Development of the 2-MV injector for HIF (open access)

Development of the 2-MV injector for HIF

The 2-MV Injector consists of a 17-cm-diameter surface ionization source, an extraction diode, and an electrostatic quadrupole (ESQ) accelerator, with maximum current of 0.8 A of potassium beam at 2 MeV. Previous performance of the Injector produced a beam with adequate current and emittance but with a hollow profile at the end of the ESQ section. We have examined the profile of the beam as it leaves the diode. The measured nonuniform beam density distribution qualitatively agrees with EGUN simulation. Implications for emittance growth in the post acceleration and transport phase will be investigated.
Date: March 17, 2000
Creator: Bieniosek, F. M.; Kwan, J. W.; Henestroza, E. & Kim, C.
System: The UNT Digital Library
Enrique: A case study of a gifted computer user (open access)

Enrique: A case study of a gifted computer user

The author has been investigating the affective and intellectual views that gifted children have about computers. These studies have used various methodological approaches in order to develop a broad perspective on the issues involved in this topic. The author has used survey instruments (Sesko, 1998) and interview techniques (Sesko, 1999) to capture both statistical and narrative data. The objective of this study is to explore in depth the interactions that one student has with the machine and its applications. The driver for this and the previous studies was the paucity of research in the area of gifted and talented children and their involvement with what has become the primary intellectual tool of the century (Turkel, 1984). The second reason is that it has been posited that the intellectual characteristics of gifted children should enable those who are interested in computers to achieve a high level of proficiency with either computer applications or programming. Further, the ability to learn things at a young age should allow gifted children who use computers to develop a large variety of computer-based activities. The author has shown evidence to support these ideas in previous work. Finally, as Hausman (1985) claims, facilities with computers should allow …
Date: March 17, 2000
Creator: Sesko, S C
System: The UNT Digital Library
The Heavy Ion Fusion Program in the USA (open access)

The Heavy Ion Fusion Program in the USA

The U.S. Department of Energy has established a new, larger inertial fusion energy program. To manage program growth, we have developed a new inertial fusion energy research and we have established a Virtual National Laboratory for Heavy Ion Fusion. There has been significant technical progress. Improvements in target design have reduced the predicted energy requirements by approximately a factor of two. There have also been important experiments on chamber dynamics and other inertial fusion technologies. The accelerator program has completed a number of small-scale experiments. Experiments with driver-scale beams are being designed -- including experiments with driver-scale ion sources and injectors. Finally we are developing the technologies needed to build a major research facility known as the Integrated Research Experiment (IRE)
Date: March 17, 2000
Creator: Bangerter, R.O.
System: The UNT Digital Library
Intense ion beam propagation in a reactor sized chamber (open access)

Intense ion beam propagation in a reactor sized chamber

The authors consider the physics of the ballistic transport of intense ion beams in a heavy ion fusion reactor chamber filled with low pressure FLIBE gas. The authors consider first a single beam envelope model and show via a simple case that emittance growth is an issue in the chamber as well as in the accelerator. They develop a model for the neutralization of beam space-charge by the electrons produced by gas ionization by the beam and derive an expression for the evolution of the neutralization factor as the beam propagates into the chamber. They then extend the envelope model from a one species beam to a beam of ions of several charge states by considering the entire beam as a set of subbeams (one for each charge state) each described with coupled envelope equation. The fully electromagnetic PIC code BPIC was used to investigate the behavior in greater detail. A parametric study of the sensitivity of the final spot radius at the target versus the ion beam stripping and gas ionization cross-sections (which are characterized by large uncertainties) shows that, in the studied regime (Hylife-II parameters), the accessible window of cross-sections for ballistic transport in the chamber through neutral …
Date: March 17, 2000
Creator: Vay, J. L. & Deutsch, C.
System: The UNT Digital Library
Investigation of the Persistence of New Building Commissioning (open access)

