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At least 235 records · Page 13

Toward a high-fidelity tritium transport modeling for retention and permeation experiments

We report Tritium Migration Analysis Program version 8 (TMAP8), the latest version of TMAP, was developed within the framework of the Multiphysics Object-Oriented Simulation Environment (MOOSE). Created at Idaho National Laboratory (INL), MOOSE is an open-source, dimension-agnostic, fully coupled, and fully implicit multiphysics platform featuring massively parallel computation capabilities. Using TMAP8, tritium transport in a divertor monoblock was analyzed to elucidate the effects of pulsed operation (up to fifty 1,600 s plasma discharge and cool-down cycles) on the tritium in-vessel inventory source term and ex-vessel release term (i.e., tritium retention and permeation) for safety analysis. With its built-in Message Passing Interface capability, TMAP8 can, in under 2 h, simulate tritium transport in three different layered materials (i.e., tungsten, copper, and copper-chromium-zirconium alloy) in 2D geometry, using a single device/computer with 10 cores. The MOOSE-based TMAP8 code can leverage other MOOSE tools developed under the Nuclear Energy Advanced Modeling and Simulation program to perform tritium and thermal transport in complex geometries and multiphysics environments. And via its massively parallel computation, MOOSE will enable the fusion pilot plant designers to conduct high-fidelity multiphysics modeling for the design of the divertor and blanket systems as well as for the safety analysis.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Energetic electron transport in magnetic fields with island chains and stochastic regions

This paper investigates energetic electron transport in magnetized toroidal plasmas with magnetic fields characterized by island chains and regions of stochastic field lines produced by coil perturbations. We report on experiments performed in the DIII-D tokamak, which utilize electron cyclotron heating and current drive pulses to ‘tag’ electron populations within different locations across the discharge. The cross-field transport of these populations is then inferred from electron cyclotron emission measurements and gamma emission signals from scintillator detectors. Two types of energetic particles are distinguished and discussed: non-relativistic suprathermal electrons and relativistic runaway electrons. The magnetic field topology in each discharge is reconstructed with field-line tracing codes, which are also used to determine the location and scale of magnetic islands and stochastic regions. Comparison of simulations and experiments suggests that suprathermal transport is suppressed when the tagging is performed at a smaller radial location than the location of the $q = 1$ island chain and enhanced otherwise. Here q is the safety factor. We further demonstrate that increasing the width of the stochastic region within the edge plasma yields enhancement of the suprathermal electron transport.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Generalized impurity pinch in partially magnetized multi-ion plasma

In a two-ion-species plasma with disparate ion masses, heavy ions tend to concentrate in the low-temperature region of collisionally magnetized plasma and in the high-temperature region of collisionally unmagnetized plasma, respectively. Moreover, collisional magnetization can be determined as the ratio of the light ion gyrofrequency to the collision frequency of light and heavy ion species, and the behavior of this effect in the intermediate regime of partially magnetized plasma is predominantly dependent on this Hall parameter. Multi-ion cross-field transport has been described before in the collisionally magnetized plasma regime, and generalized pinch relations, which describe densities of ion species in equilibrium in that plasma, are found in the literature. Here, the role of collisional magnetization and Larmor magnetization in multi-ion collisional transport is clarified, and generalized pinch relations are extended to the partially magnetized regime in which the ion Hall parameter may be small, as long as electrons remain collisionally magnetized. Equilibrium ion density profiles have the same dependence on external forces and on each other regardless of collisional magnetization of ions. The expansion of the range of validity of multi-ion collisional transport models makes them applicable to a wider range of laboratory plasma conditions. In particular, ion density profiles evolve sufficiently fast for radial impurity transport to be observable around stagnation on MagLIF, leading to expulsion of heavy ion impurities from the hotspot as long as plasma becomes sufficiently collisionally magnetized during the implosion.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Reduced models for ETG transport in the tokamak pedestal

This paper reports on the development of reduced models for electron temperature gradient (ETG) driven transport in the pedestal. Model development is enabled by a set of 61 nonlinear gyrokinetic simulations with input parameters taken from pedestals in a broad range of experimental scenarios. The simulation data have been consolidated in a new database for gyrokinetic simulation data, the multiscale gyrokinetic database (MGKDB), facilitating the analysis. The modeling approach may be considered a generalization of the standard quasilinear mixing length procedure. The parameter η, the ratio of the density to temperature gradient scale length, emerges as the key parameter for formulating an effective saturation rule. With a single order-unity fitting coefficient, the model achieves an error of 15%. A similar model for ETG particle flux is also described. We also present simple algebraic expressions for the transport informed by an algorithm for symbolic regression.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Data Needs for Modeling Low-Temperature Non-Equilibrium Plasmas: The LXCat Project, History, Perspectives and a Tutorial

