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Fundamental studies of fusion plasmas. Annual performance report
Work on ICRF interaction with the edge plasma is reported. ICRF generated convective cells have been established as an important mechanism for influencing edge transport and interaction with the H-mode, and for controlling profiles in the tokamak scrape-off-layer. Power dissipation by rf sheaths has been shown to be significant for some misaligned ICRF and IIBW antenna systems. Near-field antenna sheath work has been extended to the far-field case, important for experiments with low single pass absorption. Impurity modeling and Faraday screen design support has been provided for the ICRF community. In the area of core-ICRF physics, the kinetic theory of heating by applied ICRF waves has been extended to retain important geometrical effects relevant to modeling minority heated tokamak plasmas, thereby improving on the physics base that is standard in presently employed codes. Both the quasilinear theory of ion heating, and the plasma response function important in wave codes have been addressed. In separate studies, it has been shown that highly anisotropic minority heated plasmas can give rise to unstable field fluctuations in some situations. A completely separate series of studies have contributed to the understanding of tokamak confinement physics. Additionally, a diffraction formalism has been produced which will be …
Date:
April 27, 1993
Creator:
Aamodt, R. E.; Catto, P. J.; D`Ippolito, D. A.; Myra, J. R. & Russell, D. A.
Object Type:
Report
System:
The UNT Digital Library
Fundamental studies of fusion plasmas. Annual performance report
The major portion of this program is devoted to critical ICH phenomena. The topics include edge physics, fast wave propagation, ICH induced high frequency instabilities, and a preliminary antenna design for Ignitor. This research was strongly coordinated with the world`s experimental and design teams at JET, Culham, ORNL, and Ignitor. The results have been widely publicized at both general scientific meetings and topical workshops including the speciality workshop on ICRF design and physics sponsored by Lodestar in April 1992. The combination of theory, empirical modeling, and engineering design in this program makes this research particularly important for the design of future devices and for the understanding and performance projections of present tokamak devices. Additionally, the development of a diagnostic of runaway electrons on TEXT has proven particularly useful for the fundamental understanding of energetic electron confinement. This work has led to a better quantitative basis for quasilinear theory and the role of magnetic vs. electrostatic field fluctuations on electron transport. An APS invited talk was given on this subject and collaboration with PPPL personnel was also initiated. Ongoing research on these topics will continue for the remainder fo the contract period and the strong collaborations are expected to continue, enhancing …
Date:
May 26, 1992
Creator:
Aamodt, R. E.; Catto, P. J.; D`Ippolito, D. A.; Myra, J. R. & Russell, D. A.
Object Type:
Report
System:
The UNT Digital Library
Thomson scattering diagnostic analyses to determine the energetic particle distributions in TFTR
The research completed and in progress for the first period of this grant is reviewed. Specific scattering scenarios for TFTR and JET and ITER were studied. The Lodestar scattering code, SKATR, was upgraded to include anisotropic energetic ion distributions and an analytic diffraction formulation was completed. Research continues on JET studies and upgrading the code for JET and ITER relevant conditions.
Date:
February 12, 1993
Creator:
Aamodt, R. E.; Cheung, P. & Russell, D. A.
Object Type:
Report
System:
The UNT Digital Library
Thomson scattering diagnostic analyses to determine the energetic particle distributions in TFTR. Annual performance report
The research completed and in progress for the first period of this grant is reviewed. Specific scattering scenarios for TFTR and JET and ITER were studied. The Lodestar scattering code, SKATR, was upgraded to include anisotropic energetic ion distributions and an analytic diffraction formulation was completed. Research continues on JET studies and upgrading the code for JET and ITER relevant conditions.
Date:
February 12, 1993
Creator:
Aamodt, R. E.; Cheung, P. & Russell, D. A.
