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At least 1,423 records · Page 79
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Efficiency and coherence preservation studies of Be refractive lenses for XFELO application

Performance tests of parabolic beryllium refractive lenses, considered as X-ray focusing elements in the future X-ray free-electron laser oscillator (XFELO), are reported. Single and double refractive lenses were subject to X-ray tests, which included: surface profile, transmissivity measurements, imaging capabilities and wavefront distortion with grating interferometry. Optical metrology revealed that surface profiles were close to the design specification in terms of the figure and roughness. The transmissivity of the lenses is >94% at 8 keV and >98% at 14.4 and 18 keV. These values are close to the theoretical values of ideal lenses. Images of the bending-magnet source obtained with the lenses were close to the expected ones and did not show any significant distortion. Grating interferometry revealed that the possible wavefront distortions produced by surface and bulk lens imperfections were on the level of ~λ/60 for 8 keV photons. Thus the Be lenses can be succesfully used as focusing and beam collimating elements in the XFELO.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Understanding the formation of multiply twinned structure in decahedral intermetallic nanoparticles

The structure of monometallic decahedral multiply twinned nanoparticles (MTPs) has been extensively studied, whereas less is known about intermetallic MTPs, especially the mechanism of formation of multiply twinned structures, which remains to be understood. Here, by using aberration-corrected scanning transmission electron microscopy, a detailed structural study of AuCu decahedral intermetallic MTPs is presented. Surface segregation has been revealed on the atomic level and the multiply twinned structure was studied systematically. Significantly different from Au and Cu, the intermetallic AuCu MTP adopts a solid-angle deficiency of −13.35°, which represents an overlap instead of a gap (+7.35° gap for Au and Cu). By analysing and summarizing the differences and similarities among AuCu and other existing monometallic/intermetallic MTPs, the formation mechanism has been investigated from both energetic and geometric perspectives. Finally, a general framework for decahedral MTPs has been proposed and unknown MTPs could be predicted on this basis.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

SU-F-T-77: A Novel Test for Coincidence Between Light Fields and Electron Radiation Fields

Purpose: To validate a novel real time quality assurance device, as a means to test coincidence of light fields to electron radiation fields. Method and Materials: Use a Raven™ (LAP of America Laser Applications) detector, both light fields and electron radiation fields of various electron cones and cutouts from two Clinacs (Varian Medical) were sensed by the phosphor screen and registered by a CCD camera of the device. During measurements, the screen surface of Raven was placed at ISO center level facing the radiation field at any setup angle. Subsequently the light field and the electron radiation field (with 100 MU) were captured separately by the device. The measurements were then analyzed using the Raven software with a maximal 25 by 25 cm^2 field size and 0.25 mm resolution. The results were further compared against those using chromic graphic film (EBT3). To ensure consistence only the dimensions through the central axis were recorded. All the films were analyzed with Dose Lab Pro™ v6.70. Coincidence comparisons were done within the tests on one Clinac and between the two Clinacs. Results: The similar difference means of the field coincidence are indicated from the 18 samples by EBT films and 34 by the Raven as 1.33 ± 0.87 mm verses 1.06 ± 0.58 mm (p = 0.74). The mean differences of the field coincidence between the two Clinacs, 1.16 ± 0.68 mm (n=16) and 1.16 ± 0.48 mm (n=18) respectively, also suggest no statistical difference (p= 0.40). Conclusion: The Raven™ is a comparable quality verification device to the chromic graphic film (EBT3) in checking the coincidence between light and electron radiation fields. In this investigation, the Raven device provided highly reproducible results with real time analysis. Further improvements in its resolution and automatic analyzing capability are warranted.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

GEOPHIRES v2.0

GEOPHIRES v2.0 is a geothermal techno-economic simulation tool upgraded from GEOPHIRES v1.2. The name stands for "GEOthermal energy for Production of Heat and electricity (“IR”) Economically Simulated". GEOPHIRES combines reservoir, wellbore, and surface plant technical models with cost correlations and levelized cost models to estimate the capital and operation and maintenance costs, instantaneous and lifetime energy production, and overall levelized cost of energy of a geothermal plant. In addition to electricity generation, direct-use heat applications and combined heat and power or cogeneration can be modeled. Various upgrades have been implemented to develop GEOPHIRES v2.0, including: updating the built-in cost correlations, coupling to the external reservoir simulator TOUGH2, enhancing the built-in wellbore simulator, converting the programming language to Python, and making the code open-source. Users are encouraged to build upon the tool, e.g. by implementing their own correlations or coupling to other simulators.

