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K-shell ionization and double-ionization of Au atoms with 1.33 MeV photons

Description: At relativistic energies, the cross section for the atomic photoelectric effect drops off as does the cross section for liberating any bound electron through Compton scattering. However, when the photon energy exceeds twice the rest mass of the electron, ionization may proceed via electron-positron pair creation. We used 1.33 MeV photons impinging on Au thin foils to study double K-shell ionization and vacuum-assisted photoionization. The preliminary results yield a ratio of vacuum-assisted photoionization and pair creation of 2x10{sup -3}, a value that is substantially higher than the ratio of photo double ionization to single photoionization that is found to be 0.5-1x10{sup -4}. Because of the difficulties and large error bars associated with the small cross sections additional measurements are needed to minimize systematic errors.
Date: January 15, 2000
Creator: Belkacem, A.; Dauvergne, D.; Feinberg, B.; Ionescu, D.; Maddi, J. & Sorensen, A.H.
Partner: UNT Libraries Government Documents Department

Worst-Case Bias During Total Dose Irradiation of SOI Transistors

Description: The worst case bias during total dose irradiation of partially depleted SOI transistors (from SNL and from CEA/LETI) is correlated to the device architecture. Experiments and simulations are used to analyze SOI back transistor threshold voltage shift and charge trapping in the buried oxide.
Date: August 15, 2000
Creator: FERLET-CAVROIS,V.; COLLADANT,T.; PAILLET,P.; LERAY,J.-L; MUSSEAU,O.; SCHWANK,JAMES R. et al.
Partner: UNT Libraries Government Documents Department

Thermodynamic Modeling of Sr/TRU Removal

Description: This report summarizes the development and application of a thermodynamic modeling capability designed to treat the Envelope C wastes containing organic complexants. A complete description of the model development is presented. In addition, the model was utilized to help gain insight into the chemical processes responsible for the observed levels of Sr, TRU, Fe, and Cr removal from the diluted feed from tank 241-AN-107 which had been treated with Sr and permanganate. Modeling results are presented for Sr, Nd(III)/Eu(III), Fe, Cr, Mn, and the major electrolyte components of the waste (i.e. NO{sub 3}, NO{sub 2}, F,...). On an overall basis the added Sr is predicted to precipitate as SrCO{sub 3}(c) and the MnO{sub 4}{sup {minus}} reduced by the NO{sub 2}{sup {minus}} and precipitated as a Mn oxide. These effects result in only minor changes to the bulk electrolyte chemistry, specifically, decreases in NO{sub 2}{sup {minus}} and CO{sub 3}{sup 2{minus}}, and increases in NO{sub 3}{sup {minus}} and OH{sup {minus}}. All of these predictions are in agreement with the experimental observations. The modeling also indicates that the majority of the Sr, TRU's (or Nd(III)/Eu(III)) analogs, and Fe are tied up with the organic complexants. The Sr and permanganate additions are not predicted to effect these chelate complexes significantly owing to the precipitation of insoluble Mn oxides or SrCO{sub 3}. These insoluble phases maintain low dissolved concentrations of Mn and Sr which do not affect any of the other components tied up with the complexants. It appears that the removal of the Fe and TRU'S during the treatment process is most likely as a result of adsorption or occlusion on/into the Mn oxides or SrCO{sub 3}, not as direct displacement from the complexants into precipitates. Recommendations are made for further studies that are needed to help resolve these issues.
Date: August 15, 2000
Creator: Felmy, AR
Partner: UNT Libraries Government Documents Department

Pair creation and plasma oscillations.

Description: We describe aspects of particle creation in strong fields using a quantum kinetic equation with a relaxation-time approximation to the collision term. The strong electric background field is determined by solving Maxwell's equation in tandem with the Vlasov equation. Plasma oscillations appear as a result of feedback between the background field and the field generated by the particles produced. The plasma frequency depends on the strength of the initial background fields and the collision frequency, and is sensitive to the necessary momentum-dependence of dressed-parton masses.
Date: December 15, 2000
Creator: Prozorkevich, A. V.; Vinnik, D. V.; Schmidt, S. M.; Hecht, M. B. & Roberts, C. D.
Partner: UNT Libraries Government Documents Department

Flibe assessments.

Description: 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.
Partner: UNT Libraries Government Documents Department

Direct Energy Conversion Fission Reactor September through November 1999

Description: OAK - B135 The initial kickoff meeting/brainstorming session was held as Albuquerque with the other participants in this study. The prompt critical pulse reactor was proposed at the brainstorming session. The other participants in this study, Sandia National Laboratories (lead), Los Alamos National Laboratory, University of Florida and Texas A and M University are separately funded and their work is separately reported. The combined reporting is done by Sandia.
Date: January 15, 2000
Creator: Brown, Lloyd C.
Partner: UNT Libraries Government Documents Department

