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18th IAEA Fusion Energy Conference Summary of Technology and Power Plans (open access)

18th IAEA Fusion Energy Conference Summary of Technology and Power Plans

There were 90 papers presented at the Conference in the category of Technology and Power Plants accounting for about 25% of the total number of contributions. As was the case at the previous meeting, a large number of papers dealt with the ITER-Engineering Design Activity (EDA) and ITER technology R&D. In the author's opinion, the rapid progress made during the ITER EDA extension on the completion of the new ITER-FEAT design and its physics and technology R&D validation stands out as the highlight of the meeting. Steady progress is being made on several other technology fronts as well. The results point towards emerging research trends in the following areas: steady-state operation with advanced performance and the increasingly important role of enabling technologies in achieving this goal, advanced, high-performance, environmentally attractive materials for the fusion energy goal, reactor and near-term applications studies that exploit advances both in the physics and technology fronts for lower cost of electricity and improved safety and environmental features, and socioeconomic studies that are helping to promote the attractive features of fusion and its public acceptance. The remaining sections of this paper are organized along the lines of these major themes; namely, ITER EDA Design, ITER Technology …
Date: March 9, 2001
Creator: Milora, S. L.
System: The UNT Digital Library
e-A PHYSICS AT A COLLIDER. (open access)

e-A PHYSICS AT A COLLIDER.

An electron-nucleus (e-A) collider with center-of-mass energy in excess of 50 GeV per electron-nucleon collision will allow the physics community to obtain unprecedented new knowledge of the partonic structure of nuclei. If reliable information is to be extracted on these partonic densities, it is essential to realize that with our current level of understanding of QCD, momentum transfers to the struck partons greater than 1 GeV/c are necessary. This requirement puts a priority on high center-of-mass energy if partonic densities are to be measured over a wide range. Comparing the partonic structure of the free nucleon to that of bound nucleons and measuring the systematic changes in that structure as a function of nucleon number (A) will provide deeper insight into the origins and dynamics of nuclear binding. In addition, e-A collisions will allow the exploration of partonic densities appreciably higher than is accessible in e-p collisions. An e-A collider will allow one to measure the gluonic structure functions of nuclei down to x {approx} 10{sup -3}, information valuable in its own right and essential to a quantitative understanding of highly relativistic A-A collisions. The time-space evolution of partons can only be investigated by studying the modifications of hard collisions …
Date: January 9, 2001
Creator: GARVEY, G. T.
System: The UNT Digital Library
Analysis of Americium in Transplutonium Process Solutions (open access)

Analysis of Americium in Transplutonium Process Solutions

One of the more difficult analyses in the transplutonium field is the determination of americium at trace levels in a complex matrix such as a process dissolver solution. Because of these conditions a highly selective separation must precede the measurement of americium. The separation technique should be mechanically simple to permit remote operation with master-slave manipulators. For subsequent americium measurement by the mass spectroscopic isotopic-dilution technique, plutonium and curium interferences must also have been removed.
Date: March 9, 2001
Creator: Ferguson, R.B.
System: The UNT Digital Library
Automated real-time testing (ARTT) for embedded control systems (ECS). (open access)

Automated real-time testing (ARTT) for embedded control systems (ECS).

Many of today's automated real-time testing systems for embedded systems were developed using expensive custom hardware and software. In this article they describe how to use commercially available off-the-shelf hardware and software to design and develop an automated real-time test systems for Embedded Programmable Logic Controller (PLC) Based Control Systems. The system development began with the implementation of the VALI/TEST Pro testing methodology as a means for structuring the testing. Using this methodology, they were able to decompose system requirement documents for a Personnel Safety System (PSS) into its high, intermediate and detail level requirements. next, the validation procedures for the PSS system were decomposed into testing units called builds, test runs and test cases. To measure the PSS system's test coverage three levels of system requirements were mapped to their respective unit level of test using a specially constructed validation matrix that was designed to handle over 150 test cases and requirements. All of the above work led to the development of an Automated Real-Time Test System (ARTTS) that is capable of performing complete black box testing in real-time for Embedded PLC Based Control Systems. Also note, that the PSS system under test and mentioned in this paper is …
Date: August 9, 2001
Creator: Hawkins, Jon; Howard, Reginald B. & Nguyen, Haung V.
System: The UNT Digital Library
Benefits of microscopy with super resolution (open access)