Beckers, Koenraad↗
DOE OSTI2024

Peering into cloud physics using ultra-fine resolution radar and lidar systems

Cloud microphysical processes, such as droplet activation, condensational growth, and collisional growth, play a central role in the evolution of clouds and precipitation. Accurate representations of these processes in numerical models are challenging partially due to incomplete understanding of them at the process-level arising from limited systematic observations. Most surface-based active remote sensors, including today’s operational cloud radars and lidars, have a resolution on the order of tens of meters. This resolution is insufficient to resolve cloud microphysical processes that manifest at finer (meter and sub-meter) scales. A new set of ultra-high-resolution ground-based radar and lidar systems have been developed to address this observational gap. The newly developed 94-GHz cloud radar has a range resolution down to 2.8 m, or a factor of 10 finer than typical radars, using a large bandwidth and quadratic phase coding techniques. The lidar has a range resolution down to 10 cm, or a factor of 100 finer than typical lidars, using a time-gated time-correlated single photon counting technique. Such high-resolution observations were previously only achievable through in situ aircraft measurements. Even then, aircraft measurements do not permit continuous long-term cloud observation as is possible with ground-based remote sensing instruments. In this study, the first-light cloud observations from the new radar and lidar systems are shown to reveal detailed cloud structures that conventional sensors could only perceive in a bulk sense, thus providing new avenues to investigate cloud microphysical processes and their impact on weather and climate.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

The Extraordinary March 2022 East Antarctica “Heat” Wave. Part I: Observations and Meteorological Drivers

Abstract Between 15 and 19 March 2022, East Antarctica experienced an exceptional heat wave with widespread 30°–40°C temperature anomalies across the ice sheet. This record-shattering event saw numerous monthly temperature records being broken including a new all-time temperature record of −9.4°C on 18 March at Concordia Station despite March typically being a transition month to the Antarctic coreless winter. The driver for these temperature extremes was an intense atmospheric river advecting subtropical/midlatitude heat and moisture deep into the Antarctic interior. The scope of the temperature records spurred a large, diverse collaborative effort to study the heat wave’s meteorological drivers, impacts, and historical climate context. Here we focus on describing those temperature records along with the intricate meteorological drivers that led to the most intense atmospheric river observed over East Antarctica. These efforts describe the Rossby wave activity forced from intense tropical convection over the Indian Ocean. This led to an atmospheric river and warm conveyor belt intensification near the coastline, which reinforced atmospheric blocking deep into East Antarctica. The resulting moisture flux and upper-level warm-air advection eroded the typical surface temperature inversions over the ice sheet. At the peak of the heat wave, an area of 3.3 million km 2 in East Antarctica exceeded previous March monthly temperature records. Despite a temperature anomaly return time of about 100 years, a closer recurrence of such an event is possible under future climate projections. In Part II we describe the various impacts this extreme event had on the East Antarctic cryosphere. Significance Statement In March 2022, a heat wave and atmospheric river caused some of the highest temperature anomalies ever observed globally and captured the attention of the Antarctic science community. Using our diverse collective expertise, we explored the causes of the event and have placed it within a historical climate context. One key takeaway is that Antarctic climate extremes are highly sensitive to perturbations in the midlatitudes and subtropics. This heat wave redefined our expectations of the Antarctic climate. Despite the rare chance of occurrence based on past climate, a future temperature extreme event of similar magnitude is possible, especially given anthropogenic climate change.

