A Mathematical Analysis of Atomistic-to-Continuum (AtC) Multiscale Approaches (open access)

A Mathematical Analysis of Atomistic-to-Continuum (AtC) Multiscale Approaches

We development a general framework for information-passing and concurrent discrete to continuum scale bridging and applied it to biological, electro-mechanical and thermo-electrical systems. Funds were used for partial support of two post-doctoral research associates (Aiqin Li, Dawei Zhang) and three graduate students (Renge Li, Mohan Nuggehally, Joseph Riendeau).
Date: February 24, 2009
Creator: Fish, Jacob & Shephard, Mark
Object Type: Report
System: The UNT Digital Library
Next Generation Integrated Environment for Collaborative Work Across Internets (open access)

Next Generation Integrated Environment for Collaborative Work Across Internets

We are now well-advanced in our development, prototyping and deployment of a high performance next generation Integrated Environment for Collaborative Work. The system, aimed at using the capability of ESnet and Internet2 for rapid data exchange, is based on the Virtual Room Videoconferencing System (VRVS) developed by Caltech. The VRVS system has been chosen by the Internet2 Digital Video (I2-DV) Initiative as a preferred foundation for the development of advanced video, audio and multimedia collaborative applications by the Internet2 community. Today, the system supports high-end, broadcast-quality interactivity, while enabling a wide variety of clients (Mbone, H.323) to participate in the same conference by running different standard protocols in different contexts with different bandwidth connection limitations, has a fully Web-integrated user interface, developers and administrative APIs, a widely scalable video network topology based on both multicast domains and unicast tunnels, and demonstrated multiplatform support. This has led to its rapidly expanding production use for national and international scientific collaborations in more than 60 countries. We are also in the process of creating a 'testbed video network' and developing the necessary middleware to support a set of new and essential requirements for rapid data exchange, and a high level of interactivity in …
Date: February 24, 2009
Creator: Newman, Harvey B.
Object Type: Report
System: The UNT Digital Library
Characterizing the Properties of Clusters of Galaxies As a Function of Luminosity and Redshift (open access)

Characterizing the Properties of Clusters of Galaxies As a Function of Luminosity and Redshift

Abstract: We report the application of the new Monte Carlo method, Smoothed Particle Inference (SPI, described in a pair of companion papers), towards analysis and interpretation of X-ray observations of clusters of galaxies with the XMM-Newton satellite. Our sample consists of publicly available well-exposed observations of clusters at redshifts z > 0.069, totaling 101 objects. We determine the luminosity and temperature structure of the X-ray emitting gas, with the goal to quantify the scatter and the evolution of the L{sub X} - T relation, as well as to investigate the dependence on cluster substructure with redshift. This work is important for the establishment of the potential robustness of mass estimates from X-ray data which in turn is essential towards the use of clusters for measurements of cosmological parameters. We use the luminosity and temperature maps derived via the SPI technique to determine the presence of cooling cores, via measurements of luminosity and temperature contrast. The L{sub X}-T relation is investigated, and we confirm that L{sub X} {proportional_to} T{sup 3}. We find a weak redshift dependence ({proportional_to} (1 + z){sup {beta}{sub LT}}, {beta}{sub LT} = 0.50 {+-} 0.34), in contrast to some Chandra results. The level of dynamical activity is established …
Date: February 24, 2009
Creator: Andersson, K.; Peterson, J. R.; Madejski, G. & Goobar, A.
Object Type: Article
System: The UNT Digital Library
Polarimeters and Energy Spectrometers for the ILC Beam Delivery System (open access)

