Drift waves in stellarator geometry (open access)

Drift waves in stellarator geometry

Drift waves are investigated in a real three-dimensional stellarator geometry. A linear system, based on the cold ion fluid model and a ballooning mode formalism, is solved numerically in the geometry of the stellarator H1-NF. The spectra of stable and unstable modes, as well as localization, are discussed. The dependence of the spectrum of the unstable modes on the wavevector, plasma density variation, and the location in the plasma is presented.
Date: February 7, 2000
Creator: Persson, M.; Nadeem, M.; Lewandowski, J.L.V. & Gardner, H.J.
Object Type: Report
System: The UNT Digital Library
3-D Numerical Modeling of a Complex Salt Structure (open access)

3-D Numerical Modeling of a Complex Salt Structure

Reliably processing, imaging, and interpreting seismic data from areas with complicated structures, such as sub-salt, requires a thorough understanding of elastic as well as acoustic wave propagation. Elastic numerical modeling is an essential tool to develop that understanding. While 2-D elastic modeling is in common use, 3-D elastic modeling has been too computationally intensive to be used routinely. Recent advances in computing hardware, including commodity-based hardware, have substantially reduced computing costs. These advances are making 3-D elastic numerical modeling more feasible. A series of example 3-D elastic calculations were performed using a complicated structure, the SEG/EAGE salt structure. The synthetic traces show that the effects of shear wave propagation can be important for imaging and interpretation of images, and also for AVO and other applications that rely on trace amplitudes. Additional calculations are needed to better identify and understand the complex wave propagation effects produced in complicated structures, such as the SEG/EAGE salt structure.
Date: February 17, 2000
Creator: House, L.; Larsen, S. & Bednar, J. B.
Object Type: Article
System: The UNT Digital Library
Texas Labor Market Review, February 2000 (open access)

Texas Labor Market Review, February 2000

Monthly newsletter documenting statistics related to employment in Texas including nonagricultural job trends, labor force numbers, and other relevant indicators as well as information on related topics.
Date: February 2000
Creator: Texas Workforce Commission. Labor Market Information.
Object Type: Journal/Magazine/Newsletter
System: The Portal to Texas History
Spectroscopic Measurements of Target Preheating on OMEGA (open access)

Spectroscopic Measurements of Target Preheating on OMEGA

The preheating of laser-heated microballoon targets has been measured by time-resolved x-ray and extreme ultraviolet (euv) spectroscopy on the 30 kJ, 351 nm, 60-beam laser-fusion system at the University of Rochester Laboratory for Laser Energetics. Thin coatings of aluminum overcoated with magnesium served as indicators. both the sequence of the x-ray line emission and the intensity of euv radiation were used to determine a preheating peaking at {approx} 10 ns prior to onset of the main laser pulse, with a power density {approx_equal}1% of the main pulse. The measurements are supported by numerical modeling. Further information is provided by absorption spectra from the aluminum coating, backlighted by continuum from the heated surface. The exact source of the preheating energy remains unknown at present, but most likely arrives from early laser leakage through the system. The present target diagnostic is particularly useful when all beams cannot be monitored directly at all laser wavelengths.
Date: February 28, 2000
Creator: Elton, R. C.; Griem, H. R. & Iglesias, E. J.
Object Type: Article
System: The UNT Digital Library
FORMATION ENERGETICS OF CERAMIC PHASES RELATED TO SURPLUS PLUTONIUM DISPOSITION (open access)

FORMATION ENERGETICS OF CERAMIC PHASES RELATED TO SURPLUS PLUTONIUM DISPOSITION

None
Date: February 2000
Creator: Putnam, Robert L.; Gallegos, Ubaldo F.; Ebbinghaus, Bart B.; Navrotsky, Alexandra; Helean, Katheryn B.; Ushakov, Sergey V. et al.
Object Type: Report
System: The UNT Digital Library
Soft X-Ray Spectroscopic Measurements of Plasma Conditions at Early Times in ICF Experiments on OMEGA. Final technical report (open access)

Soft X-Ray Spectroscopic Measurements of Plasma Conditions at Early Times in ICF Experiments on OMEGA. Final technical report

Our previously-reported observation of a disruptive prepulse on OMEGA, possibly as large as 1% of the extreme ultraviolet (euv) radiation measured from the main pulse, has recently been substantiated by the measurement of euv absorption spectra, prior to the main pulse. The absorption features have been identified with n=2 photoionization in aluminum atoms and ions up to Al5+. Cold aluminum is originally present as a 0.0125-um thick sealant coating applied to a neon-filled (10 atm) CH microballoon, with an euv transmission at the L-absorption edge of {approx}50%. The aluminum in turn is overcoated with 2 um of Mg. The spectra which show the absorption also include continua as well as line emissions from Mg9+ to Mg11+ ions. These occur prior to the onset of laser target irradiation by at least 10 ns, and imply a prepulse irradiance of about 10{sup 12} W/cm{sup 2}. Since the neon and CH are opaque to euv radiation from the rear, a likely scenario is early (prepulse) vaporization of the outer Mg layer, perhaps in hot spots, followed by laser radiation transmitted through the thin Al layer, thereby heating the CH surface. This could provide an euv continuum backlighter for the aluminum that leads to …
Date: February 28, 2000
Creator: Griem, Hans R. & Elton, Raymond C.
Object Type: Report
System: The UNT Digital Library
Aluminum-Free Semiconductors and Packaging (open access)

