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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 1,333 records · Page 74
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Photon Activation Analysis at the Idaho Accelerator Center

Activation methods require minimal sample preparation and provide sufficiently high sensitivity for detecting the vast majority of the elements throughout the periodic table. In this paper we shall discuss photon activation analysis (PAA) at the Idaho Accelerator Center. The process of PAA begins with exposing a sample with photons in the energy range of 10 to 30 MeV. Many nuclides in the sample will become activated and, in turn, these radionuclides will decay by emitting characteristic radiation. These characteristic radiation decays are the telltale signatures for identifying elements which can then be measured with spectrometers such as a high-purity Germanium detector. PAA is not an 'absolute' method, as the samples under investigation must be irradiated along with a reference or calibrating material having a well-known elemental composition. The quantitative evaluation is performed through comparing the two resulting element spectra from the unknown sample and reference material. Besides the obvious advantage of being non-destructive, PAA has minimal contamination issues. Moreover, materials that are difficult to treat chemically, such as certain refractory metals, dusts, ashes, etc., offer no hindrance to the technique of PAA. A further advantage is that PAA is very well suited for investigated minute samples (sub-milligram dust particles) to very large ones (in the multi-kg range). PAA is a robust technique as there are no real limitations concerning the nature of material to be studied.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Thermal conductivity and Seebeck coefficients of icosahedral boron arsenide films on silicon carbide

The thermal conductivity of icosahedral boron arsenide (B{sub 12}As{sub 2}) films grown on (0001) 6H-SiC substrates by chemical vapor deposition was studied by the 3{omega} technique. The room temperature thermal conductivity decreased from 27.0 to 15.3 W/m K as the growth temperature was decreased from 1450 to 1275 deg. C. This is mainly attributed to the differences in the impurity concentration and microstructure, determined from secondary ion mass spectrometry and high resolution transmission electron microscopy, respectively. Callaway's theory was applied to calculate the temperature-dependent thermal conductivity, and the results are in good agreement with the experimental data. Seebeck coefficients were determined as 107 {mu}V/K and 136 {mu}V/K for samples grown at 1350 deg. C with AsH{sub 3}/B{sub 2}H{sub 6} flow ratio equals to 1:1 and 3:5, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2010

New developments in the diagnostics for the fusion products on JET in preparation for ITER (invited)

Notwithstanding the advances of the past decades, significant developments are still needed to satisfactorily diagnose ''burning plasmas.'' D-T plasmas indeed require a series of additional measurements for the optimization and control of the configuration: the 14 MeV neutrons, the isotopic composition of the main plasma, the helium ash, and the redistribution and losses of the alpha particles. Moreover a burning plasma environment is in general much more hostile for diagnostics than purely deuterium plasmas. Therefore, in addition to the development and refinement of new measuring techniques, technological advances are also indispensable for the proper characterization of the next generation of devices. On JET an integrated program of diagnostic developments, for JET future and in preparation for ITER, has been pursued and many new results are now available. In the field of neutron detection, the neutron spectra are now routinely measured in the energy range of 1-18 MeV by a time of flight spectrometer and they have allowed studying the effects of rf heating on the fast ions.A new analysis method for the interpretation of the neutron cameras measurements has been refined and applied to the data of the last trace tritium campaign (TTE). With regard to technological upgrades, chemical vapor deposition diamond detectors have been qualified both as neutron counters and as neutron spectrometers, with a potential energy resolution of about one percent. The in situ calibration of the neutron diagnostics, in preparation for the operation with the ITER-like wall, is also promoting important technological developments. With regard to the fast particles, for the first time the temperature of the fast particle tails has been obtained with a new high purity Germanium detector measuring the gamma emission spectrum from the plasma. The effects of toroidal Alfven eigenmodes modes and various MHD instabilities on the confinement of the fast particles have been determined with a combination of gamma ray cameras, neutral particle analyzers, scintillator probe, and Faraday cups. From a more technological perspective, various neutron filters have been tested to allow measurement of the gamma ray emission also at high level of neutron yield.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

H{sub 2}/N{sub 2} plasma damage on porous dielectric SiOCH film evaluated by in situ film characterization and plasma diagnostics

This study investigates the mechanism of H{sub 2}/N{sub 2} plasma ashing damage of porous SiOCH films. Porous SiOCH films were treated by a H{sub 2}/N{sub 2} plasma using a 100-MHz capacitively coupled plasma etcher. The impact of ions, radicals, and vacuum ultraviolet radiation on the porous SiOCH films was investigated using in situ bulk analysis techniques such as spectroscopic ellipsometry and Fourier-transform infrared spectroscopy and ex situ film characterization techniques such as dynamic secondary ion mass spectrometry and x-ray photoelectron spectroscopy. In addition, plasma analysis including vacuum ultraviolet absorption spectroscopy was performed. The film characterization and plasma analysis show that the extraction of methyl by H radicals was enhanced by light while N radicals were responsible for inhibit the extraction of Si-CH{sub 3} bonds by forming nitride layer. The H{sub 2}/N{sub 2} plasma damage mechanism is discussed based on characterization of the film and plasma diagnostics.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

