States

Approximate Near-Field Blast Theory: A Generalized Approach (open access)

Approximate Near-Field Blast Theory: A Generalized Approach

A method for analyzing strong shock waves in arbitrary one-dimensional geometry is presented. An approximation to classical Taylor-Sedov theory is extended to the near-field case where source mass is not negligible, accounting for differences in the chemical properties of the source mass and ambient medium. Results from example calculations are compared with previously published analytical formulae.
Date: October 25, 1999
Creator: Hutchens, G.J.
Object Type: Article
System: The UNT Digital Library
Awards of Attorney's Fees to Small Businesses and Labor Organizations that Prevail Against the NLRB or OSHA: H.R. 1987, 106th Congress (open access)

Awards of Attorney's Fees to Small Businesses and Labor Organizations that Prevail Against the NLRB or OSHA: H.R. 1987, 106th Congress

H.R. 1987, 106th Congress, the Fair Access to Indemnity and Reimbursement (FAIR) Act, which was reported by the Committee on Education and the Workforce on October 14, 1999, would make it easier for small businesses and labor organizations that prevail against the NLRB or OSHA, in administrative or court proceedings, to recover their attorneys' fees from the government. It would do so by requiring fees to be awarded automatically in cases to which it applied, instead of only when the government's position was not substantially justified.
Date: October 25, 1999
Creator: Cohen, Henry
Object Type: Report
System: The UNT Digital Library
Beam dynamics studies in a high-brightness photo-injector (open access)

Beam dynamics studies in a high-brightness photo-injector

A high-brightness photo-injector has been developed at Fermilab in collaboration with the TTF project at DESY. Two systems have been commissioned, one at DESY and one at Fermilab. The injector [1] consists of a 1.625-cell cavity RF gun, a superconducting niobium cavity (both 1.3 GHz), and a magnetic chicane. The gun is designed for an electric field of up to 50 MV/m on the cathode. Emittance compensation solenoids surround the gun to correct the linear space charge emittance growth. A high quantum efficiency Cs{sub 2}Te photocathode located in the first half-cell produces electrons when illuminated by 263 nm wavelength light (fourth harmonic of the Nd:YLF laser). The laser [2] was designed to produce a train of up to 800 equal amplitude, 10 {micro}J UV pulses spaced by 1 {micro}s at 1 Hz repetition rate. The laser pulse length is adjustable between 1 and 20 ps FWHM. The superconducting cavity is a 9-cell Nb structure fabricated by industry for TTF. It was tested with RF at DESY before being sent to Fermilab. At present, the cavity is operated at {approx}11 MeV/m. Beam measurements with the injector at Fermilab are in progress. Preliminary results for emittance and bunch length will be discussed …
Date: October 25, 1999
Creator: Carneiro, Jean-Paul
Object Type: Article
System: The UNT Digital Library
Chiral Condensate in the Deconfined Phase of Quenched Gauge Theories (open access)

Chiral Condensate in the Deconfined Phase of Quenched Gauge Theories

The authors compute the low lying spectrum of the overlap Dirac operator in the deconfined phase of finite-temperature quenched gauge theory. It suggests the existence of a chiral condensate which they confirm with a direct stochastic estimate. They show that the part of the spectrum responsible for the chiral condensate can be understood as arising from a dilute gas of instantons and anti-instantons.
Date: October 25, 1999
Creator: Edwards, Robert G.; Heller, Urs M.; Kiskis, Joe & Narayanan, Rajamani
Object Type: Article
System: The UNT Digital Library
Clean cities: Award winning coalition -- Maricopa (open access)

Clean cities: Award winning coalition -- Maricopa

The Maricopa Association of Governments (MAG) Regional Council initiated the Maricopa Clean Cities Program on June 20, 1995. Its purpose was to encourage the use of alternative fuels in the Maricopa region and to obtain recognition for the steps the region had already taken to support the use of alternative fuels. One key element to Maricopa Clean Cities' success is the strong support it receives from the Arizona legislation. The Maricopa Clean Cities stakeholders are committed to increasing the number of alternative fuel vehicles and developing the infrastructure to support those vehicles.
Date: October 25, 1999
Creator: O'Connor, K. & Raye, M.
Object Type: Book
System: The UNT Digital Library
Clean cities: Award winning coalition -- Paso del Norte (open access)

