ENCAPSULATION OF PALLADIUM IN POROUS WALL HOLLOW GLASS MICROSPHERES (open access)

ENCAPSULATION OF PALLADIUM IN POROUS WALL HOLLOW GLASS MICROSPHERES

A new encapsulation method was investigated in an attempt to develop an improved palladium packing material for hydrogen isotope separation. Porous wall hollow glass microspheres (PWHGMs) were produced by using a flame former, heat treating and acid leaching. The PWHGMs were then filled with palladium salt using a soak-and-dry process. The palladium salt was reduced at high temperature to leave palladium inside the microspheres.
Date: April 9, 2008
Creator: Heung, L.; George Wicks, G. & Ray Schumacher, R.
Object Type: Article
System: The UNT Digital Library
ELECTROCHEMICAL CORROSION TEST RESULTS FOR TANK 241-SY-102 SUPERNATE GRAB SAMPLES (open access)

ELECTROCHEMICAL CORROSION TEST RESULTS FOR TANK 241-SY-102 SUPERNATE GRAB SAMPLES

This report describes the electrochemical corrosion scans and conditions for testing of SY-102 supernatant samples taken December 2004. The testing was performed because the tank was under a Justification for Continued Operation allowing the supernatant composition to be outside the chemistry limits of Administrative Control 5.16, 'Corrosion Mitigation program'. A new electrochemical working electrode of A516 Grade 60 carbon steel was used for each scan; all scans were measured against a saturated calomel electrode, with carbon counter electrodes, and all scans were carried out at 50 C. The samples were scanned twice, once as received and once sparged with argon to deoxygenate the sample. For those scans conducted after argon purging, the corrosion rates ranged from 0.012 to 0.019 mpy. A test for stress corrosion cracking was carried out on one sample (2SY-04-07) with negative results.
Date: April 9, 2007
Creator: JB, DUNCAN
Object Type: Report
System: The UNT Digital Library
Ion Exclusion by Sub 2-nm Carbon Nanotube Pores (open access)

Ion Exclusion by Sub 2-nm Carbon Nanotube Pores

Carbon nanotubes offer an outstanding platform for studying molecular transport at nanoscale, and have become promising materials for nanofluidics and membrane technology due to their unique combination of physical, chemical, mechanical, and electronic properties. In particular, both simulations and experiments have proved that fluid flow through carbon nanotubes of nanometer size diameter is exceptionally fast compared to what continuum hydrodynamic theories would predict when applied on this length scale, and also, compared to conventional membranes with pores of similar size, such as zeolites. For a variety of applications such as separation technology, molecular sensing, drug delivery, and biomimetics, selectivity is required together with fast flow. In particular, for water desalination, coupling the enhancement of the water flux with selective ion transport could drastically reduce the cost of brackish and seawater desalting. In this work, we study the ion selectivity of membranes made of aligned double-walled carbon nanotubes with sub-2 nm diameter. Negatively charged groups are introduced at the opening of the carbon nanotubes by oxygen plasma treatment. Reverse osmosis experiments coupled with capillary electrophoresis analysis of permeate and feed show significant anion and cation rejection. Ion exclusion declines by increasing ionic strength (concentration) of the feed and by lowering solution …
Date: April 9, 2008
Creator: Fornasiero, F; Park, H G; Holt, J K; Stadermann, M; Grigoropoulos, C P; Noy, A et al.
Object Type: Article
System: The UNT Digital Library
IMPLEMENTING CHANGES TO AN APPROVED AND IN-USE DOCUMENTED SAFETY ANALYSIS (open access)

IMPLEMENTING CHANGES TO AN APPROVED AND IN-USE DOCUMENTED SAFETY ANALYSIS

None
Date: April 9, 2008
Creator: JP, KING
Object Type: Article
System: The UNT Digital Library
Secretory pathway Ca2+/Mn2+-ATPase isoform 2 and lactation: specific localization of plasmalemmal and secretory pathway Ca2+ pump isoforms in the mammary gland (open access)

