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7,051 Matching Results
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Particle identification in ultrarelativistic nuclear collisions
The role of particle identification (PID) in both fixed-target and colliding-beam studies of ultrarelativistic nuclear (URN) collisions is examined. The demands placed on the PID systems by peculiarities of URN collisions, such as large multiplicities and the need for simultaneous measurement of a number of observables, are discussed. A variety of PID techniques are reviewed, with emphasis on their applicability and efficiency in the environment of such collisions. Two examples of PID as incorporated into existing fixed-target nuclear-beam experiments are presented. 18 refs., 5 figs.
Date:
April 1, 1986
Creator:
DiGiacomo, N.J.
System:
The UNT Digital Library
Computation of self-consistent 2-D MHD with neutral-beam and bootstrap currents in elongated plasmas
The observation of substantial current drive from neutral beam injection (NBI) in TFTR, JET and DIII-D has led to renewed interest in a steady state, non-inductively driven tokamak. The discovery of apparently considerable neoclassical (bootstrap) current in TFTR, makes a steady state device even more attractive since the bootstrap portion of the current could be obtained without additional power input. Motivated by these results, we have developed a code, ACCOME, which self-consistently computes the 2-D MHD equilibrium with the current driven by neutral beams, bootstrap and the electric field. In this paper we first describe some details of the code in the next section and in the subsequent section show some applications to DIII-D and to a possible ITER design.
Date:
April 5, 1983
Creator:
Devoto, R. S.; Tani, K. & Azumi, M.
System:
The UNT Digital Library
Cause of pitting in beryllium
Light microscopy, bare-film radiography, secondary ion mass spectroscopy, electron microprobe and physical testing were used to examine beryllium specimens exhibiting a stratified, pitted, pattern after chemical milling. The objective was to find the cause of this pattern. Specimens were found to have voids in excess of density specification allowances. These voids are attributed, at least in part, to the sublimation of beryllium fluoride during the vacuum hot pressing operation. The origin of the pattern is attributed to these voids and etching out of fines and associated impurities. Hot isostatic pressing with a subsequent heat treatment close residual porosity and dispersed impurities enough to correct the problem.
Date:
April 16, 1982
Creator:
Kershaw, R. P.
System:
The UNT Digital Library
Report of the Working Group on Media Accelerators
A summary is given of the activities of those in the Media Accelerator Group. Attention was focused on the Inverse Cherenkov Accelerator, the Laser Focus Accelerator, and the Beat Wave Accelerator. For each of these the ultimate capability of the concept was examined as well as the next series of experiments which needs to be performed in order to advance the concept.
Date:
April 12, 1982
Creator:
Sessler, Andrew M.
System:
The UNT Digital Library
HTGR-GT closed-cycle gas turbine: a plant concept with inherent cogeneration (power plus heat production) capability
The high-grade sensible heat rejection characteristic of the high-temperature gas-cooled reactor-gas turbine (HTGR-GT) plant is ideally suited to cogeneration. Cogeneration in this nuclear closed-cycle plant could include (1) bottoming Rankine cycle, (2) hot water or process steam production, (3) desalination, and (4) urban and industrial district heating. This paper discusses the HTGR-GT plant thermodynamic cycles, design features, and potential applications for the cogeneration operation modes. This paper concludes that the HTGR-GT plant, which can potentially approach a 50% overall efficiency in a combined cycle mode, can significantly aid national energy goals, particularly resource conservation.
Date:
April 1, 1980
Creator:
McDonald, C. F.
System:
The UNT Digital Library
Computer-aided visualization of database structural relationships
Interactive computer graphic displays can be extremely useful in augmenting understandability of data structures. In complexly interrelated domains such as bibliographic thesauri and energy information systems, node and link displays represent one such tool. This paper presents examples of data structure representations found useful in these domains and discusses some of their generalizable components. 2 figures.
Date:
April 1, 1980
Creator:
Cahn, D.F.
System:
The UNT Digital Library
Permeability damage to natural fractures caused by fracturing fluid polymers
Formation damage studies using artificially fractured, low-permeability sandstone cores indicate that viscosified fracturing fluids can severely restrict gas flow through these types of narrow fractures. These studies were performed in support of the Department of Energy's Multiwell Experiment (MWX). Extensive geological and production evaluations at the MWX site indicate that the presence of a natural fracture system is largely responsible for unstimulated gas production. The laboratory formation damage studies were designed to examine changes in cracked core permeability to gas caused by fracturing fluid residues introduced into such narrow fractures during fluid leakoff. Polysaccharide polymers caused significant reduction (up to 95%) to gas flow through cracked cores. Polymer fracturing fluid gels used in this study included hydroxypropyl guar, hydroxyethyl cellulose, and xanthan gum. In contrast, polyacrylamide gels caused little or no reduction in gas flow through cracked cores after liquid cleanup. Other components of fracturing fluids (surfactants, breakers, etc.) caused less damage to gas flows. Other factors affecting gas flow through cracked cores were investigated, including the effects of net confining stress and non-Darcy flow parameters. Results are related to some of the problems observed during the stimulation program conducted for the MWX. 24 refs., 4 figs., 7 tabs.
