A Tutorial on Basic Principles of Microwave Reflectometry Applied to Fluctuation Measurements in Fusion Plasmas (open access)

A Tutorial on Basic Principles of Microwave Reflectometry Applied to Fluctuation Measurements in Fusion Plasmas

Microwave reflectometry is now routinely used for probing the structure of magnetohydrodynamic and turbulent fluctuations in fusion plasmas. Conditions specific to the core of tokamak plasmas, such as small amplitude of density irregularities and the uniformity of the background plasma, have enabled progress in the quantitative interpretation of reflectometer signals. In particular, the extent of applicability of the 1-D [one-dimensional] geometric optics description of the reflected field is investigated by direct comparison to 1-D full wave analysis. Significant advances in laboratory experiments are discussed which are paving the way towards a thorough understanding of this important measurement technique. Data is presented from the Tokamak Fusion Test Reactor [R. Hawryluk, Plasma Physics and Controlled Fusion 33 (1991) 1509] identifying the validity of the geometric optics description of the scattered field and demonstrating the feasibility of imaging turbulent fluctuations in fusion scale devices.
Date: February 16, 2001
Creator: Nazikian, R.; Kramer, G. J. & Valeo, E.
Object Type: Report
System: The UNT Digital Library
Greening Federal Facilities: An Energy, Environmental, and Economic Resource Guide for Federal Facility Managers and Designers (open access)

Greening Federal Facilities: An Energy, Environmental, and Economic Resource Guide for Federal Facility Managers and Designers

Greening Federal Facilities, Second Edition, is a nuts-and-bolts resource guide compiled to increase energy and resource efficiency, cut waste, and improve the performance of Federal buildings and facilities. The guide highlights practical actions that facility managers, design and construction staff, procurement officials, and facility planners can take to save energy and money, improve the comfort and productivity of employees, and benefit the environment. It supports a national effort to promote energy and environmental efficiency in the nation's 500,000 Federal buildings and facilities. Topics covered include current Federal regulations; environmental and energy decision-making; site and landscape issues; building design; energy systems; water and wastewater; materials; waste management, and recycling; indoor environmental quality; and managing buildings.
Date: May 16, 2001
Creator: Wilson, A.
Object Type: Book
System: The UNT Digital Library
X-ray and vibrational spectroscopy of manganese complexes relevant to the oxygen-evolving complex of photosynthesis (open access)

X-ray and vibrational spectroscopy of manganese complexes relevant to the oxygen-evolving complex of photosynthesis

Manganese model complexes, relevant to the oxygen-evolving complex (OEC) in photosynthesis, were studied with Mn K-edge X-ray absorption near-edge spectroscopy (XANES), Mn Kb X-ray emission spectroscopy (XES), and vibrational spectroscopy. A more detailed understanding was obtained of the influence of nuclearity, overall structure, oxidation state, and ligand environment of the Mn atoms on the spectra from these methods. This refined understanding is necessary for improving the interpretation of spectra of the OEC. Mn XANES and Kb XES were used to study a di-(mu)-oxo and a mono-(mu)-oxo di-nuclear Mn compound in the (III,III), (III,IV), and (IV,IV) oxidation states. XANES spectra show energy shifts of 0.8 - 2.2 eV for 1-electron oxidation-state changes and 0.4 - 1.8 eV for ligand-environment changes. The shifts observed for Mn XES spectra were approximately 0.21 eV for oxidation state-changes and only approximately 0.04 eV for ligand-environment changes. This indicates that Mn Kb XES i s more sensitive to the oxidation state and less sensitive to the ligand environment of the Mn atoms than XANES. These complimentary methods provide information about the oxidation state and the ligand environment of Mn atoms in model compounds and biological systems. A versatile spectroelectrochemical apparatus was designed to aid the interpretation …
Date: May 16, 2001
Creator: Visser, Hendrik
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Closed Loop Feedback of MHD Instabilities on DIII-D (open access)

