Recent Results from a Folded Waveguide ICRF Antenna Development Project (open access)

Recent Results from a Folded Waveguide ICRF Antenna Development Project

Preliminary high power tests have been performed on a folded waveguide (FWG) ICRF launcher with a curved coupling faceplate installed. Two alternative faceplate configurations have been built and tested at low power and will be tested at high power in the near future. The new designs include a dipole plate which provides a 0-<font face="symbol">p</font> launch spectrum and a more transparent, flexible monopole face plate configuration. This FWG design is a 12 vane, 57 MHz design with a 0.31 m square cross section. The FWG can be installed with either fast wave or ion-Bernstein wave polarization and can also be retracted behind a vacuum isolation valve. A 1 x 4 FWG array optimized for fast wave current drive on DIII-D has been conceptualized.
Date: April 12, 1999
Creator: Baity, F. W.; Barber, G. C.; Bigelow, T. S.; Carter, M. D.; Fadnek, A.; Ryan, P. M. et al.
Object Type: Article
System: The UNT Digital Library
Design of RF Systems for the RTD Mission VASIMR (open access)

Design of RF Systems for the RTD Mission VASIMR

The first flight test of the variable specific impulse magnetoplasma rocket (VASIMR) is tentatively scheduled for the Radiation and Technology Demonstration (RTD) in 2003. This mission to map the radiation environment out to several earth radii will employ both a Hall thruster and a VASIMR during its six months duration, beginning from low earth orbit. The mission will be powered by a solar array providing 12 kW of direct current electricity at 50 V. The VASIMR utilizes radiofrequency (RF) power both to generate a high-density plasma in a helicon source and to accelerate the plasma ions to high velocity by ion cyclotron resonance heating (ICRH). The VASIMR concept is being developed by the National Aeronautics and Space Administration (NASA) in collaboration with national laboratories and universities. Prototype plasma sources, RF amplifiers, and antennas are being developed in the experimental facilities of the Advanced Space Propulsion Laboratory (ASPL).
Date: April 12, 1999
Creator: Baity, F. W.; Barber, G. C.; Carter, M. D.; Chang-Diaz, F. R.; Goulding, R. H.; McCaskill, G. E. et al.
Object Type: Article
System: The UNT Digital Library
THE LONGITUDINAL HIGH--FREQUENCY IMPEDANCE OF A PERIODIC ACCELERATING STRUCTURE (open access)

THE LONGITUDINAL HIGH--FREQUENCY IMPEDANCE OF A PERIODIC ACCELERATING STRUCTURE

In many future collider and FEL designs intense, short bunches are accelerated in a linear accelerator. For example, in parts of the Linac Coherent Light Source (LCLS) a bunch with a peak current of 3.4 kA and an rms length of 30 microns will be accelerated in the SLAC linac. In such machines, in order to predict the beam quality at the end of acceleration it is essential to know the short range wakefields or, equivalently, the high frequency impedance of the accelerating structure. R. Gluckstern [1] has derived the longitudinal, high-frequency impedance of a periodic structure, a solution which is valid for a structure with a small gap-to-period ratio. We use his approach to derive a more general result, one that is not limited to small gaps. In addition, we compare our results with numerical results obtained using a field matching computer program.
Date: April 12, 1999
Creator: Bane, Karl L. F.
Object Type: Report
System: The UNT Digital Library
SCATTERING MATRIX ANALYSIS OF THE NLC ACCELERATING STRUCTURE (open access)