Polarimeters and Energy Spectrometers for the ILC Beam Delivery System

This article gives an overview of current plans and issues for polarimeters and energy spectrometers in the Beam Delivery System of the ILC. It is meant to serve as a useful reference for the Detector Letter of Intent documents currently being prepared. Concepts for high precision polarization and energy measurements exist. These concepts have resulted in detailed system layouts that are included in the RDR description for the Beam Delivery System. The RDR includes both upstream and downstream polarimeters and energy spectrometers for both beams. This provides needed complementarity and redundancy for achieving the precision required, with adequate control and demonstration of systematic errors. The BDS polarimeters and energy spectrometers need to be a joint effort of the ILC BDS team and the Detector collaborations, with collaboration members responsible for the performance and accuracy of the measurements. Details for this collaboration and assigning of responsibilities remain to be worked out. There is also a demonstrated need for Detector physicists to play an active role in the design and evaluation of accelerator components that impact beam polarization and beam energy capabilities, including the polarized source and spin rotator systems. A workshop was held in 2008 on ILC Polarization and Energy measurements, …
Date: February 24, 2009
Creator: Boogert, S.; Hildreth, M.; Kafer, D.; List, J.; Monig, K.; Moffeit, K. C. et al.
Object Type: Report
System: The UNT Digital Library
Electrical Signal Path Study and Component Assay for the MAJORANA N-Type Segmented Contact Detector (open access)

Electrical Signal Path Study and Component Assay for the MAJORANA N-Type Segmented Contact Detector

The purpose of the present electrical signal path study is to explore the various issues related to the deployment of highly-segmented low-background Ge detectors for the MAJORANA double-beta decay experiment. A significant challenge is to simultaneously satisfy competing requirements for the mechanical design, electrical readout performance, and radiopurity specifications from the MAJORANA project. Common to all rare search experiments, there is a very stringent limit on the acceptable radioactivity level of all the electronics components involved. Some of the findings are summarized in this report.
Date: February 24, 2009
Creator: Amman, Mark; Bergevin, Marc; Chan, Yuen-Dat; Detwiler, Jason A.; Fujikawa, Brian .; Lesko, Kevin T. et al.
Object Type: Report
System: The UNT Digital Library
First Step Towards a Non-Adiabatic Description of the Fission Process Based on the Generator Coordinate Method (open access)

First Step Towards a Non-Adiabatic Description of the Fission Process Based on the Generator Coordinate Method

Among the different theoretical approaches able to describe fission, microscopic ones can help us in the understanding of this process, as they have the advantage of describing the nuclear structure and the dynamics in a consistent manner. The sole input of the calculations is the nucleon-nucleon interaction. Such a microscopic time-dependent and quantum mechanical formalism has already been used, based on the Gaussian Overlap Approximation of the Generator Coordinate Method with the adiabatic approximation, to analyze the collective dynamics of low-energy fission in {sup 238}U. However, at higher energies, a few MeV above the barrier, the adiabatic approximation doesn't seem valid anymore. Indeed, manifestations of proton pair breaking have been observed in {sup 238}U and {sup 239}U for an excitation energy of 2.3 MeV above the barrier. Taking the intrinsic excitations into account during the fission process will enable us to determine the coupling between collective and intrinsic degrees of freedom, in particular from saddle to scission. Guidelines of the new formalism under development are presented and some preliminary results on overlaps between non excited and excited states are discussed.
Date: November 24, 2009
Creator: Bernard, R; Goutte, H; Gogny, D; Dubray, N & Lacroix, D
Object Type: Article
System: The UNT Digital Library
First Direct Observation of a Nearly Ideal Graphene Band Structure (open access)

First Direct Observation of a Nearly Ideal Graphene Band Structure

None
Date: November 24, 2009
Creator: Sprinkle, M; Siegel, D; Hu, Y; Hicks, J; Tejeda, A; Taleb-Ibrahimi, A et al.
Object Type: Article
System: The UNT Digital Library
The REBUS-MCNP Linkage. (open access)

The REBUS-MCNP Linkage.