Clean cities: Award winning coalition -- Paso del Norte

Designated the 41st Clean Cities coalition in November 1995, the Paso del Norte Clean Cities Coalition (PDNCCC) is the first in the country to gain international participation. Spanning the US-Mexico border; the coalition includes stakeholders from El Paso, Texas; Ciudad Juarez, Mexico; and Las Cruces, New Mexico. PDNCCC developed a comprehensive plan to jump-start its program place, alternative fuel vehicles (AFVs) on the road, and eliminate barriers inhibiting alternative fuel market growth. PDNCC raised more than $2.3 million for alternative fuel activities and clean air initiatives in less than 26 months. In 1998, the US Department of Energy (DOE) recognized that PDNCCC accomplishment with its Rainmaker Award for leveraging the most funds from outside sources. PDNCCC is proud of its efforts to drive the alternative fuels and AFV market in the El Paso/Juarez region.
Date: October 25, 1999
Creator: O'Connor, K.
Object Type: Book
System: The UNT Digital Library
Cobalt Source Calibration (open access)

Cobalt Source Calibration

The data obtained from these tests determine the dose rate of the two cobalt sources in SRTC. This testing used chemical dosimetry to measure the dose rate of a radioactive source.
Date: October 25, 1999
Creator: Barnes, M.
Object Type: Report
System: The UNT Digital Library
Deformation behavior in reactor pressure vessel steels as a clue to understanding irradiation hardening. (open access)

Deformation behavior in reactor pressure vessel steels as a clue to understanding irradiation hardening.

In this paper, we examine the post-yield true stress vs true strain behavior of irradiated pressure vessel steels and iron-based alloys to reveal differences in strain-hardening behavior associated with different irradiating particles (neutrons and electrons) and different alloy chernky. It is important to understand the effects on mechanical properties caused by displacement producing radiation of nuclear reactor pressure steels. Critical embrittling effects, e.g. increases in the ductile-to-brittle-transition-temperature, are associated with irradiation-induced increases in yield strength. In addition, fatigue-life and loading-rate effects on fracture can be related to the post-irradiation strain-hardening behavior of the steels. All of these properties affect the expected service life of nuclear reactor pressure vessels. We address the characteristics of two general strengthening effects that we believe are relevant to the differing defect cluster characters produced by neutrons and electrons in four different alloys: two pressure vessel steels, A212B and A350, and two binary alloys, Fe-0.28 wt%Cu and Fe-0.74 wt%Ni. Our results show that there are differences in the post-irradiation mechanical behavior for the two kinds of irradiation and that the differences are related both to differences in damage produced and alloy chemistry. We find that while electron and neutron irradiations (at T {le} 60 C) of …
Date: October 25, 1999
Creator: DiMelfi, R. J.; Alexander, D. E. & Rehn, L. E.
Object Type: Article
System: The UNT Digital Library
Disaster Mitigation Bills in the 106th Congress: H.R. 707, S. 1691 Compared (open access)

Disaster Mitigation Bills in the 106th Congress: H.R. 707, S. 1691 Compared

The Robert T. Stafford Disaster Relief and Emergency Assistance Act authorizes the President to declare that an emergency or major disaster exists that overwhelms state and local resources. Legislation before the 106th Congress (H.R. 707 and S. 1691) would, among other matters, amend the Act to: (1) fund hazard mitigation projects designed to reduce future disaster losses; (2) add conditions to assistance; and (3) consolidate provisions governing the distribution of aid to disaster victims. This report compares provisions of the two bills, and will be updated as legislative action occurs.
Date: October 25, 1999
Creator: Bea, Keith
Object Type: Report
System: The UNT Digital Library
The effect of actinides on the microstructural development in a metallic high-level nuclear waste form (open access)

The effect of actinides on the microstructural development in a metallic high-level nuclear waste form

Waste forms to contain material residual from an electrometallurgical treatment of spent nuclear fuel have been developed by Argonne National Laboratory. One of these waste forms contains waste stainless steel (SS), fission products that are noble to the process (e.g., Tc, Ru, Pd, Rh), Zr, and actinides. The baseline composition of this metallic waste form is SS-15wt.% Zr. The metallurgy of this baseline alloy has been well characterized. On the other hand, the effects of actinides on the alloy microstructure are not well understood. As a result, SS-Zr alloys with added U, Pu, and/or Np have been cast and then characterized, using scanning electron microscopy, transmission electron microscopy, and neutron diffraction, to investigate the microstructural development in SS-Zr alloys that contain actinides. Actinides were found to congregate non-uniformally in a Zr(Fe,Cr,Ni){sub 2+x} phase. Apparently, the actinides were contained in varying amounts in the different polytypes (C14, C15, and C36) of the Zr(Fe,Cr,Ni){sub 2+x} phase. Heat treatment of an actinide-containing SS-15 wt.% Zr alloy showed the observed microstructure to be stable.
Date: October 25, 1999
Creator: Keiser, D. D. Jr.; Sinkler, W.; Abraham, D. P.; Richardson, J. W., Jr. & McDeavitt, S. M.
Object Type: Article
System: The UNT Digital Library
Fate of SO{sub 2} During Plasma Treatment of Diesel Engine Exhaust (open access)