SCATTERING MATRIX ANALYSIS OF THE NLC ACCELERATING STRUCTURE

In the Next Linear Collider (NLC)[1], long trains of short, intense bunches are accelerated through the linac on their way to the collision point. One serious problem that needs to be addressed is the multi-bunch, beam break-up instability in the linac. To counteract this instability the accelerating structures are designed so that the dipole mode wakefields are detuned and weakly damped. Detuning is accomplished by gradually varying the dimensions of the 206 cavity cells in each structure, and weak damping by surrounding the structure with four manifolds, which allow the dipole modes to weakly couple out of the cells. In order to design and predict the performance of such a structure in the NLC, it is necessary to be able to calculate accurately the strength of its long-range wakefields. NLC detuned structures were designed first using an equivalent circuit approach, for example, the double band model of Ref. [2]. With the introduction of weak damping, a more elaborate equivalent circuit approach was required[3]. Other methods that have been used for detuned structures are the open-mode, field expansion method[4], and a finite element calculation employing 206 parallel processors[5]. A scattering matrix method can also be applied to cavities that consist of …
Date: April 12, 1999
Creator: Bane, Karl LF
Object Type: Report
System: The UNT Digital Library
Predicting Sediment and Cesium-137 Transported to Offsite During Extreme Floods (open access)

Predicting Sediment and Cesium-137 Transported to Offsite During Extreme Floods

This paper presents the methods and results of a research project for predicting contaminated sediment transport from Oak Ridge Reservation to offside under potential extreme flood conditions. A computer model, Hydrologic Simulation Program--FORTRANE (HSPF), was calibrated and validated for White Oak Creek watershed using a five-year data. The model was then used to quantify the effects of a potential 100-year flood event in terms of the sediment transport and {sup 137}Cs movement. Results from computer simulation showed that during a 100-year flood event the watershed and channel bed became the major sources of the {sup 137}Cs. A 100-year flood event may result in 3.2 Ci of the total annual release of {sup 137}Cs which is six times of the averaged annual release observed during a five-year time period.
Date: April 12, 1999
Creator: Bao, Y.
Object Type: Article
System: The UNT Digital Library
Local One-Dimensional ICRF Full-Wave Solutions Valid to All Orders in k-Perpendicular-Rho (open access)

Local One-Dimensional ICRF Full-Wave Solutions Valid to All Orders in k-Perpendicular-Rho

High harmonic ion cyclotron resonances are important for understanding future fast wave heating experiments on NSTX 1 as well as recent ICRF flow drive experiments on PBX-M<sup>2</sup> and TFTR<sup>3</sup>. Unfortunately, many of our ICRF wave analysis codes are based on an expansion to second order in k-perpendicular-Rho where k-perpendicular is the perpendicular wave number, and Rho is the Larmor radius. Such codes are limited to cyclotron harmonics less than or equal to 2. Integral codes<sup>4,5</sup> on the other hand, are valid to all orders in both k-perpendicular-Rho and Rho/<i>L</i>L where <i>L</i> is the equilibrium scale length. But velocity space integrals in these codes require long running times. Here we take a simpler approach which assumes a local plasma conductivity (Rho/<i>L</i> << 1), while still retaining all orders in k-perpendicular-Rho. This allows high harmonic fast wave and flow drive applications, while requiring less computing time than conventional integral codes.
Date: April 12, 1999
Creator: Batchelor, D. B.; Berry, L. A. & Jaeger, E. F.
Object Type: Article
System: The UNT Digital Library
Accessibillity of Electron Bernstein Modes in Over-Dense Plasma (open access)

Accessibillity of Electron Bernstein Modes in Over-Dense Plasma

Mode-conversion between the ordinary, extraordinary and electron Bernstein modes near the plasma edge may allow signals generated by electrons in an over-dense plasma to be detected. Alternatively, high frequency power may gain accessibility to the core plasma through this mode conversion process. Many of the tools used for ion cyclotron antenna de-sign can also be applied near the electron cyclotron frequency. In this paper, we investigate the possibilities for an antenna that may couple to electron Bernstein modes inside an over-dense plasma. The optimum values for wavelengths that undergo mode-conversion are found by scanning the poloidal and toroidal response of the plasma using a warm plasma slab approximation with a sheared magnetic field. Only a very narrow region of the edge can be examined in this manner; however, ray tracing may be used to follow the mode converted power in a more general geometry. It is eventually hoped that the methods can be extended to a hot plasma representation. Using antenna design codes, some basic antenna shapes will be considered to see what types of antennas might be used to detect or launch modes that penetrate the cutoff layer in the edge plasma.
Date: April 12, 1999
Creator: Batchelor, D. B.; Bigelow, T. S. & Carter, M. D.
Object Type: Article
System: The UNT Digital Library
Prospects for Advanced RF Theory and Modeling (open access)

