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3,034 Matching Results
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BEAM-PROFILE INSTRUMENTATION FOR BEAM-HALO MEASUREMENT : OVERALL DESCRIPTION, OPERATION, AND BEAM DATA.
The halo experiment presently being conducted at the Low Energy Demonstration Accelerator (LEDA) at Los Alamos National Laboratory (LANL) has specific instruments that acquire horizontally and vertically projected particle-density beam distributions out to greater than 10{sup 5}:1 dynamic range. They measure the core of the distributions using traditional wire scanners, and the tails of the distribution using water-cooled graphite scraping devices. The wire scanner and halo scrapers are mounted on the same moving frame whose location is controlled with stepper motors. A sequence within the Experimental Physics and Industrial Control System (EPICS) software communicates with a National Instrument LabVIEW virtual instrument to control the motion and location of the scanner/scraper assembly. Secondary electrons from the wire scanner 0.03-mm carbon wire and protons impinging on the scraper are both detected with a lossy-integrator electronic circuit. Algorithms implemented within EPICS and in Research Systems Interactive Data Langugage (IDL) subroutines analyse and plot the acquired distributions. This paper describes this beam profile instrument, describes their experience with its operation, compares acquired profile data with simulations, and discusses various beam profile phenomena specific to the halo experiment.
Date:
January 1, 2001
Creator:
Gilpatrick, J. D. (John Douglas); Barr, D. S. (Dean S.); Day, L. A. (Lisa A.); Stettler, M. W. (Matthew W.); Valdiviez, R. (Robert); Gruchalla, M. (Michael) et al.
Object Type:
Article
System:
The UNT Digital Library
Beam Quality at Jefferson Lab
The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab is a $600M CW electron accelerator in Newport News, Virginia. The machine is a recirculating, superconducting 5-pass linac initially commissioned for 4 GeV with a maximum beam power of 1 MW. With improvements in our RF cavity performance and an upgrade to magnet power supplies we are now capable of reliable operations at up to 5.7 GeV. We employ a three-laser photocathode gun to provide a CW electron beam with 80% polarization to three experimental endstations in currents ranging from 100 pA to 200 mA. Establishing clear criteria for beam quality and developing the means to verify and maintain beam quality is essential to a successful physics program.
Date:
January 1, 2001
Creator:
Spata, M. F.
Object Type:
Article
System:
The UNT Digital Library
Bench test of a residual gas ionization profile monitor (RGIPM)
An RGIPM has been designed1, constructed and bench tested to verify that all components are functioning properly and that the desired resolution of about 50 {micro}m rms can be achieved. This paper will describe major considerations that went into the bench test and some results.
Date:
January 1, 2001
Creator:
Sellyey, W. C. (William C.); Gilpatrick, J. D. (John Douglas) & Senior, R. (Ralph)
Object Type:
Article
System:
The UNT Digital Library
Benchmarking ten codes against the recent GSI measurements of the nuclide yields from [sup 208]Pb, [sup 197]Au, and [sup 238]U + p reactions at 1 GeV/nucleon
A qualitative and quantitative comparison of the recent GSI measurements of the nuclide yields from {sup 208}Pb and {sup 238}U at 1 GeV/nucleon and {sup 198}Au at 800 MeV/nucleon interactions with protons with the codes LAHET (with both ISABEL and Bertini options), CEM95, CEM97, CEM2k, CASCADE, CASCADE/INPE, YIELDX, HETC, and INUCL is presented. The predictive power of these codes is reasonable for nuclides in the near spallation region but is worse for deep spallation and much worse in the fission region. None of these codes agree well with the data in the whole mass region of product nuclides and all must be improved to become reliable tools for accelerator-driven applications.
Date:
January 1, 2001
Creator:
Prael, R. E. (Richard E.); Sierk, A. J. (Arnold J.); Batyaev, V. F. (Vyacheslav F.); Kvasova, S. V. (Svetlana V.); Mulambetov, R. D. (Ruslan D.); Titarenko, Y. E. (Yury E.) et al.
Object Type:
Article
System:
The UNT Digital Library
Better Duct Systems for Home Heating and Cooling.
