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What product might a renewal of Heavy IonFusion development offerthat competes with methane microbes and hydrogen HTGRs

Description: In 1994 a Fusion Technology journal publication by Logan, Moir and Hoffman described how exploiting unusually-strong economy-of-scale for large (8 GWe-scale) multi-unit HIF plants sharing a driver and target factory among several low cost molten salt fusion chambers {at} < $40M per 2.4 GW fusion each (Fig. 1), could produce electricity below 3 cts/kWehr, even lower than similar multi-unit fission plants. The fusion electric plant could cost $12.5 B for 7.5 GWe and produce hydrogen fuel by electrolysis at prices competitive with gasoline-powered hybrids getting fuel from oil at $20$/bbl. At $60/bbl oil, the fusion plant can cost $35B and compete {at} 10% APR financing. Given massive and still-increasing world demand for transportation fuel even with oil climbing above $60/bbl, large HIF plants producing both low cost electricity and hydrogen could be more relevant to motivate new R&D funding for HIF development in the next few years. Three major challenges to get there: (1) NIF ignition in indirect drive geometry for liquid chambers, (2) a modular accelerator to enable a one-module IRE < $100 M, (3) compatible HIF target, driver and chamber allowing a small driver {at}< $500 M cost for a >100MWe net power DEMO. This scoping study, at a very preliminary conceptual level, attempts to identify how we might meet the last two great challenges taking advantage of several recent ideas and advances which motivate reconsideration of modular HIF drivers: >60X longitudinal compression of neutralized ion beams using a variable waveform induction module in NDCX down to 2 nanosecond bunches, the proof-of-principle demonstration of fast optical-gated solid state SiC switches by George Caporaso's group at LLNL (see George's RPIA06 paper), and recent work by Ed Lee, John Barnard and Hong Qin on methods for time-dependent correction of chromatic focusing errors in neutralized beams with up to 10 % ...
Date: April 19, 2006
Creator: Logan, Grant; Lee, Ed; Yu, Simon; Briggs, Dick; Barnard, John; Friedman, Alex et al.
Partner: UNT Libraries Government Documents Department

Obtaining the Bidirectional Transfer Distribution Function ofIsotropically Scattering Materials Using an Integrating Sphere

Description: This paper demonstrates a method to determine thebidirectional transfer distribution function (BTDF) using an integratingsphere. Information about the sample's angle dependent scattering isobtained by making transmittance measurements with the sample atdifferent distances from the integrating sphere. Knowledge about theilluminated area of the sample and the geometry of the sphere port incombination with the measured data combines to an system of equationsthat includes the angle dependent transmittance. The resulting system ofequations is an ill-posed problem which rarely gives a physical solution.A solvable system is obtained by using Tikhonov regularization on theill-posed problem. The solution to this system can then be used to obtainthe BTDF. Four bulk-scattering samples were characterised using both twogoniophotometers and the described method to verify the validity of thenew method. The agreement shown is great for the more diffuse samples.The solution to the low-scattering samples contains unphysicaloscillations, butstill gives the correct shape of the solution. Theorigin of the oscillations and why they are more prominent inlow-scattering samples are discussed.
Date: October 19, 2006
Creator: Jonsson, Jacob C. & Branden, Henrik
Partner: UNT Libraries Government Documents Department

ELLIPTIC FLOW, INITIAL ECCENTRICITY AND ELLIPTIC FLOW FLUCTUATIONS IN HEAVY ION COLLISIONS AT RHIC.

Description: We present measurements of elliptic flow and event-by-event fluctuations established by the PHOBOS experiment. Elliptic flow scaled by participant eccentricity is found to be similar for both systems when collisions with the same number of participants or the same particle area density are compared. The agreement of elliptic flow between Au+Au and Cu+Cu collisions provides evidence that the matter is created in the initial stage of relativistic heavy ion collisions with transverse granularity similar to that of the participant nucleons. The event-by-event fluctuation results reveal that the initial collision geometry is translated into the final state azimuthal particle distribution, leading to an event-by-event proportionality between the observed elliptic flow and initial eccentricity.
Date: February 19, 2007
Creator: NOUICER,R.; ALVER, B.; BACK, B.B.; BAKER, M.D.; BALLINTIJN, M.; BARTON, D.S. et al.
Partner: UNT Libraries Government Documents Department