Technologies based on non-equilibrium, low-temperature plasmas are ubiquitous in today’s society. Plasma modeling plays an essential role in their understanding, development and optimization. An accurate description of electron and ion collisions with neutrals and their transport is required to correctly describe plasma properties as a function of external parameters. LXCat is an open-access, web-based platform for storing, exchanging and manipulating data needed for modeling the electron and ion components of non-equilibrium, low-temperature plasmas. The data types supported by LXCat are electron- and ion-scattering cross-sections with neutrals (total and differential), interaction potentials, oscillator strengths, and electron- and ion-swarm/transport parameters. Online tools allow users to identify and compare the data through plotting routines, and use the data to generate swarm parameters and reaction rates with the integrated electron Boltzmann solver. In this review, the historical evolution of the project and some perspectives on its future are discussed together with a tutorial review for using data from LXCat.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Recent achievements in module reliability research

After 10 years of extensive research on crystalline-silicon flat-plate photovoltaic modules, the emphasis of recent reliability research has shifted to the emerging first-generation thin-film amorphous-silicon modules. These modules share much in common with their crystalline precursors, but also include many materials and processes that demand the development of reliability technologies. Key research thrusts include light-induced effects, cell corrosion, thermal diffusion, hot-spot heating, and electrical isolation of the cells from the module exterior. Research goals and recent achievements are described in each of these areas.

Ross, R. G., Jr.↗

NASA/DoD Aerospace Knowledge Diffusion Research Project. Paper 29: The US government technical report and the transfer of federally funded aerospace R and D

This article discusses the U.S. government technical report and the transfer of federally funded aerospace research and development in a conceptual framework of the federal government as a producer of scientific and technical information. The article summarizes current literature and research and discusses U.S. government technical report use and the importance of using data obtained from the NASA/DoD Aerospace Knowledge Diffusion Research Project. The authors make a case for changing existing U.S. technology policy and present a research agenda for the U.S. government technical report.

Pinelli, Thomas E.↗

The U.S. government technical report and the transfer of federally funded aerospace R & D

This article discusses the U.S. government technical report and the transfer of federally funded aerospace research and development in a conceptual framework of the federal government as a producer of scientific and technical information. The article summarizes current literature and research and discusses U.S. government technical report use and the importance of using data obtained from the NASA/DoD Aerospace Knowledge Diffusion Research Project. The authors make a case for changing existing U.S. technology policy and present a research agenda for the U.S. government technical report.

Pinelli, Thomas E.↗

NASA/DOD Aerospace Knowledge Diffusion Research Project. Use of Communications Sources: An Intercultural Investigation of Practices in the US and Russia

The purpose of this paper is to investigate the impact of U.S./Russian cultural differences in communications among scientists and engineers in applied technology industries. This is important because the advent of perestroika, the breakup of the Soviet Union, and massive moves toward privatization make Russia a potential partner in economic endeavors and, at the same time, a possible competitor in the international arena. Unfortunately the results of U.S./Soviet collaborative endeavors have not always met with expectations. Since 1987, when the former USSR adopted a law on joint ventures, evidence has emerged as to the causes of many failures of these cooperative arrangements. While international strategic alliances face many structural barriers, failures of these cooperative ventures have often resulted from a lack of understanding of the more intangible barrier of major differences in cultural environments between the partners (Cattaneo, 1992). Cultural differences not only affect business operations but also raise questions for scholars and practitioners who have advocated that U.S. management theories apply abroad. Boyacigiller and Adler (1991), Doktor, Tung, and Von Glinow (1991), and Hofstede (1993) observed that most U.S. scholars have continued to export management concepts and practices abroad assuming the concepts were universally valid despite the fact that Western organizational theory has placed little emphasis on factors such as history, social setting, culture, and government (Boyacigiller & Adler, 1991). High technology industries such as aerospace, which includes the cormmercial aviation segment, have characteristics that make the industry an excellent platform to study cultural implications for technical communications. The investigation of this group is worthwhile for several reasons. First, high technology industries are becoming more international and more engaged in collaborative endeavors. Second, the industries are highly dependent on effective innovation diffusion which, according to Fischer (1979), is essentially information exchange. And, third, studies of innovative project management have found that information availability was a critical factor in project success or failure (e.g., Link & Zmud, 1987; Tushman, 1978, 1979). We propose that a gap in the literature exists that centers on whether U.S. paradigms of commnunications behavior apply to other cultures. First, we will explore early findings in the U.S. that held that the choice of an information source was a function of the 'law of least effort' rather than quality (e.g., Allen, 1977; Cuinan, 1983; DeWhirst, 1971; Hardy, 1982; O'Reilly, 1982; Rosenberg, 1967). Second, we will explore the contingency approaches such as that of Tushman (1979) and the later work of Daft and Lengel (1984, 1987), Huber and Daft (1987) and Lengel and Daft (1988) who held that information choice was a function of the nature of the task at hand. A third issue to be addressed is the confounding problem of presumed differences between scientists and engineers in information gathering behavior (Allen, 1977). Finally, we will investigate whether cultural differences cast doubt on the applicability of findings from U.S. situations to other cultures.

