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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Osiris-Rex Post-Tag Observation Trajectory Design and Navigation Performance

NASA’s OSIRIS-REx spacecraft successfully collected a sample of asteroid regolith from the surface of near-Earth asteroid Bennu in October of 2020. Subsequent imaging of the sampler head showed material leaking from the collection mechanism, thus stowage of the sample precluded execution of any planned maneuvers in the following days. Optical navigation imaging also ceased in the days following sample collection. The desire to image the sample site to investigate the results of the spacecraft-to-surface interaction led to the Navigation team designing a trajectory to return to Bennu after several months in order to image the surface one final time. After several iterations a trajectory design was created that satisfied the numerous constraints that were levied in order to place utmost importance on the safety of the spacecraft and stowed sample, while also closely emulating previously obtained imaging conditions to provide a close comparison of site pre- and post-contact. Significant analysis was necessary in order to reliably reacquire the asteroid after several months without optical navigation imagery. The final design required five maneuvers to return the spacecraft to Bennu and perform a final flyby of the asteroid at a distance of 3.8 kilometers. Successful execution of the phase provided key insights regarding the performance of the sample collection activities and the subsurface composition of the asteroid.

Daniel R Wibben↗
NASA NTRSDate not supplied

Monodisperse Single-Material Granular Tribocharging Modeling and Experimental Validation

Charge transfer between insulating grains has been a topic of interest for many years as this phenomenon is extremely important to many areas in industry. Of particular interest to NASA is the behavior of electrically insulative dust grains such as those found on the lunar surface. Whether poured from a scoop during sample collection activities, agitated inside a drum via mining robots, or fluidized by a gas plume, particle-particle interactions between similar granular materials will be widespread on the Moon. Designers hope to have a predictive model for how dust grains are charged, transported, and deposited on flight systems to better understand issues electrostatics may cause in future missions. While difference in work function is often seen as a driver for charge transfer between two materials, this is an incomplete representation for insulative particles. Other asymmetries in the system can also lead to charge being transferred: one such being the difference between static vs dynamic particles. Experiments performed under vacuum in the Electrostatics and Surface Physics Laboratory (ESPL) clearly show that particles having more contacts with other particles tend to charge positively and particles having fewer contacts tend to charge negatively, despite being made from the same material. During these experiments, monodisperse (population of single diameter) spherical particles were held in a reservoir which was then elevated at one end to slope into a Faraday cup used to measure bulk charge of the grains. Care was taken to limit the number of spheres bouncing out of the cup, to isolate the beads from the container itself so that only grain-to-grain interactions occurred, and to assure neutrality of the beads before the experiment began. A discrete element method (DEM) modeling package already incorporating many granular mechanics interactions was augmented to include the electrostatic behaviors seen in experiments. The model can reproduce the experimental results above by tracking the number of contacts between pairs of individual grains and applying a charge transfer condition related to this contact parameter. The experimental results as well as their incorporation into the improved modeling suite will be discussed. Future work includes adding additional asymmetries into the experiments/model such as polydisperse populations of spherical particles and irregularly shaped grains.

granular↗
NASA NTRSDate not supplied

Monodisperse Single-Material Granular Tribocharging Modeling and Experimental Validation