Sum Frequency Generation Vibrational Spectroscopy Studies on ModelPeptide Adsorption at the Hydrophobic Solid-Water and HydrophilicSolid-Water Interfaces

Description: Sum frequency generation (SFG) vibrational spectroscopy has been used to study the interfacial structure of several polypeptides and amino acids adsorbed to hydrophobic and hydrophilic surfaces under a variety of experimental conditions. Peptide sequence, peptide chain length, peptide hydrophobicity, peptide side-chain type, surface hydrophobicity, and solution ionic strength all affect an adsorbed peptide's interfacial structure. Herein, it is demonstrated that with the choice of simple, model peptides and amino acids, surface specific SFG vibrational spectroscopy can be a powerful tool to elucidate the interfacial structure of these adsorbates. Herein, four experiments are described. In one, a series of isosequential amphiphilic peptides are synthesized and studied when adsorbed to both hydrophobic and hydrophilic surfaces. On hydrophobic surfaces of deuterated polystyrene, it was determined that the hydrophobic part of the peptide is ordered at the solid-liquid interface, while the hydrophilic part of the peptide appears to have a random orientation at this interface. On a hydrophilic surface of silica, it was determined that an ordered peptide was only observed if a peptide had stable secondary structure in solution. In another experiment, the interfacial structure of a model amphiphilic peptide was studied as a function of the ionic strength of the solution, a parameter that could change the peptide's secondary structure in solution. It was determined that on a hydrophobic surface, the peptide's interfacial structure was independent of its structure in solution. This was in contrast to the adsorbed structure on a hydrophilic surface, where the peptide's interfacial structure showed a strong dependence on its solution secondary structure. In a third experiment, the SFG spectra of lysine and proline amino acids on both hydrophobic and hydrophilic surfaces were obtained by using a different experimental geometry that increases the SFG signal. Upon comparison of these spectra to the SFG spectra of interfacial polylysine and ...
Date: December 19, 2007
Creator: York, Roger L.
Partner: UNT Libraries Government Documents Department

High Efficiency, Ultra-Low Emission, Integrated Process Heater System

Description: The team of TIAX LLC, ExxonMobil Research and Engineering Company, and Callidus Technologies, LLC conducted a six-year program to develop an ultra-low emission process heater burner and an advanced high efficiency heater design. This project addresses the critical need of process heater operators for reliable, economical emission reduction technologies to comply with stringent emission regulations, and for heater design alternatives that reduce process heater energy requirements without significant cost increase. The key project targets were NOx emissions of 10 ppm (@ 3% O2), and a heater thermal efficiency of 95 percent. The ultra low NOx burner was developed through a series of pilot-scale and field tests combined with computational fluid dynamic modeling to arrive at simultaneous low emissions and suitable flame shape and stability. Pilot scale tests were run at TIAX, at the 2 MMBtu/hr scale, and at Callidus at 8 MMBtu/hr. The full scale burner was installed on a 14 burner atmospheric pipestill furnace at an ExxonMobil refinery. A variety of burner configurations, gas tips and flame stabilizers were tested to determine the lowest emissions with acceptable flame shape and stability. The resulting NOx emissions were 22 ppm on average. Starting in 2001, Callidus commercialized the original ultra low NOx burner and made subsequent design improvements in a series of commercial burners evolving from the original concept and/or development. Emissions in the field with the ultra low-NOx burner over a broad spectrum of heater applications have varied from 5 ppm to 30 ppm depending on heater geometry, heater service, fuel and firing capacity. To date, 1550 of the original burners, and 2500 of subsequent generation burners have been sold by Callidus. The advanced heater design was developed by parametric evaluations of a variety of furnace and combustion air preheater configurations and technologies for enhancing convective and radiative heat transfer. ...
Date: June 19, 2006
Creator: Mason, Howard; Boral, Anindya; Chhotray, San & Martin, Matthew
Partner: UNT Libraries Government Documents Department