Fate of SO{sub 2} During Plasma Treatment of Diesel Engine Exhaust

Several catalytic aftertreatment technologies rely on the conversion of NO to NO{sub 2} to achieve efficient reduction of NO{sub x} and particulates in diesel engine exhaust. These technologies require low sulfur fuel because the catalyst component that is active in converting NO to NO{sub 2} is also active in converting SO{sub 2} to SO{sub 3}. A non-thermal plasma can be used for the selective partial oxidation of NO to NO{sub 2} in the gas-phase under diesel engine exhaust conditions. This paper discusses how a non-thermal plasma can efficiently oxidize NO to NO{sub 2} without oxidizing SO{sub 2} to SO{sub 3}. It is shown that the presence of hydrocarbons in the plasma is essential for enhancing the selective partial oxidation of NO and suppressing the oxidation of SO{sub 2}.
Date: October 25, 1999
Creator: Brusasco, R.M.; Merritt, B.T. & Vogtlin, G.E.
Object Type: Article
System: The UNT Digital Library
First results of the Fermilab high-brightness RF photoinjector (open access)

First results of the Fermilab high-brightness RF photoinjector

A collaboration has been formed between FNAL, UCLA, INFN Milano, the University of Rochester, and DESY to develop the technology of an RF photoinjector, followed by a superconducting cavity, to produce high bunch charge (8 nC) with low normalized emittance (< 20 mm {center_dot} mrad) in trains of 800 bunches separated by 1{micro}s. The activities of the collaboration fall into two categories: (1) the development of Injector II for the TeSLA/TTF accelerator [1]. This photoinjector (TTF RF Gun)was tested at Fermilab in September and October 1998 and installed at DESY in November 1998; (2) the installation at the A0 Hall of Fermilab of a modified version of the TTF photoinjector, for photoinjector R&D and to study novel applications of high-brightness, pulsed electrons beams. This photoinjector (A0 RF Gun) produced its first beam in March 1999. This paper presents a summary of the tests done at Fermilab on the TTF Injector II and the first results obtained on the new Fermilab photoinjector.
Date: October 25, 1999
Creator: Carneiro, Jean-Paul
Object Type: Article
System: The UNT Digital Library
FPIX1: An advanced pixel readout chip (open access)

FPIX1: An advanced pixel readout chip

At Fermilab, a pixel detector for BTeV is proposed for installation a few millimeters from the beam. Its information will be used in on-line track finding for the lowest level trigger system. This requires a high-speed readout and immediate data transfer from the pixel chip to the trigger processor. It is also believed that a 2-4 bits of analog information is required to achieve the targeted spatial resolution [1] with 50{micro} wide pixels. Our first prototype, FPIX0 [2], is now being used in a beam test to confirm physics simulations and to determine the required resolution of the analog ''information''. Our 2nd prototype, FPIX1, is a 160X18 pixel readout chip compatible with the ATLAS family of detectors. We have build and tested 4 FPIX1-detector assemblies. FPIX1 is realized in the HP 0.5{micro} process. The main features of FPIX1 are: 2bit flash ADC on each cell for maximum speed; Triggered or stand alone operation; and High speed sparse and time ordered Readout.
Date: October 25, 1999
Creator: al., A. Mekkaoui et
Object Type: Article
System: The UNT Digital Library
Germanium orthogonal strip detectors with amorphous-semiconductor contacts (open access)

Germanium orthogonal strip detectors with amorphous-semiconductor contacts

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Date: October 25, 1999
Creator: Luke, P. N.; Amman, M.; Phlips, B. F.; Johnson, W. N. & Kroeger, R. A.
Object Type: Article
System: The UNT Digital Library
High Voltage GaN Schottky Rectifiers (open access)