III-V Nanowire Array Growth by Selective Area Epitaxy

III-V semiconductor nanowires are unique material phase due to their high aspect ratio, large surface area, and strong quantum confinement. This affords the opportunity to control charge transport and optical properties for electrical and photonic applications. Nanoscale selective area metalorganic chemical vapor deposition growth (NS-SAG) is a promising technique to maximize control of nanowire diameter and position, which are essential for device application. In this work, InP and GaAs nanowire arrays are grown by NS-SAG. We observe enhanced sidewall growth and array uniformity disorder in high growth rate condition. Disorder in surface morphology and array uniformity of InP nanowire array is explained by enhanced growth on the sidewall and stacking faults. We also find that AsH{sub 3} decomposition on the sidewall affects the growth behavior of GaAs nanowire arrays.

36 MATERIALS SCIENCE↗
DOE OSTI2012

High resolution ion Doppler spectroscopy at Prairie View Rotamak

A fast ion Doppler spectroscopy (IDS) diagnostic system is installed on the Prairie View Rotamak to measure ion temperature and plasma flow. The diagnostic employs a single channel photomultiplier tube and a Jarrell-Ash 50 monochromator with a diffraction grating line density of 1180 lines/mm, which allows for first order spectra of 200-600 nm. The motorized gear of the monochromator allows spectral resolution of 0.01 nm. Equal IDS measurements are observed for various impurity emission lines of which carbon lines exhibit stronger intensities. Furthermore, the diagnostics is examined in an experiment where plasma experiences sudden disruption and quick recovery. In this case, the IDS measurements show {approx}130% increase in ion temperature. Flow measurements are shown to be consistent with plasma rotation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

A high etendue spectrometer suitable for core charge eXchange recombination spectroscopy on ITER

A feasibility study for the use of core charge exchange recombination spectroscopy on ITER has shown that accurate measurements on the helium ash require a spectrometer with a high etendue of 1mm{sup 2}sr to comply with the measurement requirements [S. Tugarinov et al., Rev. Sci. Instrum. 74, 2075 (2003)]. To this purpose such an instrument has been developed consisting of three separate wavelength channels (to measure simultaneously He/Be, C/Ne, and H/D/T together with the Doppler shifted direct emission of the diagnostic neutral beam, the beam emission (BES) signal), combining high dispersion (0.02 nm/pixel), sufficient resolution (0.2 nm), high efficiency (55%), and extended wavelength range (14 nm) at high etendue. The combined measurement of the BES along the same sightline within a third wavelength range provides the possibility for in situ calibration of the charge eXchange recombination spectroscopy signals. In addition, the option is included to use the same instrument for measurements of the fast fluctuations of the beam emission intensity up to 2 MHz, with the aim to study MHD activity.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Plasma process optimization for N-type doping applications

Plasma doping (PLAD) has been adopted across the implant technology space and into high volume production for both conventional DRAM and NAND doping applications. PLAD has established itself as an alternative to traditional ion implantation by beamline implantation. The push for high doping concentration, shallow doping depth, and conformal doping capability expand the need for a PLAD solution to meet such requirements. The unique doping profile and doping characteristics at high dose rates allow for PLAD to deliver a high throughput, differentiated solution to meet the demand of evolving transistor technology. In the PLAD process, ions are accelerated to the wafer as with a negative wafer bias applied to the wafer. Competing mechanisms, such as deposition, sputtering, and etching inherent in plasma doping require unique control and process optimization. In this work, we look at the distinctive process tool control and characterization features which enable an optimized doping process using n-type (PH{sub 3} or AsH{sub 3}) chemistries. The data in this paper will draw the relationship between process optimization through plasma chemistry study to the wafer level result.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Plasma chemistry study of PLAD processes

Plasma doping (PLAD) shows very different impurity profiles compared to the conventional beam-line-based ion implantations due to its non-mass separation property and plasma environment. There is no simulation for PLAD process so far due to a lack of a dopant profile model. Several factors determine impurity profiles of PLAD process. The most significant factors are: plasma chemistry and deposition/etching characteristics of multi-ion species plasmas. In this paper, we present plasma chemistry and deposition/etching characteristics of PLAD processes versus co-gas dilutions. Four dopant plasmas including B{sub 2}H{sub 6}, BF{sub 3}, AsH{sub 3}, and PH{sub 3}, and two non-dopant plasmas including CH{sub 4} and GeH{sub 4} are studied and demonstrated.