Prospects for Advanced RF Theory and Modeling

This paper represents an attempt to express in print the contents of a rather philosophical review talk. The charge for the talk was not to summarize the present status of the field and what we can do, but to assess what we will need to do in the future and where the gaps are in fulfilling these needs. The objective was to be complete, covering all aspects of theory and modeling in all frequency regimes, although in the end the talk mainly focussed on the ion cyclotron range of frequencies (ICRF). In choosing which areas to develop, it is important to keep in mind who the customers for RF modeling are likely to be and what sorts of tasks they will need for RF to do. This occupies the first part of the paper. Then we examine each of the elements of a complete RF theory and try to identify the kinds of advances needed.
Date: April 12, 1999
Creator: Batchelor, D.B.
Object Type: Article
System: The UNT Digital Library
Population Viability Analysis of Riverine Fishes (open access)

Population Viability Analysis of Riverine Fishes

Many utilities face conflkts between two goals: cost-efficient hydropower generation and protecting riverine fishes. Research to develop ecological simulation tools that can evaluate alternative mitigation strategies in terms of their benefits to fish populations is vital to informed decision-making. In this paper, we describe our approach to population viability analysis of riverine fishes in general and Snake River white sturgeon in particular. We are finding that the individual-based modeling approach used in previous in-stream flow applications is well suited to addressing questions about the viability of species of concern for several reasons. Chief among these are: (1) the abiIity to represent the effects of individual variation in life history characteristics on predicted population viabili~, (2) the flexibili~ needed to quanti~ the ecological benefits of alternative flow management options by representing spatial and temporal variation in flow and temperaturty and (3) the flexibility needed to quantifi the ecological benefits of non-flow related manipulations (i.e., passage, screening and hatchery supplementation).
Date: April 12, 1999
Creator: Bates, P.; Chandler, J.; Jager, H. I.; Lepla, K. & Van Winkle, W.
Object Type: Article
System: The UNT Digital Library
Detection of illegal drugs using passive infrared sensing (open access)

Detection of illegal drugs using passive infrared sensing

This report summarizes results on experiments testing the feasibility of detecting illegal drugs using passive infrared spectroscopy in the 8-13 micrometer spectral band.
Date: April 12, 1996
Creator: Bennett, C. L.; Carter, M. R. & Fields, D. J.
Object Type: Report
System: The UNT Digital Library
Investigation of High Voltage Breakdown and Arc Localization in RF Structures (open access)

Investigation of High Voltage Breakdown and Arc Localization in RF Structures

An effort is underway to improve the voltage standoff capabilities of ion cyclotron range of frequencies (ICRF) heating and current drive systems. One approach is to develop techniques for determining the location of an electrical breakdown (arc) when it occurs. A technique is described which uses a measurement of the reflection coefficient of a swept frequency signal to determine the arc location. The technique has several advantages including a requirement for only a small number of sensors and very simple data interpretation. In addition a test stand is described which will be used for studies of rf arc behavior. The device uses a quarter-wave resonator to produce voltages to 90 kV in the frequency range of 55-80 MHz.
Date: April 12, 1999
Creator: Bigelow, T. S.; Goulding, R. H. & Swain, D. W.
Object Type: Article
System: The UNT Digital Library
Assuring both quality and creativity in basic research (open access)