Investigation of the Persistence of New Building Commissioning

Commissioning is gaining increasing recognition as a cost-effective strategy for reducing commercial building energy use. Although the success and cost-effectiveness of commissioning projects depends on how well the benefits of commissioning persist over time, this aspect of commissioning is not well understood. The persistence of commissioning benefits was recently studied in a PIER project evaluating ten buildings that were commissioned at building start-up at least two years ago. The researchers examined the commissioning reports, control algorithms, EMCS point measurements, and energy use data, and conducted operator and commissioning provider interviews to investigate the persistence of commissioning benefits. In addition, they conducted site visits in a sample of the buildings. A set of commissioning measures was selected for each building to compare the persistence of benefits. Persistence was measured both qualitatively through a discussion of occupant comfort and decreased maintenance and quantitatively through estimations of energy savings. This paper reports the results of the study. The discussion includes how well the benefits of commissioning persisted over time, reasons for declining performance, and methods for improving persistence. The results provide valuable insight into how to estimate the persistence of commissioning information central to the cost benefit analyses routinely performed for commissioning measures.
Date: March 17, 2002
Creator: Potter, Amanda; Friedman, Hannah; Haasl, Tudi & Claridge, David
System: The UNT Digital Library
Adaptive Optics Applications in Vision Science (open access)

Adaptive Optics Applications in Vision Science

Adaptive optics can be used to correct the aberrations in the human eye caused by imperfections in the cornea and the lens and thereby, improve image quality both looking into and out of the eye. Under the auspices of the NSF Center for Adaptive Optics and the DOE Biomedical Engineering Program, Lawrence Livermore National Laboratory has joined together with leading vision science researchers around the country to develop and test new ophthalmic imaging systems using novel wavefront corrector technologies. Results of preliminary comparative evaluations of these technologies in initial system tests show promise for future clinical utility.
Date: March 17, 2003
Creator: Olivier, S. S.
System: The UNT Digital Library
CDF - Run II Status and Prospects (open access)

CDF - Run II Status and Prospects

After a five year upgrade period, the CDF detector located at the Fermilab Tevatron Collider is back in operation taking high quality data with all subsystems functional. We report on the status of the CDF experiment in Run II and discuss the start-up of the Tevatron accelerator. First physics results from CDF are presented. We also discuss the prospects for B physics in RunII, in particular the measurements of B{sub S}{sup 0} flavour oscillations and CP violation in B decays.
Date: March 17, 2003
Creator: Paulini, Manfred
System: The UNT Digital Library
Impact Analysis of Spent Fuel Dry Casks Under Accidental Drop Scenarios. (open access)

Impact Analysis of Spent Fuel Dry Casks Under Accidental Drop Scenarios.

A series of analyses were performed to assess the structural response of spent nuclear fuel dry casks subjected to various handling and on-site transfer events. The results of these analyses are being used by the Nuclear Regulatory Commission (NRC) to perform a probabilistic risk assessment (PRA). Although the PRA study is being performed for a specific nuclear plant, the PRA study is also intended to provide a framework for a general methodology that could also be applied to other dry cask systems at other nuclear plants. The dry cask system consists of a transfer cask, used for handling and moving the multi-purpose canister (MPC) that contains the fuel, and a storage cask, used to store the MPC and fuel on a concrete pad at the site. This paper describes the analyses of the casks for two loading events. The first loading consists of dropping the transfer cask while it is lowered by a crane to a concrete floor at ground elevation. The second loading consists of dropping the storage cask while it is being transferred to the concrete storage pad outdoors. Three dimensional finite element models of the transfer cask and storage cask, containing the MPC and fuel, were utilized …
Date: March 17, 2003
Creator: Braverman, J. I.; Morante, R. J.; Xu, J.; Hofmayer, C. H. & Shaukat, S. K.
System: The UNT Digital Library
Initial experience with the CDF layer 00 silicon detector (open access)

Initial experience with the CDF layer 00 silicon detector

We report on initial experience with the CDF Layer 00 Detector. Layer 00 is an innovative, low-mass, silicon detector installed in CDF during the upgrade for Run 2A of the Tevatron. Noise pickup present during operation at CDF is discussed. An event-by-event pedestal correction implemented by CDF is presented. This off-line solution prevents L00 from being used in the current incarnation of the on-line displaced track trigger. Preliminary performance of Layer 00 is described.
Date: March 17, 2003
Creator: Hill, C.
System: The UNT Digital Library
Numerical Simulation of Damage using an Elastic-Viscoplastic Model with Directional Tensile Failure (open access)

