2-pi Photoproduction from CLAS and CB-ELSA - The Search for Missing Resonances (open access)

2-pi Photoproduction from CLAS and CB-ELSA - The Search for Missing Resonances

2-pi-photoproduction is one of the promising reactions to search for baryon resonances that have been predicted but have not yet been observed. The gamma-rho --> rho-pi{sup 0}-pi{sup 0}(CB-ELSA) and the gamma-rho --> rho-pi{sup +}-pi{sup -} (CLAS) data show interesting resonance structures. A partial wave analysis (PWA) has to be done to determine which baryon resonances contribute what their quantum numbers and their relative couplings to the different accessible rho-2-pi-channels and to the photon are. First preliminary PWA-results on the lowest energy rho-pi{sup 0}-pi{sup 0} data (sq rt s<1.8 GeV)look very promising. From an extension of this analysis to higher energies combining the rho-pi{sup 0}-pi{sup 0} and the rho-pi{sup +}-pi{sup -}-data, one can expect; interesting results on resonances decaying into Delta-pi, N-rho, N(pi-pi)s, N*-pi, and Delta*-pi.
Date: October 1, 2003
Creator: Thoma, Ulrike
System: The UNT Digital Library
3-D Thermal Evaluations for a Fueled Experiment in the Advanced Test Reactor (open access)

3-D Thermal Evaluations for a Fueled Experiment in the Advanced Test Reactor

The DOE Advanced Fuel Cycle Initiative and Generation IV reactor programs are developing new fuel types for use in the current Light Water Reactors and future advanced reactor concepts. The Advanced Gas Reactor program is planning to test fuel to be used in the Next Generation Nuclear Plant (NGNP) nuclear reactor. Preliminary information for assessing performance of the fuel will be obtained from irradiations performed in the Advanced Test Reactor large “B” experimental facility. A test configurations has been identified for demonstrating fuel types typical of gas cooled reactors or fast reactors that may play a role in closing the fuel cycle or increasing efficiency via high temperature operation Plans are to have 6 capsules, each containing 12 compacts, for the test configuration. Each capsule will have its own temperature control system. Passing a helium-neon gas through the void regions between the fuel compacts and the graphite carrier and between the graphite carrier and the capsule wall will control temperature. This design with three compacts per axial level was evaluated for thermal performance to ascertain the temperature distributions in the capsule and test specimens with heating rates that encompass the range of initial heat generation rates.
Date: October 1, 2004
Creator: Ambrosek, Richard; Chang, Gray & Utterbeck, Debra
System: The UNT Digital Library
14th Workshop on Crystalline Silicon Solar Cells& Modules: Materials and Processes; Summary of Discussion Sessions (open access)

14th Workshop on Crystalline Silicon Solar Cells& Modules: Materials and Processes; Summary of Discussion Sessions

The 14th Workshop discussion sessions addressed funding needs for Si research and for R&D to enhance U.S. PV manufacturing. The wrap-up session specifically addressed topics for the new university silicon program. The theme of the workshop, Crystalline Silicon Solar Cells: Leapfrogging the Barriers, was selected to reflect the astounding progress in Si PV technology during last three decades, despite a host of barriers and bottlenecks. A combination of oral, poster, and discussion sessions addressed recent advances in crystal growth technology, new cell structures and doping methods, silicon feedstock issues, hydrogen passivation and fire through metallization, and module issues/reliability. The following oral/discussion sessions were conducted: (1) Technology Update; (2) Defects and Impurities in Si/Discussion; (3) Rump Session; (4) Module Issues and Reliability/Discussion; (5) Silicon Feedstock/Discussion; (6) Novel Doping, Cells, and Hetero-Structure Designs/Discussion; (7) Metallization/Silicon Nitride Processing/Discussion; (8) Hydrogen Passivation/Discussion; (9) Characterization/Discussion; and (10) Wrap-Up. This year's workshop lasted three and a half days and, for the first time, included a session on Si modules. A rump session was held on the evening of August 8, which addressed efficiency expectations and challenges of c Si solar cells/modules. Richard King of DOE and Daren Dance of Wright Williams& Kelly (formerly of Sematech) spoke …
Date: October 1, 2004
Creator: Sopori, B.; Tan, T.; Sinton, R. & Swanson, D.
System: The UNT Digital Library
2nd International Conference on Pathways, Networks, and Systems: Theory and Experiments (open access)

2nd International Conference on Pathways, Networks, and Systems: Theory and Experiments