Secretory pathway Ca2+/Mn2+-ATPase isoform 2 and lactation: specific localization of plasmalemmal and secretory pathway Ca2+ pump isoforms in the mammary gland

The supply of calcium to the developing neonate via milk is an important physiological process. Until recently the mechanism for the enrichment of milk with calcium was thought to be almost entirely mediated via the secretory pathway. However, recent studies suggest that a specific isoform of the plasma membrane calcium ATPase, PMCA2, is the primary mechanism for calcium transport into milk, highlighting a major role for apical calcium transport. We compared the expression of the recently identified secretory calcium ATPase, SPCA2, and SPCA1, in the mouse mammary gland during different stages of development. SPCA2 levels increased over 35 fold during lactation, while SPCA1 increased only a modest two fold. The potential importance of SPCA2 in lactation was also highlighted by its localization to luminal secretory cells of the mammary gland during lactation, while SPCA1 was expressed throughout the cells of the mammary gland. We also observed major differences in the localization of PMCA2 and PMCA1 during lactation. Using the SCp2 mouse mammary epithelial cell 3D culture model, differences in the sub-cellular distribution of PMCA2 and PMCA1 were clear. These studies highlight the likely specific roles of PMCA2 and SPCA2 in lactation, and link the recently characterized SPCA2 calcium pump to …
Date: April 9, 2008
Creator: Faddy, Helen M.; Smart, Chanel E.; Xu, Ren; Lee, Genee Y.; Kenny, Paraic A.; Feng, Mingye et al.
Object Type: Article
System: The UNT Digital Library
Constructing a large-scale 3D Geologic Model for Analysis of the Non-Proliferation Experiment (open access)

Constructing a large-scale 3D Geologic Model for Analysis of the Non-Proliferation Experiment

We have constructed a regional 3D geologic model of the southern Great Basin, in support of a seismic wave propagation investigation of the 1993 Nonproliferation Experiment (NPE) at the Nevada Test Site (NTS). The model is centered on the NPE and spans longitude -119.5{sup o} to -112.6{sup o} and latitude 34.5{sup o} to 39.8{sup o}; the depth ranges from the topographic surface to 150 km below sea level. The model includes the southern half of Nevada, as well as parts of eastern California, western Utah, and a portion of northwestern Arizona. The upper crust is constrained by both geologic and geophysical studies, while the lower crust and upper mantle are constrained by geophysical studies. The mapped upper crustal geologic units are Quaternary basin fill, Tertiary deposits, pre-Tertiary deposits, intrusive rocks of all ages, and calderas. The lower crust and upper mantle are parameterized with 5 layers, including the Moho. Detailed geologic data, including surface maps, borehole data, and geophysical surveys, were used to define the geology at the NTS. Digital geologic outcrop data were available for both Nevada and Arizona, whereas geologic maps for California and Utah were scanned and hand-digitized. Published gravity data (2km spacing) were used to determine …
Date: April 9, 2008
Creator: Wagoner, J & Myers, S
Object Type: Report
System: The UNT Digital Library
Highly Insulating Glazing Systems using Non-Structural Center Glazing Layers (open access)

Highly Insulating Glazing Systems using Non-Structural Center Glazing Layers

Three layer insulating glass units with two low-e coatings and an effective gas fill are known to be highly insulating, with center-of-glass U-factors as low as 0.57 W/m{sup 2}-K (0.10 Btu/h-ft{sup 2}- F). Such units have historically been built with center layers of glass or plastic which extend all the way through the spacer system. This paper shows that triple glazing systems with non-structural center layers which do not create a hermetic seal at the edge have the potential to be as thermally efficient as standard designs, while potentially removing some of the production and product integration issues that have discouraged the use of triples.
Date: April 9, 2008
Creator: Kohler, Christian; Arasteh, Dariush; Goudey, Howdy & Kohler, Christian
Object Type: Article
System: The UNT Digital Library
Effects of uncertainty in rock-physics models on reservoirparameter estimation using marine seismic AVA and CSEM data (open access)

