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Serial/Series Title
Country
Year
Month
Day
A 3He{sup +}{sup +} RFQ accelerator for the production of PET isotopes
Project status of the 3He{sup +}{sup +} 10.5 MeV RFQ Linear Accelerator for the production of PET isotopes will be presented. The accelerator design was begun in September of 1995 with a goal of completion and delivery of the accelerator to BRF in Shreveport, Louisiana by the summer of 1997. The design effort and construction is concentrated in Lab G on the Fermilab campus. Some of the high lights include a 25 mA peak current 3He` ion source, four RFQ accelerating stages that are powered by surplus Fermilab linac RF stations, a gas jet charge doubler, and a novel 540 degree bending Medium Energy Beam Transport (MEBT). The machine is designed to operate at 360 Hz repetition rate with a 2.5% duty cycle. The average beam current is expected to be 150-300 micro amperes electrical, 75- 150 micro amperes particle current.
Date:
May 1, 1997
Creator:
Pasquinelli, R.J. & Collaboration, E887
Object Type:
Article
System:
The UNT Digital Library
6th International Meshing Roundtable '97
The goal of the 6th International Meshing Roundtable is to bring together researchers and developers from industry, academia, and government labs in a stimulating, open environment for the exchange of technical information related to the meshing process. In the pas~ the Roundtable has enjoyed significant participation born each of these groups from a wide variety of countries. The Roundtable will consist of technical presentations from contributed papers and abstracts, two invited speakers, and two invited panels of experts discussing topics related to the development and use of automatic mesh generation tools. In addition, this year we will feature a "Bring Your Best Mesh" competition and poster session to encourage discussion and participation from a wide variety of mesh generation tool users. The schedule and evening social events are designed to provide numerous opportunities for informal dialog. A proceedings will be published by Sandia National Laboratories and distributed at the Roundtable. In addition, papers of exceptionally high quaIity will be submitted to a special issue of the International Journal of Computational Geometry and Applications. Papers and one page abstracts were sought that present original results on the meshing process. Potential topics include but are got limited to: Unstructured triangular and tetrahedral …
Date:
September 1, 1997
Creator:
White, D.
Object Type:
Report
System:
The UNT Digital Library
7th International Workshop on the Identification of Transcribed Sequences: Beyond the Identification of Transcribed Sequences. Program
None
Date:
November 1, 1997
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Ab initio calculation of tight-binding parameters
We calculate ab initio values of tight-binding parameters for the f- electron metal Ce and various phases of Si, from local-density functional one-electron Hamiltonian and overlap matrix elements. Our approach allows us to unambiguously test the validity of the common minimal basis and two-center approximations as well as to determine the degree of transferability of both nonorthogonal and orthogonal hopping parameters in the cases considered.
Date:
December 1, 1997
Creator:
McMahan, A. K. & Klepeis, J. E.
Object Type:
Article
System:
The UNT Digital Library
Ab-initio calculations of density of states for Ti-oxide
Electron energy-loss spectroscopy has been shown to be a powerful tool to determine the chemistry and the electronic structure at grain boundaries by analyzing the energy loss near edge structure (ELNES). This paper describes the ability of ab-initio density of state calculations to perform detailed quantitative analysis at interfaces.
Date:
April 1, 1997
Creator:
Duscher, G.; Koestlmeier, S. & Elsaesser, C.
Object Type:
Article
System:
The UNT Digital Library
Aberration analysis calculations for synchrotron radiation beamline design
The application of ray deviation calculations based on aberration coefficients for a single optical surface for the design of beamline optical systems is reviewed. A systematic development is presented which allows insight into which aberration may be causing the rays to deviate from perfect focus. A new development allowing analytical calculation of line shape is presented.
Date:
September 1, 1997
Creator:
McKinney, W.R.; Howells, M. & Padmore, H.A.
Object Type:
Article
System:
The UNT Digital Library
Abnormal grain growth -- The origin of recrystallization nuclei?