This is a series of six guides intended to provide a working knowledge of residential heating and cooling duct systems, an understanding of the major issues concerning efficiency, comfort, health, and safety, and practical tips on installation and repair of duct systems. These guides are intended for use by contractors, system designers, advanced technicians, and other HVAC professionals. The first two guides are also intended to be accessible to the general reader.
Date:
January 1, 2001
Creator:
Andrews, J.
Object Type:
Report
System:
The UNT Digital Library
Beyond integrated safeguards: performance-based assessments for future nuclear controls.
In the future, iE the nuclear nonproliferation and arms control agendas are to advance, they will likely become increasingly seen as parallel undertakings with the objective of comprehensive cradle-to-grave controls over nuclear materials and possibly even warheads removed from defense programs along with materials in civilian use. This 'back to the future' prospect was envisioned in the Acheson-Lillienthal Report and the Baruch Plan, and more modestly in the Atoms-for-Peace Proposal. Unlike the grand plans of the early nuclear years, today's and tomorrow's undertakings will more likely consist of a series of incremental steps with the goal of expanding nuclear controls. These steps will be undertaken at a time of fundamental change in the IAEA safeguards system, and they will be influenced by those changes in profound ways. This prospective influence needs to be taken into account as the IAEA develops and implements integrated safeguards, including its efforts to establish new safeguards criteria, undertake technological and administrative improvements in safeguards, implement credible capabilities for the detection of undeclared nuclear facilities and activities and, perhaps, provide for a more intensive involvement in applying safeguards in new roles such as the verification of a fissile materials cutoff treaty. Performance-based criteria offer one promising …
Date:
January 1, 2001
Creator:
Pilat, Joseph F. & Budlong-Sylvester, K. W. (Kory W.)
Object Type:
Article
System:
The UNT Digital Library
BOLIDE FRAGMENTATION PROCESSES : SINGLE-BODY MODELING VERSUS THE CATASTROPHIC FRAGMENTATION LIMIT.
The catastrophic 'pancake' fragmentation process, proposed as being generally applicable to very large meteoroid entry in the early 1990's by a number of workers, has been carefully examined. In this effort, the transition from the traditional single-body dynamics and energetics model to a catastrophic 'pancake' fragmentation process has been delineated. The key parameters are the {mu} parameter originally proposed by Levin and the fragmentation scale height, Hf, which we have derived from {mu}. It has been found that this break-up process can only occur for an optimum set of circumstances.
Date:
January 1, 2001
Creator:
ReVelle, D. O. (Douglas O.)
Object Type:
Article
System:
The UNT Digital Library
BOLIDE PHYSICAL THEORY WITH APPLICATION TO PN AND EN FIREBALLS.
Using data on 22 'precise bolides' with up to 882 individual points on their trajectories and using data on 29 'bright bolides' and on 10 artificial meteors, we tried to derive dependence of ablation and shape-density coefficients, and of luminous efficiency on various time dependent parameters. The only significant dependence we found was that on v{sub {infinity}} - v (on difference of initial and instantaneous velocities). We present the results as Eq. 3, 4 and 8, with coefficients a{sub 1}, a{sub 2}, a{sub 3}, a{sub 4}, b{sub 1}, b{sub 2}, a{sub 3}, c{sub 1}, c{sub 2}, computed for different bolide types. Also average values of ablation, and shape-density coefficients as well as average luminous efficiencies for individual bolide types are given.
Date:
January 1, 2001
Creator:
ReVelle, D. O. (Douglas O.)
Object Type:
Article
System:
The UNT Digital Library
Building the Mass Storage System at Jefferson Lab
Thomas Jefferson National Accelerator Facility (Jefferson Lab) is a U.S. Department of Energy Facility [1] conducting Nuclear Physics experiments that currently have data collection rates of up to 20 MB / second. Future experiments, however, are expected to greatly exceed these rates. Post processing and data analysis produce similar amounts of data. Both the raw and processed data are stored on tape and need to be easily accessible. Between data collection and processing, the Mass Storage System at Jefferson Lab currently moves over 2 TB of data per day.