Effects of uncertainty in rock-physics models on reservoirparameter estimation using marine seismic AVA and CSEM data

This study investigates the effects of uncertainty inrockphysics models on estimates of reservoir parameters from jointinversion of seismic AVA and CSEMdata. The reservoir parameters arerelated to electrical resistivity using Archie's law, and to seismicvelocity and density using the Xu-White model. To account for errors inthe rock-physics models, we use two methods to handle uncertainty: (1)the model outputs are random functions with modes or means given by themodel predictions, and (2) the parameters of the models are themselvesrandom variables. Using a stochastic framework and Markov Chain MonteCarlo methods, we obtain estimates of reservoir parameters as well as ofthe uncertainty in the estimates. Synthetic case studies show thatuncertainties in both rock-physics models and their associated parameterscan have significant effects on estimates of reservoir parameters. Ourmethod provides a means of quantifying how the uncertainty in theestimated reservoir parameters increases with increasing uncertainty inthe rock-physics model and in the model parameters. We find that in theexample we present, the estimation of water saturation is relatively lessaffected than is the estimation of clay content and porosity.
Date: April 9, 2007
Creator: Chen, Jinsong & Dickens, Thomas
Object Type: Article
System: The UNT Digital Library
2007 Annual Health Physics Report for the HEU Transparency Program (open access)

2007 Annual Health Physics Report for the HEU Transparency Program

During the 2007 calendar year, Lawrence Livermore National Laboratory (LLNL) provided health physics support for the Highly Enriched Uranium (HEU) Transparency Program for external and internal radiation protection and technical expertise related to BDMS radioactive sources and Russian radiation safety regulatory compliance. For the calendar year 2007, there were 172 person-trips that required dose monitoring of the U.S. monitors. Of the 172 person-trips, 160 person-trips were SMVs and 12 person-trips were Transparency Monitoring Office (TMO) trips. There were 12 monitoring visits by TMO monitors to facilities other than UEIE and 10 to UEIE itself. There were two monitoring visits (source changes) that were back to back with 14 monitors. LLNL's Hazard Control Division laboratories provided the dosimetry services for the HEU Transparency monitors.
Date: April 9, 2008
Creator: Radev, R
Object Type: Report
System: The UNT Digital Library
Renewable Portfolio Standards in the United States - A Status Report with Data Through 2007 (open access)

Renewable Portfolio Standards in the United States - A Status Report with Data Through 2007

Renewables portfolio standards (RPS) have proliferated at the state level in the United States since the late 1990s. In combination with Federal tax incentives, state RPS requirements have emerged as one of the most important drivers of renewable energy capacity additions. The focus of most RPS activity in the U.S. has been within the states. Nonetheless, the U.S. House of Representatives and Senate have, at different times, each passed versions of a Federal RPS; a Federal RPS, however, has not yet been signed into law. The design of an RPS can and does vary, but at its heart an RPS simply requires retail electricity suppliers (also called load-serving entities, or LSEs) to procure a certain minimum quantity of eligible renewable energy. An RPS establishes numeric targets for renewable energy supply, applies those targets to retail electricity suppliers, and seeks to encourage competition among renewable developers to meet the targets in a least-cost fashion. RPS purchase obligations generally increase over time, and retail suppliers typically must demonstrate compliance on an annual basis. Mandatory RPS policies are backed by various types of compliance enforcement mechanisms, and many--but not all--such policies include the trading of renewable energy certificates (RECs). Renewables portfolio standards are …
Date: April 9, 2008
Creator: Wiser, Ryan; Wiser, Ryan; Barbose, Galen; Bird, Lori; Churchill, Susannah; Deyette, Jeff et al.
Object Type: Report
System: The UNT Digital Library
Large Eddy Simulation of Turbulent Flow and Dispersion in Urban Areas and Forest Canopies (open access)