Numerical Simulation of Damage using an Elastic-Viscoplastic Model with Directional Tensile Failure

A new continuum model for directional tensile failure has been developed that can simulate weakening and void formation due to directional tensile failure. The model is developed within the context of a properly invariant nonlinear thermomechanical theory. A second order damage tensor is introduced which allows simulation of weakening to tension applied in one direction, without weakening to subsequent tension applied in perpendicular directions. This damage tensor can be advected using standard methods in computer codes. Porosity is used as an isotropic measure of volumetric void strain and its evolution is influenced by tensile failure. The rate of dissipation due to directional tensile failure takes a particularly simple form, which can be analyzed easily. Specifically, the model can be combined with general constitutive equations for porous compaction and dilation, as well as viscoplasticity. A robust non-iterative numerical scheme for integrating these evolution equations is proposed. This constitutive model has been implemented into an Eulerian shock wave code with adaptive mesh refinement. A number of simulations of complicated shock loading of different materials have been performed including problems of fracture of rock. These simulations show that directionality of damage can play a significant role in material failure.
Date: March 17, 2003
Creator: Lomov, I
System: The UNT Digital Library
Poroelastic Analysis of Thomsen Parameters in Finely Layed VTI Media (open access)

Poroelastic Analysis of Thomsen Parameters in Finely Layed VTI Media

Thomsen's anisotropy parameters for weak elastic and poroelastic anisotropy are now commonly used in exploration, and can be conveniently expressed in terms of the layer averages of Backus. Although there are five effective shear moduli for any layered VTI medium, only one effective shear modulus for the layered system contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves in VTI media. The effects of the pore fluids on this effective shear modulus can be substantial when the medium behaves in an undrained fashion, as might be expected at higher frequencies such a sonic and ultrasonic for well-logging or laboratory experiments, or at seismic frequencies for lower permeability regions of reservoirs.
Date: March 17, 2003
Creator: Berger, E. L.
System: The UNT Digital Library
Status of the MINOS Experiment (open access)

Status of the MINOS Experiment

We report on the status of the MINOS long baseline neutrino experiment presently under construction at the Fermi National Accelerator Laboratory and the Soudan mine. There is growing evidence that the solar neutrino and atmospheric neutrino anomalies [1] are the result of neutrino oscillations. The MINOS experiment is a long baseline neutrino oscillation experiment designed to study the region of parameter space indicated by the SuperKamiokande atmospheric neutrino results [2]. The experiment consists of two detectors, one with a mass of 980 tons located at Fermilab (the near detector) and the other of mass 5400 tons located 731 km away in the Soudan mine in northern Minnesota (the far detector). The third component is the neutrino beam which is currently under construction at Fermilab.
Date: March 17, 2003
Creator: Buckley-Geer, Elizabeth
System: The UNT Digital Library
SUSY SIGNATURES IN ATLAS AT LHC. (open access)

SUSY SIGNATURES IN ATLAS AT LHC.

This talk summarizes work by the ATLAS Collaboration at the CERN Large Hadron Collider on the search SUSY particles and Higgs bosons and on possible measurements of their properties.
Date: March 17, 2003
Creator: PAIGE,F. E.
System: The UNT Digital Library
Coherent phase argument for inflation (open access)

Coherent phase argument for inflation

Cosmologists have developed a phenomenally successful picture of structure in the universe based on the idea that the universe expanded exponentially in its earliest moments. There are three pieces of evidence for this exponential expansion--inflation--from observations of anisotropies in the cosmic microwave background. First, the shape of the primordial spectrum is very similar to that predicted by generic inflation models. Second, the angular scale at which the first acoustic peak appears is consistent with the flat universe predicted by inflation. Here the author describes the third piece of evidence, perhaps the most convincing of all: the phase coherence needed to account for the clear peak/trough structure observed by the WMAP satellite and its predecessors. The author also discusses alternatives to inflation that have been proposed recently and explain how they produce coherent phases.
Date: March 17, 2004
Creator: Dodelson, Scott
System: The UNT Digital Library
Commissioning the CDF offline software (open access)