Date:
January 1, 2001
Creator:
Bird, I.; Hess, B. & Kowalski, A.
Object Type:
Article
System:
The UNT Digital Library
Bulk Fe-based metallic glass with extremely soft ferromagnetic properties
The authors have investigated the DC and AC magnetic properties of a bulk glassy Fe{sub 65.5}Cr{sub 4}Mo{sub 4}Ga{sub 4}P{sub 12}B{sub 5.5}C{sub 5} alloy. In the annealed state the alloy has coercivity H{sub C} and maximum DC permeability {mu}{sub m} of approximately 0.4 A/m (5 mOe) and 2.8 x 10{sup 5}, comparable to those found in annealed zero-magnetostriction Co-based alloys. The low H{sub C} found in the bulk glassy alloy is attributed to the low ratio of surface-roughness to sample thickness, and low residual internal-stress. The total power loss in the annealed bulk glass is about one order of magnitude lower than that of rapidly quenched Fe-based glassy ribbons. This is attributed to a low anomalous eddy-current loss.
Date:
January 1, 2001
Creator:
Shen, T. D. (Tongde D.); Harms, U. S. (Ulrich S.) & Schwarz, R. B. (Ricardo B.)
Object Type:
Article
System:
The UNT Digital Library
CALCULATIONS OF SHAPE CHANGE AND FRAGMENTATION PARAMETERS USING VERY PRECISE BOLIDE DATA.
Using the theoretical formalism of ReVelle (2001d), we have analyzed 22 European (EN) and US Prairie Network fireballs (PN) with the most precise trajectory information available for shape change and fragmentation effects. For 14 bolides the shape change parameter, {mu}, was always > 0 and for the other 8 cases there were instances of {mu} < 0, but with large oscillations in its sign with height or time. When the shape change parameter, {mu}, was < 0, the fragmentation scale height was > 0 and in a few instances was briefly even smaller than the pressure scale height. This is the necessary condition in addition to the sufficient condition of {mu} < 0 for the onset of the catastrophic fragmentation process ('pancake' break-up). A histogram of all computed {mu} values indicates that an average value was <{mu} > {approx} 0.10, indicating that substantial shape change has taken place during entry for these bolides. This is fully consistent with the recent analyses of ReVelle and Ceplecha (2001g) of the changes in the shape-density coefficient, K, with time as well. Thus, the use of the {mu} = 2/3 (self-similar solution with no shape change) is not recommended for bolide modeling efforts. From …
Date:
January 1, 2001
Creator:
ReVelle, D. O. (Douglas O.) & Ceplecha, Zdeněk
Object Type:
Article
System:
The UNT Digital Library
Calibration of a gamma calibration well with an energy-compensated Geiger-Mueller (G-M) tube.
A working-standard Radcal model 1515 radiation monitor with the 1800cc ion chamber was used previously at Los Alamos National Laboratory (LANL) to calibrate and perform routine QA checks on the low-level gamma well, which produces exposure rates in the range of 0.2 mR/h to 10 mR/h. During long integration times (e.g. 24-48 hrs) with the 1800 cc ion chamber, which were required to obtain the necessary precision, changes in temperature and pressure and fluctuations in the zero offset introduced errors that were difficult to account for. An energy compensated G-M tube (SHP-270) was calibrated as a Working Standard to calibrate and perform QA checks on the low-level gamma well. Energy correction factors were determined since the SHP-270 does not have a linear energy response. Monte Carlo N-Particle (MCNP) code was used to determine the exposure rate in 50 keV energy bins as a function of source distance in the well. The results of these calculations were folded into the energy correction factors of the SHP-270 to determine the Corrected Exposure Rate as a function of source distance. To recalibrate the gamma well, the Corrected Exposure Rates were loaded into the source control algorithm, which was then verified to work correctly.
Date:
January 1, 2001
Creator:
George, G. L. (Gerald L.); Seagraves, D. T. (David T.) & Valdez, D. T. (Darlene T.)