The origin of recrystallization nuclei is reviewed with particular emphasis on materials in which well-developed cells are present in the deformed state. Nucleation is discussed in terms of coarsening of the subgrain network that develops on annealing and an analogy is made with abnormal grain growth. The results of a theoretical analysis of abnormal growth are summarized. The Monte Carlo model for grain growth is adapted for variable grain boundary energy and mobility in order to investigate the behavior of individual grains with special properties. The simulation results show that both energy and mobility affect abnormal growth as expected from the theoretical analysis. The results are discussed in terms of the stability that subgrain networks may exhibit depending on their mean misorientation.
Date:
August 1, 1997
Creator:
Rollett, A. D. & Holm, E. A.
Object Type:
Report
System:
The UNT Digital Library
AC magnetic field losses in BSCCO-2223 superconducting tapes
The AC magnetic losses at power frequencies (60 Hz) were investigated for mono- and multifilament Ag-sheathed (Bi, Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} (BSCCO-2223) tapes with similar transport critical current (I{sub c}) values at 77 K. The multifilament sample exhibited higher losses than the monofilament under the same conditions. Loss peaks are discussed in terms of intergranular, intragranular and eddy current losses. Because of BSCCO`s anisotropy, field orientation has a large effect on the magnitude of these peaks, even at relatively small angles. Losses for fields applied parallel to the c-axis of the textured BSCCO grains are larger by more than one order of magnitude than those applied perpendicular.
Date:
September 1, 1997
Creator:
Lelovic, M.; Mench, S. & Deis, T.
Object Type:
Article
System:
The UNT Digital Library
ACAB software upgrade
This report address two issues, namely the ``Selection of the most current nuclear data libraries available`` and the ``User`s manual of the updated ACAB code``. A general summary of the major features of ACAB is provides in Section 1 which highlights the new capabilities included in the present version of ACAB. We address the issue of the nuclear data libraries selected as starting point in preparing the libraries to be used directly by ACAB. Section II describes the main features of the selected libraries. In Section IV, the impact of using these libraries in Inertial Fusion Energy, IFE, applications is assessed by comparing activation results obtained using different activation cross-sections data libraries. The points considered are the processing of libraries and libraries adapted to be directly read by ACAB. The ``processing`` efforts made within the frame of this project have been focused on the COLLAPSE code. Important modifications have been made, and in Section IV we provide an overall description of the new version. The content of the data bases employed by the updated ACAB code are described in Section V. The input data file for running ACAB is dealt with in Section VI, and some example problems are discussed …
Date:
October 1, 1997
Creator:
Sanz, J. & Balmisa, J.M.
Object Type:
Report
System:
The UNT Digital Library
Acccelerator Physics Issues of a Very Large Hadron Collider
A Very Large Hadron Collider (VLHC) was proposed for the post-LHC future. This paper gives a quick survey of a number of accelerator physics issues based on the information obtained from a parameter spreadsheet SSP. The main technical challenges to build such a machine appear to be: the large number of events per crossing (in hundreds), enormous beam stored energy (equivalent to tens tons of TNT), ground motion (which is particularly harmful when the synchrotron frequency is in the sub-Hertz range), small dynamic aperture (due to long filling time), fast growth of the resistive wall instability (in a fraction of one turn), low threshold of the single bunch transverse instability (due to big machine size), strong synchrotron radiation (at a level close to the LEP) and short radiation damage lifetime, etc. Possible solutions to some of these problems will also be discussed.
Date:
June 1, 1997
Creator:
Chou, W.