Benefits of microscopy with super resolution

Transmission Electron Microscopy developed from an imagingtool into a quantitative electron beam characterization tool that locallyaccesses structure, chemistry, and bonding in materials with sub Angstromresolution. Experiments utilize coherently and incoherently scatteredelectrons. In this contribution, the interface between gallium nitrideand sapphire as well as thin silicon gate oxides are studied tounderstand underlying physical processes and the strength of thedifferent microscopy techniques. An investigation of the GaN/sapphireinterface benefits largely from the application of phase contrastmicroscopy that makes it possible to visualize dislocation corestructures and single columns of oxygen and nitrogen at a closest spacingof 85 pm. In contrast, it is adequate to investigate Si/SiOxNy/poly-Siinterfaces with incoherently scattered electrons and electronspectroscopy because amorphous and poly crystalline materials areinvolved. Here, it is demonstrated that the SiOxNy/poly-Si interface isrougher than the Si/SiOx interface, that desirable nitrogen diffusiongradients can be introduced into the gate oxide, and that a nitridationcoupled with annealing increases its physical width while reducing theequivalent electrical oxide thickness to values approaching 1.2 nm.Therefore, an amorphous SiNxOy gate dielectric seems to be a suitablesubstitute for traditional gate oxides to further increase device speedby reducing dimensions in Si technology.
Date: July 9, 2001
Creator: Kisielowski, C.; Principe, E.; Freitag, B. & Hubert, D.
System: The UNT Digital Library
The BOUT Project: Validation and Benchmark of BOUT Code and Experimental Diagnostic Tools for Fusion Boundary Turbulence (open access)

The BOUT Project: Validation and Benchmark of BOUT Code and Experimental Diagnostic Tools for Fusion Boundary Turbulence

A boundary plasma turbulence code BOUT is presented. The preliminary encouraging results have been obtained when comparing with probe measurements for a typical Ohmic discharge in CT-7 tokamak. The validation and benchmark of BOUT code and experimental diagnostic tools for fusion boundary plasma turbulence is proposed.
Date: August 9, 2001
Creator: Xu, X Q
System: The UNT Digital Library
Carbon and hydrogen isotope signatures associated with microbial iron reduction (open access)

Carbon and hydrogen isotope signatures associated with microbial iron reduction

None
Date: January 9, 2001
Creator: Horita, J.
System: The UNT Digital Library
Chemical Inhomogeneities and Pulsation (open access)

Chemical Inhomogeneities and Pulsation

Major improvements in models of chemically peculiar stars have been achieved in the past few years. With these new models it has been possible to test quantitatively some of the processes involved in the formation of abundance anomalies and their effect on stellar structure. The models of metallic A (Am) stars have shown that a much deeper mixing has to be present to account for observed abundance anomalies. This has implications on their variability, which these models also reproduce qualitatively. These models also have implications for other chemically inhomogeneous stars such as HgMn B stars which are not known to be variable and {lambda} Booetis stars which can be. The study of the variability of chemically inhomogeneous stars can provide unique information on the dynamic processes occurring in many types of stars in addition to modeling of the evolution of their surface composition.
Date: October 9, 2001
Creator: Turcotte, S
System: The UNT Digital Library
A compact 64-pixel CsI(T1)/Si PIN photodiode imaging module with IC readout (open access)