Closed Loop Feedback of MHD Instabilities on DIII-D

A system of coils, sensors and amplifiers has been installed on the DIII-D tokamak to study the physics of feedback stabilization of low-frequency MHD [magnetohydrodynamic] modes such as the Resistive Wall Mode (RWM). Experiments are being performed to assess the effectiveness of this minimal system and benchmark the predictions of theoretical models and codes. In the last campaign, the experiments have been extended to a regime where the RWM threshold is lowered by a fast ramp of the plasma current. In these experiments, the onset time of the RWM is very reproducible. With this system, the onset of the RWM has been delayed by up to 100 msec without degrading plasma performance. The growth rate of the mode increases proportional to the length of delay, suggesting that the plasma is evolving towards a more unstable configuration. The present results have suggested directions for improving the feedback system including better sensors and improved feedback algorithms.
Date: January 16, 2001
Creator: Fredrickson, E. D.; Bialek, J.; Garofalo, A. M.; Johnson, L. C.; La Haye, R. J. & Lazarus, E. A.
Object Type: Report
System: The UNT Digital Library
MUON COOLING - EMITTANCE EXCHANGE. (open access)

MUON COOLING - EMITTANCE EXCHANGE.

Muon Cooling is the key factor in building of a Muon collider, (to a less degree) Muon storage ring, and a Neutrino Factory. Muon colliders potential to provide a probe for fundamental particle physics is very interesting, but may take a considerable time to realize, as much more work and study is needed. Utilizing high intensity Muon sources - Neutrino Factories, and other intermediate steps are very important and will greatly expand our abilities and confidence in the credibility of high energy muon colliders. To obtain the needed collider luminosity, the phase-space volume must be greatly reduced within the muon life time. The Ionization cooling is the preferred method used to compress the phase space and reduce the emittance to obtain high luminosity muon beams. We note that, the ionization losses results not only in damping, but also heating. The use of alternating solenoid lattices has been proposed, where the emittance are large. We present an overview of the cooling and discuss formalism, solenoid magnets and some beam dynamics.
Date: February 16, 2001
Creator: PARSA,Z.
Object Type: Article
System: The UNT Digital Library
Frontiers in Nuclear Structure (open access)

Frontiers in Nuclear Structure

The main objective of this brief review was to discuss various facts of nuclear structure physics. The list of topics covered is by no means complete due to time and space constraints. In years to come, they shall see substantial progress in their understanding of molecular structure--a rich and interdisciplinary field. An important element in this task is to extend the study of nuclei into new domains. New radioactive beam facilities, together with advanced multi-detector arrays and mass/change separators, is essential in probing nuclei in new domains where new phenomena, likely to be different from anything they have observed to date, will occur. The new data are expected to bring qualitatively new information about the fundamental properties of the nucleonic many-body system and will be crucial for developing a unified description of the nucleus.
Date: January 16, 2001
Creator: Nazarewicz, W.
Object Type: Article
System: The UNT Digital Library
Field analysis of a dielectric-loaded rectangular waveguide accelerating structure. (open access)

Field analysis of a dielectric-loaded rectangular waveguide accelerating structure.

In this paper, we present a detailed analysis of the modes of a dielectric-loaded rectangular waveguide accelerating structure. In general, the acceleration field in a synchronous acceleration mode is non-uniform in the two transverse dimensions. However, we could use an array of these structures rotated alternatively by 90 degrees to get a focusing-defocusing force continuously as a simple FODO lattice, while maintaining uniform energy gain. The expressions of characteristic parameters such as R/Q, group velocity and attenuation constant are given. The longitudinal wake field experienced by a relativistic charged particle beam in the structure is also presented. These analytical results are also compared with numerical calculations using the MAFIA code suite demonstrating the validity of our analytic approach.
Date: July 16, 2001
Creator: Xiao, L.; Gai, W. & Sun, X.
Object Type: Article
System: The UNT Digital Library
Quarkonia production and polarization studies with CDF (open access)

Quarkonia production and polarization studies with CDF

In this paper the authors present results on production and polarization of the J/{psi}, {psi}(2S), {chi}e, {Upsilon} and {chi}b states at {radical}s = 1.8 TeV. These results were obtained from data taken with the CDF detector at Fermilab. They cover recently completed analyses of the 1992--96 collider run.
Date: April 16, 2001
Creator: Papadimitriou, Vaia
Object Type: Article
System: The UNT Digital Library
Tevatron optics with magnet moves for Roman pots at CDF (open access)