Assuring both quality and creativity in basic research

How does one assure that both quality and creativity are obtained in basic research environments QA theoreticians have attempted to develop workable definitions of quality, but in more reflective moments, these definitions often fail to capture the deeper essence of the idea of quality.'' This paper asserts that creativity (as a product of the human mind) is a concrete interface between perfunctory definitions of quality (conformance to specifications) and more philosophical speculations about the nature of quality- related ultimates'' like elegance or beauty. In addition, we describe the distinction between creative ideas and creative acts and highlight one of the major inhibitors of creativity, fear. Finally we show that highly creative people often have an irreverent attitude toward boundaries and established authority, and discuss how one can allow for this when designing a QA program in a basic research environment.
Date: April 12, 1990
Creator: Bodnarczuk, Mark
Object Type: Article
System: The UNT Digital Library
Heat transfer studies. Final report (open access)

Heat transfer studies. Final report

Many simple (without thermal effects) ground-water flow models have been used for analysis of water resource problems since the 1960`s. The emphasis on more complicated ground-water flow models began to shift with the focus on waste management problems during the 1970`s. The ground-water flow model development has shifted to unsaturated flow models because the unsaturated zone at Yucca Mountain was selected as a potential high-level radioactive waste disposal site. Many unsaturated flow models have been developed and used since the mid-1980`s. A few unsaturated flow models have also been developed in the 1990`s. Under the U.S. Department of Energy (DOE), the Civilian Radioactive Waste Management System Management and Operating Contractor (CRWMS M&O) has the responsibility to review, evaluate, and document the existing computer models; to conduct performance assessments; and to develop performance assessment models, where necessary. Two major regulatory requirements are the main criteria for selection of ground-water flow models in the unsaturated zone. One is of calculating the pre-emplacement ground-water travel time. Our work has focused on visualization techniques, and experiments that could have more application quantitatively. Many studies are summarized in this report.
Date: April 12, 1996
Creator: Boehm, R. & Chen, Y.T.
Object Type: Report
System: The UNT Digital Library
Welfare Reform: Work Trigger Time Limits, Exemptions and Sanctions under TANF (open access)

Welfare Reform: Work Trigger Time Limits, Exemptions and Sanctions under TANF

None
Date: April 12, 1999
Creator: Burke, Vee & Gish, Melinda
Object Type: Report
System: The UNT Digital Library
Toroidal Effects on ICRF Heating and Current Drive (open access)

Toroidal Effects on ICRF Heating and Current Drive

Numerical studies, performed with the Monte-Carlo code FIDO [1], of the evolution of the resonant-ion distribution function in the presence of ICRH in toroidal geometry are presented. In particular it is pointed out how the absorption of toroidal momentum from a wave field with finite parallel wave numbers causes spatial drift and diffusion, which together with the finite orbit widths of the tail ions is shown to have a large effect on the temperature profile of the resonant ion species and also to cause losses of high-energy ions to the wall [2]. Furthermore, it is found that the finite orbit width and the inward drift occuring for negative parallel wave numbers [3] each give rise to a new mechanism of minority-ion cyclotron current drive as compared to earlier models where the drift orbits of the resonant ions are confined to the magnetic flux surfaces. For high levels of coupled power these new mechanisms are found to be the dominating ones [4,5].
Date: April 12, 1999
Creator: Carlsson, J.; Hedin, J. & Hellsten, T.
Object Type: Article
System: The UNT Digital Library
RF Systems for a Proposed Next Step Option (FIRE) (open access)

RF Systems for a Proposed Next Step Option (FIRE)

FIRE (Fusion Ignition Research Experiment) is a high-field, burning-plasma tokamak that is being studied as a possible option for future fusion research. Preliminary parameters for this machine are R<sub>0</sub> approximately equal to 2 m, a approximately equal to 0.5 m, B<sub>0</sub> approximately equal to 10 T, and I<sub>p</sub> approximately equal to 6 MA. Magnetic field coils are to be made of copper and precooled with LN<sub>2</sub> before each shot. The flat-top pulse length desired is greater than or equal to 10s. Ion cyclotron and lower hybrid rf systems will be used for heating and current drive. Present specifications call for 30 MW of ion cyclotron heating power, with 25 MW of lower hybrid power as an upgrade option.
Date: April 12, 1999
Creator: Carter, M. D. & Swain, D. W.
Object Type: Article
System: The UNT Digital Library
Treatment of metal-laden hazardous wastes with advanced Clean Coal Technology by-products (open access)

