Resource Type

Language

Optical and EUV light curves of dwarf nova outbursts (open access)

Optical and EUV light curves of dwarf nova outbursts

We combine AAVSO and VSS/RASNZ optical and Extreme Ultraviolet Explorer EUV light curves of dwarf novae in outburst to place constraints on the nature of dwarf nova outbursts. From the observed optical-EUV time delays of {approx} 0.75-1.5 days, we show that the propagation velocity of the dwarf nova instability heating wave is {approx} 3 km s{sup -1}.
Date: November 15, 2000
Creator: Mauche, C W; Mattei, J A & Bateson, F M
System: The UNT Digital Library
The role of the multi buffer layer technique on the structural quality of GaN (open access)

The role of the multi buffer layer technique on the structural quality of GaN

None
Date: November 15, 2000
Creator: Benamara, Mourad; Liliental-Weber, Z.; Mazur, J.H.; Swider, W.; Washburn, J.; Iwaya, M. et al.
System: The UNT Digital Library
Liquid Lithium Experiments in CDX-U (open access)

Liquid Lithium Experiments in CDX-U

The initial results of experiments involving the use of liquid lithium as a plasma facing component in the Current Drive Experiment-Upgrade (CDX-U) are reported. Studies of the interaction of a steady-state plasma with liquid lithium in the Plasma Interaction with Surface and Components Experimental Simulator (PISCES-B) are also summarized. In CDX-U a solid or liquid lithium covered rail limiter was introduced as the primary limiting surface for spherical torus discharges. Deuterium recycling was observed to be reduced, but so far not eliminated, for glow discharge-cleaned lithium surfaces. Some lithium influx was observed during tokamak operation. The PISCES-B results indicate that the rates of plasma erosion of lithium can exceed predictions by an order of magnitude at elevated temperatures. Plans to extend the CDX-U experiments to large area liquid lithium toroidal belt limiters are also described.
Date: November 15, 2000
Creator: Majeski, R.; Doerner, R.; Kaita, R.; Antar, G.; Timberlake, J. & al, et
System: The UNT Digital Library
Flibe assessments. (open access)

Flibe assessments.

An assessment of the issues on using flibe for fusion applications has been made. It is concluded that sufficient tritium breeding can be achieved for a flibe blanket, especially if a few cm of Be is include in the blanket design. A key issue is the control of the transmutation products such as TF and F{sub 2}. A REDOX (Reducing-Oxidation) reaction has to be demonstrated which is compatible to the blanket design. Also, MHD may have strong impact on heat transfer if the flow is perpendicular to the magnetic field. The issues associated with the REDOX reaction and the MHD issues have to be resolved by both experimental program and numerical solutions.
Date: November 15, 2000
Creator: Sze, D. K.; McCarthy, K.; Sawan, M.; Tillack, M.; Ying, A. & Zinkle, S.
System: The UNT Digital Library
Recent Progress in MHD Stability Calculations of Compact Stellarators (open access)

Recent Progress in MHD Stability Calculations of Compact Stellarators

A key issue for compact stellarators is the stability of beta-limiting MHD modes, such as external kink modes driven by bootstrap current and pressure gradient. We report here recent progress in MHD stability studies for low-aspect-ratio Quasi-Axisymmetric Stellarators (QAS) and Quasi-Omnigeneous Stellarators (QOS). We find that the N = 0 periodicity-preserving vertical mode is significantly more stable in stellarators than in tokamaks because of the externally generated rotational transform. It is shown that both low-n external kink modes and high-n ballooning modes can be stabilized at high beta by appropriate 3D shaping without a conducting wall. The stabilization mechanism for external kink modes in QAS appears to be an enhancement of local magnetic shear due to 3D shaping. The stabilization of ballooning mode in QOS is related to a shortening of the normal curvature connection length.
Date: November 15, 2000
Creator: Fu, G. Y.; Ku, L. P.; Redi, M. H.; Kessel, C.; Monticello, D. A.; Reiman, A. et al.
System: The UNT Digital Library
Uncertainty Analysis of Decomposing Polyurethane Foam (open access)