Tevatron optics with magnet moves for Roman pots at CDF

CDF would like to install high precision track detectors. There is ample room on A-sector side, but space needs to be created at B11. The favored plan is to shove the first 3 B11 dipoles inwards toward the IP by 2.274 m. This would require removal of the inert Q1 quadrupole and its spool plus an extensive number of other mechanical and cryogenic modifications. The orbit distortion these modifications introduce would then be compensated by shifting the six B16 and B17 dipoles outwards by about half that amount. Space for this dipole move could be generated by replacing the 72 inch spool at B18 with a short 43 inch spool, and removing the 16.5 inch spacer after B17-5. The above scheme certainly recloses the orbit, and doesn't require the detector to move. However, by moving the B16 and B17 dipoles, the B17 and B18 arc quadrupoles also get shifted downstream--B17 by 1.115 m, and B18 by 0.696 m. Longitudinal movements of arc quads by such large fractions of their magnetic lengths will clearly impact the overall machine optics.
Date: August 16, 2001
Creator: Johnstone, John A.
Object Type: Report
System: The UNT Digital Library
Centrifugally confined plasmas for magnetic fusion energy. Final technical report for period March 15, 1998 - September 1, 2000 (open access)

Centrifugally confined plasmas for magnetic fusion energy. Final technical report for period March 15, 1998 - September 1, 2000

The purpose of the research funded under this study grant was to investigate the feasibility of a small scale experiment to test the concept of centrifugal confinement as a magnetic fusion energy scheme and to develop conceptual designs for important components of such an experiment. This work falls in the category of Innovative Confinement Concepts, as defined by the Office of Fusion Energy. The results of the funded work were very successful in that various studies were conducted which showed the concept to be viable and these studies led to design improvements. In addition, the major components of an experiment were identified and designed at least to the conceptual stage. In September, 2000 the Maryland Centrifugal Torus was funded for construction, in no small part because of the progress made during the time period reported here. The centrifugal confinement concept for fusion is based on three principles: (1) centrifugal forces from supersonic plasma rotation perpendicular to a strong magnetic field can provide effective confinement along the field; (2) the concomitant large velocity shear will suppress even macro-MHD instabilities; and (3) the sheared rotation will heat the plasma via viscous dissipation. Technical progress was made in clarifying and quantifying these concepts …
Date: July 16, 2001
Creator: Ellis, Richard F.
Object Type: Report
System: The UNT Digital Library
Parametric Investigations of Miniaturized Cylindrical and Annular Hall Thrusters (open access)

Parametric Investigations of Miniaturized Cylindrical and Annular Hall Thrusters

A cylindrical geometry Hall thruster may overcome certain physical and technological limitations in scaling down of Hall thrusters to miniature sizes. The absence of the inner wall and use of the cusp magnetic field can potentially reduce heating of the thruster parts and erosion of the channel. A 2.6 cm miniaturized Hall thruster of a flexible design was built and successfully operated in the power range of 50-300 W. Comparison of preliminary results obtained for cylindrical and annular thruster configurations is presented.
Date: October 16, 2001
Creator: Smirnov, A.; Raitses, Y. & Fisch, N. J.
Object Type: Article
System: The UNT Digital Library
Contributions to the Workshop on an e+e- collider in the VLHC tunnel (open access)