Date:
April 1, 1988
Creator:
Gall, B. L.; Sattler, A. R.; Maloney, D. R. & Raible, C. J.
System:
The UNT Digital Library
Energy-consumption modelling
A highly sophisticated and accurate approach is described to compute on an hourly or daily basis the energy consumption for space heating by individual buildings, urban sectors, and whole cities. The need for models and specifically weather-sensitive models, composite models, and space-heating models are discussed. Development of the Colorado State University Model, based on heat-transfer equations and on a heuristic, adaptive, self-organizing computation learning approach, is described. Results of modeling energy consumption by the city of Minneapolis and Cheyenne are given. Some data on energy consumption in individual buildings are included.
Date:
April 1980
Creator:
Reiter, Elmar R.
System:
The UNT Digital Library
Monitoring the materials and chemistry of a geothermal plant
The components of geothermal brines that cause corrosion and scaling problems are reviewed, especially brine pH, CO/sub 2/, H/sub 2/S, oxygen (from air), silicia, calcium, sulfides, and suspended particulates. Instrumental methods for on-line measurement are discussed to show how to keep costs low by operating a geothermal plant from a position of knowledge of what is occurring to the plant materials. The US Department of Energy research and development program in brine chemistry and on-line instrument development at Pacific Northwest Laboratory is discussed along with the strategy for commercial availability of new instruments to the geothermal industry.
Date:
April 1, 1988
Creator:
Shannon, D.W.
System:
The UNT Digital Library
Rf cavity primer for cyclic proton accelerators
The purpose of this note is to describe the electrical and mechanical properites of particle accelerator rf cavities in a manner which will be useful to physics and engineering graduates entering the accelerator field. The discussion will be limited to proton (or antiproton) synchrotron accelerators or storage rings operating roughly in the range of 20 to 200 MHz. The very high gradient, fixed frequency UHF or microwave devices appropriate for electron machines and the somewhat lower frequency and broader bandwidth devices required for heavy ion accelerators are discussed extensively in other papers in this series. While it is common pratice to employ field calculation programs such as SUPERFISH, URMEL, or MAFIA as design aids in the development of rf cavities, we attempt here to elucidate various of the design parameters commonly dealt with in proton machines through the use of simple standing wave coaxial resonator expressions. In so doing, we treat only standing wave structures. Although low-impedance, moderately broad pass-band travelling wave accelerating systems are used in the CERN SPS, such systems are more commonly found in linacs, and they have not been used widely in large cyclic accelerators. Two appendices providing useful supporting material regarding relativistic particle dynamics and …
Date:
April 1, 1988
Creator:
Griffin, J.E.
System:
The UNT Digital Library
Indoor concentrations of radon 222 and its daughters: sources, range, and environmental influences
The author here reviews what is presently known about factors affecting indoor concentrations of radon 222 and its daughters. In US single-family homes, radon concentrations are found to average about 1.5 pCi/1, but substantially higher concentrations occur frequently: perhaps a million US homes have concentrations exceeding 8 pCi/1 (from which occupants receive radiation doses comparable to those now experienced by uranium miners). The major contributor to indoor radon is ordinary soil underlying homes, with this radon being transported indoors primarily by the slight depressurization that occurs toward the bottom of a house interior (due to indoor-outdoor temperature differences and winds). Water from underground sources contributes significantly in a minority of cases, primarily residences with private wells, with public water supplies contributing only a few percent of indoor radon, even when drawn from wells. The strong variability in indoor concentrations is associated primarily with variability in the amount of radon entering homes from these various sources, and secondarily with differences in ventilation rates. However, for a given entry rate, the ventilation rate is the key determinant of indoor concentrations. Human doses are also influenced strongly by the chemical behavior of the daughters (i.e., decay products of radon), and considerable progress has …
Date:
April 1, 1985
Creator:
Nero, A.V. Jr.
System:
The UNT Digital Library
Excited state absorption measurements of Sm sup 2+ in CaF sub 2 , SrF sub 2 , and SrCl sub 2
We measured the pump-probe spectrum of the Sm{sup 2+} ion in three materials: CaF{sub 2}, SrF{sub 2}, and SrCl{sub 2}. The onset of the observed prominent excited-state absorption band is consistent with an electrostatic model for impurity levels in a solid-state material. 15 refs., 4 figs., 1 tab.
