Ablation gas dynamics of low-Z materials illuminated by soft x-rays (open access)

Ablation gas dynamics of low-Z materials illuminated by soft x-rays

Though many of our results will have much greater generality, the main purpose of this paper is to provide a simple, accurate, physical theory of what happens when a Planckian spectrum of soft x-rays is incident on one side of the slab of initially cold, dense material, of small nuclear charge Z. Our approach will be to consider in some detail the idealized situation. A semi-infinite (x {le} 0) slab of initially cold (T < 300 K), dense ({rho} {approximately} 1 {minus} 10 g/cc), low-Z (Z < 5) material is suddenly subjected at time t = 0 and thereafter to radiation incoming from x = +{infinity} with a specific intensity in directions toward the slab that is Planckian, characterized by a black-body temperature, T{sub R} in the soft x-ray region.
Date: September 6, 1991
Creator: Hatchett, S.P.
System: The UNT Digital Library
A high resolution capacitive imaging sensor for manufacturing applications (open access)

A high resolution capacitive imaging sensor for manufacturing applications

A high resolution capacitive image sensing technique for measuring edge and surface profiles during manufacturing processes has been invented. A prototype device utilizing this technique consists of two 0.020 in. (500 {mu}m) diameter electrodes fabricated on a printed circuit board with a 0.010 in. (250 {mu}m) gap between them. As the device is mechanically scanned over the workpiece, the spatial variations in the edge or surface to be measured interfere with an electric field imposed between the electrodes, altering the mutual capacitance. The sensor functions as a near field proximity sensor producing range images of surface imperfections. This sensor has been used in applications requiring a preview image of burrs on the edge of a machined part and other processes requiring an inspection image after automated deburring operations. 10 refs., 8 figs.
Date: September 6, 1990
Creator: Novak, J. L. & Wiczer, J. J.
System: The UNT Digital Library
Design of Long Induction Linacs (open access)

Design of Long Induction Linacs

A self-consistent design strategy for induction linacs is presented which addresses the issues of brightness preservation against space charge induced emittance growth, minimization of the beam breakup instability and the suppression of beam centroid motion due to chromatic effects (corkscrew) and misaligned focusing elements. A simple steering algorithm is described that widens the effective energy bandwidth of the transport system.
Date: September 6, 1990
Creator: Caporaso, G.J. & Cole, A.G.
System: The UNT Digital Library
Three Problems: Nuclear Energy, National Defense and International Cooperation (open access)

Three Problems: Nuclear Energy, National Defense and International Cooperation

A little more than half a century into the Nuclear Age, we cannot look back on a peaceful period, but we can say that the second (nuclear) half of the century has seen much less violence than the first half with its two violent wars. Also the second half of the century has seen the fortunate ending of the Cold War. But as to the future, we are left with three great questions. (1) How can the world be provided with ample energy? (2) How can we avoid the potentially devastating sudden applications of new destructive technologies? And finally, (3) How can we preserve the development of the world's new potentialities without producing a continuation of violent conflicts? The development of nuclear reactors appears to provide a most interesting new initiative to make energy available to every one. The reality of this promise is at least indicated by progress in France where electricity now is 80% ''nuclear.'' Unfortunately, fear of radioactivity and fear of weapons proliferation has turned public opinion in many parts of the world against nuclear energy. The fear of radioactivity seems to be exaggerated, as indicated, for instance, in the recent international conference in Vienna on the …
Date: September 6, 1999
Creator: Teller, E.
System: The UNT Digital Library
Advanced, Environmentally Friendly Hydroelectric Turbines for the Restoration of Fish and Water Quality (open access)

Advanced, Environmentally Friendly Hydroelectric Turbines for the Restoration of Fish and Water Quality

Hydroelectric power contributes about 10 percent of the electrical energy generated in the United States, and nearly 20 percent of the world�s electrical energy. The contribution of hydroelectric generation has declined in recent years, often as a consequence of environmental concerns centering around (1) restriction of upstream and downstream fish passage by the dam, and (2) alteration of water quality and river flows by the impoundment. The Advanced Hydropower Turbine System (AHTS) Program of the U.S. Department of Energy is developing turbine technology which would help to maximize global hydropower resources while minimizing adverse environmental effects. Major technical goals for the Program are (1) the reduction of mortality among turbine-passed fish to 2 percent or less, compared to current levels ranging up to 30 percent or greater; and (2) development of aerating turbines that would ensure that water discharged from reservoirs has a dissolved oxygen concentration of at least 6 mg/L. These advanced, �environmentally friendly� turbines would be suitable both for new hydropower installations and for retrofitting at existing dams. Several new turbine designs that have been he AHTS program are described.
Date: September 6, 1999
Creator: Brookshier, P. A.; Cada, G. F.; Flynn, J. V.; Rinehart, B. N.; Sale, M. J. & Sommers, G. L.
System: The UNT Digital Library
Towards Atomic Column-by-Column Spectroscopy (open access)