High Voltage GaN Schottky Rectifiers

Mesa and planar GaN Schottky diode rectifiers with reverse breakdown voltages (V{sub RB}) up to 550V and >2000V, respectively, have been fabricated. The on-state resistance, R{sub ON}, was 6m{Omega}{center_dot} cm{sup 2} and 0.8{Omega}cm{sup 2}, respectively, producing figure-of-merit values for (V{sub RB}){sup 2}/R{sub ON} in the range 5-48 MW{center_dot}cm{sup -2}. At low biases the reverse leakage current was proportional to the size of the rectifying contact perimeter, while at high biases the current was proportional to the area of this contact. These results suggest that at low reverse biases, the leakage is dominated by the surface component, while at higher biases the bulk component dominates. On-state voltages were 3.5V for the 550V diodes and {ge}15 for the 2kV diodes. Reverse recovery times were <0.2{micro}sec for devices switched from a forward current density of {approx}500A{center_dot}cm{sup -2} to a reverse bias of 100V.
Date: October 25, 1999
Creator: Cao, X. A.; Cho, H.; Chu, S. N. G.; Chuo, C. C.; Chyi, J. I.; Dang, G. T. et al.
Object Type: Article
System: The UNT Digital Library
Hydrodynamic effects of eroded materials on response of plasma-facing component during a tokamak disruption (open access)

Hydrodynamic effects of eroded materials on response of plasma-facing component during a tokamak disruption

Loss of plasma confinement causes surface and structural damage to plasma-facing materials (PFMs) and remains a major obstacle for tokamak reactors. The deposited plasma energy results in surface erosion and structural failure. The surface erosion consists of vaporization, spallation, and liquid splatter of metallic materials, while the structural damage includes large temperature increases in structural materials and at the interfaces between surface coatings and structural members. Comprehensive models (contained in the HEIGHTS computer simulation package) are being used self-consistently to evaluate material damage. Splashing mechanisms occur as a result of volume bubble boiling and liquid hydrodynamic instabilities and brittle destruction mechanisms of nonmelting materials. The effect of macroscopic erosion on total mass losses and lifetime is evaluated. The macroscopic erosion products may further protect PFMs from severe erosion (via the droplet-shielding effect) in a manner similar to that of the vapor shielding concept.
Date: October 25, 1999
Creator: Hassanein, A. & Konkashbaev, I.
Object Type: Article
System: The UNT Digital Library
Laboratory measurements of compressional and shear wave speeds through methane hydrate (open access)

Laboratory measurements of compressional and shear wave speeds through methane hydrate

Simultaneous measurements of compressional and shear wave speeds through polycrystalline methane hydrate have been made. Methane hydrate, grown directly in a wave speed measurement chamber, was uniaxially compacted to a final porosity below 2%. At 277 K, the compacted material's compressional wave speed was 3650 {+-} 50 m/s. The shear wave speed, measured simultaneously, was 1890 {+-} 30 m/s. From these wave speed measurements, we derive Vp/Vs, Poisson's Ratio, bulk, shear and Young's moduli.
Date: October 25, 1999
Creator: Durham, W B; Waite, WF; Pinkston, J C; Stern, L A; Kirby, S H; Helgerud, M B et al.
Object Type: Article
System: The UNT Digital Library
Lighting recommendations for the Social Security Administration Frank Hagel Federal Building in Richmond CA (open access)

Lighting recommendations for the Social Security Administration Frank Hagel Federal Building in Richmond CA

Specific recommendations are made to improve the lighting quality and energy efficiency of the lighting system at the Social Security Administration Frank Hagel Building in Richmond, CA. The main recommendation is to replace the recessed fluorescent lighting system in the general office area with indirect lighting. Indirect lighting will improve lighting quality, will provide an energy efficient solution and will be about the same cost as the direct lighting system originally proposed.
Date: October 25, 1999
Creator: Rubinstein, Francis M.
Object Type: Report
System: The UNT Digital Library
Methane hydrate dissociation rates as 0.1 MPa and temperatures above 272K (open access)

Methane hydrate dissociation rates as 0.1 MPa and temperatures above 272K

We performed rapid depressurization experiments on methane hydrate under isothermal conditions above 272 K to determine the amount and rate of methane evolution. Sample temperatures rapidly drop below 273 K and stabilize near 272.5 K during dissociation. This thermal anomaly and the persistence of methane hydrate are consistent with the reported recovery of partially dissociated methane hydrate from ocean drilling cores.
Date: October 25, 1999
Creator: Durham, W. B.; Circone, S.; Stern, L. A.; Kirby, S. H. & Pinkston, J. C.
Object Type: Article
System: The UNT Digital Library
A new gap separation mechanism for APS insertion devices. (open access)

A new gap separation mechanism for APS insertion devices.