A compact 64-pixel CsI(T1)/Si PIN photodiode imaging module with IC readout

We characterize the performance of a complete 64-pixel compact gamma camera imaging module consisting of optically isolated 3 mm 3 mm 5 mm CsI(Tl) crystals coupled to a custom array of low-noise Si PIN photodiodes read out by a custom IC. At 50 V bias the custom 64-pixel photodiode arrays demonstrate an average leakage current of 28 pA per 3 mm 3 mm pixel, a 98.5 percent yield of pixels with <100 pA leakage, and a quantum efficiency of about 80 percent for 540 nm CsI(Tl) scintillation photons. The custom 64-channel readout IC uses low-noise preamplifiers, shaper amplifiers, and a winner-take-all (WTA) multiplexer. The IC demonstrates maximum gain of 120 mV / 1000 e-, the ability to select the largest input signal in less than 150 ns, and low electronic noise at 8 ms peaking time ranging from 25 e- rms (unloaded) to an estimated 180 e- rms (photodiode load of 3 pF, 50 pA). At room temperature a complete 64-pixel detector module employing a custom photodiode array and readout IC demonstrates an average energy resolution of 23.4 percent fwhm and an intrinsic spatial resolution of 3.3 mm fwhm for the 140 keV emissions of 99mTc. Construction of an array …
Date: August 9, 2001
Creator: Gruber, Gregory J.; Choong, Woon-Seng; Moses, William W.; Derenzo, Stephen E.; Holland, Stephen E.; Pedrali-Noy, Marzio et al.
System: The UNT Digital Library
Composition-structure-property-performance relationship inMn-substituted LiMn2O4 (open access)

Composition-structure-property-performance relationship inMn-substituted LiMn2O4

The spinel LiMn{sub 2}O{sub 4} has been extensively studied as a positive electrode active material in lithium rechargeable batteries. Partial substitution of Mn by another metal has also been the subject of recent study in an effort to improve the cycling performance. In general, the literature has shown that Mn substitution results in improved cycling stability at the expense of capacity (1,2). Resistance to the formation of tetragonal phase upon lithiation of the starting spinel (via a higher nominal Mn oxidation state in the substituted spinel) has been suggested as a mechanism for the improved performance. The degree of substitution is an important factor to optimize in order to minimize capacity loss and costs. The spectroscopic investigations on LiMn{sub 2}O{sub 4} described in the previous paper (LixMn2O4) confirmed that the cooperative Jahn-Teller effect (CJTE) from the [Mn{sup 3+}O{sub 6}] octahedra is the mechanism for the cubic to tetragonal phase transformation. The driving force for the CJTE is based upon the electronic structure, therefore changes in electronic structure should lead to changes in the phase behavior. The fact that the LiMn{sub 1.5}Ni{sub 0.5}O{sub 4} does not form tetragonal phase upon discharging (FUJI3, MUCK?), unlike the 100% Mn{sup 4+} spinel Li{sub 4}Mn{sub …
Date: March 9, 2001
Creator: Horne, Craig R.; Richardson, Thomas J.; Gee, B.; Tucker, Mike; Grush, Melissa M.; Bergmann, Uwe et al.
System: The UNT Digital Library
Compressional and Shear Wave Velocities for Artificial Granular Media Under Simulated Near Surface Conditions (open access)

Compressional and Shear Wave Velocities for Artificial Granular Media Under Simulated Near Surface Conditions

Laboratory ultrasonic experiments were made on artificial soil samples in order to observe the effects of slight overburden, sand/clay ratio and pore fluid saturation on compressional and shear wave velocities. Up to several meters of overburden were simulated by applying low uniaxial stress of about 0.1 MPa to a restrained sample. Samples were fabricated from Ottawa sand mixed with a swelling clay (Wyoming bentonite). The amount of clay added was 1 to 40 percent by mass. Most measurements were made under room-dry conditions, but some measurements were made for fully-saturated sand-clay mixtures and for partially-saturated sand samples. For the dry sand-clay samples, compressional (P) velocities were low, ranging from about 200 to 500 m/s for the mixtures at low stress. Shear (S) velocities were about half of the compressional velocity, about 70 to 250 m/s. Dramatic increases in all velocities occurred with small uniaxial loads, indicating strong nonlinearity. Composition and grain packing control the mechanical response at grain contacts and the resulting nonlinear response at low stresses. P and S velocities are sensitive to the amount of clay added, even at low concentrations. At these low equivalent overburden conditions, adhesion and capillarity at grain contacts affect wave amplitudes, velocities, and …
Date: September 9, 2001
Creator: Bonner, B. P.; Berge, P. A. & Wildenschild, D.
System: The UNT Digital Library
Consequences of return to power after a beam interruption in the blanket of an accelerator driven system. (open access)

Consequences of return to power after a beam interruption in the blanket of an accelerator driven system.