Note on numerical study of the beam energy spread in NDCX-I

Description: The kinetic energy spread (defined here as the standard deviation of the beam particle energies) sets the ultimate theoretical limit on the longitudinal compression that can be attained on NDCX-I and NDCX-II. Experimental measurements will inevitably include the real influences on the longitudinal phase space of the beam due to injector and accelerator field imperfections1. These induced energy variations may be the real limit to the longitudinal compression in an accelerator. We report on a numerical investigation of the energy spread evolution in NDCX-I; these studies do not include all the real imperfections, but rather are intended to confirm that there are no other intrinsic mechanisms (translaminar effects, transverse-longitudinal anisotropy instability, etc.) for significant broadening of the energy distribution. We have performed Warp simulations that use a realistic Marx voltage waveform which was derived from experimental measurements (averaged over several shots), a fully-featured model of the accelerating and focusing lattice, and new diagnostics for computing the local energy spread (and temperature) that properly account for linear correlations that arise from the discrete binning along each physical dimension (these capabilities reproduce and extend those of the earlier HIF code BPIC). The new diagnostics allow for the calculation of multi-dimensional maps of energy spread and temperature in 2-D axisymmetric or 3-D Cartesian space at selected times. The simulated beam-line was terminated at z = 3 m by a conducting plate, so as to approximately reproduce the experimental conditions at the entrance of the spectrometer that was used for mapping the longitudinal phase space. Snapshots of the beam projection and current, as well as the Marx waveform and history of beam kinetic energy collected at the end plate, are shown in Fig. 1. A two-dimensional axisymmetric map of energy spread from simulations of a typical NDCX-I configuration is shown in Fig. 2 (a). ...
Date: January 19, 2011
Creator: Vay, J.-L.; Seidl, P.A. & Friedman, A.
Partner: UNT Libraries Government Documents Department

DX magnet requirements for p-Au operation

Description: This document addresses the question of moving the DX magnets for p-Au operations. First the beam geometry is addressed. Next, the beam sizes are covered. Finally, a conclusion is presented.
Date: January 19, 2012
Creator: Tepikian, S.; Trbojevic&#44 & D.
Partner: UNT Libraries Government Documents Department

Friction Factor Measurements in an Equally Spaced Triangular Tube Array

Description: Friction factor data for adiabatic cross-flow of water in a staggered tube array was obtained over a Reynolds number range (based on hydraulic diameter and gap velocity) of about 10,000 to 250,000. The tubes were 12.7mm (0.5 inch) outer diameter, in a uniformly spaced triangular arrangement with a pitch-to-diameter ratio of 1.5. The friction factor was compared to several literature correlations, and was found to be best matched by the Idelchik correlation. Other correlations were found to vary significantly from the test data. Based on the test data, a new correlation is proposed for this tube bundle geometry which covers the entire Reynolds number range tested.
Date: March 19, 2007
Creator: Vassallo P, Symolon P
Partner: UNT Libraries Government Documents Department

Light-Front Quantization and AdS/QCD: An Overview

Description: We give an overview of the light-front holographic approach to strongly coupled QCD, whereby a confining gauge theory, quantized on the light front, is mapped to a higher-dimensional anti de Sitter (AdS) space. The framework is guided by the AdS/CFT correspondence incorporating a gravitational background asymptotic to AdS space which encodes the salient properties of QCD, such as the ultraviolet conformal limit at the AdS boundary at z {yields} 0, as well as modifications of the geometry in the large z infrared region to describe confinement and linear Regge behavior. There are two equivalent procedures for deriving the AdS/QCD equations of motion: one can start from the Hamiltonian equation of motion in physical space time by studying the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. To a first semiclassical approximation, where quantum loops and quark masses are not included, this leads to a light-front Hamiltonian equation which describes the bound state dynamics of light hadrons in terms of an invariant impact variable {zeta} which measures the separation of the partons within the hadron at equal light-front time. Alternatively, one can start from the gravity side by studying the propagation of hadronic modes in a fixed effective gravitational background. Both approaches are equivalent in the semiclassical approximation. This allows us to identify the holographic variable z in AdS space with the impact variable {zeta}. Light-front holography thus allows a precise mapping of transition amplitudes from AdS to physical space-time. The internal structure of hadrons is explicitly introduced and the angular momentum of the constituents plays a key role.
Date: August 19, 2011
Creator: de Teramond, Guy F.; U., /Costa Rica; Brodsky, Stanley J. & /SLAC /Stanford U., Phys. Dept.
Partner: UNT Libraries Government Documents Department