36 MATERIALS SCIENCE↗
DOE OSTI2012

The NOvA Experiment

The NOνA experiment aims to study the mixing behavior of neutrinos and will attempt to resolve the neutrino mass hierarchy. The experiment will rely on data collected at two detectors, one near Fermilab\'s NuMI (Neutrinos at the Main Injector) target and one 810 km north at Ash River, MN. The detectors are 14 mrad off the beam axis, which results in an almost monoenergetic beam of 2 GeV neutrinos. The construction of the far detector started early this year, the instrumentation will commence this fall, and we hope to take our first data in the beginning of next year. In this talk I will focus on the exciting possibilities of our detector in light of recent neutrino results and will discuss our plans to measure the neutrino mixing angle θ13 as well as to attempt to resolve the neutrino mass hierarchy and to understand the effects of the CP violating phase angle δ. I will also survey the rich physics program provided by our 14 kT fully active far detector, such as searches for magnetic monopoles and detection of supernovaneutrinos.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Accumulation of Pb and Cu heavy metals in sea water, sediment, and leaf and root tissue of Enhalus sp. in the seagrass bed of Banten Bay

Banten Bay in Indonesia is a coastal area which has been highly affected by human activity. Previous studies have reported the presence of lead (Pb) and copper (Cu) heavy metals in the seawater of this area. This study was conducted to measure the accumulation of Pb and Cu in seawater, sediment, leaf tissue, and root tissue of the seagrass species Enhalus sp. Sampling was conducted at two observation stations in Banten Bay: Station 1 (St.1) was located closer to the coastline and to industrial plants as source of pollution, while Station 2 (St.2) was located farther away offshore. At each station, three sampling points were established by random sampling. Field sampling was conducted at two different dates, i.e., on 29 May 2012 and 30 June 2012. Samples were processed by wet ashing using concentrated HNO{sub 3} acid and measured using Atomic Absorption Spectrometry (AAS). Accumulation of Pb was only detected in sediment samples in St.1, while Cu was detected in all samples. Average concentrations of Cu in May were as follows: sediment St.1 = 0.731 ppm, sediment St.2 = 0.383 ppm, seawater St.1 = 0.163 ppm, seawater St.2 = 0.174 ppm, leaf St.1 = 0.102 ppm, leaf St.2 = 0.132 ppm, root St.1= 0.139 ppm, and root St.2 = 0.075 ppm. Average measurements of Cu in June were: sediment St.1 = 0.260 ppm, leaf St.1 = 0.335 ppm, leaf St.2 = 0.301 ppm, root St.1= 0.047 ppm, and root St.2 = 0.060 ppm. In June, Cu was undetected in St.2 sediment and seawater at both stations. In May, Cu concentration in seawater exceeded the maximum allowable threshold for water as determined by the Ministry of the Environment. Spatial and temporal variation in Pb and Cu accumulation were most probably affected by distance from source and physical conditions of the environment (e.g., water current and mixing)

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Annealing effects on microstrain of cobalt oxide nanoparticles

Cobalt oxide nanoparticles in different phases have been synthesized using ash supported method. The effect of isochronal annealing on micro-strain of cobalt oxide nanoparticles has been studied. The lattice strain contribution to the x-ray diffraction line broadening in the nanoparticles was analyzed using Williamson Hall (W-H) plot. It is observed that micro-strain was released at higher annealing temperature.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Description of the prototype diagnostic residual gas analyzer for ITER

The diagnostic residual gas analyzer (DRGA) system to be used during ITER tokamak operation is being designed at Oak Ridge National Laboratory to measure fuel ratios (deuterium and tritium), fusion ash (helium), and impurities in the plasma. The eventual purpose of this instrument is for machine protection, basic control, and physics on ITER. Prototyping is ongoing to optimize the hardware setup and measurement capabilities. The DRGA prototype is comprised of a vacuum system and measurement technologies that will overlap to meet ITER measurement requirements. Three technologies included in this diagnostic are a quadrupole mass spectrometer, an ion trap mass spectrometer, and an optical penning gauge that are designed to document relative and absolute gas concentrations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Energy and frequency dependence of the alpha particle redistribution produced by internal kink modes

The redistribution of alpha particles due to internal kink modes is studied. The exact particle trajectories in the total fields, equilibrium plus perturbation, are calculated. The equilibrium has circular cross section and the plasma parameters are similar to those expected in ITER. The alpha particles are initially distributed according to a slowing down distribution function and have energies between 18 keV and 3.5 MeV. The (1, 1), (2, 2), and (2, 1) modes are included and the effect of changing their amplitude and frequency is studied. When only the (1, 1) mode is included, the spreading of high energy (E≳1 MeV) alpha particles increases slowly with the energy and mode frequency. At lower energies, the redistribution is more sensitive to the mode frequency and particle energy. When a (2, 1) mode is added, the spreading increases significantly and particles can reach the edge of the plasma. Trapped particles are the most affected and the redistribution parameter can have maxima above 1 MeV, depending on the mode frequency. These results can have important implications for ash removal.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Extending Helium Partial Pressure Measurement Technology to JET DTE2 and ITER