A sudden drop in power after a beam interruption leads to thermal fatigue effects in structural components in the blanket of an accelerator driven system. These thermal fatigue effects limit component lifetimes. A sudden return to power after a beam interruption can contribute significant additional thermal fatigue and greatly reduce component lifetimes. One obvious solution is a gradual return to power after a beam interruption. There are two potential problems with this solution. One problem involves interruptions that are longer than the thermal time constants of thin structural members but shorter than the time constants of thick structural members. In such a case, a gradual return to power reduces the additional thermal fatigue in the thin structural members but increases the thermal fatigue in thick structural members. Some compromise is necessary. The other problem is that for thick components with long thermal time constants a long, gradual return to power is required to minimize additional thermal fatigue. Such a slow return to power can reduce the utilization or the effective load factor of the system. Specific examples of beam interruptions with various assumptions on return to power are provided for a preliminary design for the blanket of the Accelerator Driven …
Date: August 9, 2001
Creator: Dunn, F.
System: The UNT Digital Library
Design and measurements of a deflecting mode cavity for an RF separator (open access)

Design and measurements of a deflecting mode cavity for an RF separator

The Fermilab Main Injector can produce intense 120 GeV/c proton beams for fixed target experimentation. Two deflecting mode RF systems can be used to separate charged kaons from a momentum selected secondary beam, consisting of pions, kaons and protons, using a time of flight method. We present the RF design of a 3.9 GHz superconducting cavity which operates in the deflecting (TM110) pi-mode and the dependence of the RF parameters on the cavity shape, as determined with finite difference calculations. End cell compensation has been treated, providing cell-to-cell field flatness. First results from measurements on a prototype cavity are shown. We demonstrated that it is possible to tune the deflecting mode of a cell cavity with bead pull measurements. Effects relating the polarization of the modes are discussed.
Date: July 9, 2001
Creator: Bellantoni, Leo
System: The UNT Digital Library
Direct contact pyrolysis of methane using nuclear reactor heat. (open access)

Direct contact pyrolysis of methane using nuclear reactor heat.

None
Date: November 9, 2001
Creator: Lewis, M. A.; Serban, M.; Marshall, C. L. & Lewis, D.
System: The UNT Digital Library
Djehuty: A Code for Modeling Whole Stars in Three Dimensions (open access)

Djehuty: A Code for Modeling Whole Stars in Three Dimensions

The DJEHUTY project is an intensive effort at the Lawrence Livermore National Laboratory (LLNL) to produce a general purpose 3-D stellar structure and evolution code to study dynamic processes in whole stars.
Date: October 9, 2001
Creator: Turcotte, S.; Bazan, G.; Castor, J.; Cavallo, R.; Cohl, M.; Cook, K. et al.
System: The UNT Digital Library
Evaluation of Creep Property of AS800 Silicon Nitride from As-Processed Surface Regions (open access)

Evaluation of Creep Property of AS800 Silicon Nitride from As-Processed Surface Regions

Tensile creep studies were carried out to evaluate the creep performance of AS800 silicon nitride samples extracted from the surface and bulk regions of as-processed billets at 1350 C in air. The objective of this study was to understand the creep properties of the silicon nitride in the as-processed surface region and determine if they are comparable to those obtained from the bulk region. The results indicated that samples from the as-processed surface region exhibited higher creep rates and shorter lifetimes as compared with those obtained from the bulk region. The poor creep performance of material from the as-processed surface region was due to the higher content of glassy phase enriched with oxygen and sintering additive elements.
Date: March 9, 2001
Creator: Lin, H. T.
System: The UNT Digital Library
Experimental Determination of Hydrogen Diffusion Rates in Hydrous Minerals Using the Ion Microprobe (open access)

Experimental Determination of Hydrogen Diffusion Rates in Hydrous Minerals Using the Ion Microprobe