The Reduced Enrichment Research and Test Reactor (RERTR) Program uses the REBUS-PC computer code to provide reactor physics and core design information such as neutron flux distributions in space, energy, and time, and to track isotopic changes in fuel and neutron absorbers with burnup. REBUS-PC models the complete fuel cycle including shuffling capability. REBUS-PC evolved using the neutronic capabilities of multi-group diffusion theory code DIF3D 9.0, but was extended to apply the continuous energy Monte Carlo code MCNP for one-group fluxes and cross-sections. The linkage between REBUS-PC and MCNP has recently been modernized and extended, as described in this manual. REBUS-PC now calls MCNP via a system call so that the user can apply any valid MCNP executable. The interface between REBUS-PC and MCNP requires minimal changes to an existing MCNP model, and little additional input. The REBUS-MCNP interface can also be used in conjunction with DIF3D neutronics to update an MCNP model with fuel compositions predicted using a DIF3D based depletion.
Date: April 24, 2009
Creator: Stevens, J. G.
Object Type: Report
System: The UNT Digital Library
LIFETIME PREDICTION FOR MODEL 9975 O-RINGS IN KAMS (open access)

LIFETIME PREDICTION FOR MODEL 9975 O-RINGS IN KAMS

The Savannah River Site (SRS) is currently storing plutonium materials in the K-Area Materials Storage (KAMS) facility. The materials are packaged per the DOE 3013 Standard and transported and stored in KAMS in Model 9975 shipping packages, which include double containment vessels sealed with dual O-rings made of Parker Seals compound V0835-75 (based on Viton{reg_sign} GLT). The outer O-ring of each containment vessel is credited for leaktight containment per ANSI N14.5. O-ring service life depends on many factors, including the failure criterion, environmental conditions, overall design, fabrication quality and assembly practices. A preliminary life prediction model has been developed for the V0835-75 O-rings in KAMS. The conservative model is based primarily on long-term compression stress relaxation (CSR) experiments and Arrhenius accelerated-aging methodology. For model development purposes, seal lifetime is defined as a 90% loss of measurable sealing force. Thus far, CSR experiments have only reached this target level of degradation at temperatures {ge} 300 F. At lower temperatures, relaxation values are more tolerable. Using time-temperature superposition principles, the conservative model predicts a service life of approximately 20-25 years at a constant seal temperature of 175 F. This represents a maximum payload package at a constant ambient temperature of 104 F, …
Date: November 24, 2009
Creator: Hoffman, E. & Skidmore, E.
Object Type: Report
System: The UNT Digital Library
Selection and Traceability of Parameters To Support Hanford-Specific RESRAD Analyses -- Fiscal Year 2008 Status Report (open access)

Selection and Traceability of Parameters To Support Hanford-Specific RESRAD Analyses -- Fiscal Year 2008 Status Report

In fiscal years 2007 and 2008, the Hanford Site Groundwater Remediation Project, formerly managed by Fluor Hanford, Inc., requested the Pacific Northwest National Laboratory (PNNL) to support the development and initial implementation of a strategy to establish and maintain, under configuration control, a set of Hanford-specific flow and transport parameter estimates that can be used to support Hanford Site assessments. This document provides a summary of those efforts, culminating in a set of best-estimate Hanford-specific parameters for use in place of the default parameters used in the RESRAD code. The RESRAD code is a computer model designed to estimate radiation doses and risks from RESidual RADioactive materials. The long-term goals of the PNNL work are to improve the consistency, defensibility, and traceability of parameters and their ranges of variability, and to ensure a sound basis for assigning parameters for flow and transport models in the code. The strategy was to start by identifying the existing parameter data sets most recently used in site assessments, documenting these parameter data sets and the raw data sets on which they were based, and using the existing parameter sets to define best-estimate parameters for use in the RESRAD code. The Hanford-specific assessment parameters compiled …
Date: July 24, 2009
Creator: Last, George V.; Rockhold, Mark L.; Murray, Christopher J. & Cantrell, Kirk J.
Object Type: Report
System: The UNT Digital Library
September 2008 monitoring results for Centralia, Kansas. (open access)

September 2008 monitoring results for Centralia, Kansas.