Experimental Criticality Benchmarks for SNAP 10A/2 Reactor Cores

Description: This report describes computational benchmark models for nuclear criticality derived from descriptions of the Systems for Nuclear Auxiliary Power (SNAP) Critical Assembly (SCA)-4B experimental criticality program conducted by Atomics International during the early 1960's. The selected experimental configurations consist of fueled SNAP 10A/2-type reactor cores subject to varied conditions of water immersion and reflection under experimental control to measure neutron multiplication. SNAP 10A/2-type reactor cores are compact volumes fueled and moderated with the hydride of highly enriched uranium-zirconium alloy. Specifications for the materials and geometry needed to describe a given experimental configuration for a model using MCNP5 are provided. The material and geometry specifications are adequate to permit user development of input for alternative nuclear safety codes, such as KENO. A total of 73 distinct experimental configurations are described.
Date: December 19, 2005
Creator: Krass, A.W.
Partner: UNT Libraries Government Documents Department

APPLICATIONS OF CFD METHOD TO GAS MIXING ANALYSIS IN A LARGE-SCALED TANK

Description: The computational fluid dynamics (CFD) modeling technique was applied to the estimation of maximum benzene concentration for the vapor space inside a large-scaled and high-level radioactive waste tank at Savannah River site (SRS). The objective of the work was to perform the calculations for the benzene mixing behavior in the vapor space of Tank 48 and its impact on the local concentration of benzene. The calculations were used to evaluate the degree to which purge air mixes with benzene evolving from the liquid surface and its ability to prevent an unacceptable concentration of benzene from forming. The analysis was focused on changing the tank operating conditions to establish internal recirculation and changing the benzene evolution rate from the liquid surface. The model used a three-dimensional momentum coupled with multi-species transport. The calculations included potential operating conditions for air inlet and exhaust flows, recirculation flow rate, and benzene evolution rate with prototypic tank geometry. The flow conditions are assumed to be fully turbulent since Reynolds numbers for typical operating conditions are in the range of 20,000 to 70,000 based on the inlet conditions of the air purge system. A standard two-equation turbulence model was used. The modeling results for the typical gas mixing problems available in the literature were compared and verified through comparisons with the test results. The benchmarking results showed that the predictions are in good agreement with the analytical solutions and literature data. Additional sensitivity calculations included a reduced benzene evolution rate, reduced air inlet and exhaust flow, and forced internal recirculation. The modeling results showed that the vapor space was fairly well mixed and that benzene concentrations were relatively low when forced recirculation and 72 cfm ventilation air through the tank boundary were imposed. For the same 72 cfm air inlet flow but without forced recirculation, the ...
Date: March 19, 2007
Creator: Lee, S & Richard Dimenna, R
Partner: UNT Libraries Government Documents Department

Structural characterization of terrestrial microbial Mn oxides from Pinal Creek, AZ

Description: The microbial catalysis of Mn(II) oxidation is believed to be a dominant source of abundant sorption- and redox-active Mn oxides in marine, freshwater, and subsurface aquatic environments. In spite of their importance, environmental oxides of known biogenic origin have generally not been characterized in detail from a structural perspective. Hyporheic zone Mn oxide grain coatings at Pinal Creek, Arizona, a metals-contaminated stream, have been identified as being dominantly microbial in origin and are well studied from bulk chemistry and contaminant hydrology perspectives. This site thus presents an excellent opportunity to study the structures of terrestrial microbial Mn oxides in detail. XRD and EXAFS measurements performed in this study indicate that the hydrated Pinal Creek Mn oxide grain coatings are layer-type Mn oxides with dominantly hexagonal or pseudo-hexagonal layer symmetry. XRD and TEM measurements suggest the oxides to be nanoparticulate plates with average dimensions on the order of 11 nm thick x 35 nm diameter, but with individual particles exhibiting thickness as small as a single layer and sheets as wide as 500 nm. The hydrated oxides exhibit a 10-A basal-plane spacing and turbostratic disorder. EXAFS analyses suggest the oxides contain layer Mn(IV) site vacancy defects, and layer Mn(III) is inferred to be present, as deduced from Jahn-Teller distortion of the local structure. The physical geometry and structural details of the coatings suggest formation within microbial biofilms. The biogenic Mnoxides are stable with respect to transformation into thermodynamically more stable phases over a time scale of at least 5 months. The nanoparticulate layered structural motif, also observed in pure culture laboratory studies, appears to be characteristic of biogenic Mn oxides and may explain the common occurrence of this mineral habit in soils and sediments.
Date: March 19, 2008
Creator: Bargar, John; Fuller, Christopher; Marcus, Matthew A.; Brearley, Adrian J.; Perez De la Rosa, M.; Webb, Samuel M. et al.
Partner: UNT Libraries Government Documents Department