With the availability of whole genome sequences, research attention shifts from gene sequences and genome content to protein functions and systems biology. Genes comprise a major component of the ''parts list'' that is required for building and maintaining of living organisms. Genome DNA sequences reveal the genetic inventory for a rapidly increasing number of species. Defining and interpreting the instruction manual for protein functions, individually and collectively, is the emerging challenge. Defining protein functions is a complex problem because each gene typically encodes several distinct proteins. As a result, the protein inventory includes as many as 100,000 distinct proteins. Protein functions can vary with developmental stage, anatomical location, and environmental context. Like the problem of sequencing the human genome, the multidimensional nature of protein functions in time, space and context constitutes one of the ''big'' problems in biomedical research. Resolving this problem is key to revolutionizing health care where a deep understanding of complex biological systems will lead to more powerful and specific ways to treat, and perhaps, even prevent birth defects and adult diseases. The meeting addressed the above issues.
Date: October 1, 2004
Creator: Aegean Conferences
System: The UNT Digital Library
3D CFD Electrochemical and Heat Transfer Model of an Integrated-Planar Solid Oxide Electrolysis Cells (open access)

3D CFD Electrochemical and Heat Transfer Model of an Integrated-Planar Solid Oxide Electrolysis Cells

A three-dimensional computational fluid dynamics (CFD) electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in a new novel integrated planar porous-tube supported solid oxide electrolysis cell (SOEC). The model is of several integrated planar cells attached to a ceramic support tube. This design is being evaluated with modeling at the Idaho National Laboratory. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, Nernst potential, operating potential, activation over-potential, anode-side gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Mean per-cell area-specific-resistance (ASR) values decrease with increasing current density. Predicted mean outlet hydrogen and steam concentrations vary linearly with current density, as expected. Effects of variations in operating temperature, gas flow rate, cathode and anode exchange current density, and contact resistance from the base case are presented. Contour plots …
Date: October 1, 2008
Creator: Hawkes, Grant & O'Brien, James E.
System: The UNT Digital Library
3D CFD Model of a Tubular Porous-Metal Supported Solid Oxide Electrolysis Cell (open access)

3D CFD Model of a Tubular Porous-Metal Supported Solid Oxide Electrolysis Cell

Currently there is strong interest in the large-scale production of hydrogen as an energy carrier for the non-electrical market [1, 2, and 3]. High-temperature nuclear reactors have the potential for substantially increasing the efficiency of hydrogen production from water splitting, with no consumption of fossil fuels, no production of greenhouse gases, and no other forms of air pollution. A high-temperature advanced nuclear reactor coupled with a high-efficiency high-temperature electrolyzer could achieve a competitive thermal-to-hydrogen conversion efficiency of 45 to 55%. A research program is under way at the INL to simultaneously address the research and scale-up issues associated with the implementation of solid-oxide electrolysis cell technology for hydrogen production from steam. The future SOEC market includes the 1200MW GEN4 reactor which has projected 40-50% efficiency, 400 tones H2 production per day (at 5kg H2/car/300 mile day this corresponds to 80,000 cars/day). DOE is planning for 26GW of nuclear hydrogen production by 2025.
Date: October 1, 2007
Creator: Hawkes, G. L.; Hawkes, B. D.; Sohal, M. S.; Torgerson, P. T.; Armstrong, T. & Williams, M. C.
System: The UNT Digital Library
Above- and belowground competition from longleaf pine plantations limits performance of reintroduced herbaceous species. (open access)

Above- and belowground competition from longleaf pine plantations limits performance of reintroduced herbaceous species.

Although overstory trees limit the abundance and species richness of herbaceous vegetation in longleaf pine (Pinus palustris Mill.) plantations, the responsible mechanisms are poorly understood because of confounding among limiting factors. In fall 1998, research was initiated to determine the separate effects of above- and belowground competition and needlefall from overstory pines on understory plant performance. Three 13- to 15-yr-old plantations near Aiken, SC, were thinned to 0, 25, 50, or 100% of nonthinned basal area (19.5 m2 ha-1). Combinations of trenching (to eliminate root competition) and needlefall were applied to areas within each plot, and containerized seedlings of 14 perennial herbaceous species and longleaf pine were planted within each. Overstory crown closure ranged from 0 to 81%, and soil water and available nitrogen varied consistently with pine stocking, trenching, or their combination. Cover of planted species decreased an average of 16.5 and 14.1% as a result of above- and below-ground competition, respectively. Depending on species, needlefall effects were positive, negative, or negligible. Results indicate that understory restoration will be most successful when herbaceous species are established within canopy openings (0.1-0.2 ha) managed to minimize negative effects from above- and belowground competition and needlefall.
Date: October 1, 2003
Creator: Harrington, T. B.; Dagley, C. M. & Edwards., M. B.
System: The UNT Digital Library
Abstract: Air, Thermal and Water Management for PEM Fuel Cell Systems (open access)