Uncertainty Analysis of Decomposing Polyurethane Foam

None
Date: November 15, 2000
Creator: Hobbs, Michael L. & Romero, Vicente J.
System: The UNT Digital Library
Local Physics Basis of Confinement Degradation in JET ELMy H-Mode Plasmas and Implications for Tokamak Reactors (open access)

Local Physics Basis of Confinement Degradation in JET ELMy H-Mode Plasmas and Implications for Tokamak Reactors

ELMy H-mode plasmas form the basis of conservative performance predictions for tokalmak reactors of the size of ITER. Relatively high performace for long durations has been achieved and the scaling is favorable. It will be necessary to sustain low Zeff and high density for high fusion yield. This paper studies the degradation in confinement and increase in the anomalous heat transport observed in two JET plasmas: one in which the degradation occurs with an intense gas puff, and the other with a spontaneous transition at the heating power threshold from Type I to III ELMs. Linear gryokinetic analysis gives the growth rate, glin of the fastest growing mode. Our results indicate that the flow-shearing rate wExB and glin are large near the top of the pedestal. Their ratio decreases approximately when the confinement degrades and the transport increases. This suggests that tokamak reactors may require intense toroidal or poloidal torque input to maintain sufficiently high *wExB*/glin near the top of the pedestal for high confinement.
Date: November 15, 2000
Creator: Budny, R.V.
System: The UNT Digital Library
Improvement of JT-60U Negative Ion Source Performance (open access)

Improvement of JT-60U Negative Ion Source Performance

The negative ion neutral beam system now operating on JT-60U was the first application of negative ion technology to the production of beams of high current and power for conversion to neutral beams, and has successfully demonstrated the feasibility of negative ion beam heating systems for ITER and future tokamak reactors [1, 2]. It also demonstrated significant electron heating[3] and high current drive efficiency in JT-60U[4]. Because this was such a large advance in the state of the art with respect to all system parameters, many new physical processes appeared during the earlier phases of the beam injection experiments. We have explored the physical mechanisms responsible for these processes, and implemented solutions for some of them, in particular excessive beam stripping, the secular dependence of the arc and beam parameters, and nonuniformity of the plasma illuminating the beam extraction grid. This has reduced the percentage of beam heat loading on the downstream grids by roug hly a third, and permitted longer beam pulses at higher powers. Progress is being made in improving the negative ion current density, and in coping with the sensitivity of the cesium in the ion sources to oxidation by tiny air or water leaks, and the …
Date: November 15, 2000
Creator: Grisham, L. R.; Kuriyama, M.; Kawai, M.; Itoh, T.; Umeda, N. & Team, JT-60U
System: The UNT Digital Library
Global Stability of the Field Reversed Configuration (open access)

Global Stability of the Field Reversed Configuration

New computational results are presented which provide a theoretical basis for the stability of the Field Reversed Configuration (FRC). The FRC is a compact toroid with negligible toroidal field in which the plasma is confined by a poloidal magnetic field associated with toroidal diamagnetic current. Although many MHD modes are predicted to be unstable, FRCs have been produced successfully by several formation techniques and show surprising macroscopic resilience. In order to understand this discrepancy, we have developed a new 3D nonlinear hybrid code (kinetic ions and fluid electrons), M3D-B, which is used to study the role of kinetic effects on the n = 1 tilt and higher n modes in the FRC. Our simulations show that there is a reduction in the tilt mode growth rate in the kinetic regime, but no absolute stabilization has been found for s bar less than or approximately equal to 1, where s bar is the approximate number of ion gyroradii between the field null and the separatrix. However, at low values of s bar, the instabilities saturate nonlinearly through a combination of a lengthening of the initial equilibrium and a modification of the ion distribution function. These saturated states persist for many Alfven …
Date: November 15, 2000
Creator: Belova, E. V.; Jardin, S. C.; Ji, H.; Kulsrud, R. M.; Park, W. & Yamada, M.
System: The UNT Digital Library
Fast Particle Effects on the Internal Kink, Fishbone and Alfven Modes (open access)