Reaction Between Thin Gold Wires and Pb-Sn-In Solder (37.5%, 37.5%, 25%), Part A: The Radial Reaction Inside The Solder Mounds, Its Linear Reaction Model, Statistical Variation of Reaction Rate, and Induced Structural Changes In The Solder Mounds.

Description: Thermodynamics favors the reaction between indium and gold, since the heat of formation of AuIn{sub 2} is 6 kcal/mole, substantially larger than the heat of formation of any other possible reaction product. Thermodynamic equilibrium between gold and the elements in the solder mound is reached only when ALL gold is converted to AuIn{sub 2}. There are two aspects to this conversion: (A) the reaction WITHIN the solder mound (called here 'radial reaction') and (B) the reaction OUTSIDE the solder mound (called here 'axial reaction') and the transition from (A) to (B). The reaction between thin gold detonator wires and the In/Pb/Sn solder mound in older detonators has been looked at repeatedly. There are, in addition, two studies which look at the reaction between indium and gold in planar geometry. All data are shown in tables I to V. It is the objective of this section dealing with aspect (A), to combine all of these results into a reaction model and to use this reaction model to reliably and conservatively predict the gold-solder reaction rate of soldered gold bridge-wires as a function of storage temperature and time.
Date: January 19, 2011
Creator: Siekhaus, W J
Partner: UNT Libraries Government Documents Department

A comparison of dispersion calculations in bluff body wakes using LES and unsteady RANS

Description: Accurate modeling of the dispersion behavior of sprays or particles is critical for a variety of problems including combustion, urban pollution or release events, and splash and spray transport around heavy vehicles. Bluff body wakes are particularly challenging since these flows are both highly separated and strongly unsteady. Attempting to model the dispersion of droplets or particles interacting with bluff body wakes is even more difficult since small differences in the flow field encountered by particles can lead to large differences in the dispersion behavior. Particles with finite inertia can exhibit additional complicating effects such as preferential concentration. In this preliminary study, we consider the dispersion of solid particles in the wake of a rectangular plane at a Reynolds number (Re) of 10000 and that of droplets in the wake of a simplified tractor-trailer geometry at Re = 2 x 10{sup 6} using both the Large Eddy Simulation (LES) and Unsteady Reynolds-Averaged Navier-Stokes (URANS) turbulence modeling approaches. The calculations were performed using identical meshes for both the LES and URANS models. Particle stresses are not backcoupled to the carrier fluid velocity solution. In the case of the rectangular plane wake, the LES calculation predicts a finer-scale and more persistent wake structure than the URANS one; the resulting particle dispersion is considerably ({approx} 40%) underpredicted for low inertia particles. For the case of the simplified tractor-trailer geometry, although the LES is underresolved, similar trends are observed with strong differences in the vertical and horizontal dispersion of the smallest particles. These results suggest that it may be necessary to use LES to accurately capture the dispersion behavior of small, low inertia particles or droplets, but that URANS may be sufficient for problems in which only large particles with substantial inertia are of primary concern.
Date: January 19, 2006
Creator: Paschkewitz, J S
Partner: UNT Libraries Government Documents Department