Pinelli, Thomas E.↗

Formed platelet combustor liner construction feasibility, phase A

Environments generated in high pressure liquid rocket engines impose severe requirements on regeneratively cooled combustor liners. Liners fabricated for use in high chamber pressures using conventional processes suffer from limitations that can impair operational cycle life and can adversely affect wall compatibility. Chamber liners fabricated using formed platelet technology provide an alternative to conventional regeneratively cooled liners (an alternative that has many attractive benefits). A formed platelet liner is made from a stacked assembly of platelets with channel features. The assembly is diffusion bonded into a flat panel and then three-dimensionally formed into a section of a chamber. Platelet technology permits the liner to have very precisely controlled and thin hot gas walls and therefore increased heat transfer efficiency. Further cooling efficiencies can be obtained through enhanced design flexibility. These advantages translate into increased cycle life and enhanced wall compatibility. The increased heat transfer efficiency can alternately be used to increase engine performance or turbopump life as a result of pressure drop reductions within the regeneratively cooled liner. Other benefits can be obtained by varying the materials of construction within the platelet liner to enhance material compatibility with operating environment or with adjoining components. Manufacturing cost savings are an additional benefit of a formed platelet liner. This is because of reduced touch labor and reduced schedule when compared to conventional methods of manufacture. The formed platelet technology is not only compatible with current state-of-the art combustion chamber structural support and manifolding schemes, it is also an enabling technology that allows the use of other high performance and potentially low cost methods of construction for the entire combustion chamber assembly. The contract under which this report is submitted contains three phases: (1) phase A - feasibility study and technology development; (2) phase B - sub-scale fabrication feasibility; and (3) phase C - large scale fabrication validation. This report covers the Phase A activities, which began in December of 1988.

Hayes, W. A.↗

Use of GC/MS and Microtome Techniques as Methods to Evaluate ODC Free Cleaner Diffusion and Evaporation in Insulation and Phenolic Case Material

Because of the 1990 Clean Air Act Amendment (CAAA) many chlorinated solvents used in the aerospace industry are being phased out. Replacement of the ODC (ozone-depleting chemicals) with less volatile, non-ozone depleting cleaners has been extensively studied over the past seven years at Thiokol Propulsion, a Division of Cordant Technologies, Inc. The down selection of ODC replacement cleaners has been based on several factors including the diffusion evaporation of the cleaners in selected substrates. Methodologies were developed to evaluate the cleaner content in substrates. Methods of cutting thin slices of material (microtoming) were combined with GC/MS (gas chromatography/mass spectroscopy) analysis. Substrates evaluated in this study include potential solid rocket motor materials: ASNBR (asbestos-filled nitrile butadiene rubber) and CFEPDM (carbon-filled ethylene propylene dimonomer) insulation and glass (GCP), carbon (CCP) and silica (SCP) cloth phenolic substrates with fibers either parallel (0 deg) or perpendicular (90 deg) to the surface. Residue profiles indicate both cleaner and substrate composition affect the diffusion and subsequent evaporation of the cleaner from the substrate surface.