Wille, Jonathan D.↗
DOE OSTI2015

Soft x-ray free-electron laser induced damage to inorganic scintillators

An irreversible response of inorganic scintillators to intense soft x-ray laser radiation was investigated at the FLASH (Free-electron LASer in Hamburg) facility. Three ionic crystals, namely, Ce:YAG (cerium-doped yttrium aluminum garnet), PbWO4 (lead tungstate), and ZnO (zinc oxide), were exposed to single 4.6 nm ultra-short laser pulses of variable pulse energy (up to 12 μJ) under normal incidence conditions with tight focus. Damaged areas produced with various levels of pulse fluences, were analyzed on the surface of irradiated samples using differential interference contrast (DIC) and atomic force microscopy (AFM). The effective beam area of 22.2 ± 2.2 μm2 was determined by means of the ablation imprints method with the use of poly(methyl methacrylate) - PMMA. Applied to the three inorganic materials, this procedure gave almost the same values of an effective area. The single-shot damage threshold fluence was determined for each of these inorganic materials. The Ce:YAG sample seems to be the most radiation resistant under the given irradiation conditions, its damage threshold was determined to be as high as 660.8 ± 71.2 mJ/cm2. Contrary to that, the PbWO4 sample exhibited the lowest radiation resistance with a threshold fluence of 62.6 ± 11.9 mJ/cm2. The threshold for ZnO was found to be 167.8 ± 30.8 mJ/cm2. Both interaction and material characteristics responsible for the damage threshold difference are discussed in the article.

36 MATERIALS SCIENCE↗
DOE OSTI2016

AmeriFlux US-CRT Curtice Walter-Berger cropland

This is the AmeriFlux version of the carbon flux data for the site US-CRT Curtice Walter-Berger cropland. Site Description - The conventional cropland site is rain fed and no irrigation is applied. As it is located in a part of the historic Great Black Swamp, drainage tiles are deployed around 0.5–1.0 m beneath the ground surface in order to draw down the water level. The soil is classified as silty clay and silty clay loam. The cultivation practices include minimum tillage and both insect and weed control. During the study period, the cropland was planted with soybean and winter wheat.

Chen, Jiquan↗
DOE OSTI2023

AmeriFlux FLUXNET-1F US-CRT Curtice Walter-Berger cropland

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site US-CRT Curtice Walter-Berger cropland. This is the FLUXNET version of the carbon flux data for the site US-CRT Curtice Walter-Berger cropland produced by applying the standard ONEFlux (1F) software. Site Description - The conventional cropland site is rain fed and no irrigation is applied. As it is located in a part of the historic Great Black Swamp, drainage tiles are deployed around 0.5–1.0 m beneath the ground surface in order to draw down the water level. The soil is classified as silty clay and silty clay loam. The cultivation practices include minimum tillage and both insect and weed control. During the study period, the cropland was planted with soybean and winter wheat.

Chen, Jiquan↗
DOE OSTI2014

Development of a 1 x N Fiber Optic Sensor Array for Carbon Sequestration Site Monitoring

A fiber sensor array for sub-surface CO 2 concentrations measurements was developed for monitoring geologic carbon sequestration sites. The fiber sensor array uses a single temperature tunable distributed feedback (DFB) laser operating with a nominal wavelength of 2.004 μm. Light from this DFB laser is direct to one of the 4 probes via an in-line 1 x 4 fiber optic switch. Each of the 4 probes are buried and allow the sub-surface CO 2 to enter the probe through Millipore filters that allow the soil gas to enter the probe but keeps out the soil and water. Light from the DFB laser interacts with the CO 2 before it is directed back through the in-line fiber optic switch. The DFB laser is tuned across two CO 2 absorption features where a transmission measurement is made allowing the CO 2 concentration to be retrieved. The fiber optic switch then directs the light to the next probe where this process is repeated allowing sub-surface CO 2 concentration measurements at each of the probes to be made as a function of time. The fiber sensor array was deployed for fifty-eight days beginning June 19, 2012 at the Zero Emission Research Technology (ZERT) field site where sub-surface CO 2 concentrations were monitored. Background measurements indicate the fiber sensor array can monitor background levels as low as 1,000 parts per million (ppm). A thirty four day sub-surface release of 0.15 tones CO 2 /day began on July 10, 2012. The elevated subsurface CO 2 concentration was easily detected by each of the four probes with values ranging to over 60,000 ppm, a factor of greater than 6 higher than background measurements. The fiber sensor array was also deploy at the Big Sky Carbon Sequestration Partnership (BSCSP) site in north-central Montana between July 9th and August 7th, 2013 where background measurements were made in a remote sequestration site with minimal infrastructure. The project provided opportunities for two graduate students to participate in research directly related to geologic carbon sequestration. Furthermore, commercialization of the technology developed is being pursued with five different companies via the Department of energy SBIR/STTR program

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

A Fast-Cycle Charge Noise Measurement for Better Qubits

Defects in materials are an ongoing challenge for quantum bits, so called qubits. Solid state qubits—both spins in semiconductors and superconducting qubits—suffer from losses and noise caused by two-level-system (TLS) defects thought to reside on surfaces and in amorphous materials. Understanding and reducing the number of such defects is an ongoing challenge to the field. Superconducting resonators couple to TLS defects and provide a handle that can be used to better understand TLS. We develop noise measurements of superconducting resonators at very low temperatures (20 mK) compared to the resonant frequency, and low powers, down to single photon occupation.