A new gap separation mechanism for use with the standard Advanced Photon Source (APS) 3.3-cm-period undulator magnetic structures has been designed and built and the first system has been installed in the APS storage ring. The system allows a minimum magnetic gap of 10 mm for use with the APS 8-mm insertion device vacuum chambers. The mechanism is a bolted steel frame structure with a simple 4-motor mechanical drive train. The control system uses servomotors with incremental rotary encoders and virtual absolute linear encoders.
Date: October 25, 1999
Creator: Trakhtenberg, E. M.; Tcheskidov, V.; Den Hartog, P. K.; Deriy, B.; Erdmann, M.; Makarov, O. et al.
Object Type: Article
System: The UNT Digital Library
New W mass results from CDF and D0 (open access)

New W mass results from CDF and D0

This article describes recent measurements of the W mass by the CDF and D0 Collabo-rations. CDF obtains a preliminary result of 80.473 ± 0.113 GeV for the W mass in the electron channel and D0 reports a preliminary result of 80.766 ± 0.234 GeV for electrons in the more forward (Endcap) rapidities. When combined with all previous measurements, the current average for the W mass measured at the Tevatron is 80.450 ± 0.063 GeV.
Date: October 25, 1999
Creator: Carithers, B.
Object Type: Article
System: The UNT Digital Library
On the Relationship Between Microstructure and Electrical and Hydraulic Properties of Sand-Clay Mixtures (open access)

On the Relationship Between Microstructure and Electrical and Hydraulic Properties of Sand-Clay Mixtures

A series of laboratory experiments were performed on saturated sand-clay mixtures, including electrical properties, permeability and porosity. Different mixtures and configurations of quartz sand and 0 to 10% Na-montmorillonite clay saturated with solutions of CaCl{sub 2} and deionized water were investigated. The electrical properties were dependent on clay content, fluid conductivity, and microstructure in a complex fashion. Two main regions of conduction exist: a region dominated by surface conduction and a region where the ionic strength of the saturating fluid controlled conduction. For low fluid conductivities, the sample geometry was found to greatly affect the magnitude of the surface conductance. The influence of the microstructural properties on the electrical properties was quantified by estimating formation factors, {Lambda}-parameters, and surface conductances. We suggest that high and low bounds on the expected surface and bulk conductance of natural systems can be derived from the measurements on these artificial configurations.
Date: October 25, 1999
Creator: Wildenschild, D.; Roberts, J. J. & Carlsberg, E. D.
Object Type: Report
System: The UNT Digital Library
The Physics of Fast Z Pinches (open access)

The Physics of Fast Z Pinches

The spectacular progress made during the last few years in reaching high energy densities in fast implosions of annular current sheaths (fast Z pinches) opens new possibilities for a broad spectrum of experiments, from x-ray generation to controlled thermonuclear fusion and astrophysics. Presently Z pinches are the most intense laboratory X ray sources (1.8 MJ in 5 ns from a volume 2 mm in diameter and 2 cm tall). Powers in excess of 200 TW have been obtained. This warrants summarizing the present knowledge of physics that governs the behavior of radiating current-carrying plasma in fast Z pinches. This survey covers essentially all aspects of the physics of fast Z pinches: initiation, instabilities of the early stage, magnetic Rayleigh-Taylor instability in the implosion phase, formation of a transient quasi-equilibrium near the stagnation point, and rebound. Considerable attention is paid to the analysis of hydrodynamic instabilities governing the implosion symmetry. Possible ways of mitigating these instabilities are discussed. Non-magnetohydrodynamic effects (anomalous resistivity, generation of particle beams, etc.) are summarized. Various applications of fast Z pinches are briefly described. Scaling laws governing development of more powerful Z pinches are presented. The survey contains 36 figures and more than 300 references.
Date: October 25, 1999
Creator: Ryutov, D. D.; Derzon, Mark S. & Matzen, M. Keith
Object Type: Article
System: The UNT Digital Library
Portable X-Ray, K-Edge Heavy Metal Detector (open access)

Portable X-Ray, K-Edge Heavy Metal Detector

The X-Ray, K-Edge Heavy Metal Detection System was designed and built by Ames Laboratory and the Center for Nondestructive Evaluation at Iowa State University. The system uses a C-frame inspection head with an X-ray tube mounted on one side of the frame and an imaging unit and a high purity germanium detector on the other side. the inspection head is portable and can be easily positioned around ventilation ducts and pipes up to 36 inches in diameter. Wide angle and narrow beam X-ray shots are used to identify the type of holdup material and the amount of the contaminant. Precise assay data can be obtained within minutes of the interrogation. A profile of the containerized holdup material and a permanent record of the measurement are immediately available.
Date: October 25, 1999
Creator: Fricke, V.
Object Type: Report
System: The UNT Digital Library