Charge transfer between insulating grains has been a topic of interest for many years as this phenomenon is extremely important to many areas in industry. Of particular interest to NASA is the behavior of electrically insulative dust grains such as those found on the lunar surface. Whether poured from a scoop during sample collection activities, agitated inside a drum via mining robots, or fluidized by a gas plume, particle-particle interactions between similar granular materials will be widespread on the Moon. Designers hope to have a predictive model for how dust grains are charged, transported, and deposited on flight systems to better understand issues electrostatics may cause in future missions. While difference in work function is often seen as a driver for charge transfer between two materials, this is an incomplete representation for insulative particles. Other asymmetries in the system can also lead to charge being transferred: one such being the difference between static vs dynamic particles. Experiments performed under vacuum in the Electrostatics and Surface Physics Laboratory (ESPL) clearly show that particles having more contacts with other particles tend to charge positively and particles having fewer contacts tend to charge negatively, despite being made from the same material. During these experiments, monodisperse (population of single diameter) spherical particles were held in a reservoir which was then elevated at one end to slope into a Faraday cup used to measure bulk charge of the grains. Care was taken to limit the number of spheres bouncing out of the cup, to isolate the beads from the container itself so that only grain-to-grain interactions occurred, and to assure neutrality of the beads before the experiment began. A discrete element method (DEM) modeling package already incorporating many granular mechanics interactions was augmented to include the electrostatic behaviors seen in experiments. The model can reproduce the experimental results above by tracking the number of contacts between pairs of individual grains and applying a charge transfer condition related to this contact parameter. The experimental results as well as their incorporation into the improved modeling suite will be discussed. Future work includes adding additional asymmetries into the experiments/model such as polydisperse populations of spherical particles and irregularly shaped grains.

electrostatics↗
NASA NTRS2024

KSC Child Development Center (PRL 149) Confirmatory Sampling Report and Interim Measures Work Plan

The National Aeronautics and Space Administration (NASA) Resource Conservation and Recovery Act (RCRA) permit requires identification and evaluation of known Solid Waste Management Units (SWMU) located at the Kennedy Space Center (KSC). The KSC Child Development Center (KCDC), the “site,” is designated as potential release location (PRL) 149 under the NASA RCRA permit. This report summarizes the results of the Confirmatory Sampling (CS) activities carried out on March 19, 2022, and May 16, 2023, at KCDC, PRL 149, KSC, Florida. This report additionally presents the results of an assessment conducted between July 7 and July 27, 2023, to determine whether construction activities in 2023 to replace certain playground equipment and the rubberized play surface released arsenic (As) contaminated soil.

CDC↗
DOE OSTI2017

Current Status of the Irradiated Materials Characterization Laboratory at INL with Limited PIE Microstructural Characterization

The Irradiated Materials Characterization Laboratory at Idaho National Laboratory is a post-irradiation examination (PIE) facility focused on high end microscopy enclosed in shielded enclosures. Planned PIE activities include: sample preparation, microscopy (FIB, EPMA, and TEM), and thermal property measurements. An overview of the facility, its operational status, and its future growth will be presented. A detailed discussion of the shielding/confinement surrounding the PIE equipment will be provided. The shielded sample preparation area, SSPA, will be discussed, focusing on instruments being incorporated to achieve high quality sample finishes for microscopy and thermal property measurements. With various instruments of IMCL operational, PIE results of irradiated fuels using the EPMA, FIB, and TEM will be provided. A detailed explanation of the capabilities of the PIE equipment will be presented and how these instruments are being incorporated in preforming high quality microstructural characterization on highly irradiated materials.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Microbial Diversity in the Deep Sandstones of a Carbon Sequestration Well

A lack of data on microbes in the deep subsurface hinders our ability to predict how these microbial communities will respond to carbon sequestration. Previous studies predicted how microbial communities may shift due to an influx of carbon dioxide (CO2) by 1) examining waters with naturally-occurring elevated CO2 concentration; and/or 2) via experiments involving exposure of laboratory microbial strains to elevated concentrations of CO2 relative to their native subsurface environment. To identify microbes naturally found in carbon sequestration target reservoirs, water samples were collected from three potential target reservoirs in the Powder River Basin, Wyoming which include the Hulett, Lakota, and Minnelusa sandstones. Water samples were collected at depths of 8,060 ft (Lakota), 8,330 ft (Hulett), 9,380 ft (Minnelusa), 9,463 ft (Minnelusa), and 9,544 ft (Minnelusa) for microbial DNA analysis as well as water chemistry and stable isotope analyses to look for any microbial trends that could be related to water chemistry alone. Identification of microbial communities present in the sampled water was determined via 16S rRNA sequencing; these data were compared to 16S rRNA isolated from drilling mud to distinguish native from any microbes introduced via drilling processes. Enrichment experiments reveal that the collected water samples contain active (e.g., growing) microbes and how the microbial community may adapt upon the introduction of CO2.