Contributions to the Workshop on an e+e- collider in the VLHC tunnel

This Workshop was extremely useful in fleshing out many of the details related to the VLLC. For example, at the workshop it became very clear that the large machine could not provide high luminosity polarized beams at both the Z0 pole and at high energy, and it would be best to provide the Z0 factory function in the injector. In addition, the workshop identified a number of topics for further R and D. A list of some of these topics follows: What is the lower limit on {beta}{sub y}* in the high energy collider? What is a reasonable upper limit on the beam-beam parameter at 183 GeV? Is there a way to coalesce electron bunches at high energy to finesse the TMCI current limit at injection, allowing a smaller beam pipe aperture to be used? Can feedback systems be useful to combat the TMCI instability at injection? In the 45 GeV Z{sup 0} factory, are two rings essential? Are wigglers essential for polarization in the Z{sup 0} factory? How can polarization at high energies be optimized? What is the optimum method of pumping the long vacuum chamber sections? How much cost and power minimization is possible in the complete design? …
Date: July 16, 2001
Creator: al., E Keil et
Object Type: Article
System: The UNT Digital Library
WindPACT Turbine Design Scaling Studies Technical Area 2: Turbine, Rotor and Blade Logistics (open access)

WindPACT Turbine Design Scaling Studies Technical Area 2: Turbine, Rotor and Blade Logistics

Through the National Renewable Energy Laboratory (NREL), the United States Department of Energy (DOE) implemented the Wind Partnership for Advanced Component Technologies (WindPACT) program. This program will explore advanced technologies that may reduce the cost of energy (COE) from wind turbines. The initial step in the WindPACT program is a series of preliminary scaling studies intended to determine the optimum sizes for future turbines, help define sizing limits for certain critical technologies, and explore the potential for advanced technologies to contribute to reduced COE as turbine scales increase. This report documents the results of Technical Area 2-Turbine Rotor and Blade Logistics. For this report, we investigated the transportation, assembly, and crane logistics and costs associated with installation of a range of multi-megawatt-scale wind turbines. We focused on using currently available equipment, assembly techniques, and transportation system capabilities and limitations to hypothetically transport and install 50 wind turbines at a facility in south-central South Dakota.
Date: July 16, 2001
Creator: Smith, K.
Object Type: Report
System: The UNT Digital Library
Structural Distortions in the Paramagnetic Insulating Phase of LA(0.7)CA(0.3)MNO(3). (open access)

Structural Distortions in the Paramagnetic Insulating Phase of LA(0.7)CA(0.3)MNO(3).

We report x-ray scattering studies of polarons and tilt ordering in the high-temperature, paramagnetic insulating phase of La{sub 0.7}Ca{sub 0.3}MnO{sub 3}. The temperature dependence of scattering due to individual and correlated polarons was measured, and the latter was found to disappear at {approximately}400 K. The scattering due to tilt ordering, which was observed by tuning the incident photon energy near the La L{sub 1} edge, was also measured as a function of temperature. The destruction of tilt ordering at {approximately}690 K is believed to be associated with the orthorhombic-rhombohedral structural transition.
Date: April 16, 2001
Creator: Nelson, C. S.; Kim, Y. J.; Hill, J. P.; Gibbs, D.; Kiryukhin, V.; Koo, T. Y. et al.
Object Type: Article
System: The UNT Digital Library
High Energy Physics Division semiannual report of research activities, January 1, 2000 - June 30, 2000. (open access)

High Energy Physics Division semiannual report of research activities, January 1, 2000 - June 30, 2000.

This report describes the research conducted in the High Energy Physics Division of Argonne National Laboratory during the period of January 1, 2000 through June 30, 2000. Topics covered here include experimental and theoretical particle physics, advanced accelerator physics, detector development, and experimental facilities research. Lists of Division publications and colloquia are included.
Date: January 16, 2001
Creator: Norem, J.
Object Type: Report
System: The UNT Digital Library
Technologies for Distributed Energy Resources. Federal Energy Management Program (FEMP) Technical Assistance Fact Sheet (open access)

Technologies for Distributed Energy Resources. Federal Energy Management Program (FEMP) Technical Assistance Fact Sheet

This four-page fact sheet describes distributed energy resources for Federal facilities, which are being supported by the U.S. Department of Energy's (DOE's) Federal Energy Management Program (FEMP). Distributed energy resources include both existing and emerging energy technologies: advanced industrial turbines and microturbines; combined heat and power (CHP) systems; fuel cells; geothermal systems; natural gas reciprocating engines; photovoltaics and other solar systems; wind turbines; small, modular biopower; energy storage systems; and hybrid systems. DOE FEMP is investigating ways to use these alternative energy systems in government facilities to meet greater demand, to increase the reliability of the power-generation system, and to reduce the greenhouse gases associated with burning fossil fuels.
Date: July 16, 2001
Creator: Pitchford, P. & Brown, T.
Object Type: Book
System: The UNT Digital Library
Effects of structural defects on the activation of sulfur donors in GaN/x/As/1-x/ formed by N implantation (open access)

