Resource Type

Month

Simulation of Plasma Fluxes to Material Surfaces with Self-Consistent Edge Turbulence and Transport for Tokamaks (open access)

Simulation of Plasma Fluxes to Material Surfaces with Self-Consistent Edge Turbulence and Transport for Tokamaks

The edge-plasma profiles and fluxes to the divertor and walls of a divertor tokamak with a magnetic X-point are simulated by coupling a 2D transport code (UEDGE) and a 3D turbulence code (BOUT). An relaxed iterative coupling scheme is used where each code is run on its characteristic time scale, resulting in a statistical steady state. Plasma variables of density, parallel velocity, and separate ion and electron temperatures are included, together with a fluid neutral model for recycling neutrals at material surfaces. Results for the DIII-D tokamak parameters show that the turbulence is preferentially excited in the outer radial region of the edge where magnetic curvature is destabilizing and that substantial plasma particle flux is transported to the main chamber walls. These results are qualitatively consistent with some experimental observations. The coupled transport/turbulence simulation technique provides a strategy to understanding edge-plasma physics in more detailed than previously available and to significantly enhance the realism of predictions of the performance of future devices.
Date: May 24, 2004
Creator: Rognlien, T.; Umansky, M.; Xu, X.; Cohen, R. & LoDestro, L.
System: The UNT Digital Library
Comparison of Plasma Parameters Between QH and ELMing Phases of the Same Discharges (open access)

Comparison of Plasma Parameters Between QH and ELMing Phases of the Same Discharges

H-mode confinement is observed for many energy confinement times without edge localized modes (ELMs) in QH (quiescent high-confinement)-mode discharges in DIII-D. To find critical differences between ELMing and QH modes we compared electron temperature (T{sub e}), density (n{sub e}), and ion temperature (T{sub i}), in the pedestal and scrape-off layer (SOL) for a group of discharges. We also compared the electron pressures P{sub ped}, and maximum pressure gradients P{sub e,ped,max grad} because of their importance in confinement and stability. Experimental results show that the core line averaged density, median T{sub e} (pedestal), SOL T{sub e}, and T{sub e} pedestal width, and SOL T{sub i} are nearly the same in QH mode as that during ELMs. The n{sub e} (average pedestal), n{sub e} pedestal width, P{sub ped}, and P{sub e,ped,max grad} are similar to corresponding values in QH mode and at various times between ELMs. However, the pedestal T{sub i} is 1.6 times higher in QH mode than during ELMing.
Date: May 24, 2004
Creator: Lasnier, C.; West, W.; Burrell, K.; deGrassie, J.; Doyle, E. & Osborne, T.
System: The UNT Digital Library
New physics searches with photons in CDF (open access)

New physics searches with photons in CDF

A brief review of searches for physics beyond the Standard Model with photons using the CDF detector at the Tevatron is given here. These include searches for supersymmetry, extra dimensions, excited electrons and W/Z+{gamma} production, as well as anomalous photon production. Recent results from CDF Run II experiment are presented, but some results from Run I are also reviewed.
Date: May 24, 2004
Creator: Lee, Sungwon
System: The UNT Digital Library
Elimination of Whole Effluent Toxicity NPDES Permit Limits through the Use of an Alternative Testing Species and Reasonable Potential Analysis (open access)

Elimination of Whole Effluent Toxicity NPDES Permit Limits through the Use of an Alternative Testing Species and Reasonable Potential Analysis

The cladoceran, Ceriodaphnia dubia (C. dubia), is required by the State of South Carolina to be used in whole effluent toxicity (WET) compliance tests in order to meet limits contained within National Pollutant Discharge Elimination System (NPDES) permits. Westinghouse Savannah River Company (WSRC) experienced WET test failures for no clear reason over a long period of time. Toxicity identification examinations on effluents did not indicate the presence of toxicants; therefore, the WET test itself was brought under suspicion. Research was undertaken with an alternate cladoceran, Daphnia ambigua (D. ambigua). It was determined that this species survives better in soft water, so approval was obtained from regulating authorities to use this ''alternate'' species in WET tests. The result was better test results and elimination of non-compliances. The successful use of D. ambigua allowed WSRC to gain approval from the South Carolina Department of Health and Environmental Control (SCDHEC) to remove WET limits from the NPDES permit.
Date: May 24, 2004
Creator: PAYNE, W.L.
System: The UNT Digital Library
Investigation on a summer operation effect of a district energy system at Kitakyushu science research city (open access)

Investigation on a summer operation effect of a district energy system at Kitakyushu science research city

In Kitakyushu Science and Research Park, a new district energy system has been introduced. In this study, we chose this system as a case study and have carried out an analysis on the efficiency of the power generation and heat release utilization of the fuel cell and gas engine in summer by using the recorded data. The results can be summarized as follows; (1) Although the power generation efficiencies of the gas engine and fuel cell are a little bit lower than the standard designated value, they are almost running at stable condition. (2) The collected heat energy is lower than the designated value. The heat release utilization, which is used for cooling and hot water, is fairly low. Considering the efficient use of energy, it is a key to have a good use of heat release when we introduce a district energy system. (3) The discarded heat energy of the system is very big in this investigation when evaluating the system as a whole. It is fundamental to the future of energy conservation to use primary energy more efficiently.
Date: May 24, 2004
Creator: Gao, Weijun; Zhou, Nan; Nishida, Masaru; Sagara, Noriyasu; Ryu, Yuji & Ojima, Toshio
System: The UNT Digital Library
Simulation of Plasma Fluxes to Material Surfaces with Self-consistent Edge Turbulence and Transport for Tokamaks (open access)