Wawrousek, K↗
DOE OSTI2016

Design of a Supercritical Carbon Dioxide Corrosion Test Rig for Tube-to-Tubesheet Joint and High Temperature Insulation Testing

Supercritical carbon dioxide (S-CO{sub 2}) Brayton cycles are attractive for thermal power generation since they offer highly efficient means of power generation (thermal solar, coal, nuclear, etc.) with a compact footprint, resulting in potential cost savings. The University of California, Berkeley (UCB) is developing an S-CO{sub 2}- Brayton Cycle design for advanced reactors using sodium and molten salt coolants. Coiled tube gas heaters (CTGH) made from 316L stainless steel are presently foreseen to transfer heat from a sodium or molten salt coolant at atmospheric pressure (approximately 0.1 MPa) to an S-CO{sub 2} power conversion fluid at very high pressure (approximately 20 MPa or more). CTGHs operate at temperatures of 400 to 700 deg. C where time-dependent creep is an important design issue. Given the high external pressure conditions and compressive stress, the highest stresses and creep rates in CTGH are expected to occur at the tube-to-tubesheet joints. UCB has developed different diffusion bonding techniques to fabricate 316L stainless steel tube-to-tubesheet joint dummies representative of the final design: press fitting and diffusion bonding, tube expansion and diffusion bonding as well as hybrid friction diffusion bonding. High pressure/temperature testing of such joints in an S-CO{sub 2} environment is important prior to deployment and will be foreseen with the corrosion test rig introduced in this work. This summary provides a brief overview of an Innovative S-CO, creep corrosion test rig for tube-to-tube sheet joint testing currently under construction at UCB. In contrast to other comparable test rigs, the design (1) makes the samples an active part of the pressure barrier and (2) uses internal insulation to reduce the temperature at the vessel wall, allowing the vessel to be manufactured from commercial carbon steel. (authors)

42 ENGINEERING↗
DOE OSTI2012

A CATALOG OF ROTATION AND ACTIVITY IN EARLY-M STARS

We present a catalog of rotation and chromospheric activity in a sample of 334 M dwarfs of spectral types M0-M4.5 populating the parameter space around the boundary to full convection. We obtain high-resolution optical spectra for 206 targets and determine projected rotational velocity, vsin i, and H{alpha} emission. The data are combined with measurements of vsin i in field stars of the same spectral type from the literature. Our sample adds 157 new rotation measurements to the existing literature and almost doubles the sample of available vsin i. The final sample provides a statistically meaningful picture of rotation and activity at the transition to full convection in the solar neighborhood. We confirm a steep rise in the fraction of active stars at the transition to full convection known from earlier work. In addition, we see a clear rise in rotational velocity in the same stars. In very few stars, no chromospheric activity but a detection of rotational broadening is reported. We argue that all of them are probably spurious detections; we conclude that in our sample all significantly rotating stars are active, and all active stars are significantly rotating. The rotation-activity relation is valid in partially and in fully convective stars. Thus, we do not observe any evidence for a transition from a rotationally dominated dynamo in partially convective stars to a rotation-independent turbulent dynamo in fully convective stars; turbulent dynamos in fully convective stars of spectral types around M4 are still driven by rotation. Finally, we compare projected rotational velocities of 33 stars to rotational periods derived from photometry in the literature and determine inclinations for a few of them.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

Detecting active comets with SDSS

Using a sample of serendipitously discovered active comets in the Sloan Digital Sky Survey (SDSS), we develop well-controlled selection criteria for greatly increasing the efficiency of comet identification in the SDSS catalogs. After follow-up visual inspection of images to reject remaining false positives, the total sample of SDSS comets presented here contains 19 objects, roughly one comet per 10 million other SDSS objects. The good understanding of selection effects allows a study of the population statistics, and we estimate the apparent magnitude distribution to r {approx} 18, the ecliptic latitude distribution, and the comet distribution in SDSS color space. The most surprising results are the extremely narrow range of colors for comets in our sample (e.g. root-mean-square scatter of only {approx}0.06 mag for the g-r color), and the similarity of comet colors to those of jovian Trojans. We discuss the relevance of our results for upcoming deep multi-epoch optical surveys such as the Dark Energy Survey, Pan-STARRS, and the Large Synoptic Survey Telescope (LSST), and estimate that LSST may produce a sample of about 10,000 comets over its 10-year lifetime.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