Abstract: Air, Thermal and Water Management for PEM Fuel Cell Systems

PEM fuel cells are excellent candidates for transportation applications due to their high efficiencies. PEM fuel cell Balance of Plant (BOP) components, such as air, thermal, and water management sub-systems, can have a significant effect on the overall system performance, but have traditionally not been addressed in research and development efforts. Recognizing this, the U.S. Department of Energy and Honeywell International Inc. are funding an effort that emphasizes the integration and optimization of air, thermal and water management sub-systems. This effort is one of the major elements to assist the fuel cell system developers and original equipment manufacturers to achieve the goal of an affordable and efficient power system for transportation applications. Past work consisted of: (1) Analysis, design, and fabrication of a motor driven turbocompressor. (2) A systematic trade study to select the most promising water and thermal management systems from five different concepts (absorbent wheel humidifier, gas to gas membrane humidifier, porous metal foam humidifier, cathode recycle compressor, and water injection pump.) This presentation will discuss progress made in the research and development of air, water and thermal management sub-systems for PEM fuel cell systems in transportation applications. More specifically, the presentation will discuss: (1) Progress of the …
Date: October 1, 2008
Creator: Mirza, Mark K. Gee Zia
System: The UNT Digital Library
Accelerator Preparations for Muon Physics Experiments at Fermilab (open access)

Accelerator Preparations for Muon Physics Experiments at Fermilab

The use of existing Fermilab facilities to provide beams for two muon experiments - the Muon to Electron Conversion Experiment (Mu2e) and the New g-2 Experiment - is under consideration. Plans are being pursued to perform these experiments following the completion of the Tevatron Collider Run II, utilizing the beam lines and storage rings used today for antiproton accumulation without considerable reconfiguration. Operating scenarios being investigated and anticipated accelerator improvements or reconfigurations will be presented.
Date: October 1, 2009
Creator: Syphers, M.J.
System: The UNT Digital Library
Accelerator R&D toward Muon Collider and Neutrino Factory (open access)

Accelerator R&D toward Muon Collider and Neutrino Factory

Over the last decade there has been significant progress in developing the concepts and technologies needed to produce, capture, accelerate and collide high intensity beams of muons. At present, a high-luminosity multi-TeV muon collider presents a viable option for the next generation lepton-lepton collider, which is believed to be needed to fully explore high energy physics in the era following LHC discoveries. Such a collider can offer superb energy resolution, smaller size, and potentially cost and power consumption compared to multi-TeV e{sup +}e{sup -} linear colliders. This article briefly reviews the motivation, design and status of accelerator R&D for Muon Collider and Neutrino Factory.
Date: October 1, 2009
Creator: Shiltsev, Vladimir
System: The UNT Digital Library
ACCURACY OF CO2 SENSORS (open access)

ACCURACY OF CO2 SENSORS

Are the carbon dioxide (CO2) sensors in your demand controlled ventilation systems sufficiently accurate? The data from these sensors are used to automatically modulate minimum rates of outdoor air ventilation. The goal is to keep ventilation rates at or above design requirements while adjusting the ventilation rate with changes in occupancy in order to save energy. Studies of energy savings from demand controlled ventilation and of the relationship of indoor CO2 concentrations with health and work performance provide a strong rationale for use of indoor CO2 data to control minimum ventilation rates1-7. However, this strategy will only be effective if, in practice, the CO2 sensors have a reasonable accuracy. The objective of this study was; therefore, to determine if CO2 sensor performance, in practice, is generally acceptable or problematic. This article provides a summary of study methods and findings ? additional details are available in a paper in the proceedings of the ASHRAE IAQ?2007 Conference8.
Date: October 1, 2008
Creator: Fisk, William J.; Faulkner, David & Sullivan, Douglas P.
System: The UNT Digital Library
Acoustic Tests of Small Wind Turbines: Preprint (open access)