Fast Particle Effects on the Internal Kink, Fishbone and Alfven Modes

The issues of linear stability of low frequency perturbative and nonperturbative modes in advanced tokamak regimes are addressed based on recent developments in theory, computational methods, and progress in experiments. Perturbative codes NOVA and ORBIT are used to calculate the effects of TAEs on fast particle population in spherical tokamak NSTX. Nonperturbative analysis of chirping frequency modes in experiments on TFTR and JT-60U is presented using the kinetic code HINST, which identified such modes as a separate branch of Alfven modes - resonance TAE (R-TAE). Internal kink mode stability in the presence of fast particles is studied using the NOVA code and hybrid kinetic-MHD nonlinear code M3D.
Date: November 15, 2000
Creator: Gorelenkov, N. N.; Bernabei, S.; Cheng, C. Z.; Fu, G. Y.; Hill, K.; Kaye, S. et al.
System: The UNT Digital Library
Emerging Technologies and MOUT (open access)

Emerging Technologies and MOUT

Operating in a potentially hostile city is every soldier's nightmare. The staggering complexity of the urban environment means that deadly threats--or non-combatants-may lurk behind every corner, doorway, or window. Urban operations present an almost unparalleled challenge to the modern professional military. The complexity of urban operations is further amplified by the diversity of missions that the military will be called upon to conduct in urban terrain. Peace-making and peace-keeping missions, urban raids to seize airports or WMD sites or to rescue hostages, and extended urban combat operations all present different sorts of challenges for planners and troops on the ground. Technology almost never serves as a magic bullet, and past predictions of technological miracles pile high on the ash heap of history. At the same time, it is a vital element of planning in the modern age to consider and, if possible, take advantage of emerging technologies. We believe that technologies can assist military operations in urbanized terrain (MOUT) in three primary areas, which are discussed.
Date: November 15, 2000
Creator: YONAS,GEROLD & MOY,TIMOTHY DAVID
System: The UNT Digital Library
Role of Zonal Flow in Turbulent Transport Scaling (open access)

Role of Zonal Flow in Turbulent Transport Scaling

Transport scalings with respect to collisionality (n*) and device size (r*) are obtained from massively parallel gyrokinetic particle simulations of toroidal ion-temperature-gradient (ITG) turbulence in the presence of zonal flows. Simulation results show that ion thermal transport from electrostatic ITG turbulence depends on ion-ion collisions due to the neo-classical damping of self-generated EXB zonal flows that regulate the turbulence. Fluctuations and heat transport levels exhibit bursting behavior with a period corresponding to the collisional damping time of poloidal flows. Results from large-scale full torus simulations with device-size scans for realistic parameters show that Bohm-like transport can be driven by microscopic scale fluctuations in the ITG turbulence with isotropic spectra. These simulation results resolve some apparent physics contradictions between experimental observations and turbulent transport theories.
Date: November 15, 2000
Creator: Lin, Z.; Hahm, T. S.; Krommes, J. A.; Lee, W. W.; Lewandowski, J.; Mynick, H. et al.
System: The UNT Digital Library
Flibe blanket concept for transmuting transuranic elements and long lived fission products. (open access)

Flibe blanket concept for transmuting transuranic elements and long lived fission products.