Object Type:
Report
System:
The UNT Digital Library
Thomson scattering diagnostic analyses to determine the energetic particle distributions in TFTR. Final report
Lodestar has been an active participant in the low power Collective Thomson Scattering (CTS) diagnostic at TFTR in collaboration with MIT. Extensive studies were conducted regarding the use of gyrotron scattering as a low cost diagnostic for both energetic ions and alpha particles on TFTR. The numerical scattering code has been improved and compared with similar code developed at JET. The authors have participated and assisted in the CTS experiments through onsite visits and have successfully performed most of the data analysis tasks remotely. Through their analysis on the initial data base accumulated, they are able to understand qualitatively the general features of the anomalous large scattered signal, have proposed an explanation for its generation mechanism, and have suggested a potential new use of CTS as an edge diagnostic.
Date:
February 16, 1995
Creator:
Aamodt, R. E.; Cheung, P. Y. & Russell, D. A.
Object Type:
Report
System:
The UNT Digital Library
ICRF heating and current drive in TFTR supershot plasmas: Data analysis and interpretation of ICRF/edge interactions. Research Progress report
The relevance of rf-sheath-plasma interactions to ICRF operation in TFTR has been studied. Screen-screen and screen-limiter rf sheaths have been identified and analyzed for the old and new Bay M geometries on TFIR, including sheath voltages driven by both feeders and the central antenna conductor. Calculations have been carried out to determine the effects of ICRF on edge transport (profile flattening by E {times} B convection), impurity influx ({delta}Z{sub eff}) and edge electron heating (FS glow phenomena) as a function of edge plasma parameters, rf power and antenna phasing. It was found that many of the experimentally observed ICRF-edge plasma interactions on TFIR are consistent with the predictions of rf sheath theory.
Date:
September 22, 1993
Creator:
Aamodt, R. E.; D`Ippolito, D. A. & Myra, J. R.
Object Type:
Report
System:
The UNT Digital Library
Fundamental studies of fusion plasmas. Final report
Lodestar has carried out a vigorous research program in the areas of rf, edge plasma and divertor physics, with emphasis largely geared towards improving the understanding and performance of ion-cyclotron heating and current drive (ICRF) systems. Additionally, a research program in the field of edge plasma and divertor modeling was initiated. Theoretical work on high power rf sheath formation for multi-strap rf arrays was developed and benchmarked against recent experimental data from the new JET A2 antennas. Sophisticated modeling tools were employed to understand the sheath formation taking into account realistic three-dimensional antenna geometry. A novel physics explanation of an observed anomaly in the low power loading of antennas was applied to qualitatively interpret data on DIII-D in terms of rf sheaths, and potential applications of the idea to develop a near-field sheath diagnostic were explored. Other rf-wave related topics were also investigated. Full wave ICRF modeling studies were carried out in support of ongoing and planned tokamaks experiments, including the investigation of low frequency plasma heating and current drive regimes for IGNITOR. In a cross-disciplinary study involving both MHD and ICRF physics, ponderomotive feedback stabilization by rf was investigated as a potential means of controlling external kink mode disruptions. …
Date:
January 30, 1998
Creator:
Aamodt, R.E.
Object Type:
Report
System:
The UNT Digital Library
Oak Ridge Isotope Products and Services - Current and Expected Supply and Demand
Oak Ridge National Laboratory (ORNL) has been a major center of isotope production research, development, and distribution for over 50 years. Currently, the major isotope production activities include (1) the production of transuranium element radioisotopes, including 252 Cf; (2) the production of medical and industrial radioisotopes; (3) maintenance and expansion of the capabilities for production of enriched stable isotopes; and, (4) preparation of a wide range of custom-order chemical and physical forms of isotope products, particularly in accelerator physics research. The recent supply of and demand for isotope products and services in these areas, research and development (R&D), and the capabilities for future supply are described in more detail below. The keys to continuing the supply of these important products and services are the maintenance, improvement, and potential expansion of specialized facilities, including (1) the High Flux Isotope Reactor (HFIR), (2) the Radiochemical Engineering Development Center (REDC) and Radiochemical Development Laboratory (RDL) hot cell facilities, (3) the electromagnetic calutron mass separators and the plasma separation process equipment for isotope enrichment, and (4) the Isotope Research Materials Laboratory (IRML) equipment for preparation of specialized chemical and physical forms of isotope products. The status and plans for these ORNL isotope production facilities …
Date:
August 29, 1999
Creator:
Aaron, W. S.; Alexander, C. W.; Cline, R. L.; Collins, E. D.; Klein, J. A.; Knauer, J. B., Jr. et al.