Acoustic Tests of Small Wind Turbines: Preprint

Eight small wind turbines ranging from 400 watts to 100 kW in rated power were tested for acoustic emissions at the U.S. Department of Energy's National Renewable Energy Laboratory. Rigorous test procedures based on international standards were followed for measurements and data analyses. Results are presented in the form of sound pressure level versus wind speed, where the sound was recorded downwind of the turbine at a distance equal to the hub height plus half the rotor diameter. When there was sufficient separation between wind turbine noise and background noise, the apparent sound power level was calculated. In several cases, this was not possible. The implications of this problem are discussed briefly. Some of the configurations tested were specifically developed to reduce the noise level of their predecessors. Test data for these machines demonstrate marked progress toward quieter turbines.
Date: October 1, 2003
Creator: Migliore, P.; van Dam, J. & Huskey, A.
System: The UNT Digital Library
Active Filter Hardware Design & Performance for the DIII-D Plasma Control System (open access)

Active Filter Hardware Design & Performance for the DIII-D Plasma Control System

OAK-B135 The digital plasma control system (PCS), currently in operation on the DIII-D tokamak, requires inputs from a large number of sensors. Due to the nature of the digitizers and the relative noisy environment from which these signals are derived, each of the 32 signals must be conditioned via an active filter. Two different types of filters, Chebyshev and Bessel with fixed frequencies: 100 Hz Bessel was used for filtering the motional Stark effect diagnostic data. 800 Hz Bessel was designed to filter plasma control data and 1200 Hz Chebyshev is used with closed loop control of choppers. The performance of the plasma control system is greatly influenced by how well the actual filter responses match the software model used in the control system algorithms. This paper addresses the various issues facing the designer in matching the electrical design with the theoretical.
Date: October 1, 2003
Creator: Sellers, D.; Ferron, J. R.; Walker, M. L. & Broesch, J. D.
System: The UNT Digital Library
ACTIVE MODE CALIBRATION OF THE COMBINED THERMAL EPITHERMAL NEUTRON (CTEN) SYSTEM (open access)

ACTIVE MODE CALIBRATION OF THE COMBINED THERMAL EPITHERMAL NEUTRON (CTEN) SYSTEM

None
Date: October 1, 2001
Creator: Veilleux, J. M.
System: The UNT Digital Library
Active Nuclear Material Detection and Imaging (open access)

Active Nuclear Material Detection and Imaging

An experimental evaluation has been conducted to assess the operational performance of a coded-aperture, thermal neutron imaging system and its detection and imaging capability for shielded nuclear material in pulsed photonuclear environments. This evaluation used an imaging system developed by Brookhaven National Laboratory. The active photonuclear environment was produced by an operationallyflexible, Idaho National Laboratory (INL) pulsed electron accelerator. The neutron environments were monitored using INL photonuclear neutron detectors. Results include experimental images, operational imaging system assessments and recommendations that would enhance nuclear material detection and imaging performance.
Date: October 1, 2005
Creator: Norman, Daren; Jones, James; KevinHaskell; Vanmier, Peter E. & Forman, Leon
System: The UNT Digital Library
The Activities of the International Criticality Safety Benchmark Evaluation Project (ICSBEP) (open access)

The Activities of the International Criticality Safety Benchmark Evaluation Project (ICSBEP)

The International Criticality Safety Benchmark Evaluation Project (ICSBEP) was initiated in 1992 by the United States Department of Energy. The ICSBEP became an official activity of the Organization for Economic Cooperation and Development (OECD) – Nuclear Energy Agency (NEA) in 1995. Representatives from the United States, United Kingdom, France, Japan, the Russian Federation, Hungary, Republic of Korea, Slovenia, Yugoslavia, Kazakhstan, Spain, and Israel are now participating. The purpose of the ICSBEP is to identify, evaluate, verify, and formally document a comprehensive and internationally peer-reviewed set of criticality safety benchmark data. The work of the ICSBEP is published as an OECD handbook entitled “International Handbook of Evaluated Criticality Safety Benchmark Experiments”. The 2001 Edition of the Handbook contains benchmark specifications for 2642 critical or subcritical configurations that are intended for use in validation efforts and for testing basic nuclear data.
Date: October 1, 2001
Creator: Briggs, Joseph Blair
System: The UNT Digital Library
Adaptive Projection Subspace Dimension for the Thick-Restart Lanczos Method (open access)