36 MATERIALS SCIENCE↗
DOE OSTI2022

High Average Power RF Window with Improved Multipactor Coating

Multipactor emission can be a serious issue for vacuum electron devices operating at megawatt power levels. It can lead to catastrophic failure from surface arcs or excessive heating of ceramic windows. Titanium nitride is effective at suppressing multipactor emission; however, sputter coating is not strongly bonded to surfaces and issue related to lifetime have arisen. It’s difficult to ensure a uniform coating over large surfaces. This research investigated atomic layer deposition (ALD) as an improved alternative to sputtered coatings. Test windows were fabricated and coated with TiN using ALD, then tested for RF loss and secondary emission. All ALD samples showed RF loss less than 0.01dB with secondary emission yield equal to or better than reported measurements with sputter coated windows. The program also designed a preliminary ALD system capable of coating windows up to 24 inches in diameter.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Response of a store with tunable natural frequencies in compressible cavity flow

Fluid–structure interactions that occur during aircraft internal store carriage were experimentally explored at Mach 0.58–1.47 using a generic, aerodynamic store installed in a rectangular cavity having a length-to-depth ratio of seven. The store vibrated in response to the cavity flow at its natural structural frequencies, and it exhibited a directionally dependent response to cavity resonance frequencies. Cavity tones excited the store in the streamwise and wall-normal directions consistently, whereas the spanwise response to cavity tones was much more limited. Increased surface area associated with tail fins raised vibration levels. The store had interchangeable components to vary its natural frequencies by about 10–300 Hz. By tuning natural frequencies, mode-matched cases were explored where a prominent cavity tone frequency matched a structural natural frequency of the store. Mode matching in the streamwise and wall-normal directions produced substantial increases in peak store vibrations, though the response of the store remained linear with dynamic pressure. Near mode-matched frequencies, changes in cavity tone frequencies of only 1% altered store peak vibrations by as much as a factor of two. In conclusion, mode matching in the spanwise direction did little to increase vibrations.

42 ENGINEERING↗
DOE OSTI2022

Collisional Excitation and Non-LTE Modeling of Interstellar Chiral Propylene Oxide

Abstract The first set of theoretical rotational cross sections for propylene oxide (CH 3 CHCH 2 O) colliding with cold He atoms has been obtained at the full quantum level using a high-accuracy potential energy surface. By scaling the collision reduced mass, rotational rate coefficients for collisions with para-H 2 are deduced in the temperature range 5–30 K. These collisional coefficients are combined with radiative data in a non-LTE radiative transfer model in order to reproduce observations of propylene oxide made toward the Sagittarius B2(N) molecular cloud with the Green Bank and Parkes radio telescopes. The three detected absorption lines are found to probe the cold (∼10 K) and translucent ( n H ∼ 2000 cm −3 ) gas in the outer edges of the extended Sgr B2(N) envelope. The derived column density for propylene oxide is N tot ∼ 3 × 10 12 cm −2 , corresponding to a fractional abundance relative to total hydrogen of ∼2.5 × 10 −11 . The present results are expected to help our understanding of the chemistry of propylene oxide, including a potential enantiomeric excess, in the cold interstellar medium.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

ORNLERASE - EPA COUNTS PER MINUTE CALCULATOR CONVERSION FACTORS

This database is used in the EPA's Superfund Counts Per Minute (CPM) Calculator (https://epa-cpm.ornl.gov/index.html). This database contains conversion factors used in the calculator that help users estimate the expected radiation detector reading, in counts per minute (CPM), corresponding to a measured radioactivity level reported in either pCi/cm² or pCi/g. Because surface contamination and volumetric contamination behave differently, the tool uses separate conversion processes, each based on Monte Carlo N-Particle (MCNP)–derived conversion factors. The CPM Calculator supports conversions for a range of common environmental media—including soil, steel, glass, drywall, concrete, and wood—to generate detector-ready CPM values. The primary goal of this tool is to enable more efficient, real-time field measurements, reducing reliance on laboratory analyses and ultimately saving both time and money during Superfund assessments.