Large Eddy Simulation of Turbulent Flow and Dispersion in Urban Areas and Forest Canopies

Under the sponsorship of the U.S. DOE and DHS, we have developed a CFD model for simulating flow and dispersion of chemical and biological agents released in the urban environment. Our model, FEM3MP (Chan and Stevens, 2000), is based on solving the three-dimensional, time-dependent, incompressible Navier-Stokes equations on massively parallel computer platforms. The model uses the finite element method for accurate representation of complex building shapes and variable terrain, together with a semi-implicit projection method and modern iterative solvers for efficient time integration (Gresho and Chan, 1998). Physical processes treated include turbulence modeling via the RANS (Reynolds Averaged Navier-Stokes) and LES (Large Eddy Simulation) approaches, atmospheric stability, aerosols, UV radiation decay, surface energy budget, and vegetative canopies, etc. Predictions from our model are continuously being verified and validated against data from wind tunnel (Chan and Stevens, 2000; Chan, et al., 2001) and field experiments (Chan, et al., 2002, 2003; Lee, et al., 2002; Humphreys, et al., 2003; and Calhoun, et al., 2004). Discussed below are several examples to illustrate the use of FEM3MP in simulating flow and dispersion in urban areas and forest canopies, with model results compared against available field measurements.
Date: April 9, 2004
Creator: Chan, Stevens T.
Object Type: Article
System: The UNT Digital Library
Diffusion and Settling in Ap/Bp Stars (open access)

Diffusion and Settling in Ap/Bp Stars

Ap/Bp stars are magnetic chemically peculiar early A and late B type stars of the main sequence. They exhibit peculiar surface abundance anomalies that are thought to be the result of gravitational settling and radiative levitation. The physics of diffusion in these stars are reviewed briefly and some model predictions are discussed. While models reproduce some observations reasonably well, more work is needed before the behavior of diffusing elements in a complex magnetic field is fully understood.
Date: April 9, 2003
Creator: Turcotte, S
Object Type: Article
System: The UNT Digital Library
Testing a Variety of Encryption Technologies (open access)

Testing a Variety of Encryption Technologies

Review and test speeds of various encryption technologies using Entrust Software. Multiple encryption algorithms are included in the product. Algorithms tested were IDEA, CAST, DES, and RC2. Test consisted of taking a 7.7 MB Word document file which included complex graphics and timing encryption, decryption and signing. Encryption is discussed in the GIAC Kickstart section: Information Security: The Big Picture--Part VI.
Date: April 9, 2001
Creator: Henson, T J
Object Type: Report
System: The UNT Digital Library
Plasma Simulation Using Gyrokinetic-Gyrofluid Hybrid Models (open access)

Plasma Simulation Using Gyrokinetic-Gyrofluid Hybrid Models

We are developing kinetic ion models for the simulation of extended MHD phenomena. The model they have developed uses full Lorentz force ions, and either drift-kinetic or gyro-kinetic electrons. Quasi-neutrality is assumed and the displacement current is neglected. They are also studying alpha particle driven Toroidal Alfven Eigenmodes (TAE) in the GEM gyrokinetic code [Chen 07]. The basic kinetic ion MHD model was recently reported in an invited talk given by Dan Barnes at the 2007 American Physical Society - Division of Plasma Physics (APS-DPP) and it has been published [Jones 04, Barnes 08]. The model uses an Ohm's law that includes the Hall term, pressure term and the electron inertia [Jones 04]. These results focused on the ion physics and assumed an isothermal electron closure. It is found in conventional gyrokinetic turbulence simulations that the timestep cannot be made much greater than the ion cyclotron period. However, the kinetic ion MHD model has the compressional mode, which further limits the timestep. They have developed an implicit scheme to avoid this timestep constraint. They have also added drift kinetic electrons. This model has been benchmarked linearly. Waves investigated where shear and compressional Alfven, whisterl, ion acoustic, and drift waves, including …
Date: April 9, 2009
Creator: Parker, Scott
Object Type: Report
System: The UNT Digital Library
Evaporated Lithium Surface Coatings in NSTX (open access)