In September 2005, periodic sampling of groundwater was initiated by the Commodity Credit Corporation of the U.S. Department of Agriculture (CCC/USDA) in the vicinity of a grain storage facility formerly operated by the CCC/USDA at Centralia, Kansas. The sampling at Centralia is being performed on behalf of the CCC/USDA by Argonne National Laboratory, in accord with a monitoring program approved by the Kansas Department of Health and Environment (KDHE). The objective is to monitor levels of carbon tetrachloride contamination identified in the groundwater at Centralia (Argonne 2003, 2004, 2005a). Under a KDHE-approved monitoring plan (Argonne 2005b), the groundwater was sampled twice yearly (for a recommended period of two years) for analyses for volatile organic compounds (VOCs), as well as measurement of selected geochemical parameters to aid in the evaluation of possible natural contaminant degradation (reductive dechlorination) processes in the subsurface environment. The sampling in September 2007 represented the fifth and final monitoring event performed under the two-year twice yearly monitoring program (Argonne 2006a,b, 2007a, 2008a). The results from the two-year monitoring program demonstrated the presence of carbon tetrachloride contamination at levels exceeding the KDHE Tier 2 Risk-Based Screening Level of 5 {micro}g/L for this compound in a broad groundwater plume …
Date: February 24, 2009
Creator: LaFreniere, L. M.
Object Type: Report
System: The UNT Digital Library
STEAM REFORMING TECHNOLOGY DEMONSTRATION FOR THE DESTRUCTION OF ORGANICS ON ACTUAL DOE SAVANNAH RIVER SITE TANK 48H WASTE 9138 (open access)

STEAM REFORMING TECHNOLOGY DEMONSTRATION FOR THE DESTRUCTION OF ORGANICS ON ACTUAL DOE SAVANNAH RIVER SITE TANK 48H WASTE 9138

This paper describes the design of the Bench-scale Steam Reformer (BSR); a processing unit for demonstrating steam reforming technology on actual radioactive waste [1]. It describes the operating conditions of the unit used for processing a sample of Savannah River Site (SRS) Tank 48H waste. Finally, it compares the results from processing the actual waste in the BSR to processing simulant waste in the BSR to processing simulant waste in a large pilot scale unit, the Fluidized Bed Steam Reformer (FBSR), operated at Hazen Research Inc. in Golden, CO. The purpose of this work was to prove that the actual waste reacted in the same manner as the simulant waste in order to validate the work performed in the pilot scale unit which could only use simulant waste.
Date: February 24, 2009
Creator: Burket, P
Object Type: Article
System: The UNT Digital Library
Wind-To-Hydrogen Energy Pilot Project (open access)

Wind-To-Hydrogen Energy Pilot Project

WIND-TO-HYDROGEN ENERGY PILOT PROJECT: BASIN ELECTRIC POWER COOPERATIVE In an effort to address the hurdles of wind-generated electricity (specifically wind's intermittency and transmission capacity limitations) and support development of electrolysis technology, Basin Electric Power Cooperative (BEPC) conducted a research project involving a wind-to-hydrogen system. Through this effort, BEPC, with the support of the Energy & Environmental Research Center at the University of North Dakota, evaluated the feasibility of dynamically scheduling wind energy to power an electrolysis-based hydrogen production system. The goal of this project was to research the application of hydrogen production from wind energy, allowing for continued wind energy development in remote wind-rich areas and mitigating the necessity for electrical transmission expansion. Prior to expending significant funding on equipment and site development, a feasibility study was performed. The primary objective of the feasibility study was to provide BEPC and The U.S. Department of Energy (DOE) with sufficient information to make a determination whether or not to proceed with Phase II of the project, which was equipment procurement, installation, and operation. Four modes of operation were considered in the feasibility report to evaluate technical and economic merits. Mode 1 - scaled wind, Mode 2 - scaled wind with off-peak, Mode …
Date: April 24, 2009
Creator: Rebenitsch, Ron; Bush, Randall; Boushee, Allen; Stevens, Brad G.; Williams, Kirk D.; Woeste, Jeremy et al.
Object Type: Report
System: The UNT Digital Library
Conveyorized Photoresist Stripping Replacement for Flex Circuit Fabrication (open access)