Object Type:
Article
System:
The UNT Digital Library
Accelerated life test of the USDOE OC-OTEC experimental system refurbished with magnetic bearings for the 3rd stage vacuum compressor. Final report
This report documents the accelerated life test (time-to-failure) performed, at the request of DOE, to evaluate the viability of the magnetic bearing system installed in the stage 3 vacuum pump. To this effect the plant was successfully operated for over 500 hours during the period September-November 1996. The first part of this report discusses system performance by deriving subsystem and system performance parameters from a typical record. This is followed by the discussion of the life tests. The instrumentation used to estimate the performance parameters given here is depicted. The third stage pump was operated for 535 hours without incident. It is concluded that magnetic bearings are the preferable choice for the OC-OTEC centrifugal vacuum pumps.
Date:
April 1, 1997
Creator:
Vega, L.A.
Object Type:
Report
System:
The UNT Digital Library
Accelerated stress rupture lifetime assessment for fiber composites
Objective was to develop a theoretical and experimental framework for predicting stress rupture lifetime for fiber polymer composites based on short-term accelerated testing. Originally a 3-year project, it was terminated after the first year, which included stress rupture experiments and viscoelastic material characterization. In principle, higher temperature, stress, and saturated environmental conditions are used to accelerate stress rupture. Two types of specimens were to be subjected to long-term and accelerated static tensile loading at various temperatures, loads in order to quantify both fiber and matrix dominated failures. Also, we were to apply state-of-the-art analytical and experimental characterization techniques developed under a previous DOE/DP CRADA for capturing and tracking incipient degradation mechanisms associated with mechanical performance. Focus was increase our confidence to design, analyze, and build long-term composite structures such as flywheels and hydrogen gas storage vessels; other applications include advanced conventional weapons, infrastructures, marine and offshore systems, and stockpile stewardship and surveillance. Capabilities developed under this project, though not completed or verified, are being applied to NIF, AVLIS, and SSMP programs.
Date:
February 1, 1997
Creator:
Groves, Scott E.; DeTeresa, Steven J.; Sanchez, Roberto J.; Zocher, Marvin A. & Christensen, Richard M.
Object Type:
Report
System:
The UNT Digital Library
Accelerating Cleanup: Focus on 2006. Discussion draft
This executive summary addresses the activities associated with the National Transuranic (TRU) Program managed by the Carlsbad Area Office (CAO). The CAO programmatically reports to the Assistant Secretary for Environmental Management and receives administrative support through the Albuquerque Operations Office. The mission of the Carlsbad Area Office (CAO) is to protect human health and the environment by opening and operating the Waste Isolation Pilot Plant for site disposal of TRU waste and by establishing an effective system for management of TRU waste from generation to disposal. It includes personnel assigned to the CAO, the Waste Isolation Pilot Plant (WIPP) site operations, and other activities associated with the National TRU Program. The CAO develops and directs implementation of the program, while the DOE Headquarters establishes policy and guidelines. The CAO assesses compliance with the program guidance, as well as the commonality of activities and assumptions among all the sites. Since the development of the February 28, 1997, database used to develop this Discussion Draft, the opening of the WIPP facility for receipt of Contact Handled waste has been delayed from November 1997 to May 1998. This slippage is significant enough to require a change in the milestones and volumes included in …
Date:
June 1, 1997
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Acceleration and collision of ultra-high energy particles using crystal channels
We assume that, independent of any near-term discoveries, the continuing goal of experimental high-energy physics (HEP) will be to achieve ultra-high center-of-mass energies early in the next century. To progress to these energies in such a brief span of time will require a radical change in accelerator and collider technology. We review some of our recent theoretical work on high-gradient acceleration of charged particles along crystal channels and the possibility of colliding them in these same strong-focusing atomic channels. An improved understanding of energy and emittance limitations in natural crystal accelerators leads to the suggestion that specially manufactured nano-accelerators may someday enable us to accelerate particles beyond 10{sup 8} eV with emittances limited only by the uncertainty principle of quantum mechanics.
Date:
April 1, 1997
Creator:
Chen, P. & Noble, R.J.