Effects of structural defects on the activation of sulfur donors in GaN/x/As/1-x/ formed by N implantation

The effects of structural defects on the electrical activity of S doped GaN{sub x}As{sub 1-x} layers formed by S and N coimplantation in GaAs are reported. S and N ions were implanted to the depth of about 0.4 {micro}m. Electrochemical capacitance voltage measurements on samples annealed at 945 C for 10s show that in a thin (<0.1 {micro}m) surface layer the concentration of active shallow donors is almost an order of magnitude larger in S and N co-implanted samples than in samples implanted with S alone. The activation efficiency of S donors also shows a broad minimum at a depth of about 0.2 {micro}m below the surface. The results of these electrical measurements are correlated with the distribution of structural defects revealed by transmission electron microscopy (TEM). The TEM micrographs show that in addition to a band of dislocation loops commonly found in ion implanted GaAs, an additional band of small voids is observed in samples co-implanted with S and N. The location of this band correlates well with the region of reduced electrical activation of S donors, suggesting that formation of the voids through N accumulation results in a lower concentration of active, substitutional N atoms.
Date: July 16, 2001
Creator: Jasinski, J.; Yu, K.M.; Walukiewicz, W.; Liliental-Weber, Z. & Washburn, J.
Object Type: Article
System: The UNT Digital Library
Extruded plastic scintillator for the MINOS calorimeters (open access)

Extruded plastic scintillator for the MINOS calorimeters

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Date: January 16, 2001
Creator: Pla-Dalmau, A.
Object Type: Article
System: The UNT Digital Library
NEUTRINO FACTORIES - PHYSICS POTENTIALS. (open access)

NEUTRINO FACTORIES - PHYSICS POTENTIALS.

The recent results from Super-Kamiokande atmospheric and solar neutrino observations opens a new era in neutrino physics and has sparked a considerable interest in the physics possibilities with a Neutrino Factory based on the muon storage ring. We present physics opportunities at a Neutrino Factory, and prospects of Neutrino oscillation experiments. Using the precisely known flavor composition of the beam, one could envision an extensive program to measure the neutrino oscillation mixing matrix, including possible CP violating effects. These and Neutrino Interaction Rates for examples of a Neutrino Factory at BNL (and FNAL) with detectors at Gran Sasso, SLAC and Sudan are also presented.
Date: February 16, 2001
Creator: PARSA,Z.
Object Type: Article
System: The UNT Digital Library
Communications and Collaboration Keep San Francisco VA Medical Center Project on Track (open access)

Communications and Collaboration Keep San Francisco VA Medical Center Project on Track

This case study about energy saving performance contacts (ESPCs) presents an overview of how the Veterans Affairs Medical Center in San Francisco established an ESPC contract and the benefits derived from it. The Federal Energy Management Program instituted these special contracts to help federal agencies finance energy-saving projects at their facilities.
Date: May 16, 2001
Creator: Federal Energy Management Program
Object Type: Book
System: The UNT Digital Library
A Five-Watts G-M/J-T Refrigerator for Lhe Target at Bnl. (open access)

A Five-Watts G-M/J-T Refrigerator for Lhe Target at Bnl.