Biegert, L. L.↗

The ePix10k 2-megapixel hard X-ray detector at LCLS

The ePix10ka2M (ePix10k) is a new large area detector specifically developed for X-ray free-electron laser (XFEL) applications. The hybrid pixel detector was developed at SLAC to provide a hard X-ray area detector with a high dynamic range, running at the 120 Hz repetition rate of the Linac Coherent Light Source (LCLS). The ePix10k consists of 16 modules, each with 352 × 384 pixels of 100 µm × 100 µm distributed on four ASICs, resulting in a 2.16 megapixel detector, with a 16.5 cm × 16.5 cm active area and ∼80% coverage. The high dynamic range is achieved with three distinct gain settings (low, medium, high) as well as two auto-ranging modes (high-to-low and medium-to-low). Here the three fixed gain modes are evaluated. The resulting dynamic range (from single photon counting to 10000 photons pixel −1 pulse −1 at 8 keV) makes it suitable for a large number of different XFEL experiments. The ePix10k replaces the large CSPAD in operation since 2011. The dimensions of the two detectors are similar, making the upgrade from CSPAD to ePix10k straightforward for most setups, with the ePix10k improving on experimental performance. The SLAC-developed ePix cameras all utilize a similar platform, are tailored to target different experimental conditions and are designed to provide an upgrade path for future high-repetition-rate XFELs. Here the first measurements on this new ePix10k detector are presented and the performance under typical XFEL conditions evaluated during an LCLS X-ray diffuse scattering experiment measuring the 9.5 keV X-ray photons scattered from a thin liquid jet.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Application of Molecular Adsorber Coatings in Chamber A for the James Webb Space Telescope

As a coating made of highly porous zeolite materials, the Molecular Adsorber Coating (MAC) was developed to capture outgassed molecular contaminants, such as hydrocarbons and silicones. For spaceflight applications, the adsorptive capabilities of the coating can alleviate on-orbit outgassing concerns on or near sensitive surfaces and instruments within the spacecraft. Similarly, this sprayable paint technology has proven to be significantly beneficial for ground-based space applications, in particular, for vacuum chamber environments. This presentation describes the application of the MAC technology for the James Webb Space Telescope (JWST) at NASA Johnson Space Center (JSC). The coating was used as a mitigation tool to entrap outgassed contaminants, specifically silicone-based diffusion pump oil, from within JSCs cryogenic optical vacuum chamber test facility called Chamber A. This presentation summarizes the background, fabrication, installation, chemical analysis test results, and future plans for the MAC technology, which was effectively used to protect the JWST test equipment from vacuum chamber contamination. As a coating made of highly porous zeolite materials, the Molecular Adsorber Coating (MAC) was developed to capture outgassed molecular contaminants, such as hydrocarbons and silicones. For spaceflight applications, the adsorptive capabilities of the coating can alleviate on-orbit outgassing concerns on or near sensitive surfaces and instruments within the spacecraft. Similarly, this sprayable paint technology has proven to be significantly beneficial for ground-based space applications, in particular, for vacuum chamber environments. This presentation describes the application of the MAC technology for the James Webb Space Telescope (JWST) at NASA Johnson Space Center (JSC). The coating was used as a mitigation tool to entrap outgassed contaminants, specifically silicone-based diffusion pump oil, from within JSCs cryogenic optical vacuum chamber test facility called Chamber A. This presentation summarizes the background, fabrication, installation, chemical analysis test results, and future plans for the MAC technology, which was effectively used to protect the JWST test equipment from vacuum chamber contamination.

molecular contamination↗

Fast and Universal Kohn-Sham Density Functional Theory Algorithm for Warm Dense Matter to Hot Dense Plasma

Understanding many processes, e.g., fusion experiments, planetary interiors, and dwarf stars, depends strongly on microscopic physics modeling of warm dense matter and hot dense plasma. This complex state of matter consists of a transient mixture of degenerate and nearly free electrons, molecules, and ions. This regime challenges both experiment and analytical modeling, necessitating predictive ab initio atomistic computation, typically based on quantum mechanical Kohn-Sham density functional theory (KS-DFT). However, cubic computational scaling with temperature and system size prohibits the use of DFT through much of the warm dense matter regime. A recently developed stochastic approach to KS-DFT can be used at high temperatures, with the exact same accuracy as the deterministic approach, but the stochastic error can converge slowly and it remains expensive for intermediate temperatures (< 50 eV). Here we have developed a universal mixed stochastic-deterministic algorithm for DFT at any temperature. This approach leverages the physics of KS-DFT to seamlessly integrate the best aspects of these different approaches. We demonstrate that this method significantly accelerated self-consistent field calculations for temperatures from 3 to 50 eV, while producing stable molecular dynamics and accurate diffusion coefficients.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Wireless infrared communications for space and terrestrial applications