Object Type:
Article
System:
The UNT Digital Library
Status of stable isotope enrichment, products, and services at the Oak Ridge National Laboratory
The Oak Ridge National Laboratory (ORNL) has been supplying enriched stable and radioactive isotopes to the research, medical, and industrial communities for over 50 years. Very significant changes have occurred in this effort over the past several years, and, while many of these changes have had a negative impact on the availability of enriched isotopes, more recent developments are actually improving the situation for both the users and the producers of enriched isotopes. ORNL is still a major producer and distributor of radioisotopes, but future isotope enrichment operations conducted at the Isotope Enrichment Facility (IEF) will be limited to stable isotopes. Among the positive changes in the enriched stable isotope area are a well-functioning, long-term contract program, which offers stability and pricing advantages; the resumption of calutron operations; the adoption of prorated conversion charges, which greatly improves the pricing of isotopes to small users; SIO 9002 registration of the IEF`s quality management system; and a much more customer-oriented business philosophy. Efforts are also being made to restore and improve upon the extensive chemical and physical form processing capabilities that once existed in the enriched stable isotope program. Innovative ideas are being pursued in both technical and administrative areas to encourage …
Date:
October 1, 1996
Creator:
Aaron, W.S.; Tracy, J.G. & Collins, E.D.
Object Type:
Article
System:
The UNT Digital Library
Gas cylinder disposal pit remediation waste minimization and management
A remediation of a gas cylinder disposal pit at Sandia National Laboratories, New Mexico has recently been completed. The cleanup prevented possible spontaneous releases of hazardous gases from corroded cylinders that may have affected nearby active test areas at Sandia`s Technical Area III. Special waste management, safety, and quality plans were developed and strictly implemented for this project. The project was conceived from a waste management perspective, and waste minimization and management were built into the planning and implementation phases. The site layout was planned to accommodate light and heavy equipment, storage of large quantities of suspect soil, and special areas to stage and treat gases and reactive chemicals removed from the pit, as well as radiation protection areas. Excavation was a tightly controlled activity using experienced gas cylinder and reactive chemical specialists. Hazardous operations were conducted at night under lights, to allow nearby daytime operations to function unhindered. The quality assurance plan provided specific control of, and documentation for, critical decisions, as well as the record of daily operations. Both hand and heavy equipment excavation techniques were utilized. Hand excavation techniques were utilized. Hand excavation techniques allows sealed glass containers to be exhumed unharmed. In the end, several dozen …
Date:
February 1, 1995
Creator:
Aas, C. A.; Solow, A.; Brannon, R.; Schwender, J. M.; Criswell, C. W.; Eckman, C. K. et al.
Object Type:
Article
System:
The UNT Digital Library
XAF/XANES studies of plutonium-loaded sodalite/glass composite waste forms.
A sodalite/glass ceramic waste form has been developed to immobilize highly radioactive nuclear wastes in chloride form, as part of an electrochemical cleanup process. Simulated waste forms have been fabricated which contain plutonium and are representative of the salt from the electrometallurgical process to recover uranium from spent nuclear fuel. X-ray absorption fine structure spectroscopy (XAFS) and x-ray absorption near-edge spectroscopy (XANES) studies were performed to determine the location, oxidation state and form of the plutonium within these waste forms. Plutonium, in the non-fission-element case, was found to segregate as plutonium(IV) oxide with a crystallite size of at least 20 nm. With fission elements present, the crystallite size was about 2 nm. No plutonium was observed within the sodalite or glass in the waste form.
Date:
July 14, 1999
Creator:
Aase, S. B.; Kropf, A. J.; Lewis, M. A.; Reed, D. T. & Richmann, M. K.
Object Type:
Article
System:
The UNT Digital Library
Dissolution of low-enriched UO{sub 2}/Al dispersion plates in alkaline peroxide solution.