Conveyorized Photoresist Stripping Replacement for Flex Circuit Fabrication

A replacement conveyorized photoresist stripping system was characterized to replace the ASI photoresist stripping system. This system uses the qualified ADF-25c chemistry for the fabrication of flex circuits, while the ASI uses the qualified potassium hydroxide chemistry. The stripping process removes photoresist, which is used to protect the copper traces being formed during the etch process.
Date: February 24, 2009
Creator: Donahue, Megan
Object Type: Report
System: The UNT Digital Library
Analysis of systematic errors in lateral shearing interferometry for EUV optical testing (open access)

Analysis of systematic errors in lateral shearing interferometry for EUV optical testing

Lateral shearing interferometry (LSI) provides a simple means for characterizing the aberrations in optical systems at EUV wavelengths. In LSI, the test wavefront is incident on a low-frequency grating which causes the resulting diffracted orders to interfere on the CCD. Due to its simple experimental setup and high photon efficiency, LSI is an attractive alternative to point diffraction interferometry and other methods that require spatially filtering the wavefront through small pinholes which notoriously suffer from low contrast fringes and improper alignment. In order to demonstrate that LSI can be accurate and robust enough to meet industry standards, analytic models are presented to study the effects of unwanted grating and detector tilt on the system aberrations, and a method for identifying and correcting for these errors in alignment is proposed. The models are subsequently verified by numerical simulation. Finally, an analysis is performed of how errors in the identification and correction of grating and detector misalignment propagate to errors in fringe analysis.
Date: February 24, 2009
Creator: Miyakawa, Ryan; Naulleau, Patrick & Goldberg, Kenneth A.
Object Type: Article
System: The UNT Digital Library
West Valley Demonstration Project Annual Site Environmental Report Calendar Year 2008 (open access)

West Valley Demonstration Project Annual Site Environmental Report Calendar Year 2008

Annual Site Environmental Report for the West Valley Demonstration Project (WVDP) for Calendar Year 2008. The report summarizes the calendar year (CY) 2008 environmental monitoring program data at the WVDP so as to describe the performance of the WVDP’s environmental management system (EMS), confirm compliance with standards and regulations, and highlight important programs. Monitoring and surveillance of the facilities used by the DOE are conducted to verify protection of the environment, continual improvement, prevention and/or minimization of pollution, public outreach, and stakeholder involvement. In addition to demonstrating compliance with environmental regulations and directives, evaluation of data collected in 2008 continued to indicate that WVDP activities pose no threat to public health or safety, or to the environment.
Date: September 24, 2009
Creator: Division, West Valley Environmental Services LLC (WVES) and URS - Washington
Object Type: Report
System: The UNT Digital Library
Environmental Management System Plan (open access)

Environmental Management System Plan

Executive Order 13423, Strengthening Federal Environmental, Energy, and Transportation Management establishes the policy that Federal agencies conduct their environmental, transportation, and energy-related activities in a manner that is environmentally, economically and fiscally sound, integrated, continually improving, efficient, and sustainable. The Department of Energy (DOE) has approved DOE Order 450.1A, Environmental Protection Program and DOE Order 430.2B, Departmental Energy, Renewable Energy and Transportation Management as the means of achieving the provisions of this Executive Order. DOE Order 450.1A mandates the development of Environmental Management Systems (EMS) to implement sustainable environmental stewardship practices that: (1) Protect the air, water, land, and other natural and cultural resources potentially impacted by facility operations; (2) Meet or exceed applicable environmental, public health, and resource protection laws and regulations; and (3) Implement cost-effective business practices. In addition, the DOE Order 450.1A mandates that the EMS must be integrated with a facility's Integrated Safety Management System (ISMS) established pursuant to DOE P 450.4, 'Safety Management System Policy'. DOE Order 430.2B mandates an energy management program that considers energy use and renewable energy, water, new and renovated buildings, and vehicle fleet activities. The Order incorporates the provisions of the Energy Policy Act of 2005 and Energy Independence and …
Date: March 24, 2009
Creator: Fox, Robert; Thorson, Patrick; Horst, Blair; Speros, John; Rothermich, Nancy & Hatayama, Howard
Object Type: Report
System: The UNT Digital Library
Hanford Internal Dosimetry Program Manual, PNL-MA-552 (open access)