Evaporated Lithium Surface Coatings in NSTX

Two lithium evaporators were used to evaporate more than 100 g of lithium on to the NSTX lower divertor region. Prior to each discharge, the evaporators were withdrawn behind shutters, where they also remained during the subsequent HeGDC applied for periods up to 9.5 min. After the HeGDC, the shutters were opened and the LITERs were reinserted to deposit lithium on the lower divertor target for 10 min, at rates of 10-70 mg/min, prior to the next discharge. The major improvements in plasma performance from these lithium depositions include: 1) plasma density reduction as a result of lithium deposition; 2) suppression of ELMs; 3) improvement of energy confinement in a low-triangularity shape; 4) improvement in plasma performance for standard, high-triangularity discharges; 5) reduction of the required HeGDC time between discharges; 6) increased pedestal electron and ion temperature; 7) reduced SOL plasma density; and 8) reduced edge neutral density.
Date: April 9, 2009
Creator: Kugel, H. W.; Mansfield, D.; Maingi, R.; Bel, M. G.; Bell, R. E.; Allain, J. P. et al.
Object Type: Article
System: The UNT Digital Library
Particle-in-Cell Modeling of Magnetized Argon Plasma Flow Through Small Mechanical Apertures (open access)

Particle-in-Cell Modeling of Magnetized Argon Plasma Flow Through Small Mechanical Apertures

Motivated by observations of supersonic argon-ion flow generated by linear helicon-heated plasma devices, a three-dimensional particle-in-cell (PIC) code is used to study whether stationary electrostatic layers form near mechanical apertures intersecting the flow of magnetized plasma. By self-consistently evaluating the temporal evolution of the plasma in the vicinity of the aperture, the PIC simulations characterize the roles of the imposed aperture and applied magnetic field on ion acceleration. The PIC model includes ionization of a background neutral-argon population by thermal and superthermal electrons, the latter found upstream of the aperture. Near the aperture, a transition from a collisional to a collisionless regime occurs. Perturbations of density and potential, with mm wavelengths and consistent with ion acoustic waves, propagate axially. An ion acceleration region of length ~ 200−300 λD,e forms at the location of the aperture and is found to be an electrostatic double layer, with axially-separated regions of net positive and negative charge. Reducing the aperture diameter or increasing its length increases the double layer strength.
Date: April 9, 2009
Creator: Cohen, Adam B. Sefkow and Samuel A.
Object Type: Article
System: The UNT Digital Library
Kootenai River Fisheries Investigations: Salmonid Studies Project Progress Report, 2007-2008 Annual Report. (open access)

Kootenai River Fisheries Investigations: Salmonid Studies Project Progress Report, 2007-2008 Annual Report.

This research report addresses bull trout Salvelinus confluentus and Redband trout Oncorhynchus mykiss redd surveys, population monitoring, trout distribution, and abundance surveys in the Kootenai River drainage of Idaho. The bull trout is one of several sport fish native to the Kootenai River, Idaho that no longer supports a fishery. Because bull trout are listed under the Endangered Species Act, population data will be vital to monitoring status relative to recovery goals. Thirty-three bull trout redds were found in North and South Callahan creeks and Boulder Creek in 2007. This is a decrease from 2006 and 2005 and less than the high count in 2003. However, because redd numbers have only been monitored since 2002, the data series is too short to determine bull trout population trends based on redd counts. Redband trout still provide an important Kootenai River sport fishery, but densities are low, at least partly due to limited recruitment. The redband trout proportional stock density (PSD) in 2007 increased from 2006 for a second year after a two-year decline in 2004 and 2005. This may indicate increased recruitment to or survival in the 201-305 mm length group due to the minimum 406 mm (16 inches) length limit …
Date: April 9, 2009
Creator: Paragamian, Vaughn L.; Walters, Jody & Maiolie, Melo
Object Type: Report
System: The UNT Digital Library
A Framework for Evaluating the Effects of Degraded Digital I and C Systems on Human Performance (open access)