None
Date: January 9, 2001
Creator: Suman, K. De; Cole, David R.; Riciputi, Lee R.; Chacko, Thomas & Horita, Juske
System: The UNT Digital Library
Experimental Determination of Phase Equilibria in the System H{sub 2}O-CO{sub 2}-NaCl at 0.5 Kb from 500 to 800C (open access)

Experimental Determination of Phase Equilibria in the System H{sub 2}O-CO{sub 2}-NaCl at 0.5 Kb from 500 to 800C

An understanding of activity-composition (a/X) relations and phase equilibria for halite-bearing, mixed-species supercritical fluids is critically important to many geological and industrial applications. The authors have performed experiments on the phase equilibria of H{sub 2}O-CO{sub 2}-NaCl fluids from 500 C to 800 C at 500 bars, conditions of significant importance in studies of magma-hydrothermal systems, geothermal reservoirs and some ore deposits, to obtain highly accurate and precise data for this ternary system. These experiments are conducted using a double capsule technique. An excess of NaCl is placed in an inner Pt capsule, which is crimped shut and placed in an outer capsule containing H{sub 2}O and CO{sub 2}. During the experiment NaCl dissolves out of the inner capsule, and is deposited in the outer capsule during the quench. After the experiment the capsule is opened, and the amount of NaCl remaining in the inner capsule determined by dissolution. The difference between the initial and final amounts of NaCl in the inner capsule yields the solubility of NaCl at the P-T conditions of the experiment. At 500 C data from these experiments suggest that the vapor comer of the three-phase field lies near X(H{sub 2}O) = 0.760, X(NaCl) = 0.065, which …
Date: January 9, 2001
Creator: Anovitz, L.M.
System: The UNT Digital Library
Fast computation of statistical uncertainty for spatiotemporal distributions estimated directly from dynamic cone beam SPECT projections (open access)

Fast computation of statistical uncertainty for spatiotemporal distributions estimated directly from dynamic cone beam SPECT projections

The estimation of time-activity curves and kinetic model parameters directly from projection data is potentially useful for clinical dynamic single photon emission computed tomography (SPECT) studies, particularly in those clinics that have only single-detector systems and thus are not able to perform rapid tomographic acquisitions. Because the radiopharmaceutical distribution changes while the SPECT gantry rotates, projections at different angles come from different tracer distributions. A dynamic image sequence reconstructed from the inconsistent projections acquired by a slowly rotating gantry can contain artifacts that lead to biases in kinetic parameters estimated from time-activity curves generated by overlaying regions of interest on the images. If cone beam collimators are used and the focal point of the collimators always remains in a particular transaxial plane, additional artifacts can arise in other planes reconstructed using insufficient projection samples [1]. If the projection samples truncate the patient's body, this can result in additional image artifacts. To overcome these sources of bias in conventional image based dynamic data analysis, we and others have been investigating the estimation of time-activity curves and kinetic model parameters directly from dynamic SPECT projection data by modeling the spatial and temporal distribution of the radiopharmaceutical throughout the projected field of view …
Date: April 9, 2001
Creator: Reutter, Bryan W.; Gullberg, Grant T. & Huesman, Ronald H.
System: The UNT Digital Library
From Crisis to Transition: The State of Russian Science Based on Focus Groups with Nuclear Physicists (open access)

From Crisis to Transition: The State of Russian Science Based on Focus Groups with Nuclear Physicists

The collapse of the Soviet system led to a sharp contraction of state funding for science. Formerly privileged scientists suddenly confronted miserly salaries (often paid late), plummeting social prestige, deteriorating research facilities and equipment, and few prospects for improvement. Many departed the field of science for more lucrative opportunities, both within Russia and abroad. The number of inventions, patent applications, and publications by Russian scientists declined. Reports of desperate nuclear physicists seeking work as tram operators and conducting hunger strikes dramatized the rapid collapse of one of the contemporary world's most successful scientific establishments. Even more alarming was the 1996 suicide of Vladimir Nechai, director of the second largest nuclear research center in Russia (Chelyabinsk-70, now known as Snezhinsk). Nechai, a respected theoretical physicist who spent almost 40 years working on Soviet and Russian nuclear programs, killed himself because he could no longer endure his inability to rectify a situation in which his employees had not been paid for more than 5 months and were ''close to starvation.'' The travails of Russia's scientists sparked interest in the West primarily because of the security threat posed by their situation. The seemingly relentless crisis in science raised fears that disgruntled scientists might …
Date: December 9, 2001
Creator: Gerber, T P & Ball, D Y
System: The UNT Digital Library
Geophysics with applications to subsurface waste disposal: Case history (open access)