Commissioning the CDF offline software

CDF II is one of the two large collider experiments at Fermilab's Tevatron. Over the past two years we have commissioned the offline computing system. A task that has involved bringing up hundreds of computers and millions of lines of C++ software. This paper reports on this experience, concentrating on the software aspects of the project. We will highlight some of the successes as well as describe some of the work still to do.
Date: March 17, 2004
Creator: Murat, Elizabeth Sexton-Kennedy and Pasha
System: The UNT Digital Library
Computational Engineering of the Stability and Optical Gaps of SiC Quantum Dots (open access)

Computational Engineering of the Stability and Optical Gaps of SiC Quantum Dots

None
Date: March 17, 2004
Creator: Reboredo, F; Pizzagalli, L & Galli, G
System: The UNT Digital Library
The D0 level three data acquisition system (open access)

The D0 level three data acquisition system

The DZERO experiment located at Fermilab has recently started RunII with an upgraded detector. The RunII physics program requires the Data Acquisition to readout the detector at a rate of 1 KHz. Events fragments, totaling 250 KB, are readout from approximately 60 front end crates and sent to a particular farm node for Level 3 Trigger processing. A scalable system, capable of complex event routing, has been designed and implemented based on commodity components: VMIC 7750 Single Board Computers for readout, a Cisco 6509 switch for data flow, and close to 100 Linux-based PCs for high-level event filtering.
Date: March 17, 2004
Creator: al., D. Chapin et
System: The UNT Digital Library
Detonation in TATB Hemispheres (open access)

Detonation in TATB Hemispheres

Streak camera breakout and Fabry-Perot interferometer data have been taken on the outer surface of 1.80 g/cm{sup 3} TATB hemispherical boosters initiated by slapper detonators at three temperatures. The slapper causes breakout to occur at 54{sup o} at ambient temperatures and 42{sup o} at -54 C, where the axis of rotation is 0{sup o}. The Fabry velocities may be associated with pressures, and these decrease for large timing delays in breakout seen at the colder temperatures. At room temperature, the Fabry pressures appear constant at all angles. Both fresh and decade-old explosive are tested and no difference is seen. The problem has been modeled with reactive flow. Adjustment of the JWL for temperature makes little difference, but cooling to -54 C decreases the rate constant by 1/6th. The problem was run both at constant density and with density differences using two different codes. The ambient code results show that a density difference is probably there but it cannot be quantified.
Date: March 17, 2004
Creator: Druce, B.; Souers, P. C.; Chow, C.; Roeske, F.; Vitello, P. & Hrousis, C.
System: The UNT Digital Library
Electron beam collector with a low back flow (open access)

Electron beam collector with a low back flow

Generation of a DC electron beam in the future Fermilab electron cooler [1] employs an electrostatic acceleration and a beam energy recovery, so that electrons are decelerated from the nominal energy of 4.3 MeV they have in the cooling section to few keV in the collector. Stable performance of this scheme requires a current loss {delta}I below 10 {micro}A at the beam current up to the nominal value of I = 0.5 A. One of sources of the loss is a back flow of secondary electrons from the beam collector. The paper discusses principles and performance of a collector with the low current loss. Electric and magnetic fields in the collectors used in existing electron coolers are axially symmetrical. For practically interesting parameters, such collectors can not provide {delta}I/I<10{sup -4} because of the reversibility of trajectories in the collectors: a secondary electron with the kinetic energy equal to the energy of the primary one can come out of the collector following the trajectory of the ''parent'' electron. The back flow can be dramatically decreased if the reversibility is broken by a transverse magnetic field in the collector cavity. In our case, the field was formed by a system of permanent …
Date: March 17, 2004
Creator: Shemyakin, A.
System: The UNT Digital Library
Flame Inhibition by Phosphorus-Containing Compounds over a Range of Equivalence Ratios (open access)