Aluminum-Free Semiconductors and Packaging

The use of laser diodes instead of flashlamps to pump solid state lasers generally results in lighter weight, more compact systems with improved efficiency and reliability. These traits are important to a wide variety of applications in military, industrial and other areas. Common solid state laser systems such as yttrium aluminum garnet doped with neodymium or ytterbium (Nd:YAG and Yb:YAG, respectively) require pump light in the 800 to 1000 nm range, and such laser diodes have typically been fabricated in the AlGaAs material system on a GaAs substrate. Unfortunately, the presence of aluminum in or near the light-generating regions of these devices appears to limit their high-power performance, so for improved performance attention has turned to the aluminum-free (''Al-free'') material system of InGaAsP on a GaAs substrate. Laser diodes in this system offer the wavelength coverage similar to the AlGaAs/GaAs material system, and early results suggest that they may offer improved high-power performance. However, such Al-free diodes are more challenging to manufacture than AlGaAs-based devices. The goal of this LDRD project has been to evaluate Al-free diode technology in comparison with conventional AlGaAs-based structures for use in diode-pumped solid state lasers. This has been done by testing commercially available devices, …
Date: February 3, 2000
Creator: Emanuel, M. A.
Object Type: Report
System: The UNT Digital Library
Wetlands Regulation and the Law of Property Rights "Takings" (open access)

Wetlands Regulation and the Law of Property Rights "Takings"

When a wetland owner is denied permission to develop, or offered a permit with very burdensome conditions, the property's value may drop substantially. Wetlands programs also may impose costly development delays. For these reasons, federal and state wetlands regulation continues to generate "takings" lawsuits by land owners. Such suits allege that by narrowing or eliminating the economic uses to which a wetland can be put, the government has "taken" (permanently or temporarily) the wetland under the Fifth Amendment Takings Clause.
Date: February 17, 2000
Creator: Meltz, Robert
Object Type: Report
System: The UNT Digital Library
Potential for Advanced Carbon Capture and Sequestration Technologies in a Climate Constrained World (open access)

Potential for Advanced Carbon Capture and Sequestration Technologies in a Climate Constrained World

Potential for Advanced Carbon Capture and Sequestration Technologies in a Climate Constrained World
Date: February 1, 2000
Creator: Kim, Son H. & Edmonds, James A.
Object Type: Report
System: The UNT Digital Library
Texas Register, Volume 25, Number 7, Pages 1219-1442, February 18, 2000 (open access)

Texas Register, Volume 25, Number 7, Pages 1219-1442, February 18, 2000

A weekly publication, the Texas Register serves as the journal of state agency rulemaking for Texas. Information published in the Texas Register includes proposed, adopted, withdrawn and emergency rule actions, notices of state agency review of agency rules, governor's appointments, attorney general opinions, and miscellaneous documents such as requests for proposals. After adoption, these rulemaking actions are codified into the Texas Administrative Code.
Date: February 11, 2000
Creator: Texas. Secretary of State.
Object Type: Journal/Magazine/Newsletter
System: The Portal to Texas History
FCC Record, Volume 15, No. 4, Pages 1859 to 2555, January 24 - February 4, 2000 (open access)

FCC Record, Volume 15, No. 4, Pages 1859 to 2555, January 24 - February 4, 2000

Biweekly, comprehensive compilation of decisions, reports, public notices, and other documents of the U.S. Federal Communications Commission.
Date: February 2000
Creator: United States. Federal Communications Commission.
Object Type: Book
System: The UNT Digital Library
Congressional Record: Proceedings and Debates of the 106th Congress, Second Session, Volume 146, Part 2 (open access)

Congressional Record: Proceedings and Debates of the 106th Congress, Second Session, Volume 146, Part 2

The Congressional Record contains the records for sessions of the U.S. Congress including summaries of proceedings, letters, and speeches for the Senate and House of Representatives.
Date: February 2000
Creator: United States. Congress.
Object Type: Book
System: The UNT Digital Library
Texas Register, Volume 25, Number 8, Pages 1443-1812, February 25, 2000 (open access)

Texas Register, Volume 25, Number 8, Pages 1443-1812, February 25, 2000

A weekly publication, the Texas Register serves as the journal of state agency rulemaking for Texas. Information published in the Texas Register includes proposed, adopted, withdrawn and emergency rule actions, notices of state agency review of agency rules, governor's appointments, attorney general opinions, and miscellaneous documents such as requests for proposals. After adoption, these rulemaking actions are codified into the Texas Administrative Code.
Date: February 18, 2000
Creator: Texas. Secretary of State.
Object Type: Journal/Magazine/Newsletter
System: The Portal to Texas History
Congressional Record: Proceedings and Debates of the 106th Congress, Second Session, Volume 146, Part 1 (open access)

Congressional Record: Proceedings and Debates of the 106th Congress, Second Session, Volume 146, Part 1

The Congressional Record contains the records for sessions of the U.S. Congress including summaries of proceedings, letters, and speeches for the Senate and House of Representatives.
Date: February 2000
Creator: United States. Congress.
Object Type: Book
System: The UNT Digital Library