Voice and data communications via wireless (and fiberless) optical means has been commonplace for many years. However, continuous advances in optoelectronics and microelectronics have resulted in significant advances in wireless optical communications over the last decade. Wilton has specialized in diffuse infrared voice and data communications since 1979. In 1986, NASA Johnson Space Center invited Wilton to apply its wireless telecommunications and factory floor technology to astronaut voice communications aboard the shuttle. In September, 1988 a special infrared voice communications system flew aboard a 'Discovery' Shuttle mission as a flight experiment. Since then the technology has been further developed, resulting in a general purpose of 2Mbs wireless voice/data LAN which has been tested for a variety of applications including use aboard Spacelab. Funds for Wilton's wireless IR development were provided in part by NASA's Technology Utilization Office and by the NASA Small Business Innovative Research Program. As a consequence, Wilton's commercial product capability has been significantly enhanced to include diffuse infrared wireless LAN's as well as wireless infrared telecommunication systems for voice and data.

Crimmins, James W.↗

Jet Noise Suppression

The objectives of this chapter are to review and summarize the jet noise suppression technology, to provide a physical and theoretical model to explain the measured jet noise suppression characteristics of different concepts, and to provide a set of guidelines for evolving jet noise suppression designs. The underlying principle for all jet noise suppression devices is to enhance rapid mixing (i.e., diffusion) of the jet plume by geometric and aerothermodynamic means. In the case of supersonic jets, the shock-cell broadband noise reduction is effectively accomplished by the elimination or mitigation of the shock-cell structure. So far, the diffusion concepts have predominantly concentrated on jet momentum and energy (kinetic and thermal) diffusion, in that order, and have yielded better noise reduction than the simple conical nozzles. A critical technology issue that needs resolution is the effect of flight on the noise suppression potential of mechanical suppressor nozzles. A more thorough investigation of this mechanism is necessary for the successful development and design of an acceptable noise suppression device for future high-speed civil transports.

Gliebe, P. R.↗

Measuring Electron Diffusion and Constraining the Neutral Current $\pi^0$ Background for Single-Photon Events in MicroBooNE

Liquid Argon Time Projection Chambers (LArTPCs) are a rising technology in the field of experimental neutrino physics. LArTPCs use ionization electrons and scintillation light to reconstruct neutrino interactions with exceptional calorimetric and position resolution capabilities. Here, I present two analyses conducted in the MicroBooNE LArTPC at Fermilab: a measurement of the longitudinal electron diffusion coefficient, $D_L$, in the MicroBooNE detector and a constraint of the systematic uncertainty on MicroBooNE's single-photon analysis due to the dominant neutral current (NC) \piz{} background. Longitudinal electron diffusion modifies the spatial and timing resolution of the detector, and measuring it will help correct for these effects. Furthermore, current measurements of $D_L$ in liquid argon are sparse and in tension with one another, making the MicroBooNE measurement especially valuable. We report a measurement of $3.74^{+0.28}_{-0.29}$ cm$^2$/s. MicroBooNE is searchin g for si ngle-photon events as a potential explanation for the MiniBooNE low-energy excess (LEE) of electron neutrino-like events, which has been interpreted as evidence for low-mass sterile neutrinos. However, this search is overwhelmed by a large NC \piz{} background. By performing a sideband selection of NC \piz{} events, we apply a data-driven rate constraint to the single-photon analysis to reduce the systematic uncertainties. At present, this constraint improves the single-photon analysis' median sensitivity to the LEE-like signal from 0.9$\sigma$ to $1.5\sigma$. This sensitivity is expected to improve significantly as more data become available. Both of these measurements will not only benefit MicroBooNE, but also inform future LArTPC experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Ultrasonic Thermometer Sticking Mitigation Assessment

Ultrasonic thermometers have potential to improve on current technologies for very high temperature measurements. One issue limiting their adoption is the formation of diffusion bonds between the acoustic waveguide used as the sensor, and its surroundings (in some cases, a protective sheath). Several potential methods for reducing this diffusion bonding (known as sticking) have been identified. Prototype ultrasonic thermometers were fabricated and tested to high temperatures in order to evaluate these methods. Several showed promise for low temperature use. The most promising option was 3-D printed ceramic spacers.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