Geophysics with applications to subsurface waste disposal: Case history

Recent development in geophysical methods allows us to accurately map the distribution of seismic velocity, density and electrical conductivity beneath the surface and between boreholes. These physical properties are dependent on porosity, fluid saturation, fluid conductivity, pressure, temperature, clay content, and in some circumstances, permeability. Hydrological parameters may be measured or inferred from drill hole experiments or directly from core samples. The point measurements in a drill hole are then interpolated to the interwell volume using either statistical properties of the local geology or reasonable estimates of the geological structure and lithology. More direct evidence is obtained from well tests, and interference tests between multiple wells, but these are ill posed inverse problems when it comes to defining the properties of the entire interwell volume. Furthermore such tests are impossible in the vadose zone. The interpolation of well data is often inaccurate or misleading and the central problem for all these studies is the lack of these fundamental parameters throughout the subsurface volume of interest.
Date: August 9, 2001
Creator: Lee, K. H.
System: The UNT Digital Library
Gravitino Warm Dark Matter with Entropy Production (open access)

Gravitino Warm Dark Matter with Entropy Production

Gravitinos with a mass in the keV range are an interesting candidate for warm dark matter. Recent measurements of the matter density of the universe and of cosmic structures at the dwarf galaxy scale rule out the simplest gravitino models with thermal freeze-out. We construct a model where the decay of the messenger particles that transmit the supersymmetry breaking to the observable sector generates the required entropy to dilute the gravitino relic density by the required factor of a few to come in line with observations. The model is natural, and requires only that the coupling of the messenger sector to the standard model be set so that the decay happens at the appropriate time.
Date: August 9, 2001
Creator: Baltz, Edward A. & Murayama, Hitoshi
System: The UNT Digital Library
AN HISTORICAL OVERVIEW OF THE IMPORTANCE OF THE WEAK DECAY OF HYPERNUCLEI (open access)

AN HISTORICAL OVERVIEW OF THE IMPORTANCE OF THE WEAK DECAY OF HYPERNUCLEI

Weak decay of hypernuclei, first cousin to the {beta}-decay of conventional, nonstrange nuclei, was initially observed in the 1950s. Pionic decay rates have proven a challenge--to reconcile nuclear decay rates with that of free {lambda} decay. Pauli blocking of the decay nucleon plays an important role. Nonmesonic decay provides our only practical means of exploring the four-fermion, strangeness-changing N{Lambda} {yields} NN weak interaction. The N{Lambda}{rho} vertex can be investigated in no other way. The large momentum transfer in the nonmesonic decay process suggests a means to probe short distance aspects of the interaction, possibly revealing baryon substructure effects. Whether the {Delta}I = 1/2 rule, which governs free {Lambda} decay, also applies to the nonmesonic decay process remains an open question. The free {Lambda} does not decay by emission of a {pi}{sup +}; the {pi}{sup +} decay of {sup 4}He is a puzzle. Finally, the weak decay of strangeness -2 hypernuclei is an important topic, because the pionic decay process is central to current efforts to seek and identify {Lambda}{Lambda} hypernuclei.
Date: January 9, 2001
Creator: GIBSON, B. F.
System: The UNT Digital Library
Interacting Quantum Spin Chains (open access)

Interacting Quantum Spin Chains

A brief review of recent advances in neutron scattering studies of low-dimensional quantum magnets is followed by a particular example. The separation of single-particle and continuum states in the weakly-coupled S = l/2 chains system BaCu{sub 2}Si{sub 2}O{sub 7} is described in some detail.
Date: September 9, 2001
Creator: Zheludev, A.
System: The UNT Digital Library