Object Type:
Article
System:
The UNT Digital Library
Calibration of Thin-Foil Manganin Gages for MFG/DQA
None
Date:
January 1, 2001
Creator:
Peevy, G. R.; Rivera, W. G.; Benham, R. A. & Duggins, B. D.
Object Type:
Report
System:
The UNT Digital Library
CALLA ENERGY BIOMASS COFIRING PROJECT
This project is to be conducted in two phases. The objective of Phase I is to evaluate the technical and economic feasibility of cofiring biomass-based gasification fuel-gas in a power generation boiler. Waste coal fines are to be evaluated as the cofired fuel. The project is based on the use of commercially available technology for feeding and gas cleanup that would be suitable for deployment in municipal, large industrial and utility applications. Define a combustion system for the biomass gasification-based fuel-gas capable of stable, low-NOx combustion over the full range of gaseous fuel mixtures, with low carbon monoxide emissions and turndown capabilities suitable for large-scale power generation applications. The objective for Phase II is to Design, install and demonstrate the combined gasification and combustion system in a large-scale, long-term cofiring operation to promote acceptance and utilization of indirect biomass cofiring technology for large-scale power generation applications.
Date:
January 1, 2001
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
CARBON DIOXIDE CAPTURE FROM FLUE GAS USING DRY REGENERABLE SORBENTS
Four grades of sodium bicarbonate and two grades of trona were characterized in terms of particle size distribution, surface area, pore size distribution, and attrition. Surface area and pore size distribution determinations were conducted after calcination of the materials. The sorbent materials were subjected to thermogravimetric testing to determine comparative rates and extent of calcination (in inert gas) and sorption (in a simulated coal combustion flue gas mixture). Selected materials were exposed to five calcination/sorption cycles and showed no decrease in either sorption capacity or sorption rate. Process simulations were conducted involving different heat recovery schemes. The process is thermodynamically feasible. The sodium-based materials appear to have suitable physical properties for use as regenerable sorbents and, based on thermogravimetric testing, are likely to have sorption and calcination rates that are rapid enough to be of interest in full-scale carbon sequestration processes.
Date:
January 1, 2001
Creator:
Green, David A.; Turk, Brian S.; Gupta, Raghubir & Lopez-Ortiz, Alejandro
Object Type:
Report
System:
The UNT Digital Library
Carbon dioxide sequestration by direct mineral carbonation: process mineralogy of feed and products
Direct mineral carbonation has been investigated as a process to convert gaseous CO2 into a geologically stable final form. The process utilizes a slurry of water, with bicarbonate and salt additions, mixed with a mineral reactant, such as olivine (Mg2SiO4) or serpentine [Mg3Si2O5(OH)4]. Carbon dioxide is dissolved into this slurry, resulting in dissolution of the mineral and precipitation of magnesium carbonate (MgCO3). Optimum results have been achieved using heat pretreated serpentine feed material and high partial pressure of CO2 (PCO2). Specific conditions include: 155?C; PCO2=185 atm; 15% solids. Under these conditions, 78% conversion of the silicate to the carbonate was achieved in 30 minutes. Process mineralogy has been utilized to characterize the feed and process products, and interpret the mineral dissolution and carbonate precipitation reaction paths.
Date:
January 1, 2001
Creator:
O'Connor, William K.; Dahlin, David C.; Rush, G.E.; Dahlin, Cheryl L. & Collins, W. Keith
Object Type:
Article
System:
The UNT Digital Library
Carbon Dioxide Sequestration by Direct Mineral Carbonation: Results from Recent Studies and Current Status
Direct mineral carbonation has been investigated as a process to convert gaseous CO2 into a geologically stable, solid final form. The process utilizes a solution of sodium bicarbonate (NaHCO3), sodium chloride (NaCl), and water, mixed with a mineral reactant, such as olivine (Mg2SiO4) or serpentine [Mg3Si2O5(OH)4]. Carbon dioxide is dissolved into this slurry, by diffusion through the surface and gas dispersion within the aqueous phase. The process includes dissolution of the mineral and precipitation of magnesium carbonate (MgCO3) in a single unit operation. Optimum results have been achieved using heat pretreated serpentine feed material, with a surface area of roughly 19 m2 per gram, and high partial pressure of CO2 (PCO2). Specific conditions include: 155?C; PCO2=185 atm; 15% solids. Under these conditions, 78% stoichiometric conversion of the silicate to the carbonate was achieved in 30 minutes. Studies suggest that the mineral dissolution rate is primarily surface controlled, while the carbonate precipitation rate is primarily dependent on the bicarbonate concentration of the slurry. Current studies include further examination of the reaction pathways, and an evaluation of the resource potential for the magnesium silicate reactant, particularly olivine. Additional studies include the examination of various pretreatment options, the development of a continuous flow …
Date:
January 1, 2001
Creator:
O'Connor, William K.; Dahlin, David C.; Nilsen, David N.; Rush, G.E.; Walters, Richard P. & Turner, Paul C.