Flame Inhibition by Phosphorus-Containing Compounds over a Range of Equivalence Ratios

There is much interest in the combustion mechanism of organophosphorus compounds (OPCs) due to their role as potential halon replacements in fire suppression. A continuing investigation of the inhibition activity of organophosphorus compounds under a range of equivalence ratios was performed experimentally and computationally, as measured by the burning velocity. Updates to a previous mechanism were made by the addition and modification of reactions in the mechanism for a more complete description of the recombination reactions. In this work, the laminar flame speed is measured experimentally and calculated numerically for a premixed propane/air flame, under a range of equivalence ratios, undoped and doped with dimethyl methylphosphonate (DMMP). A detailed investigation of the catalytic cycles involved in the recombination of key flame radicals is made for two equivalence ratios, lean and rich. From this, the importance of different catalytic cycles involved in the lean versus rich case is discussed. Although the importance of certain cycles is different under different stoichiometries, the OPCs are similarly effective across the range, demonstrating the robustness of OPCs as flame suppressants. In addition, it is shown that the phosphorus compounds are most active in the high temperature region of the flame. This may, in part, explain …
Date: March 17, 2004
Creator: Jayaweera, T M; Melius, C F; Pitz, W J; Westbrook, C K; Korobeinichev, O P; Shvartsberg, V M et al.
System: The UNT Digital Library
Group Theoretical Analysis of Vibrational Modes, Rovibronic Levels and Nuclear Spin Statistics of extended aromatic C48N12 Azafullerene (open access)

Group Theoretical Analysis of Vibrational Modes, Rovibronic Levels and Nuclear Spin Statistics of extended aromatic C48N12 Azafullerene

We have presented a group theoretical analysis of the vibrational modes and rovibronic levels of a novel extended aromatic C{sub 48}N{sub 12} azafullerene. The nuclear spin multiplets and statistical weights of {sup 14}N spin-1 bosons, vibrational and rotational analysis and computed vibrational spectra are provided. We have also predicted the properties of the {sup 3}A{sub u}, {sup 3}E{sub g}, and {sup 3}E{sub u} excited states of C{sub 48}N{sub 12} that lie 1.9 eV above the {sup 1}A{sub g} ground state, and that the {sup 3}E{sub g} and {sup 3}E{sub u} states would undergo Jahn-Teller distortion into chiral structures with no symmetry and an achiral structure with C{sub i} symmetry.
Date: March 17, 2004
Creator: Balasubramanian, K
System: The UNT Digital Library
The Kinematics of the Lag-Luminosity Relationship (open access)

The Kinematics of the Lag-Luminosity Relationship

Herein I review the argument that kinematics, i.e. relativistic motions of the emitting source in gamma-ray bursts (GRBs), are the cause of the lag-luminosity relationship observed in bursts with known redshifts.
Date: March 17, 2004
Creator: Salmonson, J D
System: The UNT Digital Library
A More improved lattice action for heavy quarks (open access)

A More improved lattice action for heavy quarks

We extend the Fermilab formalism for heavy quarks to develop a more improved action. We give results of matching calculations of the improvement couplings at tree level. Finally, we estimate the discretization errors associated with the new action.
Date: March 17, 2004
Creator: al., M. B. Oktay et
System: The UNT Digital Library
Semileptonic decays of D mesons in unquenched lattice QCD (open access)

Semileptonic decays of D mesons in unquenched lattice QCD

We present our preliminary results for semileptonic form factors of D mesons in unquenched lattice QCD. Simulations are carried out with n{sub f} = 2 + 1 dynamical quarks using gauge configurations generated by the MILC collaboration. For the valence quarks, we adopt an improved staggered light quark action and the clover heavy quark action. Our results for D {yields} K and D {yields} {pi} form factors at q{sup 2} = 0 are in agreement with the experimental values.
Date: March 17, 2004
Creator: al., Masataka Okamoto et
System: The UNT Digital Library