A Generalized Portable SHMEM Library for High Performance Computing

Description: This paper describes a portable one-sided communication library GPSHMEM that follows the interfaces of the successful SHMEM library introduced by Cray Research Inc. for their distributed memory systems: the Cray T3D and T3E. The portability is achieved by relying on ARMCI, a low-level communication library developed to support one-sided communication in distributed array libraries and compiler run-time systems, and the MPI message passing interface. The paper discusses implementation, requirements, and initial experience with GPSHMEM.
Date: September 15, 2000
Creator: Parzyszek, K.; Nieplocha, J. & Kendall, R.A.
Partner: UNT Libraries Government Documents Department

Testing to Support Improvements to PV Components and Systems

Description: The National Photovoltaic (PV) Program is sponsored by the US Department of Energy and includes a PV Manufacturing Research and Development (R and D) project conducted with industry. This project includes advancements in PV components to improve reliability, reduce costs, and develop integrated PV systems. Participants submit prototypes, pre-production hardware products, and examples of the resulting final products for a range of tests conducted at several national laboratories, independent testing laboratories, and recognized listing agencies. The purpose of this testing is to use the results to assist industry in determining a product's performance and reliability, and to identify areas for potential improvement. This paper briefly describes the PV Manufacturing R and D project, participants in the area of PV systems, balance of systems, and components, and several examples of the different types of product and performance testing used to support and confirm product performance.
Date: July 15, 2000
Creator: THOMAS,H.; KROPOSKI,B.; WITT,C.; BOWER,WARD I.; BONN,RUSSELL H.; GINN,JERRY W. et al.
Partner: UNT Libraries Government Documents Department

Recent Progress in MHD Stability Calculations of Compact Stellarators

Description: 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.
Partner: UNT Libraries Government Documents Department

Improvement of JT-60U Negative Ion Source Performance

Description: 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 cathode operation is being altered.
Date: November 15, 2000
Creator: Grisham, L.R.; Kuriyama, M.; Kawai, M.; Itoh, T.; Umeda, N. & Team, JT-60U
Partner: UNT Libraries Government Documents Department

Beyond the standard model at Tevatron

Description: This article presents recent results of searches for physics beyond the Standard Model using the CDF and the D0 detector at the Fermilab Tevatron Collider. All results shown correspond to analysis performed using the past 1992--1996 Fermilab Tevatron run 1 data (roughly 100 pb{sup {minus}1} per each experiment). In particular, the authors describe recent Tevatron searches for scalar top in the b + {ell} + missing-E{sub T} channel, for squark and gluinos using like-sign dileptons (LS), for large extra space-time dimensions and the search for leptoquarks and technicolor in the missing-E{sub T}+heavy flavor jet events. Tight limits on the existence of such models have been set.
Date: September 15, 2000
Creator: Pagliarone, C.
Partner: UNT Libraries Government Documents Department

BioSig: A bioinformatic system for studying the mechanism of intra-cell signaling

Description: Mapping inter-cell signaling pathways requires an integrated view of experimental and informatic protocols. BioSig provides the foundation of cataloging inter-cell responses as a function of particular conditioning, treatment, staining, etc. for either in vivo or in vitro experiments. This paper outlines the system architecture, a functional data model for representing experimental protocols, algorithms for image analysis, and the required statistical analysis. The architecture provides remote shared operation of an inverted optical microscope, and couples instrument operation with images acquisition and annotation. The information is stored in an object-oriented database. The algorithms extract structural information such as morphology and organization, and map it to functional information such as inter-cellular responses. An example of usage of this system is included.
Date: December 15, 2000
Creator: Parvin, B.; Cong, G.; Fontenay, G.; Taylor, J.; Henshall, R. & Barcellos-Hoff, M.H.
Partner: UNT Libraries Government Documents Department

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

Description: 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.
Partner: UNT Libraries Government Documents Department

Structure of charged polymer chains in confined geometry.

Description: The intra- and interchain structure of sodium poly(styrenesulphonate) when free and when confined in contrast matched porous Vycor has been investigated by SANS. When confined, a peak is observed whose intensity increases with molecular weight and the 1/q scattering region is extended compared to the bulk. We infer that the chains are sufficiently extended, under the influence of confinement, to highlight the large scale disordered structure of Vycor. The asymptotic behavior of the observed interchain structure factor is = 1/q{sup 2} and = 1/q for free and confined chains respectively.
Date: December 15, 2000
Creator: Gilbert, E. P.; Auvray, L. & Lal, J.
Partner: UNT Libraries Government Documents Department

The Hydrostatic Mooring System. Quarterly Report for the Period April-June 2000

Description: The following topics are summarized for the 2nd quarter of 2000: (1) We amended the structural design of the buoy, moving the horizontal bulkhead from the bottom to the top of the buoy. (2) We designed the main bearing using Hilman Rollers. We discarded a parallel design using Lubron slide bearings due to concerns about keeping dirt out of the sliding surfaces. (3) We performed a preliminary failure tree risk analysis for the system as required by ABS. (4) We made various drawings of the system and sub-components.
Date: July 15, 2000
Creator: Korsgaard, Jens
Partner: UNT Libraries Government Documents Department