The detection limit for helium (He) partial pressure monitoring via the Penning discharge optical emission diagnostic, mainly used for tokamak divertor effluent gas analysis, is shown here to be possible for He concentrations down to 0.1% in predominantly deuterium effluents. This result from a dedicated laboratory study means that the technique can now be extended to intrinsically (non-injected) He produced as fusion reaction ash in deuterium-tritium experiments. The paper also examines threshold ionization mass spectroscopy as a potential backup to the optical technique, but finds that further development is needed to attain with plasma pulse-relevant response times. Both these studies are presented in the context of continuing development of plasma pulse-resolving, residual gas analysis for the upcoming JET deuterium-tritium campaign (DTE-2) and for ITER.

ITER↗
DOE OSTI2019

Evaluation of emission contributions from charge-exchange between the excited states of deuterium with He + during diagnostic of thermal helium gas beam injection and laser-induced fluorescence

Emission contributions from charge-exchange of excited deuterium ( n = 2, 3) with He + are evaluated in a1-D kinetic collisional radiative model in order to analyze their effects on the Thermal Helium Beam (THB) line-ratio diagnostic on ASDEX Upgrade and Laser Induced Fluorescence (LIF) He I density measurements in ITER. Recent charge-exchange calculations show that cross sections from excited deuterium ( n = 2, 3) with He + are over 4-orders of magnitude higher than those from the ground state ( n = 1) and occur at very low energies where they are more likely to interact with the thermal He + ions introduced by ionization of the diagnostic helium gas-puff injection. Higher densities of excited deuterium are typically present in the Scrape-Off Layer (SOL), divertor, and edge regions of tokamaks, where the LIF and THB helium diagnostics are typically used for n HeI and simultaneous determination of electron temperatures and densities and where contributions from charge-exchange emission may offset these values if not taken into account. The analysis presented in this work shows that due to the higher density of deuterium in the ground rather than in excited states and the divergent behavior of deuterium and He + density profiles along the SOL and edge regions, the deuterium-He + charge-exchange contributions to the helium puff emission are 3-orders of magnitude lower than those from electron-impact excitation. Similar plasma conditions are expected in the ITER divertor, with the exception that in the area near the strike-points and targets, the electron temperature is not high enough to excite from the ground state but deuterium, electron, and He + densities are high enough to dominate the emission from charge-exchange and recombination. These findings strengthen the assumption made in the present line-ratio model that helium emission from gas-puff into plasma is mainly dominated by electron-excitation. It is also shown that, in general, charge-exchange helium emission is 2-orders of magnitude higher than the emission due to recombination. Finally, these findings suggest the importance of including charge-exchange processes as a source of neutrals in ionic fractional abundance calculations in plasmas and helium-ash transport modeling in fusion reactors.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Toward DMRG-tailored coupled cluster method in the 4c-relativistic domain

There are three essential problems in computational relativistic chemistry: Electrons moving at relativistic speeds, close lying states, and dynamical correlation. Currently available quantum-chemical methods are capable of solving systems with one or two of these issues. However, there is a significant class of molecules in which all the three effects are present. These are the heavier transition metal compounds, lanthanides, and actinides with open d or f shells. For such systems, sufficiently accurate numerical methods are not available, which hinders the application of theoretical chemistry in this field. In this paper, we combine two numerical methods in order to address this challenging class of molecules. These are the relativistic versions of coupled cluster methods and the density matrix renormalization group (DMRG) method. To the best of our knowledge, this is the first relativistic implementation of the coupled cluster method externally corrected by DMRG. The method brings a significant reduction of computational costs as we demonstrate on the system of TlH, AsH, and SbH.

Brandejs, Jan (ORCID:0000000221073095)↗
DOE OSTI2021

Alpha particle channeling in ITER

Alpha particle channeling, the attempt to extract energy from high-energy fusion alpha particles using a combination of high- and low-frequency waves introduced in the plasma with antennae, is studied using a guiding center code. We examine the effect of the combination of cooling caused by a cyclotron mode, particle diffusion due to Alfvén modes introduced for ash removal, the inclusion of microturbulent diffusion, and the slowing down of the alpha particles on electrons. Induced cooling is achieved with a cyclotron resonance, producing additional losses of particles above 3.5 MeV in an amount about equal to the prompt loss. The removal of the low-energy cooled particles by additional modes or by microturbulent diffusion is the hardest challenge for alpha channeling. The cooled alpha particles remain deep in the plasma center, so for this removal, the method used must be capable of providing transport from the plasma center to the edge without also causing losses of high-energy particles.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