A Molten salt (Flibe) fusion blanket concept has been developed to solve the disposition problems of the spent nuclear fuel and the transuranic elements. This blanket concept can achieve the top rated solution, the complete elimination of the transuranic elements and the long-lived fission products. Small driven fusion devices with low neutron wall loading and low neutron fluence can perform this function. A 344-MW integrated fusion power from D-T plasmas for thirty years with an availability factor of 0.75 can dispose of 70,000 tons of the US inventory of spent nuclear fuel generated up to the year 2015. In addition, the utilization of this blanket concept eliminates the need for a geological repository site, which is a major advantage. This application provides an excellent opportunity to develop and to enhance the public acceptance of the fusion energy for the future. The energy from the transmutation process is utilized to produce revenue. Flibe, lithium-lead eutectic, and liquid lead are possible candidates. The liquid blankets have several features, which are suited for W application. It can operate at constant thermal power without interruption for refueling by adjusting the concentration of the transuranic elements and lithium-6. These liquids operate at low-pressure, which reduces …
Date: November 15, 2000
Creator: Gohar, Y.
System: The UNT Digital Library
Performance of a Treatment Loop for Recycling Spent Rinse Waters (open access)

Performance of a Treatment Loop for Recycling Spent Rinse Waters

This paper summarizes an evaluation of a treatment loop designed to upgrade the quality of spent rinse waters discharged from 10 wet benches located in the fab at Sandia's Microelectronics Development Laboratory (MDL). The goal of the treatment loop is to make these waters, presently being discharged to the fab's acid waste neutralization (AWN) station, suitable for recycling as feed water back into the fab's ultrapure water (UPW) plant. The MDL typically operates 2 shifts per day, 5 days per week. Without any treatment, the properties of the spent rinse waters now being collected have been shown to be compatible with recycling about 30% (50/168) of the time (weekends primarily, when the fab is idling) which corresponds to about 12% of the present water discharged from the fab to the AWN. The primary goal of adding a treatment loop is to increase the percentage of recyclable water from these 10 wet benches to near 100%, increasing the percentage of total recyclable water to near 40% of the total present fab discharge to the AWN. A second goal is to demonstrate compatibility with recycling this treated spent rinse water to the present R/O product water tank, reducing both the present volume …
Date: November 15, 2000
Creator: Donovan, Robert Patrick; Timon, Robert P.; DeBusk, Michael John; Jones, Ronald V. & Rogers, Darell M.
System: The UNT Digital Library
Carolina Geological Society 2000 Field Trip Guidebook - Geology: Improving Environmental Cleanup of the A/M Area, Savannah River Site (open access)

Carolina Geological Society 2000 Field Trip Guidebook - Geology: Improving Environmental Cleanup of the A/M Area, Savannah River Site

This guidebook will be distributed to 200 geologists for the Carolina Geological Society Meeting and the onsite field trip in November.
Date: November 15, 2000
Creator: Harris, M.K.
System: The UNT Digital Library
The Combined Effect of EPM and TAE Modes on Energetic Ion Confinement and Sawtooth Stabilization (open access)

The Combined Effect of EPM and TAE Modes on Energetic Ion Confinement and Sawtooth Stabilization

It is shown in this paper for the first time, that the chirping Alfven instabilities observed mostly during ion cyclotron range of frequency (ICRF) heating have been positively identified as Energetic Particle Modes (EPM). This has been possible because of the detailed measurement of the q-profile with the MSE (motional Stark effect) diagnostic in DIII-D. The EPMs are shown to be the leading cause of the monster sawtooth crash. It is also shown that TAEs are excited either directly or indirectly by the EPMs and they cause fast ion losses. A scenario for the stabilization and the crash of the monster sawtooth and for the degradation of the ICRF heating efficiency at high power is presented.
Date: November 15, 2000
Creator: Bernabei, S.; Budny, R.; Fredrickson, E. D.; Gorelenkov, N. N.; Hosea, J. C.; Phillips, C. K. et al.
System: The UNT Digital Library
Worst-Case Bias During Total Dose Irradiation of SOI Transistors (open access)