Some conclusions from this report are: (1) A UO{sub 2}/Al dispersion target can be successfully dissolved in alkaline peroxide solutions; (2) after destruction of the peroxide recovery of the {sup 99}Mo would be nearly identical to existing processes using basic dissolution; (3) a low-enriched UO{sub 2}/Al dispersion targets could potentially be used for the production of {sup 99}Mo; and (4) punched cores from a UO{sub 2}/Al dispersion target will be irradiated to low-level burnup and effects of this LEU target on the recovery of {sup 99}Mo will be investigated. A commercial partner will be sought for full scale demonstrations.
Date:
October 21, 1997
Creator:
Aase, S.; Conner, C.; Landsberger, S.; Vandegrift, G. F.; Wu, D. & Wygmans, D. G.
Object Type:
Article
System:
The UNT Digital Library
Drawdown behavior of gravity drainage wells
An analytical solution for drawdown in gravity drainage wells is developed. The free-surface flow is viewed as incompressible, and anisotropy effects are included. The well is a line source well, and the reservoir is infinitely large. The model is valid for small drawdowns. The uniform wellbore potential inner boundary condition is modelled using the proper Green`s function. The discontinuity at the wellbore is solved by introducing a finite skin radius, and the formulation produces a seepage face. The calculated wellbore flux distribution and wellbore pressures are in fair agreement with results obtained using a numerical gravity drainage simulator. Three distinct flow periods are observed. The wellbore storage period is caused by the moving liquid level, and the duration is short. During the long intermediate flow period, the wellbore pressure is nearly constant. In this period the free surface moves downwards, and the liquid is produced mainly by vertical drainage. At long times the semilog straight line appears. The confined liquid solutions by Theis (1935) and van Everdingen and Hurst (1949) may be used during the pseudoradial flow period if the flowrate is low. New type curves are presented that yield both vertical and horizontal permeabilities.
Date:
October 1, 1993
Creator:
Aasen, J. A. & Ramey, H. J. Jr.
Object Type:
Report
System:
The UNT Digital Library
Approaches to large scale unsaturated flow in heterogeneous, stratified, and fractured geologic media
This report develops a broad review and assessment of quantitative modeling approaches and data requirements for large-scale subsurface flow in radioactive waste geologic repository. The data review includes discussions of controlled field experiments, existing contamination sites, and site-specific hydrogeologic conditions at Yucca Mountain. Local-scale constitutive models for the unsaturated hydrodynamic properties of geologic media are analyzed, with particular emphasis on the effect of structural characteristics of the medium. The report further reviews and analyzes large-scale hydrogeologic spatial variability from aquifer data, unsaturated soil data, and fracture network data gathered from the literature. Finally, various modeling strategies toward large-scale flow simulations are assessed, including direct high-resolution simulation, and coarse-scale simulation based on auxiliary hydrodynamic models such as single equivalent continuum and dual-porosity continuum. The roles of anisotropy, fracturing, and broad-band spatial variability are emphasized. 252 refs.
Date:
August 1, 1991
Creator:
Ababou, R.
Object Type:
Report
System:
The UNT Digital Library
BIGFLOW: A numerical code for simulating flow in variably saturated, heterogeneous geologic media. Theory and user`s manaual, Version 1.1
This report documents BIGFLOW 1.1, a numerical code for simulating flow in variably saturated heterogeneous geologic media. It contains the underlying mathematical and numerical models, test problems, benchmarks, and applications of the BIGFLOW code. The BIGFLOW software package is composed of a simulation and an interactive data processing code (DATAFLOW). The simulation code solves linear and nonlinear porous media flow equations based on Darcy`s law, appropriately generalized to account for 3D, deterministic, or random heterogeneity. A modified Picard Scheme is used for linearizing unsaturated flow equations, and preconditioned iterative methods are used for solving the resulting matrix systems. The data processor (DATAFLOW) allows interactive data entry, manipulation, and analysis of 3D datasets. The report contains analyses of computational performance carried out using Cray-2 and Cray-Y/MP8 supercomputers. Benchmark tests include comparisons with other independently developed codes, such as PORFLOW and CMVSFS, and with analytical or semi-analytical solutions.
Date:
June 1, 1993
Creator:
Ababou, R. & Bagtzoglou, A. C.