NNSS Soils Monitoring: Plutonium Valley (CAU 366) FY2019

Desert Research Institute (DRI) conducted a field assessment of the potential for radionuclide-contaminated soil to be transported from the Plutonium Valley Dispersion Sites Contamination Area (CA) because of both wind and storm water runoff. This activity supported U.S. Department of Energy (DOE) Environmental Management Nevada Program (EM NV) efforts to establish post-closure monitoring plans for the Plutonium Valley Dispersion Sites Corrective Action Unit (CAU) 366. The DRI task was intended to identify the likely mechanism(s) of transport and determine the meteorological conditions that might cause the movement of radionuclide-contaminated soils. The emphasis of the work was on collecting sediment transported by channelized storm runoff and measuring airborne dust concentrations and associated wind conditions. These data will facilitate an appropriate post-closure monitoring program. In 2011, DRI installed meteorological monitoring stations north and south of the Plutonium Valley CA—known as Pu Valley North and Pu Valley South, respectively—as well as a fluvial sediment sampling station within the CA. Since installation, temperature, wind speed, wind direction, relative humidity, precipitation, solar radiation, barometric pressure, soil temperature, volumetric soil moisture content, and airborne particulate concentrations have been collected at both meteorological stations. The maximum, minimum, and average or total (as appropriate) for each of these parameters were recorded for each 10-minute interval. The sediment sampling station included an automatically activated sampling pump with collection bottles for suspended sediment, which was activated when sufficient flow was present in the channel, and passive traps for bedload material that was transported down the channel during runoff events. This report presents data collected from these stations during fiscal year (FY) 2019. During the FY2019 (October 1, 2018, through September 30, 2019) reporting period, the warmest month was July and the coldest month was February. Monthly total solar radiation was highest in June or July (depending on the station) and lowest in December. Monthly mean wind speeds were highest during February. At the Pu Valley North station, winds were commonly northerly, northwesterly, and southerly. At the Pu Valley South station, the wind direction was more variable and winds frequently came from most directions, excluding westerly and northwesterly winds. Winds above 15.0 miles per hour (mph) (24.1 kilometers per hour [km/hr]) were frequently southerly at both stations, and less-frequent strong winds were northerly (at the Pu Valley South station) or northwesterly (at the Pu Valley North station). Monthly average relative humidity ranged from 18 percent in August to 62 percent in January and February. Monthly total precipitation ranged from zero at both stations in September to 2.23 inches (in) (56.6 millimeters [mm]) during February at the Pu Valley South station and 2.09 in (53.1 mm) during March at the Pu Valley North station. From October 1, 2018, through September 30, 2019, the total precipitation was 8.23 in (209 mm) and 8.15 in (207 mm) at the Pu Valley South and Pu Valley North stations, respectively. The largest daily precipitation totals of 1.46 in (37.1 mm) and 1.14 in (29.0 mm) occurred at the Pu Valley South and Pu Valley North stations, respectively, on March 6, 2019. However, the ISCO autosampler was not activated during any storm event in FY2019 because the channel water depth measurements were insufficient for suspended sediment sample collection. Additionally, because no significant flow through the channel was indicated, no bedload samples were collected. Light breezes of 0.0 mph to 5.0 mph (0.0 km/hr to 8.0 km/hr) occurred most frequently (approximately 55 percent to 57 percent of the time). The frequency of occurrence diminished exponentially as the wind speed increased such that winds in excess of 25.0 mph (40.2 km/hr) occurred less than 0.01 percent of the time. Winds in excess of 15.0 mph (24.1 km/hr) were most commonly southerly, which is likely controlled by the topography of the valley because topographic highs define the east and west sides of the valley and converge toward the north.The concentrations of PM2.5 (particulate matter with an aerodynamic diameter ≤2.5 micrometers [μm]) and PM10 (particulate matter with an aerodynamic diameter ≤10 μm) in the air generally increase as wind speed increases. However, the particle profiler at the Pu Valley South station regularly malfunctioned, which resulted in poor data quality and a limited period of record within FY2019. Therefore, discussion of the annual dust observations is mostly limited to the Pu Valley North station. At the Pu Valley North station, significant increases in windblown dust concentrations were observed when wind speeds exceeded 15.0 mph (24.1 km/hr), especially during southerly winds. When all wind speeds were considered, high dust concentrations at the Pu Valley North station were frequently associated with northerly, northwesterly, or southerly winds. The majority of PM10 transport at the Pu Valley North station occurred when winds were blowing northerly and northwesterly because of the high frequency of winds up to 15.0 mph (24.1 km/hr). The ratio of PM10 to PM2.5 is a qualitative indicator of the proximity of dust sources to the observation point and the values of the PM10 to PM2.5 ratio tend to be higher nearer to the source. The PM10 to PM2.5 ratio increased from 1.2 to 2.8 with higher wind speeds at the Pu Valley North station. This increase suggests that some locally sourced PM10 was present in the air when local winds exceeded 15.0 mph (24.1 km/hr). Local dust suspension is interpreted during major dust events when peaks in the PM10 to PM2.5 ratio occur simultaneously with the maximum wind speed and the peak PM10 concentration. Analysis of the five major dust events in FY2019 revealed that northerly winds were dominant in three events and southerly winds were dominant in two events. Local suspension of dust within Plutonium Valley is suspected to have occurred during two of the five major events (April 9, 2019, and September 28 to 29, 2019), and a nonlocal source of dust is presumed for the three other major dust events (October 14, 2018; May 16, 2019; and September 2, 2019). The three suspected regional dust transport events exhibited winds that typically did not exceed the 15.0 mph (24.1 km/hr) wind speed threshold for local dust transport and featured PM10 to PM2.5 ratios that indicate large-scale regional dust transport. Similar event characteristics (e.g., wind speed and PM10 concentration) were observed at air monitoring stations approximately 70 mi (113 km) to the northwest within the Tonopah Test Range (TTR). Therefore, these three regional events may not reflect transport from the Plutonium Valley CA. Routine monitoring of meteorological and hydrologic parameters at Plutonium Valley has been discontinued at the request of EM NV, effective at the conclusion of FY2019. Environmental data acquisition has been completed, and both Pu Valley North and Pu Valley South meteorological stations within Plutonium Valley as well as the ISCO autosampler station within the CA were removed on October 14, 2019.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