Hanford Internal Dosimetry Program Manual, PNL-MA-552

This manual is a guide to the services provided by the Hanford Internal Dosimetry Program (IDP), which is operated by the Pacific Northwest National Laboratory.( ) for the U.S. Department of Energy Richland Operations Office, Office of River Protection and their Hanford Site contractors. The manual describes the roles of and relationships between the IDP and the radiation protection programs of the Hanford Site contractors. Recommendations and guidance are also provided for consideration in implementing bioassay monitoring and internal dosimetry elements of radiation protection programs.
Date: September 24, 2009
Creator: Carbaugh, Eugene H.; Bihl, Donald E. & Maclellan, Jay A.
Object Type: Report
System: The UNT Digital Library
Lake Whitney Comprehensive Water Quality Assessment, Phase 1B- Physical and Biological Assessment (USDOE) (open access)

Lake Whitney Comprehensive Water Quality Assessment, Phase 1B- Physical and Biological Assessment (USDOE)

Baylor University Center for Reservoir and Aquatic Systems Research (CRASR) has conducted a phased, comprehensive evaluation of Lake Whitney to determine its suitability for use as a regional water supply reservoir. The area along the Interstate 35 corridor between Dallas / Fort Worth Metroplex and the Waco / Temple Centroplex represents one of the fastest growth areas in the State of Texas and reliable water supplies are critical to sustainable growth. Lake Whitney is situated midway between these two metropolitan areas. Currently, the City of Whitney as well as all of Bosque and Hill counties obtain their potable water from the Trinity Sands aquifer. Additionally, parts of the adjoining McLennan and Burleson counties utilize the Trinity sands aquifer system as a supplement to their surface water supplies. Population growth coupled with increasing demands on this aquifer system in both the Metroplex and Centroplex have resulted in a rapid depletion of groundwater in these rural areas. The Lake Whitney reservoir represents both a potentially local and regional solution for an area experiencing high levels of growth. Because of the large scope of this project as well as the local, regional and national implications, we have designed a multifaceted approach that will …
Date: November 24, 2009
Creator: Doyle, Robert D & Byars, Bruce W
Object Type: Report
System: The UNT Digital Library
An Overview Of The ITER In-Vessel Coil Systems (open access)

An Overview Of The ITER In-Vessel Coil Systems

ELM mitigation is of particular importance in ITER in order to prevent rapid erosion or melting of the divertor surface, with the consequent risk of water leaks, increased plasma impurity content and disruptivity. Exploitable "natural" small or no ELM regimes might yet be found which extrapolate to ITER but this cannot be depended upon. Resonant Magnetic Perturbation has been added to pellet pacing as a tool for ITER to mitigate ELMs. Both are required, since neither method is fully developed and much work remains to be done. In addition, in-vessel coils enable vertical stabilization and RWM control. For these reasons, in-vessel coils (IVCs) are being designed for ITER to provide control of Edge Localized Modes (ELMs) in addition to providing control of moderately unstable resistive wall modes (RWMs) and the vertical stability (VS) of the plasma.
Date: September 24, 2009
Creator: Heitzenroeder, P. J.; Chrzanowski, J. H.; Dahlgren, F.; Hawryluk, R. J.; Loesser, G. D.; Neumeyer, C. et al.
Object Type: Article
System: The UNT Digital Library
SURFACE GEOPHYSICAL EXPLORATION OF SX TANK FARM AT THE HANFORD SITE RESULTS OF BACKGROUND CHARACTERIZATION WITH MAGNETICS AND ELECTROMAGNETICS (open access)