Object Type:
Report
System:
The UNT Digital Library
Color coherence in p pbar collisions at squareroot s = 1.8 TeV
We report on two preliminary studies of color coherence effects on {ital p}{ital {anti p}} collisions based on data collected by the D{null} detector during the 1992-1993 and 1994-1995 runs at the Fermilab Tevatron collider at a center of mass energy {radical}s = 1. 8 TeV. Demonstration of initial-to-final state color interference effects is done in a higher energy region by measuring spatial correlations between the softer third jet and the second leading- {ital E}{sub {ital T}} jet in multi-jet events and in a lower energy regime by examining particle distribution patterns in W+Jet events. The data are compared to Monte Carlo simulations with different color coherence implementations and the predictions of an NLO parton level calculation.
Date:
September 1, 1996
Creator:
Abachi, S.
Object Type:
Article
System:
The UNT Digital Library
The D0 Upgrade
In this paper we describe the approved DO Upgrade detector, and its physics capabilities. The DO Upgrade is under construction and will run during the next Fermilab collider running period in early 1999 (Run II). The upgrade is designed to work at the higher luminosities and shorter bunch spacings expected during this run. The major elements of t he upgrade are: a new tracking system with a silicon tracker, scintillating fiber tracker, a 2T solenoid, and a central preshower detector; new calorimeter electronics; new muon trigger and tracking detectors with new muon system electronics; a forward preshower detector; new trigger electronics and DAQ improvements to handle the higher rates.
Date:
July 1995
Creator:
Abachi, S.
Object Type:
Article
System:
The UNT Digital Library
The dijet mass spectrum and angular distributions with the D0 detector
We present preliminary results from an analysis of dijet data collected during the 1994-95 Tevatron Collider run with an integrated luminosity of 91 pb{sup -1}. Measurements of dijet mass spectra and dijet angular distributions in {anti p}p collisions at {radical}s- = 1.8 TeV are compared with next-to-leading order QCD theory.
Date:
July 1, 1996
Creator:
Abachi, S.
Object Type:
Article
System:
The UNT Digital Library
Diphoton production in p{bar p} collisions at {radical}s = 1.8 TeV
We present measurements of the inclusive {gamma}{gamma} cross section (as a function of invariant mass and photon {epsilon}{sub {tau}}), in p{bar p} collisions at {radical}s = 1.8 TeV, made using the D0 detector at the Fermilab Tevatron collider. The next is leading order (NLO) QCD prediction is found to be in good agreement with the data. The effects of invariant mass and diphoton balance cuts, which test the next-to-leading order contributions to the cross section, are investigated. We also compare the distribution of {kappa}{sub {tau}} between samples of diphotons and highly electromagnetic jets, and find that the NLO QCD prediction models the shape of the {gamma}{gamma} {kappa}{sub {tau}} distribution quite well.
Date:
July 1, 1995
Creator:
Abachi, S.
Object Type:
Article
System:
The UNT Digital Library
Direct photon measurements by the D{O} experiment
We report a measurement of the cross section for production of isolated photons with transverse energy E{sub T} > 12 GeV in the central (absolute value of {eta} < 0.9) and forward (1.6 < absolute value of {eta} < 2.5) rapidity regions for {bar p}p collisions at center of mass energy {radical}s = 1.8 TeV, using an integrated luminosity of 13 pb{sup {minus}1}. The cross section is compared with a next-to-leading order (NLO) QCD calculation. We also present preliminary measurements of the center of mass scattering angle distribution and of the correlations between the rapidity of the photon and that of the leading jet in the event.
Date:
July 1996
Creator:
Abachi, S.