DWARF GALAXIES WITH OPTICAL SIGNATURES OF ACTIVE MASSIVE BLACK HOLES

We present a sample of 151 dwarf galaxies (10{sup 8.5} ∼< M{sub *} ∼< 10{sup 9.5} M{sub ☉}) that exhibit optical spectroscopic signatures of accreting massive black holes (BHs), increasing the number of known active galaxies in this stellar-mass range by more than an order of magnitude. Utilizing data from the Sloan Digital Sky Survey Data Release 8 and stellar masses from the NASA-Sloan Atlas, we have systematically searched for active BHs in ∼25,000 emission-line galaxies with stellar masses comparable to the Magellanic Clouds and redshifts z < 0.055. Using the narrow-line [O III]/Hβ versus [N II]/Hα diagnostic diagram, we find photoionization signatures of BH accretion in 136 galaxies, a small fraction of which also exhibit broad Hα emission. For these broad-line active galactic nucleus (AGN) candidates, we estimate BH masses using standard virial techniques and find a range of 10{sup 5} ∼< M{sub BH} ∼< 10{sup 6} M{sub ☉} and a median of M{sub BH} ∼ 2 × 10{sup 5} M{sub ☉}. We also detect broad Hα in 15 galaxies that have narrow-line ratios consistent with star-forming galaxies. Follow-up observations are required to determine if these are true type 1 AGN or if the broad Hα is from stellar processes. The median absolute magnitude of the host galaxies in our active sample is M{sub g} = –18.1 mag, which is ∼1-2 mag fainter than previous samples of AGN hosts with low-mass BHs. This work constrains the smallest galaxies that can form a massive BH, with implications for BH feedback in low-mass galaxies and the origin of the first supermassive BH seeds.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Fluidized bed steam reformed mineral waste form performance testing to support Hanford Supplemental Low Activity Waste Immobilization Technology Selection