SURFACE GEOPHYSICAL EXPLORATION OF SX TANK FARM AT THE HANFORD SITE RESULTS OF BACKGROUND CHARACTERIZATION WITH MAGNETICS AND ELECTROMAGNETICS

This report presents the results of the background characterization of the cribs and trenches surrounding the SX tank farm prepared by HydroGEOPHYSICS Inc, Columbia Energy & Environmental Services Inc and Washington River Protection Solutions.
Date: September 24, 2009
Creator: DA, MYERS; D, RUCKER; M, LEVIT; B, CUBBAGE & C, HENDERSON
Object Type: Report
System: The UNT Digital Library
Post-Closure Inspection Letter Report for Corrective Action Units on the Nevada Test Site (open access)

Post-Closure Inspection Letter Report for Corrective Action Units on the Nevada Test Site

None
Date: March 24, 2009
Creator: National Security Technologies, LLC
Object Type: Report
System: The UNT Digital Library
A Spatially Resolving X-ray Crystal Spectrometer for Measurement of Ion-temperature and Rotation-velocity Profiles on the AlcatorC-Mod Tokamak (open access)

A Spatially Resolving X-ray Crystal Spectrometer for Measurement of Ion-temperature and Rotation-velocity Profiles on the AlcatorC-Mod Tokamak

A new spatially resolving x-ray crystal spectrometer capable of measuring continuous spatial profiles of high resolution spectra (λ/dλ > 6000) of He-like and H-like Ar Kα lines with good spatial (~1 cm) and temporal (~10 ms) resolutions has been installed on the Alcator C-Mod tokamak. Two spherically bent crystals image the spectra onto four two-dimensional Pilatus II pixel detectors. Tomographic inversion enables inference of local line emissivity, ion temperature (Ti), and toroidal plasma rotation velocity (vφ) from the line Doppler widths and shifts. The data analysis techniqu
Date: March 24, 2009
Creator: Hill, K. W.; Bitter, M. L.; Scott, S. D.; Ince-Cushman, A.; Reinke, M.; Rice, J. E. et al.
Object Type: Report
System: The UNT Digital Library
Momentum Transport in Electron-Dominated Spherical Torus Plasmas (open access)

Momentum Transport in Electron-Dominated Spherical Torus Plasmas

The National Spherical Torus Experiment (NSTX) operates between 0.35 and 0.55 T, which, when coupled to up to 7 MW of neutral beam injection, leads to central rotation velocities in excess of 300 km/s and ExB shearing rates up to 1 MHz. This level of ExB shear can be up to a factor of five greater than typical linear growth rates of long-wavelength ion (e.g., ITG) modes, at least partially suppressing these instabilities. Evidence for this turbulence suppression is that the inferred diffusive ion thermal flux in NSTX H-modes is often at the neoclassical level, and thus these plasmas operate in an electron-dominated transport regime. Analysis of experiments using n=3 magnetic fields to change plasma rotation indicate that local rotation shear influences local transport coefficients, most notably the ion thermal diffusivity, in a manner consistent with suppression of the low-k turbulence by this rotation shear. The value of the effective momentum diffusivity, as inferred from steady-state momentum balance, is found to be larger than the neoclassical value. Results of perturbative experiments indicate inward pinch velocities up to 40 m/s and perturbative momentum diffusivities of up to 4 m2/s, which are larger by a factor of several than those values inferred …
Date: February 24, 2009
Creator: Kaye, S. M.; Solomon, W.; Bell, R. E.; LeBlanc, B. P.; Levinton, F.; Menard, J. et al.
Object Type: Report
System: The UNT Digital Library