Object Type:
Article
System:
The UNT Digital Library
Carbon mitigation potential and costs of forestry options in Brazil, China, India, Indonesia, Mexico, the Philippines and Tanzania
This paper summarizes studies of carbon (C) mitigation potential and costs of about 40 forestry options in seven developing countries. Each study uses the same methodological approach - Comprehensive Mitigation Assessment Process (COMAP) - to estimate the above parameters between 2000 and 2030. The approach requires the projection of baseline and mitigation land-use scenarios. Coupled with data on a per ha basis on C sequestration or avoidance, and costs and benefits, it allows the estimation of monetary benefit per Mg C, and the total costs and carbon potential. The results show that about half (3.0 Pg C) the cumulative mitigation potential of 6.2 Petagram (Pg) C between 2000 and 2030 in the seven countries (about 200 x 106 Mg C yr-1) could be achieved at a negative cost and the remainder at costs ranging up to $100 Mg C-1. About 5 Pg C could be achieved, at a cost less than $20 per Mg C. Negative cost potential indicates that non-carbon revenue is sufficient to offset direct costs of these options. The achievable potential is likely to be smaller, however, due to market, institutional, and sociocultural barriers that can delay or prevent the implementation of the analyzed options.
Date:
January 1, 2001
Creator:
Sathaye, J.; Makundi, W.; Andrasko, K.; Boer, R.; Ravindranath, N.; Sudha, P. et al.
Object Type:
Article
System:
The UNT Digital Library
Case for TCP Vegas in High-Performance Computational Grids
Computational grids such as the Information Power Grid, Particle Physics Data Grid, and Earth System Grid depend on TCP to provide reliable communication between nodes across a wide-area network (WAN). Of the available TCP implementations, TCP Reno and its variants are the most widely deployed; however, Reno's performance in computational grids is mediocre at best. Due to conflicting results in the evaluation of TCP implementations we present a detailed simulation study that unifies the conflicting results and demonstrates the limitations of earlier work. We focus on the two most debated versions of TCP - Reno and Vegas. Using real trafJic distributions, we show that Vegas performs well over modern high-performance links and better than Reno with the proper selection of the Vegas parameters a and p. Our results exhibit ways to signijicantly enhance the performance of distributed computational grids that rely on TCP.
Date:
January 1, 2001
Creator:
Weigle, E. H. (Eric H.) & Feng, W. C. (Wu-Chun)
Object Type:
Article
System:
The UNT Digital Library
CdZnTe gamma ray spectrometer for orbital gamma ray spectroscopy.
We present the design and analysis of a new gamma ray spectrometer for planetary science that uses an array of CdZnTe detectors to achieve the detection efficiency needed for orbital measurements. The use of CdZnTe will provide significantly improved pulse height resolution relative to scintillation-based detectors, with commensurate improvement in the accuracy of elemental abundances determined by gamma ray and neutron spectroscopy. The spectrometer can be flown either on the instrument deck of the spacecraft or on a boom. For deck-mounted systems, a BGO anticoincidence shield is included in the design to suppress the response of the CdZnTe detector to gamma rays that originate in the spacecraft. The BGO shield also serves as a backup spectrometer, providing heritage from earlier planetary science missions and reducing the risk associated with the implementation of new technology.