This report describes the benchscale testing with simulant and radioactive Hanford Tank Blends, mineral product characterization and testing, and monolith testing and characterization. These projects were funded by DOE EM-31 Technology Development & Deployment (TDD) Program Technical Task Plan WP-5.2.1-2010-001 and are entitled “Fluidized Bed Steam Reformer Low-Level Waste Form Qualification”, Inter-Entity Work Order (IEWO) M0SRV00054 with Washington River Protection Solutions (WRPS) entitled “Fluidized Bed Steam Reforming Treatability Studies Using Savannah River Site (SRS) Low Activity Waste and Hanford Low Activity Waste Tank Samples”, and IEWO M0SRV00080, “Fluidized Bed Steam Reforming Waste Form Qualification Testing Using SRS Low Activity Waste and Hanford Low Activity Waste Tank Samples”. This was a multi-organizational program that included Savannah River National Laboratory (SRNL), THOR® Treatment Technologies (TTT), Pacific Northwest National Laboratory (PNNL), Oak Ridge National Laboratory (ORNL), Office of River Protection (ORP), and Washington River Protection Solutions (WRPS). The SRNL testing of the non-radioactive pilot-scale Fluidized Bed Steam Reformer (FBSR) products made by TTT, subsequent SRNL monolith formulation and testing and studies of these products, and SRNL Waste Treatment Plant Secondary Waste (WTP-SW) radioactive campaign were funded by DOE Advanced Remediation Technologies (ART) Phase 2 Project in connection with a Work-For-Others (WFO) between SRNL and TTT.

Jantzen, C. M.↗
DOE OSTI2014

Polymer surfaces graphitization by low-energy He{sup +} ions irradiation

The electrical and optical properties of surfaces of polyimide and AZ5214e graphitized by low-energy (1 keV) He{sup +} irradiation at different polymer temperatures were investigated. The conductivity of the graphitized layers can be controlled with the irradiation temperature within a broad range and can reach values up to ∼1000 S/cm. We show that the electrical transport in low-conducting samples is governed by thermally activated hopping, while the samples with a high conductivity show a typical semimetallic behavior. The transition from thermally activated to semimetallic conductance governed by the irradiation temperature could also be observed in optical measurements. The semimetallic samples show an unusually high for graphitic materials carrier concentration, which results in a high extinction coefficient in the visible light range. By analyzing the temperature dependence of the conductance of the semimetallic samples, we conclude that the scattering of charge carriers is dominated by Coulomb interactions and can be described by a weak localization model. The transition from a three to two dimensional transport mechanism at low temperatures consistently explains the change in the temperature dependence of the conductance by cooling, observed in experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Enhanced photocatalytic degradation of phenol over Ag3PO4-BiOCl1−xBrx composites