A five-watts G-M/J-T refrigerator was built and installed for the high-energy physics research at Brookhaven National Laboratory in 2001. A liquid helium target of 8.25 liters was required for an experiment in the proton beam line at the Alternating Gradient Synchrotron (AGS) of BNL. The large radiation heat load towards the target requires a five-watts refrigerator at 4.2 K to support a liquid helium flask of 0.2 meter in diameter and 0.3 meter in length which is made of Mylar film of 0.35 mm in thickness. The liquid helium flask is thermally exposed to the vacuum windows that are also made of 0.35 mm thickness Mylar film at room temperature. The refrigerator uses a two-stage Gifford-McMahon cryocooler for precooling the Joule-Thomson circuit that consists of five Linde-type heat exchangers. A mass flow rate of 0.8 {approx} 1.0 grams per second at 17.7 atm is applied to the refrigerator cold box. The two-phase helium flows between the liquid target and liquid/gas separator by means of thermosyphon. The paper presents the system design as well as the test results including the control of thermal oscillation.
Date: July 16, 2001
Creator: Jia, L. X.; Wang, L.; Addessi, L.; Miglionico, G.; Martin, D.; Leskowicz, J. et al.
Object Type: Article
System: The UNT Digital Library
{epsilon}{prime}/{epsilon} and rare KL decays from KTeV Experiment (open access)

{epsilon}{prime}/{epsilon} and rare KL decays from KTeV Experiment

The authors update the current status for the measurement of the direct-CP violation parameters {epsilon}{prime}/{epsilon} in the KTeV experiment at Fermilab. Substantial statistics have been accumulated during the 1996-7 run and 1999 run for both {epsilon}{prime}/{epsilon} and rare K{sub L} decay searches. The first KTeV result on {epsilon}{prime}/{epsilon} published last year was Re({epsilon}{prime}/{epsilon}) = (28.0 {+-} 4.1) x 10{sup {minus}4} based on the 23% data from 1996-7 run. Combining with the previous E731, NA31 and the recent preliminary NA48 results, the grand average is Re({epsilon}{prime}/{epsilon}) = (19.3 {+-} 3.6) x 10{sup {minus}4} (with S = 1:49), more than 5{sigma} above zero. More data from both KTeV and NA48 after completing the analysis will further improve the precision of this measurement in the near future and hopefully further improve the agreement. New results on the branching ratio and form factor measurements of K{sub L} {r_arrow} {mu}{sup +} {mu}{sup {minus}} {gamma} using 1997 data are also presented. We find that BR(K{sub L} {r_arrow} {mu}{sup +} {mu}{sup {minus}} {gamma}) = (3.66 {+-} 0.04{sub stat} {+-} 0.07{sub syst}) x 10{sup {minus}7}. The form factor parameter {alpha}{sub K}* is measured to be {alpha}{sub K}* = {minus}0.157{sub {minus}0.027}{sup +0.025}. We make the first measurement of the …
Date: January 16, 2001
Creator: Hsiung, Yee Bob
Object Type: Article
System: The UNT Digital Library
Summaries of recent computer-assisted Feynam diagram calculations (open access)

Summaries of recent computer-assisted Feynam diagram calculations

The AIHENP Workshop series has traditionally included cutting edge work on automated computation of Feynman diagrams. The conveners of the Symbolic Problem Solving topic in this ACAT conference felt it would be useful to solicit presentations of brief summaries of the interesting recent calculations. Since this conference was the first in the series to be held in the Western Hemisphere, it was decided that the summaries would be solicited both from attendees and from researchers who could not attend the conference. This would represent a sampling of many of the key calculations being performed. The results were presented at the Poster session; contributions from ten researchers were displayed and posted on the web. Although the poster presentation, which can be viewed at conferences.fnal.gov/acat2000/ placed equal emphasis on results presented at the conference and other contributions, here we primarily discuss the latter, which do not appear in full form in these proceedings. This brief paper can't do full justice to each contribution; interested readers can find details of the work not presented at this conference in references (1), (2), (3), (4), (5), (6), (7).
Date: August 16, 2001
Creator: Fischler, Mark
Object Type: Article
System: The UNT Digital Library
First Regional Super ESPC: Success on Kodiak Island, Alaska (open access)

First Regional Super ESPC: Success on Kodiak Island, Alaska

This case study about energy saving performance contacts (ESPCs) presents an overview of how the Coast Guard at Kodiak Island, Alaska, established an ESPC contract and the benefits derived from it. The Federal Energy Management Program instituted these special contracts to help federal agencies finance energy-saving projects at their facilities.
Date: May 16, 2001
Creator: Federal Energy Management Program
Object Type: Book
System: The UNT Digital Library