A Framework for Evaluating the Effects of Degraded Digital I and C Systems on Human Performance

New and advanced reactors will use integrated digital instrumentation and control (I&C) systems to support operators in their monitoring and control functions. Even though digital systems are typically highly reliable, their potential for degradation or failure could significantly affect operator situation awareness and performance and, consequently, impact plant safety. The U.S. Nuclear Regulatory Commission has initiated a research project to investigate the effects of degraded I&C systems on human performance and plant operations. The ultimate objective of this project is to develop the technical basis for human factors review guidance for conditions of degraded I&C, including complete failure. Based on the results of this effort, NRC will determine the need for developing new guidance or revising NUREG-0800, NUREG-0711, NUREG-0700 and other pertinent NRC review guidance. This paper reports on the first phase of the research, the development of a framework for linking degraded I&C system conditions to human performance. The framework consists of three levels: I&C subsystems, human-system interfaces, and human performance. Each level is composed of a number of discrete elements. This paper will describe the elements at each level and their integration. In the next phase of the research, the framework will be used to systematically investigate the …
Date: April 9, 2009
Creator: O'Hara, John; Gunther, Bill; Hughes, N. & Barnes, V.
Object Type: Article
System: The UNT Digital Library
Electron Cloud Observations and Cures in Rhic. (open access)

Electron Cloud Observations and Cures in Rhic.

None
Date: April 9, 2007
Creator: Fischer, W.; Blaskiewicz, M.; Brennan, M.; Huang, H.; Hseuh, H. C.; Ptitsyn, V. et al.
Object Type: Article
System: The UNT Digital Library
Measurement of the Hadronic Form factor in D0 to K- e+ nu_e Decays (open access)

Measurement of the Hadronic Form factor in D0 to K- e+ nu_e Decays

The shape of the hadronic form factor f{sub +} (q{sup 2}) in the decay D{sup 0} {yields} K{sup -} e{sup +}{nu}{sub e} has been measured in a model independent analysis and compared with theoretical calculations. They use 75 fb{sup -1} of data recorded by the BABAR detector at the PEPII electron-positron collider. The corresponding decay branching fraction, relative to the decay D{sup 0} {yields} K{sup -} {pi}{sup +}, has also been measured to be R{sub D} = BR(D{sup 0} {yields} K{sup -}e{sup +}{nu}{sub e})/BR(D{sup 0} {yields} K{sup -}{pi}{sup +}) = 0.927 {+-} 0.007 {+-} 0.012. From these results, and using the present world average value for BR(D{sup 0} {yields} K{sup -}{pi}{sup +}), the normalization of the form factor at q{sup 2} = 0 is determined to be f{sub +}(0) = 0.727 {+-} 0.007 {+-} 0.005 {+-} 0.007 where the uncertainties are statistical, systematic, and from external inputs, respectively.
Date: April 9, 2007
Creator: Aubert, B.; Bona, M.; Boutigny, D.; Karyotakis, Y.; Lees, J. P.; Poireau, V. et al.
Object Type: Article
System: The UNT Digital Library
Neutron Production Measurements Relevant to Shielding forSpace-Related Activities (open access)

Neutron Production Measurements Relevant to Shielding forSpace-Related Activities

Neutron production cross sections have been measured from290 MeV/nucleon C and 600 MeV/nucleon Ne interacting in a slab ofsimulated Martian regolith/polyethylene composite, and from 400MeV/nucleon Ne interacting in a section of wall materials from theInternational Space Station. Neutron spectra were measured at 7 anglesbetween 5 degrees and 80 degrees, and for neutron energies 5 MeV andgreater. Spectra at forward angles are dominated by the breakup of theprojectile, whereas spectra at back angles show the typical exponentialfalloff with energy that is indicative of decay from the overlap regionand the target remnant. The measured total neutron production crosssections indicate that the regolith/polyethylene composite may be a moreeffective shielding material than the ISS wall materials, in terms of thenumber of neutrons produced.
Date: April 9, 2002
Creator: Heilbronn, Lawrence; Iwata, Yoshiyuki; Murakami, Takeshi; Iwase, Hiroshi; Nakamura, Takashi; Sato, Hisaki et al.
Object Type: Article
System: The UNT Digital Library
A tool for the quantitative spatial analysis of mammary gland epithelium (open access)