Highlights: • Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} composites were successfully synthesized and characterized. • The band energy of composites can be tunable by solid-solution strategy. • Appropriate band-gap structure facilitates charge separation property and light absorption. - Abstract: In this paper, a series of Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} composites with adjustable band gap has been fabricated by using a facile two-step synthetic method. The photocatalytic activity of Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} was evaluated by photocatalytic decomposition of phenol aqueous solution under simulated solar light irradiation. The result shows that Ag{sub 3}PO{sub 4}-BiOCl{sub 0.75}Br{sub 0.25} (1:5) composite possesses the best photocatalytic activity among all the as-prepared samples. The photocatalytic activity of Ag{sub 3}PO{sub 4}-BiOCl can be enhanced mainly owing to the strong light absorption ability by loading Ag{sub 3}PO{sub 4} on the surface of BiOCl, while the photocatalytic activities of Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} (x = 0.25, 0.5, 0.75 and 1) composites could be enhanced by restraining the recombination of photo-generated electron-hole pairs. The enhanced solar-light photocatalytic activities of Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} composites could be ascribed to the adjustable energy band structure, which facilitates the separation of photoinduced carriers. In addition, superoxide radicals (O{sub 2}{sup −}), holes (h{sup +}) and OH are considered to dominate the photocatalytic degration process. Moreover, a possible mechanism of deep understanding on the base of experimental results was proposed.

36 MATERIALS SCIENCE↗
NASA NTRS1985

Emerging flux in active regions

The rates at which flux emerges in active and quiet solar regions within the sunspot belts are compared. The emerging flux regions (EFRs) were identified by the appearance of arch filament structures in H-alpha. All EFRs in high resolution films of active regions made at Big Bear in 1978 were counted. The comparable rate of flux emergence in quiet regions was obtained from SGD data and independently from EFRs detected outside the active region perimeter on the same films. The rate of flux emergence is 10 times higher in active regions than in quiet regions. A sample of all active regions in 31 days of 1983 gave a ratio of 7.5. Possible mechanisms which might funnel new magnetic flux to regions of strong magnetic field are discussed.

Liggett, M.↗
NASA NTRS1989

On the ratio of the infrared-to-ultraviolet continuum to the X-rays in quasars and active galaxies

A sample of 122 quasars and Seyfert galaxies was analyzed and it was found that the NIR 7500 A rest frame luminosity is more linearly related to the X-ray luminosity than is the optical luminosity. It is also found that the mean spectral slope between 7500 and 4200 A in the rest frame monotonically flattens with luminosity over more than three orders of magnitude. The present results support models which attribute the IR and X-ray continua to linked nonthermal processes such as synchrotron self-Compton, while the blue-UV bump comes from a different source, such as an accretion disk.

Mushotzky, R. F.↗
DOE OSTI2016

Development of a Low-Level Ar-37 Calibration Standard

Argon-37 is an important environmental signature of an underground nuclear explosion. Producing and quantifying low-level 37Ar standards is an important step in the development of sensitive field measurement instruments for use during an On-Site Inspection, a key provision of the Comprehensive Nuclear-Test-Ban Treaty. This paper describes progress at Pacific Northwest National Laboratory (PNNL) in the development of a process to generate and quantify low-level 37Ar standard material, which can then be used to calibrate sensitive field systems at activities consistent with soil background levels. The 37Ar used for our work was generated using a laboratory-scale, high-energy neutron source to irradiate powdered samples of calcium carbonate. Small aliquots of 37Ar were then extracted from the head space of the irradiated samples. The specific activity of the head space samples, mixed with P10 (90% stable argon:10% methane by mole fraction) count gas, is then derived using the accepted Length-Compensated Internal-Source Proportional Counting method. Due to the low activity of the samples, a set of three Ultra-Low Background Proportional-Counters designed and fabricated at PNNL from radio-pure electroformed copper was used to make the measurements in PNNL’s shallow underground counting laboratory. Very low background levels (<10 counts/day) have been observed in the spectral region near the 37Ar emission feature at 2.8 keV. Two separate samples from the same irradiation were measured. The first sample was counted for 12 days beginning 28 days after irradiation, the second sample was counted for 24 days beginning 70 days after irradiation (the half-life of 37Ar is 35.0 days). Both sets of measurements were analyzed and yielded very similar results for the starting activity (~0.1 Bq) and activity concentration (0.15 mBq/ccSTP argon) after P10 count gas was added. A detailed uncertainty model was developed based on the ISO Guide to the Expression of Uncertainty in Measurement. This paper presents a discussion of the measurement analysis, along with assumptions and uncertainty estimates.

Absolute radiation measurement↗