Treatment of metal-laden hazardous wastes with advanced Clean Coal Technology by-products

This twelfth quarterly report describes work done during the twelfth three-month period of the University of Pittsburgh's project on the ``Treatment of Metal-Laden Hazardous Wastes with Advanced Clean Coal Technology By-Products.'' This report describes the activities of the project team during the reporting period. The principal work has focused upon new laboratory evaluation of samples from Phase 1, discussions with MAX Environmental Technologies, Inc., on the field work of Phase 2, preparing and giving presentations, and making and responding to a number of outside contacts.
Date: April 12, 1999
Creator: Cobb, James T., Jr.; Neufeld, Ronald D. & Agostini, Jana
Object Type: Report
System: The UNT Digital Library
Replacing chemicals in recycle mills with mechanical alternatives. Progress report No. 2 (reporting period January - March 1999) (open access)

Replacing chemicals in recycle mills with mechanical alternatives. Progress report No. 2 (reporting period January - March 1999)

None
Date: April 12, 1999
Creator: Corcoran, Howard; Sung, Dong-Jin; Page, Derek & Banerjee, Sujit
Object Type: Report
System: The UNT Digital Library
ACRV instrumentation plan for NMD HTK light gas gun tests (open access)

ACRV instrumentation plan for NMD HTK light gas gun tests

In support of the NMD Hit-To-Kill Program for the US Army, twenty scaled tests on simulated nuclear targets are planned. The AEDC Light Gas Gun operated by Sverdrup Technology (SVT) in Tullahoma, TN will launch the scaled NMD projectile into scaled targets. The target for all the tests is a 1/4-scale version of the Attitude Controlled Re-Entry Vehicle (ACRV). The targets were designed and fabricated by Sandia National Laboratories (SNL) and Lawrence Livermore National Laboratory (LLNL). ITT Systems (ITT) is the integrating contractor for coordination of the multiple contractors involved in these tests. The targets are inert and contain no hazardous materials. The payloads have been instrumented to aid in post-test evaluation of the functional status of the postulated weapon systems. This document describes the instrumentation methods to be used on these tests.
Date: April 12, 1999
Creator: Dobie, D W
Object Type: Report
System: The UNT Digital Library
Electrical Testing of the Full-Scale model of the NSTX HHFW Antenna Array (open access)

Electrical Testing of the Full-Scale model of the NSTX HHFW Antenna Array

The 30 MHz high harmonic fast wave (HHFW) antenna array for NSTX consists of 12 current straps, evenly spaced in the toroidal direction. Each pair of straps is connected as a half-wave resonant loop and will be driven by one transmitter, allowing rapid phase shift between transmitters. A decoupling network using shunt stub tuners has been designed to compensate for the mutual inductive coupling between adjacent current straps, effectively isolating the six transmitters from one another. One half of the array, consisting of six full-scale current strap modules, three shunt stub decouplers, and powered by three phase-adjustable rf amplifiers had been built for electrical testing at ORNL. Low power testing includes electrical characterization of the straps, operation and performance of the decoupler system, and mapping of the rf fields in three dimensions.
Date: April 12, 1999
Creator: Fadnek, A.; Ryan, P. M.; Sparks, D. O.; Swain, D. W. & Wilgen, J. B.
Object Type: Article
System: The UNT Digital Library
Is There Hope for Fusion (open access)