Date:
April 1, 1991
Creator:
Lawson, J. K.; Lee, H. W. H.; Payne, S. A. (Lawrence Livermore National Lab., CA (United States)) & Boatner, L. A. (Oak Ridge National Lab., TN (United States))
System:
The UNT Digital Library
Optical imaging diagnostics for fusion plasmas
Imaging diagnostics are used for spatially/emdash/and temporally/emdash/resolved quantitative measurements of plasma properties such as the ionization particle source, particle and energy loss, and impurity radiation in magnetically confined fusion plasmas. Diagnostics equipped with multi-element solid-state detectors (often with image intensifiers) are well suited to the environment of large fusion machines with high magnetic field and x-ray and neutron fluxes. We have both conventional (16msframe) and highspeed video cameras to measure neutral deuterium H/sub ..cap alpha../ (6563 /angstrom/) emissions from fusion plasmas. Continuous high-speed measurements are made with video cameras operating at 0.1 to 0.5 msframe; gated cameras provide snapshots of 10 to 100 ..mu..s during each 16-ms video frame. Digital data acquisition and absolute intensity calibrations of the cameras enable detailed quantitative source measurements: these are extremely important in determining the particle balance of the plasma. In a liner confinement device, radial transport can be determined from the total particle balance. In a toroidal confinement device, the details of particle recycling can be determined. Optical imaging in other regions of the spectrum are also important, particularly for the diverter region of large tokamaks. Absolutely calibrated infrared cameras have been used to image to temperature changes in the wall and thereby …
Date:
April 1, 1988
Creator:
Allen, S.L.
System:
The UNT Digital Library
Heat transfer in underground heating experiments in granite, Stipa, Sweden
Electrical heater experiments have been conducted underground in granite at Stripa, Sweden, to investigate the effects of heating associated with nuclear waste storage. Temperature data from these experiments are compared with closed-form and finite-element solutions. Good agreement is found between measured temperatures and both types of models, but especially for a nonlinear finite-element heat conduction model incorporating convective boundary conditions, measured nonuniform initial rock temperature distribution, and temperature-dependent thermal conductivity. In situ thermal properties, determined by least-squares regression, are very close to laboratory values. A limited amount of sensitivity analysis is undertaken.
Date:
April 1, 1980
Creator:
Chan, T.; Javandel, I. & Witherspoon, P.A.
System:
The UNT Digital Library
Reducing long-term reservoir performance uncertainty
Reservoir performance is one of the key issues that have to be addressed before going ahead with the development of a geothermal field. In order to select the type and size of the power plant and design other surface installations, it is necessary to know the characteristics of the production wells and of the produced fluids, and to predict the changes over a 10--30 year period. This is not a straightforward task, as in most cases the calculations have to be made on the basis of data collected before significant fluid volumes have been extracted from the reservoir. The paper describes the methodology used in predicting the long-term performance of hydrothermal systems, as well as DOE/GTD-sponsored research aimed at reducing the uncertainties associated with these predictions. 27 refs., 1 fig.
Date:
April 1, 1988
Creator:
Lippmann, M.J.
System:
The UNT Digital Library
Tutorial on neural network applications in high energy physics: A 1992 perspective
Feed forward and recurrent neural networks are introduced and related to standard data analysis tools. Tips are given on applications of neural nets to various areas of high energy physics. A review of applications within high energy physics and a summary of neural net hardware status are given.
Date:
April 1, 1992
Creator:
Denby, B.
System:
The UNT Digital Library
Two-photon (VUV + visible) resonance ionization spectroscopy of molecular hydrogen
Two-photon transitions have been examined in molecular hydrogen using coherent vacuum ultraviolet (VUV) photons at a fixed wavelength of 118 nm and a tunable photon from a dye laser. Though the VUV intensity is very weak (/approximately/100 nJ per pulse) it was utilized very efficiently since most VUV photons in the ionoization region were absorbed. This is the first time that coherent VUV light has been employed with tunable visible light for the production of two-photon spectra and the measurement of two-photon rates. A new parameter is proposed for direct comparison of the data from various two-photon experiments. 4 refs., 2 figs., 1 tab.
Date:
April 1, 1988
Creator:
McCann, M.P.; Chen, C.H. & Payne, M.G.