Dolislager, Fred [ORNL] (ORCID:0009000325477921)↗
DOE OSTI2012

A GREEN'S FUNCTION APPROACH FOR DETERMINING DOSE RATES FOR SMALL GRAM QUANTITIES IN SHIPPING PACKAGINGS

The Small Gram Quantity (SGQ) concept is based on the understanding that small amounts of hazardous materials, in this case radioactive materials (RAM), are significantly less hazardous than large amounts of the same materials. This paper describes a methodology designed to estimate an SGQ for several neutron and gamma emitting isotopes that can be shipped in a package in compliance with 10 CFR Part 71 external radiation level limits regulations. The neutron and photon sources were calculated using both ORIGEN-S and RASTA. The response from a unit source in each neutron and photon group was calculated using MCNP5 with each unshielded and shielded container configuration. Effects of self-shielding on both neutron and photon response were evaluated by including either plutonium oxide or iron in the source region for the case with no shielded container. For the cases of actinides mixed with light elements, beryllium is the bounding light element. The added beryllium (10 to 90 percent of the actinide mass) in the cases studied represents between 9 and 47 percent concentration of the total mixture mass. For beryllium concentrations larger than 50 percent, the increase in the neutron source term and dose rate tend to increase at a much lower rate than at concentrations lower than 50%. The intimately mixed actinide-beryllium form used in these models is very conservative and thus the limits presented in this report are practical bounds on the mass that can be safely shipped. The calculated dose rate from one gram of each isotope was then used to determin the maximum amount of a single isotope that could be shipped in the Model 9977 Package (or packagings having the same or larger external dimensions as well as similar structural materials) and have the external radiation level within the regulatory dose limits at the surface of the package. The estimates of the mass limits presented would also serve as conservative limits for both the Models 9975 and 9978 packages. If a package contains a mixture of isotopes, the acceptability for shipment can be determined by a sum of fractions approach. It should be noted that the SGQ masses presented in this report represent limits that would comply with the external radiation limits under 10CFR Part 71. They do not necessarily bound lower limits that may be required to comply with other factors such as heat load of the package.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Analytical TEM characterization of modified F82H and 14YW under irradiation of simultaneous helium and neutron irradiation compared to only neutron at 500 C

A RAFM steel and an ODS ferritic alloy (F82H.mod3+CW and 14YW, respectively) were irradiated as part of the JP27 irradiation experiment conducted in the High Flux Isotope Reactor to explore He effects in structural alloys. The ISHI technique is used to implant He up to 9 µm below the surface of a NiAl coated sample at He/dpa levels up to ~50. This report summarizes the current status of TEM characterization of two irradiated alloys. The He-implanted side of the RAFM alloy exhibited significant swelling due to bubble and void formation within the matrix, on pre-existing dislocations, and at interfaces within the material. The 14YW alloy exhibited significant swelling even in the absence of implanted He, primarily through large voids that formed on the ODS particles. In addition, significant radiation-induced segregation of the Cr was observed around oxide particles and on lath boundaries, and visible α' particles could be detected via elemental mapping of the matrix of the 14YW alloy.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Treatment of Radioactive Metallic Waste from Operation of Nuclear Power Plants by Melting - The German Way for a Consistent Recycling to Minimize the Quantity of Radioactive Waste from Operation and Dismantling for Disposal - 12016

During maintenance of nuclear power plants, and during their decommissioning period, a large quantity of radioactive metallic waste will accrue. On the other hand the capacity for final disposal of radioactive waste in Germany is limited as well as that in the US. That is why all procedures related to this topic should be handled with a maximum of efficiency. The German model of consistent recycling of the radioactive metal scrap within the nuclear industry therefore also offers high capabilities for facilities in the US. The paper gives a compact overview of the impressive results of melting treatment, the current potential and further developments. Thousands of cubic metres of final disposal capacity have been saved. The highest level of efficiency and safety by combining general surface decontamination by blasting and nuclide specific decontamination by melting associated with the typical effects of homogenization. An established process - nationally and internationally recognized. Excellent connection between economy and ecology. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