Is There Hope for Fusion

From the outset in the 1950's, fusion research has been motivated by environmental concerns as well as long-term fuel supply issues. Compared to fossil fuels both fusion and fission would produce essentially zero emissions to the atmosphere. Compared to fission, fusion reactors should offer high demonstrability of public protection from accidents and a substantial amelioration of the radioactive waste problem. Fusion still requires lengthy development, the earliest commercial deployment being likely to occur around 2025--2050. However, steady scientific progress is being made and there is a wide consensus that it is time to plan large-scale engineering development. A major international effort, called the International Thermonuclear Experimental Reactor (ITER), is being carried out under IAEA auspices to design the world's first fusion engineering test reactor, which could be constructed in the 1990's. 4 figs., 3 tabs.
Date: April 12, 1990
Creator: Fowler, T. K.
Object Type: Article
System: The UNT Digital Library
The Theory of Hadronic Systems. Annual Progress Report April 12, 1993 (open access)

The Theory of Hadronic Systems. Annual Progress Report April 12, 1993

This report briefly discusses progress on the following topics: isospin breaking in the pion-nucleon system; direct capture of pions into deeply bound atomic states; knock out of secondary components in the nucleus; study of the radii of neutron distributions in nuclei; the hadronic double scattering operator; transparency in pion production; asymmetry in pion scattering and charge exchange from polarized nuclei; the mechanism of pion absorption in nuclei; the neutron-proton charge-exchange reaction; modification of the fundamental structure of nucleons in nuclei; and antiproton annihilation in nuclei.
Date: April 12, 1993
Creator: Gibbs, William R.
Object Type: Report
System: The UNT Digital Library
Design of a Tapered and Twisted Blade for the NREL Combined Experiment Rotor (open access)

Design of a Tapered and Twisted Blade for the NREL Combined Experiment Rotor

A tapered/twisted blade was designed to operate on the Combined Experiment Rotor (CER) of the National Renewable Energy Lab., which is a stall-regulated downwind wind turbine having a rated power of 20 kilowatt. The geometry of the new blade set was optimized based on annual energy production subject to the constraints imposed on the design. These constraints were mainly related to scientific needs for fundamental research in rotor aerodynamics. A trade-off study was conducted to determine the effect of the different design constraints. Based on the results of this study, which considered nonlinear twist and taper distributions as well as the NREL S809, S814, S822 and S823 airfoils, a blade having a linear taper and a nonlinear twist distribution that uses the S809 airfoil from root to tip was selected. This blade configuration is the logical continuation of the previous constant-chord twisted and untwisted blade sets and will facilitate comparison with those earlier blades. Despite the design constraints based on scientific needs, the new blade is more representative of commercial blades than the previous blade sets.
Date: April 12, 1999
Creator: Giguere, P. & Selig, M. S.
Object Type: Report
System: The UNT Digital Library
Wind Energy in the United States: Market and Research Update (open access)

Wind Energy in the United States: Market and Research Update

U.S. market activity has increased over the last two years. In 1998, new capacity totaled about 150 MW and projected 1999 capacity additions are over 600 MW. As the electricity market continues to evolve under restructuring, the U.S. Department of Energy (U.S. DOE) Wind Energy Program has positioned itself to work with industry to meet current challenges and opportunities, and prepare for the market of tomorrow. Some opportunities include green power markets and distributed applications, although a primary challenge involves the fact that avoided cost payments to renewable generators are not high enough to economically support projects. A recently incorporated power exchange in California, APX, Inc., has demonstrated that green power does attract a premium over prices on the conventional power exchange. The key elements of the U.S. DOE Wind Program are (1) Applied Research, which is critical for achieving advanced turbine designs capable of competing in a restructured market that emphasizes low cost generation; (2) Turbine Research, which supports the U.S. industry in developing competitive, high performance, reliable wind turbine technology for global energy markets; and (3) Cooperative Research and Testing, under which standards development and certification testing are the key activities for the current year.
Date: April 12, 1999
Creator: Goldman, P. R. (U.S. Department of Energy); Thresher, R. W. & Hock, S. M. (National Renewable Energy Laboratory)
Object Type: Article
System: The UNT Digital Library