Date:
January 1, 2001
Creator:
Prettyman, T. H. (Thomas H.); Feldman, W. C. (William C.); Fuller, K. R. (Kenneth R.); Storms, S. A. (Steven A.); Soldner, S. A.; Lawrence, David J. (David Jeffery), et al.
Object Type:
Article
System:
The UNT Digital Library
CdZnTe gamma ray spectrometer for orbital planetary missions
Knowledge of surface elemental composition is needed to understand the formation and evolution of planetary bodies. Gamma rays and neutrons produced by the interaction of galactic cosmic rays with surface materials can be detected from orbit and analyzed to determine composition. Using gamma ray spectroscopy, major rock forming elements such as Fe, Ti, Al, Si, Mg, and Ca can be detected. The accuracy of elemental abundance is limited by the resolution of the spectrometer. For space missions, scintillators such as BGO and NaI(Tl) have been used for gamma ray spectroscopy. New planetary science missions are being planned to explore Mars, Mercury, the asteroid belt, and the outer planets. Significant improvements in the pulse height resolution relative to scintillation detectors can be made using CdZnTe, a new room temperature detector technology. For an orbiting instrument, a CdZnTe detector at least 16 cm{sup 3} in size is needed. A 4 x 4 array of 1-cm{sup 3} coplanar grid detectors can be manufactured that meets requirements for resolution and counting efficiency. The array will shielded from gamma rays produced in the spacecraft by a BGO detector. By improving pulse height resolution by a factor of three at low energy, the CdZnTe detector will …
Date:
January 1, 2001
Creator:
Feldman, W. C. (William C.); Storms, S. A. (Steven A.); Fuller, K. R. (Kenneth R.); Moss, C. E. (Calvin E.); Browne, M. C. (Michael C.); Lawrence, David J. (David Jeffery), et al.
Object Type:
Article
System:
The UNT Digital Library
CeMIn[sub 5](M=Co,Ir,Rh) heavy fermion superconductors and the utility of high magnetic field.
We review the properties of the recently discovered CeMIn5 (M=Co, Ir, Rh) heavy fermion superconductors and discuss the present state of our understanding of these materials. A particular focus is the role that magnetic fields have played in elucidating the properties of these materials. Specifically, we discuss quantum oscillation measurements on CeMIn5, the influence of applied field on the linear coefficient of specific heat, {gamma}, and the nature of the HT phase diagrams in both the normal and superconducting states of these materials.
Date:
January 1, 2001
Creator:
Sarrao, John L.,
Object Type:
Article
System:
The UNT Digital Library
CERAMIC MEMBRANE ENABLING TECHNOLOGY FOR IMPROVED IGCC EFFICIENCY
This quarterly technical progress report will summarize work accomplished for Phase 1 Program during the quarter October to December 2000. In task 1 careful modification of the processing conditions of the OTM has improved the properties of the final element. In addition, finite element modeling has been used to predict the mechanical behavior of OTM tubes and to identify strategies for improving OTM robustness. In task 2, composite elements of PSO1d have been prepared and tested for over 800 hours without degradation in oxygen flux. Alternative materials for composite OTM and architectures have been examined with success. In task 3, modification of fabrication routes has resulted in a substantial increase in the yield of PSO1d composite elements. The work in task 4 has demonstrated that composite OTM elements can produce oxygen at atmospheric pressure of greater than 95% purity from a high-pressure air feed gas. The work in task 5 to construct a multi-tube OTM reactor has begun.
Date:
January 1, 2001
Creator:
Prasad, Ravi
Object Type:
Report
System:
The UNT Digital Library
A ceramographic evaluation of chromia refractories corroded by slag
This paper describes the ceramographic preparation of Cr{sub 2}O{sub 3}-Al{sub 2}O{sub 3} refractory bricks and subsequent microstructural analysis to determine the corrosive effects of molten slag. The porous and friable nature of the brick, especially after exposure to the slag or its individual components, presented some problems in the preparation.
Date:
January 1, 2001
Creator:
Hunt, Alton H. & Chinn, Richard E.
Object Type:
Article
System:
The UNT Digital Library