed for air versus nitrogen. Almost all charge-storage centers are spatially correlated, suggesting oxygen’s stabilization role in the PSL process. KCl:Eu2+ made in oxygen-rich air is capable of measuring a dose-to-water as low as 0.01 cGy from a 6MV photon beam with a signal-to-noise ratio greater than 6. Conclusions: Synthesis in a reduction atmosphere, for example, nitrogen, was thought to be mandatory in order to retain europium activator’s divalent status to be PSL active. Fortunately, divalent europium can be well preserved in an oxygen-rich atmosphere. More importantly, oxygen can enhance PSL by a factor of 2 to 4. HL is the founder of DoseImaging, LLC that is exclusively dedicated to commercializing this technology.

36 MATERIALS SCIENCE↗
DOE OSTI2015

TU-F-201-00: Radiochromic Film Dosimetry Update

Since the introduction of radiochromic films (RCF) for radiation dosimetry, the scope of RCF dosimetry has expanded steadily to include many medical applications, such as radiation therapy and diagnostic radiology. The AAPM Task Group (TG) 55 published a report on the recommendations for RCF dosimetry in 1998. As the technology is advancing rapidly, and its routine clinical use is expanding, TG 235 has been formed to provide an update to TG-55 on radiochromic film dosimetry. RCF dosimetry applications in clinical radiotherapy have become even more widespread, expanding from primarily brachytherapy and radiosurgery applications, and gravitating towards (but not limited to) external beam therapy (photon, electron and protons), such as quality assurance for IMRT, VMAT, Tomotherapy, SRS/SRT, and SBRT. In addition, RCF applications now extend to measurements of radiation dose in particle beams and patients undergoing medical exams, especially fluoroscopically guided interventional procedures and CT. The densitometers/scanners used for RCF dosimetry have also evolved from the He-Ne laser scanner to CCD-based scanners, including roller-based scanner, light box-based digital camera, and flatbed color scanner. More recently, multichannel RCF dosimetry introduced a new paradigm for external beam dose QA for its high accuracy and efficiency. This course covers in detail the recent advancements in RCF dosimetry. Learning Objectives: Introduce the paradigm shift on multichannel film dosimetry Outline the procedures to achieve accurate dosimetry with a RCF dosimetry system Provide comprehensive guidelines on RCF dosimetry for various clinical applications One of the speakers has a research agreement from Ashland Inc., the manufacturer of Gafchromic film.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

TU-F-201-01: General Aspects of Radiochromic Film Dosimetry

Since the introduction of radiochromic films (RCF) for radiation dosimetry, the scope of RCF dosimetry has expanded steadily to include many medical applications, such as radiation therapy and diagnostic radiology. The AAPM Task Group (TG) 55 published a report on the recommendations for RCF dosimetry in 1998. As the technology is advancing rapidly, and its routine clinical use is expanding, TG 235 has been formed to provide an update to TG-55 on radiochromic film dosimetry. RCF dosimetry applications in clinical radiotherapy have become even more widespread, expanding from primarily brachytherapy and radiosurgery applications, and gravitating towards (but not limited to) external beam therapy (photon, electron and protons), such as quality assurance for IMRT, VMAT, Tomotherapy, SRS/SRT, and SBRT. In addition, RCF applications now extend to measurements of radiation dose in particle beams and patients undergoing medical exams, especially fluoroscopically guided interventional procedures and CT. The densitometers/scanners used for RCF dosimetry have also evolved from the He-Ne laser scanner to CCD-based scanners, including roller-based scanner, light box-based digital camera, and flatbed color scanner. More recently, multichannel RCF dosimetry introduced a new paradigm for external beam dose QA for its high accuracy and efficiency. This course covers in detail the recent advancements in RCF dosimetry. Learning Objectives: Introduce the paradigm shift on multichannel film dosimetry Outline the procedures to achieve accurate dosimetry with a RCF dosimetry system Provide comprehensive guidelines on RCF dosimetry for various clinical applications One of the speakers has a research agreement from Ashland Inc., the manufacturer of Gafchromic film.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

TU-F-201-02: Applications in SRS, SBRT, IMRT, VMAT, and KV Imaging

Since the introduction of radiochromic films (RCF) for radiation dosimetry, the scope of RCF dosimetry has expanded steadily to include many medical applications, such as radiation therapy and diagnostic radiology. The AAPM Task Group (TG) 55 published a report on the recommendations for RCF dosimetry in 1998. As the technology is advancing rapidly, and its routine clinical use is expanding, TG 235 has been formed to provide an update to TG-55 on radiochromic film dosimetry. RCF dosimetry applications in clinical radiotherapy have become even more widespread, expanding from primarily brachytherapy and radiosurgery applications, and gravitating towards (but not limited to) external beam therapy (photon, electron and protons), such as quality assurance for IMRT, VMAT, Tomotherapy, SRS/SRT, and SBRT. In addition, RCF applications now extend to measurements of radiation dose in particle beams and patients undergoing medical exams, especially fluoroscopically guided interventional procedures and CT. The densitometers/scanners used for RCF dosimetry have also evolved from the He-Ne laser scanner to CCD-based scanners, including roller-based scanner, light box-based digital camera, and flatbed color scanner. More recently, multichannel RCF dosimetry introduced a new paradigm for external beam dose QA for its high accuracy and efficiency. This course covers in detail the recent advancements in RCF dosimetry. Learning Objectives: Introduce the paradigm shift on multichannel film dosimetry Outline the procedures to achieve accurate dosimetry with a RCF dosimetry system Provide comprehensive guidelines on RCF dosimetry for various clinical applications One of the speakers has a research agreement from Ashland Inc., the manufacturer of Gafchromic film.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

TU-F-201-03: Applications in Brachytherapy

Since the introduction of radiochromic films (RCF) for radiation dosimetry, the scope of RCF dosimetry has expanded steadily to include many medical applications, such as radiation therapy and diagnostic radiology. The AAPM Task Group (TG) 55 published a report on the recommendations for RCF dosimetry in 1998. As the technology is advancing rapidly, and its routine clinical use is expanding, TG 235 has been formed to provide an update to TG-55 on radiochromic film dosimetry. RCF dosimetry applications in clinical radiotherapy have become even more widespread, expanding from primarily brachytherapy and radiosurgery applications, and gravitating towards (but not limited to) external beam therapy (photon, electron and protons), such as quality assurance for IMRT, VMAT, Tomotherapy, SRS/SRT, and SBRT. In addition, RCF applications now extend to measurements of radiation dose in particle beams and patients undergoing medical exams, especially fluoroscopically guided interventional procedures and CT. The densitometers/scanners used for RCF dosimetry have also evolved from the He-Ne laser scanner to CCD-based scanners, including roller-based scanner, light box-based digital camera, and flatbed color scanner. More recently, multichannel RCF dosimetry introduced a new paradigm for external beam dose QA for its high accuracy and efficiency. This course covers in detail the recent advancements in RCF dosimetry. Learning Objectives: Introduce the paradigm shift on multichannel film dosimetry Outline the procedures to achieve accurate dosimetry with a RCF dosimetry system Provide comprehensive guidelines on RCF dosimetry for various clinical applications One of the speakers has a research agreement from Ashland Inc., the manufacturer of Gafchromic film.

60 APPLIED LIFE SCIENCES↗