Adaptive Projection Subspace Dimension for the Thick-Restart Lanczos Method

The Thick-Restart Lanczos (TRLan) method is an effective method for solving large-scale Hermitian eigenvalue problems. However, its performance strongly depends on the dimension of the projection subspace. In this paper, we propose an objective function to quantify the effectiveness of a chosen subspace dimension, and then introduce an adaptive scheme to dynamically adjust the dimension at each restart. An open-source software package, nu-TRLan, which implements the TRLan method with this adaptive projection subspace dimension is available in the public domain. The numerical results of synthetic eigenvalue problems are presented to demonstrate that nu-TRLan achieves speedups of between 0.9 and 5.1 over the static method using a default subspace dimension. To demonstrate the effectiveness of nu-TRLan in a real application, we apply it to the electronic structure calculations of quantum dots. We show that nu-TRLan can achieve speedups of greater than 1.69 over the state-of-the-art eigensolver for this application, which is based on the Conjugate Gradient method with a powerful preconditioner.
Date: October 1, 2008
Creator: Yamazaki, Ichitaro; Bai, Zhaojun; Simon, Horst; Wang, Lin-Wang & Wu, K.
System: The UNT Digital Library
ADAPTIVE TETRAHEDRAL GRID REFINEMENT AND COARSENING IN MESSAGE-PASSING ENVIRONMENTS (open access)

ADAPTIVE TETRAHEDRAL GRID REFINEMENT AND COARSENING IN MESSAGE-PASSING ENVIRONMENTS

A grid refinement and coarsening scheme has been developed for tetrahedral and triangular grid-based calculations in message-passing environments. The element adaption scheme is based on an edge bisection of elements marked for refinement by an appropriate error indicator. Hash-table/linked-list data structures are used to store nodal and element formation. The grid along inter-processor boundaries is refined and coarsened consistently with the update of these data structures via MPI calls. The parallel adaption scheme has been applied to the solution of a transient, three-dimensional, nonlinear, groundwater flow problem. Timings indicate efficiency of the grid refinement process relative to the flow solver calculations.
Date: October 1, 2000
Creator: Hallberg, J. & Stagg, A.
System: The UNT Digital Library
Addressing Different Active Neutron Interrogation Signatures from Fissionable Material (open access)

Addressing Different Active Neutron Interrogation Signatures from Fissionable Material

In a continuing effort to examine portable methods for implementing active neutron interrogation for detecting shielded fissionable material research is underway to investigate the utility of analyzing multiple time-correlated signatures. Time correlation refers here to the existence of unique characteristics of the fission interrogation signature related to the start and end of an irradiation, as well as signatures present in between individual pulses of an irradiating source. Traditional measurement approaches in this area have typically worked to detect die-away neutrons after the end of each pulse, neutrons in between pulses related to the decay of neutron emitting fission products, or neutrons or gamma rays related to the decay of neutron emitting fission products after the end of an irradiation exposure. In this paper we discus the potential weaknesses of assessing only one signature versus multiple signatures and make the assertion that multiple complimentary and orthogonal measurements should be used to bolster the performance of active interrogation systems, helping to minimize susceptibility to the weaknesses of individual signatures on their own. Recognizing that the problem of detection is a problem of low count rates, we are exploring methods to integrate commonly used signatures with rarely used signatures to improve detection capabilities …
Date: October 1, 2009
Creator: Chichester, D. L. & Seabury, E. H.
System: The UNT Digital Library
Adiabatic Rotation, Quantum Search, and Preparation of Superposition States (open access)

Adiabatic Rotation, Quantum Search, and Preparation of Superposition States

This report describes about the alternative for straight line adiabatic evalution.
Date: October 1, 2007
Creator: Siu, M. Stewart
System: The UNT Digital Library
Advanced Test Reactor Capabilities and Future Irradiation Plans (open access)

Advanced Test Reactor Capabilities and Future Irradiation Plans

The Advanced Test Reactor (ATR), located at the Idaho National Laboratory (INL), is one of the most versatile operating research reactors in the Untied States. The ATR has a long history of supporting reactor fuel and material research for the US government and other test sponsors. The INL is owned by the US Department of Energy (DOE) and currently operated by Battelle Energy Alliance (BEA). The ATR is the third generation of test reactors built at the Test Reactor Area, now named the Reactor Technology Complex (RTC), whose mission is to study the effects of intense neutron and gamma radiation on reactor materials and fuels. The current experiments in the ATR are for a variety of customers--US DOE, foreign governments and private researchers, and commercial companies that need neutrons. The ATR has several unique features that enable the reactor to perform diverse simultaneous tests for multiple test sponsors. The ATR has been operating since 1967, and is expected to continue operating for several more decades. The remainder of this paper discusses the ATR design features, testing options, previous experiment programs, future plans for the ATR capabilities and experiments, and some introduction to the INL and DOE's expectations for nuclear research …
Date: October 1, 2006
Creator: Marshall, Frances M.
System: The UNT Digital Library
Advanced Test Reactor LEU Fuel Conversion Feasibility Study -- 2006 Annual Report (open access)