Modeling of Crevice Corrosion Stability of a NiCrMo Alloy and Stainless Steel

Description: Damage of structural significance from crevice corrosion of corrosion resistant alloys requires that at least a portion of the creviced area remain active over a sufficiently long period. Stifling results shen the aggressive chemistry required inside the crevice to keep the material depassivated, i.e., actively corroding, cannot be maintained. This loss of critical chemistry occurs when the rate of mass transport out of the crevice exceeds the rate of dissolution and subsequent hydrolysis of metal ions inside the crevice. For the treatment considered here, the mass transport conditions are constant for a given geometry and potential. What then controls the stability of the internal chemistry is the interaction between the electrochemical kinetics at the interface and the crevice chemistry composition. This work focuses on the parameters that control the stability of crevice corrosion by modeling the evolution of the chemical and electrochemical conditions within a crevice open only at one end (e.g. the mouth) in which the entire crevice is initially filled with the Critical Chemistry Solution (CCS) or filled with chemistries slightly less or more aggressive than the CCS. The crevice mouth is in contact with a weak acid solution (pH 3) that provides the boundary conditions at the crevice mouth. The potential at the mouth was held constant at +0.1 V{sub sce} in most instances with selected cases held at 0.0 V{sub sce}. The material selected was Ni-22Cr-6Mo alloy. The electrochemical kinetics at the pH values of interest have been recently characterized via potentiodynamic polarization. Figure 1 shows the polarization curves for Ni-22Cr-6Mo samples tested at room temperature in various HCl solutions. These data were used in all calculations. That is as the pH changed, a new polarization curve was applied to the position in the crevice. E, pH was calculated at each position and from this data, ...
Date: May 19, 2006
Creator: Presuel-Moreno, F.J.; Bocher, F.; Scully, J.R. & Kelly, R.G.
Partner: UNT Libraries Government Documents Department

Holographic Gauge Mediation

Description: We discuss gravitational backgrounds where supersymmetry is broken at the end of a warped throat, and the SUSY-breaking is transmitted to the Standard Model via gauginos which live in (part of) the bulk of the throat geometry. We find that the leading effect arises from splittings of certain 'messenger mesons,' which are adjoint KK-modes of the D-branes supporting the Standard Model gauge group. This picture is a gravity dual of a strongly coupled field theory where SUSY is broken in a hidden sector and transmitted to the Standard Model via a relative of semi-direct gauge mediation.
Date: June 19, 2009
Creator: Benini, Francesco; U., /Princeton; Dymarsky, Anatoly; /Stanford U., ITP; Franco, Sebastian; /Santa Barbara, KITP et al.
Partner: UNT Libraries Government Documents Department

Parallel Higher-order Finite Element Method for Accurate Field Computations in Wakefield and PIC Simulations

Description: Over the past years, SLAC's Advanced Computations Department (ACD), under SciDAC sponsorship, has developed a suite of 3D (2D) parallel higher-order finite element (FE) codes, T3P (T2P) and Pic3P (Pic2P), aimed at accurate, large-scale simulation of wakefields and particle-field interactions in radio-frequency (RF) cavities of complex shape. The codes are built on the FE infrastructure that supports SLAC's frequency domain codes, Omega3P and S3P, to utilize conformal tetrahedral (triangular)meshes, higher-order basis functions and quadratic geometry approximation. For time integration, they adopt an unconditionally stable implicit scheme. Pic3P (Pic2P) extends T3P (T2P) to treat charged-particle dynamics self-consistently using the PIC (particle-in-cell) approach, the first such implementation on a conformal, unstructured grid using Whitney basis functions. Examples from applications to the International Linear Collider (ILC), Positron Electron Project-II (PEP-II), Linac Coherent Light Source (LCLS) and other accelerators will be presented to compare the accuracy and computational efficiency of these codes versus their counterparts using structured grids.
Date: June 19, 2009
Creator: Candel, A.; Kabel, A.; Lee, L.; Li, Z.; Limborg, C.; Ng, C. et al.
Partner: UNT Libraries Government Documents Department