Simulation of Plasma Fluxes to Material Surfaces with Self-consistent Edge Turbulence and Transport for Tokamaks

The edge-plasma profiles and fluxes to the divertor and walls of a divertor tokamak with a magnetic X-point are simulated by coupling a 2D transport code (UEDGE) and a 3D turbulence code (BOUT). An relaxed iterative coupling scheme is used where each code is run on its characteristic time scale, resulting in a statistical steady state. Plasma variables of density, parallel velocity, and separate ion and electron temperatures are included, together with a fluid neutral model for recycling neutrals at material surfaces. Results for the DIII-D tokamak parameters show that the turbulence is preferentially excited in the outer radial region of the edge where magnetic curvature is destabilizing and that substantial plasma particle flux is transported to the main chamber walls. These results are qualitatively consistent with some experimental observations. The coupled transport/turbulence simulation technique provides a strategy to understanding edge-plasma physics in more detailed than previously available and to significantly enhance the realism of predictions of the performance of future devices
Date: May 24, 2004
Creator: Rognlien, T.; Umanksy, M.; Xu, X.; Cohen, R. & LoDestro, L.
System: The UNT Digital Library
Design and Characterization of a Neutralized-Transport Experiment for Heavy-Ion Fusion (open access)

Design and Characterization of a Neutralized-Transport Experiment for Heavy-Ion Fusion

In heavy-ion inertial-confinement fusion systems, intense beams of ions must be transported from the exit of the final focus magnet system through the fusion chamber to hit millimeter-sized spots on the target. Effective plasma neutralization of intense ion beams in this final transport is essential for a heavy-ion fusion power plant to be economically competitive. The physics of neutralized drift has been studied extensively with particle-in-cell simulations. To provide quantitative comparisons of theoretical predictions with experiment, the Virtual National Laboratory for Heavy Ion Fusion has completed the construction and has begun experimentation with the Neutralized Transport Experiment (NTX). The experiment consists of three main sections, each with its own physics issues. The injector is designed to generate a very high-brightness, space-charge-dominated potassium beam while still allowing variable perveance by a beam aperturing technique. The magnetic-focusing section, consisting of four pulsed magnetic quadrupoles, permits the study of beam tuning, as well as the effects of phase space dilution due to higher-order nonlinear fields. In the final section, a converging ion beam exiting the magnetic section is transported through a drift region with plasma sources for beam neutralization, and the final spot size is measured under various conditions of neutralization. In this …
Date: May 24, 2004
Creator: Henderson, E.; Eylon, S.; Roy, P.; Yu, S. S.; Anders, A.; Bieniosek, F. M. et al.
System: The UNT Digital Library
ANSI/ANS 8.12, Nuclear Criticality Control and Safety of Plutonium-Uranium Fuel Mixtures Outside Reactors (open access)

ANSI/ANS 8.12, Nuclear Criticality Control and Safety of Plutonium-Uranium Fuel Mixtures Outside Reactors

None
Date: May 24, 2004
Creator: Huang, S T
System: The UNT Digital Library
Deuterium Experiments in the Sustained Spheromak Physics Experiment (open access)

Deuterium Experiments in the Sustained Spheromak Physics Experiment

In this paper we report on the results of isotope exchange experiments in the Sustained Spheromak Physics Experiment (SSPX). We have compared {approx}500 deuterium discharges with similar discharges in hydrogen. Typically, we produce plasmas with peak toroidal currents in the range of 0.6 MA, electron temperatures (T{sub e}) of {approx}200 eV and energy confinement times ({tau}{sub E}) of {approx}200 {micro}s. The D{sub 2} fueled discharges show similar results to those with H{sub 2} fueling with no obvious differences in confinement time. Electron temperatures of {approx}200 eV with similar electron densities were observed. Both the deuterium and hydrogen fueled discharges have a calculated thermal conduction below {chi}{sub e}<10 m{sup 2}/s. However, the D{sub 2} fueled discharges had a modest increase in high-Z (titanium) impurity content suggesting an increase of physical sputtering. We find no significant mass scaling effects.
Date: May 24, 2004
Creator: Wood, R; Hill, D N; Hooper, E; McLean, H; Ryutov, D & Woodruff, S
System: The UNT Digital Library
Degradation of Magnet Epoxy at NSLS X-Ray Ring. (open access)

Degradation of Magnet Epoxy at NSLS X-Ray Ring.

Epoxy resin degradation was analyzed for NSLS X-ring magnets after two decades of 2.58-2.8 GeV continuous electron-beam operation, based on results obtained from thermoluminescent dosimeters irradiated along the NSLS ring and epoxy samples irradiated at the beamline target location. A Monte Carlo-based particle transport code, MCNP, was utilized to verify the dose from synchrotron radiation distributed along the axial- and transverse-direction in a ring model, which simulates the geometry of a ring quadrupole magnet and its central vacuum chamber downstream of the bending-magnet photon ports. The actual life expectancy of thoroughly vacuum baked-and-cured epoxy resin was estimated from radiation tests on similar polymeric materials using a radiation source developed for electrical insulation and mechanical structure studies.
Date: May 24, 2004
Creator: HU,J. P.; Zhong, Z.; Haas, E.; Hulbert, S. & Hubbard, R.
System: The UNT Digital Library