Object Type:
Article
System:
The UNT Digital Library
Accelerator mass spectrometry as a bioanalytical tool
This paper presents data that supports Accelerator Mass Spectrometry (AMS) as a valid bioanalytical tool for tracing long lived radioisotopes in uses as molecular labels or elemental tracers.
Date:
October 1, 1997
Creator:
Vogel, J.S.
Object Type:
Article
System:
The UNT Digital Library
Accelerator production of tritium plant design and supporting engineering development and demonstration work
Tritium is an isotope of hydrogen with a half life of 12.3 years. Because it is essential for US thermonuclear weapons to function, tritium must be periodically replenished. Since K reactor at Savannah River Site stopped operating in 1988, tritium has been recycled from dismantled nuclear weapons. This process is possible only as long as many weapons are being retired. Maintaining the stockpile at the level called for in the present Strategic Arms Reduction Treaty (START-I) will require the Department of Energy to have an operational tritium production capability in the 2005--2007 time frame. To make the required amount of tritium using an accelerator based system (APT), neutrons will be produced through high energy proton reactions with tungsten and lead. Those neutrons will be moderated and captured in {sup 3}He to make tritium. The APT plant design will use a 1,700 MeV linear accelerator operated at 100 mA. In preparation for engineering design, starting in October 1997 and subsequent construction, a program of engineering development and demonstration is underway. That work includes assembly and testing of the first 20 MeV of the low energy plant linac at 100 mA, high-energy linac accelerating structure prototyping, radiofrequency power system improvements, neutronic efficiency …
Date:
November 1, 1997
Creator:
Lisowski, Paul W.
Object Type:
Article
System:
The UNT Digital Library
Accelerator Production of Tritium - Project Execution Plan
None
Date:
July 1, 1997
Creator:
Fultonberg, D.N.
Object Type:
Report
System:
The UNT Digital Library
Accelerator Transmutation of Waste Blanket Considerations
Accelerator transmutation of waste (ATW) is one approach for reducing the amount of actinides and long-lived fission products that eventually will be sent to a repository. The ATW accelerator generates high-energy protons, which strike a target and produce spallation neutrons. The spallation neutrons transmute waste in a region that surrounds the spallation target. It is desirable for the waste transmutation region (WTR) to have significant neutron multiplication (a factor of 10 or higher) to keep the required accelerator size reasonable. The WTR is subcritical and is thus not required to generate a self-sustaining fission reaction in the waste. The elimination of this requirement allows the ATW system to be optimized for reducing the hazard from nuclear waste without the concerns associated with safely maintaining criticality. Subcritical operation allows waste compositions with positive prompt reactivity feedback coefficients to be considered, allows waste forms optimized for processing to be considered, and allows additional design flexibility. The WTR will be designed so that criticality cannot be achieved during any credible accident scenario. The primary advantage of the ATW approach is thus the design and operational flexibility gained from subcritical operation. The primary disadvantage of the ATW approach is the expense and complexity of …
Date:
December 1, 1997
Creator:
Houts, Michael G.; Bjornberg, Mikael & Poston, David I.
Object Type:
Article
System:
The UNT Digital Library
Access control and interlock system at the Advanced Photon Source
The Advanced Photon Source (APS) consists of a linac, position accumulator ring (PAR), booster synchrotron, storage ring, and up to 70 experimental beamlines. The Access Control and Interlock System (ACIS) utilizes redundant programmable logic controllers (PLCs) and a third hard-wired chain to protect personnel from prompt radiation generated by the linac, PAR, synchrotron, and storage ring. This paper describes the ACIS`s design philosophy, configuration, hardware, functionality, validation requirements, and operational experience.
Date:
August 1, 1997
Creator:
Forrestal, J.; Hogrefe, R.; Knott, M.; McDowell, W.; Reigle, D.; Solita, L. et al.