Worst-Case Bias During Total Dose Irradiation of SOI Transistors

None
Date: November 15, 2000
Creator: Ferlet-Cavrois, V.; Collandant, T.; Paillet, P.; Leray, J. L.; Musseau, O.; Schwank, James R. et al.
System: The UNT Digital Library
Investigation of Hypergolic Fuels with Hydrogen Peroxide (open access)

Investigation of Hypergolic Fuels with Hydrogen Peroxide

None
Date: November 15, 2000
Creator: MELOF,BRIAN M. & GRUBELICH,MARK C.
System: The UNT Digital Library
Origins of Total-Dose Response Variability in Linear Bipolar Microcircuits (open access)

Origins of Total-Dose Response Variability in Linear Bipolar Microcircuits

LM1ll voltage comparators exhibit a wide range of total-dose-induced degradation. Simulations show this variability may be a natural consequence of the low base doping of the substrate PNP (SPNP) input transistors. Low base doping increases the SPNP's collector to base breakdown voltage, current gain, and sensitivity to small fluctuations in the radiation-induced oxide defect densities. The build-up of oxide trapped charge (N{sub ot}) and interface traps (N{sub it}) is shown to be a function of pre-irradiation bakes. Experimental data indicate that, despite its structural similarities to the LM111, irradiated input transistors of the LM124 operational amplifier do not exhibit the same sensitivity to variations in pre-irradiation thermal cycles. Further disparities in LM111 and LM124 responses may result from a difference in the oxide defect build-up in the two part types. Variations in processing, packaging, and circuit effects are suggested as potential explanations.
Date: November 15, 2000
Creator: Barnaby, H. J.; Cirba, C. R.; Schrimpf, R. D.; Fleetwood, D. M.; Pease, R. L.; Shaneyfelt, M. R. et al.
System: The UNT Digital Library
Carolina Geological Society 2000 Field Trip Guidebook (open access)

Carolina Geological Society 2000 Field Trip Guidebook

This guidebook will be distributed to 200 geologists for the Carolina Geological Society Meeting and the onsite field trip in November.
Date: November 15, 2000
Creator: Wyatt, D.E.
System: The UNT Digital Library
Synthesis and Characterization of Sn-Coated SFG10 Graphites as Negative Electrodes in Li-Ion Cells (open access)

Synthesis and Characterization of Sn-Coated SFG10 Graphites as Negative Electrodes in Li-Ion Cells

None
Date: November 15, 2000
Creator: VEERARAGHAVAN,B.; DURAIRAJAN,A.; WHITE,R.E.; POPOV,B.N. & GUIDOTTI,RONALD A.
System: The UNT Digital Library
Thermal fatigue due to beam interruptions in a Lead-Bismuth cooled ATW blanket (open access)

Thermal fatigue due to beam interruptions in a Lead-Bismuth cooled ATW blanket

Thermal fatigue consequences of frequent accelerator beam interruptions are quantified for both sodium and lead-bismuth cooled blankets in current designs for accelerator transmutation of waste devices. Temperature response was calculated using the SASSYS-1 systems analysis code for an immediate drop in beam current from full power to zero. Coolant temperatures from SASSYS-1 were fed into a multi-node structure temperature calculation to obtain thermal strains for various structural components. Fatigue curves from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code were used to determine the number of cycles that these components could endure, based on these thermal strains. Beam interruption frequency data from a current accelerator were used to estimate design lifetimes for components. Mitigation options for reducing thermal fatigue are discussed.
Date: November 15, 2000
Creator: Dunn, F.
System: The UNT Digital Library
Application of TIVA in Design Debug (open access)

Application of TIVA in Design Debug

None
Date: November 15, 2000
Creator: Kolachina, Siva; Taylor, Bill; Wills, Kendall Scott & Cole, Edward I., Jr.
System: The UNT Digital Library
Recent electroweak results from {nu} - N scattering at NuTeV (open access)

Recent electroweak results from {nu} - N scattering at NuTeV

None
Date: November 15, 2000
Creator: Yu, Jaehoon
System: The UNT Digital Library