Advanced Test Reactor LEU Fuel Conversion Feasibility Study -- 2006 Annual Report

The Advanced Test Reactor (ATR) is a high power density and high neutron flux research reactor operating in the U.S. Powered with highly enriched uranium (HEU), the ATR has a maximum thermal power rating of 250 MWth with a maximum unperturbed thermal neutron flux rating of 1.0 x 1015 n/cm2–s. Because of these operating parameters, and the large test volumes located in high flux areas, the ATR is an ideal candidate for assessing the feasibility of converting an HEU driven reactor to a low-enriched core. The present work investigates the necessary modifications and evaluates the subsequent operating effects of this conversion. A detailed plate-by-plate MCNP ATR 1/8th core model was developed and validated for a fuel cycle burnup comparison analysis. Using the current HEU U-235 enrichment of 93.0 % as a baseline, an analysis can be performed to determine the low-enriched uranium (LEU) density and U 235 enrichment required in the fuel meat to yield an equivalent Keff between the HEU core and a LEU core versus effective full power days (EFPD). The MCNP ATR 1/8th core model will be used to optimize the U 235 loading in the LEU core, such that the differences in Keff and heat profile …
Date: October 1, 2006
Creator: Chang, G. S. & Ambrosek, R. G.
System: The UNT Digital Library
Advanced Tokamak Operation Using the DIII-D Plasma Control System (open access)

Advanced Tokamak Operation Using the DIII-D Plasma Control System

A271 ADVANCED TOKAMAK OPERATION USING THE DIII-D PLASMA CONTROL SYSTEM. The principal focus of experimental operations in the DIII-D tokamak is the advanced tokamak (AT) regime to achieve, which requires highly integrated and flexible plasma control. In a high performance advanced tokamak, accurate regulation of the plasma boundary, internal profiles, pumping, fueling, and heating must be well coordinated with MHD control action to stabilize such instabilities as tearing modes and resistive wall modes. Sophisticated monitors of the operational regime must provide detection of off-normal conditions and trigger appropriate safety responses with acceptable levels of reliability. Many of these capabilities are presently implemented in the DIII-D plasma control system (PCS), and are now in frequent or routine operational use. The present work describes recent development, implementation, and operational experience with AT regime control elements for equilibrium control, MHD suppression, and off-normal event detection and response.
Date: October 1, 2002
Creator: Humphreys, D. A.; Ferron, J. R.; Garofalo, A. M.; Hyatt, A. W.; Jernigan, T. C.; Johnson, R. D. et al.
System: The UNT Digital Library
Advances in Comprehensive Gyrokinetic Simulations of Transport in Tokamaks (open access)

Advances in Comprehensive Gyrokinetic Simulations of Transport in Tokamaks

A continuum global gyrokinetic code GYRO has been developed to comprehensively simulate core turbulent transport in actual experimental profiles and enable direct quantitative comparisons to the experimental transport flows. GYRO not only treats the now standard ion temperature gradient (ITG) mode turbulence, but also treats trapped and passing electrons with collisions and finite {beta}, equilibrium ExB shear stabilization, and all in real tokamak geometry. Most importantly the code operates at finite relative gyroradius ({rho}{sub *}) so as to treat the profile shear stabilization and nonlocal effects which can break gyroBohm scaling. The code operates in either a cyclic flux-tube limit (which allows only gyroBohm scaling) or globally with physical profile variation. Bohm scaling of DIII-D L-mode has been simulated with power flows matching experiment within error bars on the ion temperature gradient. Mechanisms for broken gyroBohm scaling, neoclassical ion flows embedded in turbulence, turbulent dynamos and profile corrugations, are illustrated.
Date: October 1, 2004
Creator: Waltz, R. E.; Candy, J.; Hinton, F. L.; Estrada-Mila, C. & Kinsey, J. E.
System: The UNT Digital Library