A tool for the quantitative spatial analysis of mammary gland epithelium

In this paper we present a method for the spatial analysis of complex cellular systems based on a multiscale study of neighborhood relationships. A function to measure those relationships, M, is introduced. The refined Relative Neighborhood Graph is then presented as a method to establish vicinity relationships within layered cellular structures, and particularized to epithelial cell nuclei in the mammary gland. Finally, the method is illustrated with two examples that show interactions within one population of epithelial cells and between two different populations.
Date: April 9, 2004
Creator: Ortiz de Solorzano, Carlos & Fernandez-Gonzalez, Rodrigo
Object Type: Article
System: The UNT Digital Library
The QCD/SM working group: Summary report (open access)

The QCD/SM working group: Summary report

Among the many physics processes at TeV hadron colliders, we look most eagerly for those that display signs of the Higgs boson or of new physics. We do so however amid an abundance of processes that proceed via Standard Model (SM) and in particular Quantum Chromodynamics (QCD) interactions, and that are interesting in their own right. Good knowledge of these processes is required to help us distinguish the new from the known. Their theoretical and experimental study teaches us at the same time more about QCD/SM dynamics, and thereby enables us to further improve such distinctions. This is important because it is becoming increasingly clear that the success of finding and exploring Higgs boson physics or other New Physics at the Tevatron and LHC will depend significantly on precise understanding of QCD/SM effects for many observables. To improve predictions and deepen the study of QCD/SM signals and backgrounds was therefore the ambition for our QCD/SM working group at this Les Houches workshop. Members of the working group made significant progress towards this on a number of fronts. A variety of tools were further developed, from methods to perform higher order perturbative calculations or various types of resummation, to improvements in …
Date: April 9, 2004
Creator: Dobbs, Matt; Frixione, S.; Laenen, E.; De Roeck, A.; Tollefson, K.; Andersen, J. et al.
Object Type: Article
System: The UNT Digital Library
Optimization of Outer Poloidal Field (PF) Coil Configurations for Inductive PF Coil-only Plasma Start-up on Spherical Tori (open access)

Optimization of Outer Poloidal Field (PF) Coil Configurations for Inductive PF Coil-only Plasma Start-up on Spherical Tori

The elimination of in-board ohmic heating solenoid is required for the spherical torus (ST) to function as an attractive fusion power plant. An in-board ohmic solenoid, along with the shielding needed for its insulation, increases the size and, hence, the cost of the plant. Here, we investigate using static as well as dynamic codes in ST geometries a solenoid-free start-up concept utilizing a set of out-board poloidal field coils. By using the static code, an optimization of coil positions as well as coil currents was performed to demonstrate that it is indeed possible to create a high quality multi-pole field null region while retaining significant flux (volt-seconds) needed for the subsequent current ramp-up. With the dynamic code that includes the effect of vacuum vessel eddy currents, we then showed that it is possible to maintain a large size field null region for several milliseconds in which sufficient ionization avalanche can develop in the applied toroidal electric field. Under the magnetic geometry typical of a next generation spherical torus experiment, it is shown that the well-known plasma breakdown conditions for conventional ohmic solenoid start-up of E(sub)TB(sub)T/B(sub)P {approx} (0.1-1) kV/m with V(sub)loop {approx} 6 V can be readily met while retaining significant …
Date: April 9, 2004
Creator: Choe, Wonho; Kim, Jayhyun & Ono, Masayuki
Object Type: Report
System: The UNT Digital Library