System:
The UNT Digital Library
Time series analysis of reactor thermocouple data. [LMFBR]
Time-series analysis techniques are applied to nuclear reactor thermocouple data to investigate coolant temperatures measured within the fueled test assembly. The coolant temperature distribution within a fuel assembly affects the length of time a fuel assembly may be operated in a power reactor and, therefore, is an important economic consideration in the design of reactor fuel systems. Frequency-domain signal conditioning techniques were used to reveal the smoothly varying thermocouple signals from the noisy digital data. Examination of the cross-correlation function for thermocouple pairs suggested an alternate surging and ebbing of coolant flow within certain zones of the fuel assembly. These zones corresponded to thermocouples which experienced higher or lower than predicted coolant temperatures. This time series analysis contributed greatly toward the understanding of fuel assembly thermal hydraulics.
Date:
April 10, 1980
Creator:
Devary, J.L.
System:
The UNT Digital Library
Recent developments in positron emission tomography (PET) instrumentation
This paper presents recent detector developments and perspectives for positron emission tomography (PET) instrumentation used for medical research, as well as the physical processes in positron annihilation, photon scattering and detection, tomograph design considerations, and the potentials for new advances in detectors. 117 refs., 4 figs., 4 tabs.
Date:
April 1, 1986
Creator:
Derenzo, S.E. & Budinger, T.F.
System:
The UNT Digital Library
Fusion breeder
The fusion breeder is a fusion reactor designed with special blankets to maximize the transmutation by 14 MeV neutrons of uranium-238 to plutonium or thorium to uranium-233 for use as a fuel for fission reactors. Breeding fissile fuels has not been a goal of the US fusion energy program. This paper suggests it is time for a policy change to make the fusion breeder a goal of the US fusion program and the US nuclear energy program. The purpose of this paper is to suggest this policy change be made and tell why it should be made, and to outline specific research and development goals so that the fusion breeder will be developed in time to meet fissile fuel needs.
Date:
April 20, 1982
Creator:
Moir, Ralph W.
System:
The UNT Digital Library
Mode methods for strain-hardening structures
An approximation method is being developed to predict the dynamic plastic response of rigid, strain-hardening structures. This method is analogous to the instantaneous mode techniques used to treat rigid, perfectly plastic structures in that a deflection shape involving a number of arbitrary functions of time is selected, based on static deformation profiles. Two stress fields are associated with the deflection shape: One satisfies the equations of motion with appropriate boundary and continuity conditions, and the other satisfies the strain-hardening constitutive relation with appropriate boundary and smoothness conditions. The method is illustrated using the case of a simply-supported beam with a central plastic region.
Date:
April 1, 1992
Creator:
Youngdahl, C.K.
System:
The UNT Digital Library
Physical Model of Lean Suppression Pressure Oscillation Phenomena: Steam Condensation in the Light Water Reactor Pressure Suppression System (PSS)
Using the results of large scale multivent tests conducted by GKSS, a physical model of chugging is developed. The unique combination of accurate digital data and cinematic data has provided the derivation of a detailed, quantified correlation between the dynamic physical variables and the associated two-phase thermo-hydraulic phenomena occurring during lean suppression (chugging) phases of the loss-of-coolant accident in a boiling water reactor pressure suppression system.
Date:
April 1, 1980
Creator:
McCauley, E. W.; Holman, G. S.; Aust, E.; Schwan, H. & Vollbrandt, J.
System:
The UNT Digital Library
Balance in machine architecture: Bandwidth on board and offboard, integer/control speed and flops versus memory
The issues to be addressed here are those of balance'' in machine architecture. By this, we mean how much emphasis must be placed on various aspects of the system to maximize its usefulness for physics. There are three components that contribute to the utility of a system: How the machine can be used, how big a problem can be attacked, and what the effective capabilities (power) of the hardware are like. The effective power issue is a matter of evaluating the impact of design decisions trading off architectural features such as memory bandwidth and interprocessor communication capabilities. What is studied is the effect these machine parameters have on how quickly the system can solve desired problems. There is a reasonable method for studying this: One selects a few representative algorithms and computes the impact of changing memory bandwidths, and so forth. The only room for controversy here is in the selection of representative problems. The issue of how big a problem can be attacked boils down to a balance of memory size versus power. Although this is a balance issue it is very different than the effective power situation, because no firm answer can be given at this time. The …
Date:
April 1, 1992
Creator:
Fischler, M.
System:
The UNT Digital Library
Role of gas pressure and lateral stress on blistering
Both gas pressure in bubbles and lateral stress have been suggested as primary causes of blistering. An analysis of both mechanisms is presented, and the conditions for blistering are examined. To realistically predict the gas pressure in bubbles, a recently derived high-density equation of state for helium is utilized.
Date:
April 1, 1980
Creator:
Wolfer, W. G.
System:
The UNT Digital Library