Progress in Understanding Error-field Physics in NSTX Spherical Torus Plasmas

Description: The low aspect ratio, low magnetic field, and wide range of plasma beta of NSTX plasmas provide new insight into the origins and effects of magnetic field errors. An extensive array of magnetic sensors has been used to analyze error fields, to measure error field amplification, and to detect resistive wall modes in real time. The measured normalized error-field threshold for the onset of locked modes shows a linear scaling with plasma density, a weak to inverse dependence on toroidal field, and a positive scaling with magnetic shear. These results extrapolate to a favorable error field threshold for ITER. For these low-beta locked-mode plasmas, perturbed equilibrium calculations find that the plasma response must be included to explain the empirically determined optimal correction of NSTX error fields. In high-beta NSTX plasmas exceeding the n=1 no-wall stability limit where the RWM is stabilized by plasma rotation, active suppression of n=1 amplified error fields and the correction of recently discovered intrinsic n=3 error fields have led to sustained high rotation and record durations free of low-frequency core MHD activity. For sustained rotational stabilization of the n=1 RWM, both the rotation threshold and magnitude of the amplification are important. At fixed normalized dissipation, kinetic damping models predict rotation thresholds for RWM stabilization to scale nearly linearly with particle orbit frequency. Studies for NSTX find that orbit frequencies computed in general geometry can deviate significantly from those computed in the high aspect ratio and circular plasma cross-section limit, and these differences can strongly influence the predicted RWM stability. The measured and predicted RWM stability is found to be very sensitive to the E × B rotation profile near the plasma edge, and the measured critical rotation for the RWM is approximately a factor of two higher than predicted by the MARS-F code using the semi-kinetic ...
Date: May 19, 2010
Creator: E. Menard, R.E. Bell, D.A. Gates, S.P. Gerhardt, J.-K. Park, S.A. Sabbagh, J.W. Berkery, A. Egan, J. Kallman, S.M. Kaye, B. LeBlanc, Y.Q. Liu, A. Sontag, D. Swanson, H. Yuh, W. Zhu and the NSTX Research Team
Partner: UNT Libraries Government Documents Department

Safety Considerations for Laser Power on Metals in Contact with High Explosives-Experimental an Calculational Results

Description: Measurements have been made to determine safe levels of laser exposure on common metals used in contact with high explosive (HE) samples. Laser light is often used on metals in contact with HE during alignment procedures and experimental data collection. The measurements look at temperature rise of the surface of the metal in contact with HE when laser energy is incident on the opposite side of the metal. The temperature rise was measured as a function of incident laser power, spot size, metal composition and metal thickness. Numerical simulations were also performed to solve the two-dimensional heat flow problem for the experimental geometry. In order to allow a single numerical simulation to represent a large number of physical cases, the equations used in the simulation were expressed in terms of dimensionless variables. The normalized numerical solutions can then be compared with the various experimental configurations used. Calculations and experiment agree well over the range measured.
Date: April 19, 2000
Creator: Roeske, F. & Carpenter, K. H.
Partner: UNT Libraries Government Documents Department

Human supervisory approach to modeling industrial scenes using geometric primitives

Description: A three-dimensional world model is crucial for many robotic tasks. Modeling techniques tend to be either fully manual or autonomous. Manual methods are extremely time consuming but also highly accurate and flexible. Autonomous techniques are fast but inflexible and, with real-world data, often inaccurate. The method presented in this paper combines the two, yielding a highly efficient, flexible, and accurate mapping tool. The segmentation and modeling algorithms that compose the method are specifically designed for industrial environments, and are described in detail. A mapping system based on these algorithms has been designed. It enables a human supervisor to quickly construct a fully defined world model from unfiltered and unsegmented real-world range imagery. Examples of how industrial scenes are modeled with the mapping system are provided.
Date: November 19, 1997
Creator: Luck, J.P.; Little, C.Q. & Roberts, R.S.
Partner: UNT Libraries Government Documents Department

String theory and non-commutative geometry [Final report]

Description: During the period of the three-year DOE grant DEFG02-94ER-25228, granted for the period August 1, 1997 to July 31, 2000, and extended until July 31, 2001, the investigator made significant progress and achieved most of the proposed goals. He completed certain older work, discovered a number of fundamental new theoretical phenomena, developed theories about them, and we began a project to integrate twist quantum fields into constructive quantum field theory, and to determine the effects of twisting on breaking supersymmetry.
Date: November 19, 2001
Creator: Jaffe, Arthur
Partner: UNT Libraries Government Documents Department