Towards Atomic Column-by-Column Spectroscopy

The optical arrangement of the scanning transmission electron microscope (STEM) is ideally suited for performing analysis of individual atomic columns in materials. Using the incoherent Z-contrast image as a reference, and arranging incoherent conditions also for the spectroscopy, a precise correspondence is ensured between features in the inelastic image and elastic signals. In this way the exact probe position needed to maximise the inelastic signal from a selected column can be located and monitored during the analysis using the much higher intensity elastic signal. Although object functions for EELS are typically less than 1 {Angstrom} full width at half maximum, this is still an order of magnitude larger than the corresponding object functions for elastic (or diffuse) scattering used to form the Z-contrast image. Therefore the analysis is performed with an effective probe that is significantly broader than that used for the reference Z-contrast image. For a 2.2 {Angstrom} probe the effective probe is of the order of 2.5 {Angstrom}, while for a 1.3 {Angstrom} probe the effective probe is 1.6 {Angstrom}. Such increases in effective probe size can significantly reduce or even eliminate contrast between atomic columns that are visible in the image. However, this is only true if …
Date: September 6, 1998
Creator: Pennycook, S.J. & Rafferty, B.
System: The UNT Digital Library
Lightweight pressure vessels and unitized regenerative fuel cells (open access)

Lightweight pressure vessels and unitized regenerative fuel cells

Energy storage systems have been designed using lightweight pressure vessels with unitized regenerative fuel cells (URFCs). The vessels provide a means of storing reactant gases required for URFCs; they use lightweight bladder liners that act as inflatable mandrels for composite overwrap and provide a permeation barrier. URFC systems have been designed for zero emission vehicles (ZEVs); they are cost competitive with primary FC powered vehicles that operate on H/air with capacitors or batteries for power peaking and regenerative braking. URFCs are capable of regenerative braking via electrolysis and power peaking using low volume/low pressure accumulated oxygen for supercharging the power stack. URFC ZEVs can be safely and rapidly (<5 min.) refueled using home electrolysis units. Reversible operation of cell membrane catalyst is feasible without significant degradation. Such systems would have a rechargeable specific energy > 400 Wh/kg.
Date: September 6, 1996
Creator: Mitlitsky, F.; Myers, B. & Weisberg, A.H.
System: The UNT Digital Library
Spin physics at RHIC (open access)

Spin physics at RHIC

Operation of RHIC with two beams of highly polarized protons (70%, either longitudinal or transverse) at high luminosity L = 2 x 10{sup 32} cm{sup -2} sec{sup -1} for two months/year will allow the STAR and PHENIX detectors to perform high statististics studies of polarization phenomena in the perturbative region of hard scattering where both QCD and ElectroWeak theory make detailed predictions for polarization effects. The collision c.m. energy, {radical}s = 200 - 500 GeV, represents a new domain for the study of spin. Direct photon production will be used to measure the gluon polarization in the polarized proton. A new twist comes from W-boson production which is expected to be 100% parity violating and will thus allow measurements of flavor separated Quark and antiquark (u, {bar u}, d, {bar d}) polarization distributions. Searches for parity violation in strong interaction processes such as jet and leading particle production will be a sensitive way to look for new physics beyond the standard model, one possibility being quark substructure.
Date: September 6, 1996
Creator: Tannenbaum, Michael J.
System: The UNT Digital Library
Status of the BNL High Current EBIS Test Stand. (open access)

Status of the BNL High Current EBIS Test Stand.