Object Type:
Article
System:
The UNT Digital Library
Accountability report. Fiscal Year 1996, Volume 2
This report consolidates several performance-related reports into a single financial management report. Information in this report includes information previously reported in the following documents: (1) US Nuclear Regulatory Commission`s (NRC`s) annual financial statement, (2) NRC Chairman`s annual report to the President and the Congress, and (3) NRC Chairman`s semiannual report to Congress on management decisions and final actions on Office of Inspector General audit recommendations. This report also contains performance measures. The report is organized into the following subtopics: information about the US NRC, program performance, management accountability, and the audited financial statement for Fiscal Year 1996. 19 figs., 4 tabs.
Date:
May 1, 1997
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Accrediting models for the TMD COEA: A case study in face assessment
This paper describes a face validation process developed to assess computer models used in Phase I of the Theater Missile Defense (TMD) Cost and Operational Effectiveness Analysis (COEA) and to aid the COEA Study Director in making accreditation decisions for those models. The process was applied to five BMDO models, only two of which had a formal configuration management program. The process was expedient, efficient and proved to be an effective method of distilling essential information for the decision maker. Further, the process identified model deficiencies which provided a road-map for modeling improvements needed for follow-on COEA studies. The paper describes each phase of the process: preparation (including validation team membership, analyst interviews to develop needs, preparation of developer questionnaires and solicitation of preliminary responses, and the selection of assessment criteria); conduct of the panel/development team interaction; report preparation; and review cycles. The paper concludes with a list of limitations for face validation and lessons learned from the authors experience, including what did and did not work well during the model assessments. This same process has since been used by BMDO to collect information needed for planning and decision making, and to orient the continued development of TMD models consistent …
Date:
September 1, 1997
Creator:
Bravy, S.; May, W. L. & Mitchell, B. L.
Object Type:
Article
System:
The UNT Digital Library
Accumulator ring design for the NSNS project
The goal of the proposed National Spallation Neutron Source (NSNS) is to provide a short pulse proton beam of about 0.5 {mu}s with average beam power of 1 MW. To achieve such purpose, a proton storage ring operated at 60 Hz with 1 x 10{sup 14} protons per pulse at 1 GeV is required. The Accumulator Ring (AR) receives 1 msec long H{sup {minus}} beam bunches of 28 mA from a 1 GeV linac. Scope and design performance goals of the AR are presented, other possible technological choices and design options considered, but not adopted, are also briefly reviewed.
Date:
July 1, 1997
Creator:
Weng, W. T.; Alessi, J. & Beebe-Wang, J.
Object Type:
Article
System:
The UNT Digital Library
Accuracy analysis of the phase-screen propagator: implications for modeling and migration
We present formal and numerical error analyses of the phase-screen (or split-step Fourier) propagator. Numerical results suggest that the propagator is accurate up to 60 degrees of propagation angle relative the main propagation direction for media with small velocity perturbations. We investigate the errors from various approaches for splitting the exponential operator of the phase-screen propagator. The symmetrically split equations are slightly more accurate than the one-step split equations. Numerical examples show that the differences among splitting approaches are not significant. Therefore. relative to the symmetrically split equations. the one-step-free one-step-perturbation split equation is more efficient for migration in which wavefields in the space domain at all depth levels must be calculated. However. the half-step-free one-step-perturbation half-step-free split equation has almost the same efficiency as the one-step split equations for forward wave simulations.
Date:
November 1, 1997
Creator:
Huang, Lian-Jie & Fehler, M. C.
Object Type:
Article
System:
The UNT Digital Library
Accuracy estimation for supervised learning algorithms
This paper illustrates the relative merits of three methods - k-fold Cross Validation, Error Bounds, and Incremental Halting Test - to estimate the accuracy of a supervised learning algorithm. For each of the three methods we point out the problem they address, some of the important assumptions that are based on, and illustrate them through an example. Finally, we discuss the relative advantages and disadvantages of each method.
Date:
April 1, 1997
Creator:
Glover, C. W.; Oblow, E. M. & Rao, N. S. V.
Object Type:
Article
System:
The UNT Digital Library