Object Type:
Article
System:
The UNT Digital Library
Inclusive muon and b quark production cross sections in p{bar p} collisions at {radical}s = 1.8 TeV
We report on the measurement of inclusive muon and b quark production by the D0 collaboration in p{bar p} collisions at {radical}s = 1.8 TeV at the Fermilab Tevatron Collider. The results represent a refined analysis of the previously published 1992--93 data. We measure the muon cross section due to b quark decays over the kinematic range 4 < p{sub T}{sup {mu}} < 30 GeV/c and {vert_bar}y{sup {mu}}{vert_bar} < 0.8. The extracted b quark production cross section is consistent with next to leading order QCD predictions within theoretical and experimental errors. The improved inclusive b quark production cross section is 6.9 {plus_minus}0.1(stat) {plus_minus} 2.2(syst) {mu}b for p{sub T}{sup {mu}} > 6 GeV/c and {vert_bar}y{sup b}{vert_bar} < 1.0.
Date:
July 1, 1995
Creator:
Abachi, S.
Object Type:
Article
System:
The UNT Digital Library
J/{psi} production in p{anti p} collisions at {radical}s = 1.8 TeV
The authors have studied J/{psi} production in p{anti p} collisions at {radical}s = 1.8 TeV with the D0 detector at Fermilab, using a {mu}{sup +}{mu}{sup {minus}} data sample corresponding to an integrated luminosity of 13 pb{sup {minus}1}. They have measured the inclusive J/{psi} production cross section as a function of J/{psi} transverse momentum p{sub T}. For the kinematic range p{sub T} > 8 GeV/c and {vert_bar}{eta}{vert_bar} < 0.6 they obtain Br(J/{psi} {yields} {mu}{sup +}{mu}{sup {minus}}) {center_dot} {sigma}(p{anti p} {yields} J/{psi} + X) = 1.93 {+-} 0.16(stat) {+-} 0.43(syst) nb. Using the muon impact parameter they have estimated the fraction of J/{psi} mesons coming from B meson decays to be f{sub b} = 0.35 {+-} 0.09 (stat) {+-} 0.10 (syst) and inferred the inclusive b production cross section. From the information on the event topology a fraction of non-isolated J/{psi} events has been measured to be f{sub non-isol} = 0.64 {+-} 0.09(stat) {+-} 0.06(syst). They have also obtained the fraction of events resulting from radiative decays of {chi}{sub c} states as f{sub {chi}} = 0.30 {+-} 0.07(stat) {+-} 0.07(syst). They discuss the implications of the measurements for charmonium production processes.
Date:
July 1, 1995
Creator:
Abachi, S.
Object Type:
Report
System:
The UNT Digital Library
Limits on the anomalous ZZ{gamma} and Z{gamma}{gamma} couplings in p{anti p} collisions at {radical}s = 1.8 TeV
The authors performed a direct search for the anomalous ZZ{gamma} and Z{gamma}{gamma} couplings by studying p{anti p} {yields} {ell}{ell}{gamma} + X, ({ell} = e, {mu}) events at {radical}s = 1.8 TeV with the D0 detector at the Fermilab Tevatron Collider. A fit to the transverse energy spectrum of the photon in the signal events, based on the data set corresponding to an integrated luminosity of 14.3 pb{sup {minus}1} (13.7 pb{sup {minus}1}) for the electron (muon) channel, yields the following 95% confidence level limits on the anomalous CP-conserving ZZ{gamma} couplings: {vert_bar}h{sub 30}{sup Z}{vert_bar} < 1.8 (h{sub 40}{sup Z} = 0), and {vert_bar}h{sub 40}{sup Z}{vert_bar} < 0.5 (h{sub 30}{sup Z} = 0), for a form-factor scale {Lambda} = 500 GeV. Limits for the Z{gamma}{gamma} couplings and CP-violating couplings are also discussed.
Date:
July 1, 1995
Creator:
Abachi, S.
Object Type:
Article
System:
The UNT Digital Library
Measurement of B{sup 0} {minus} {bar B}{sup 0} mixing using dimuons at D0
The D0 experiment at Fermilab has determined the B{sup 0} {minus} B{sup 0} mixing probability x using dimuon events produced in p{bar p} collisions at {radical}s = 1.8 TeV. Using a sample of 172 dimuon events, we have determined the time and flavor averaged mixing probability x to be 0.09 {plus_minus} 0.04(stat){plus_minus}0.03(sys) [preliminary] in agreement with the present world average.
Date:
July 1995
Creator:
Abachi, S.
Object Type:
Report
System:
The UNT Digital Library