As part of a new, compact heavy ion injector for AGS/RHIC complex at Brookhaven National Laboratory we are developing an Electron Beam Ion Source (EBIS) that would satisfy present and future requirements. Such a source should be capable of producing intensities of e.g. Al{sup 35+} ions of about 3 x 10{sup 9} particles/pulse or U{sup 45+} of about 2 x 10{sup 9} particles/pulse. To achieve this, the required e-beam intensity is 10A, at a pulse length of 100ms. An EBIS test stand has been constructed, designed for the full electron beam power and having close to 1/2 of the trap length of an EBIS for RHIC. Initial electron beam tests have resulted in a 50{micro}s, 13A electron beam. Ion production and extraction has been shown with a 3.1 A, 50 ms electron beam, achieving an ion yield of 19 nC/pulse (neutralization degree of 61%); fast extraction trials have yielded extracted ion pulses of 1mA peak current and 18{micro}s at FWHM. Details of the test stand construction, results of the electron beam studies, and properties of the extracted ion pulse are presented.
Date: September 6, 1999
Creator: Beebe, E.
System: The UNT Digital Library
Acquisition of reliable vacuum hardware for large accelerator systems (open access)

Acquisition of reliable vacuum hardware for large accelerator systems

Credible and effective communications prove to be the major challenge in the acquisition of reliable vacuum hardware. Technical competence is necessary but not sufficient. The authors must effectively communicate with management, sponsoring agencies, project organizations, service groups, staff and with vendors. Most of Deming`s 14 quality assurance tenants relate to creating an enlightened environment of good communications. All projects progress along six distinct, closely coupled, dynamic phases. All six phases are in a state of perpetual change. These phases and their elements are discussed, with emphasis given to the acquisition phase and its related vocabulary. Large projects require great clarity and rigor as poor communications can be costly. For rigor to be cost effective, it can`t be pedantic. Clarity thrives best in a low-risk, team environment.
Date: September 6, 1995
Creator: Welch, K.M.
System: The UNT Digital Library
Selection of a management strategy for depleted uranium hexafluoride (open access)

Selection of a management strategy for depleted uranium hexafluoride

A consequence of the uranium enrichment process used in the United States (US) is the accumulation of a significant amount of depleted uranium hexafluoride (UF{sub 6}). Currently, approximately 560,000 metric tons of the material are stored at three different sites. The US Department of Energy (DOE) has recently initiated a program to consider alternative strategies for the cost-effective and environmentally safe long-term management of this inventory of depleted UF{sub 6}. The program involves a technology and engineering assessment of proposed management options (use/reuse, conversion, storage, or disposal) and an analysis of the potential environmental impacts and life-cycle costs of alternative management strategies. The information obtained from the studies will be used by the DOE to select a preferred long-term management strategy. The selection and implementation of a management strategy will involve consideration of a number of important issues such as environmental, health, and safety effects; the balancing of risks versus costs in a context of reduced government spending; socioeconomic implications, including effects on the domestic and international uranium industry; the technical status of proposed uses or technologies; and public involvement in the decision making process. Because of its provisions for considering a wide range of relevant issues and involving the …
Date: September 6, 1995
Creator: Patton, S. E.; Hanrahan, E. J. & Bradley, C. E.
System: The UNT Digital Library
Increasing the Space Charge Limit and Other Effects of Cesium Seeding in Hydrogen Negative Ion Sources (open access)

Increasing the Space Charge Limit and Other Effects of Cesium Seeding in Hydrogen Negative Ion Sources

The role of cesium seeding in increasing the negative ion current in volume sources is described. By a reduction in the local plasma potential the current of extracted electrons is vastly reduced. As a result, cesium increases the fraction of the transverse space charge limit available to the ions by as much as a factor of three. In addition, cesium can increase the total space charge limit by injection of Cs+ into the presheath-a newly recognized phenomenon consistent with experimental measurements and determined from application of a Double-Vlasov model for negative ion extraction.
Date: September 6, 1999
Creator: Bacal, M.; Bruneteau, J.; Raridon, R.J. & Whealton, J.H.
System: The UNT Digital Library
Effect of Cesium and Xenon Seeding in Negative Hydrogen Ion Sources (open access)

Effect of Cesium and Xenon Seeding in Negative Hydrogen Ion Sources

It is well known that cesium seeding in volume hydrogen negative ion sources leads to a large reduction of the extracted electron current and in some cases to the enhancement of the negative ion current. The cooling of the electrons due to the addition of this heavy impurity was proposed as a possible cause of the mentioned observations. In order to verify this assumption, the authors seeded the hydrogen plasma with xenon, which has an atomic weight almost equal to that of cesium. The plasma properties were studied in the extraction region of the negative ion source Camembert III using a cylindrical electrostatic probe while the negative ion relative density was studied using laser photodetachment. It is shown that the xenon mixing does not enhance the negative ion density and leads to the increase of the electron density, while the cesium seeding reduces the electron density.
Date: September 6, 1999
Creator: Bacal, M.; Brunteau, A. M.; Deniset, C.; Elizarov, L. I.; Sube, F.; Tontegode, A. Y. et al.
System: The UNT Digital Library