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$Sensor for measuring the atomic fraction in highly dissociated hydrogen$ (open access)

Sensor for measuring the atomic fraction in highly dissociated hydrogen

Atomic hydrogen is a very important constituent for processes ranging from cleaning oxide from GaAs and annealing amorphous silicon to the deposition of diamond. Because the usual techniques for measuring atomic fraction are either expensive and cumbersome to use, or unsuitable for application to highly dissociated hydrogen, a specially designed sensor was developed. Sensor design is based on a diffusion tube with noncatalytic walls, having one end open to the atom source and a catalytic closure at the other end. The sensor is simple and inexpensive to fabricate, and determining atom density is straightforward. Sensor design also inhibits thermal runaway, which occurs when atom density is high enough to impart enough recombination energy to the non-catalytic surface to substantially raise its temperature. While recombination coefficients for such surfaces are very low near room temperature, they increase nearly exponentially with temperature unless actively cooled. With the use of a straightforward calibration scheme to determine the variation in species fraction along the diffusion tube, the atomic fraction at the tube opening is determined. Design strategy, implementation considerations, and calibration method are presented. In addition, data obtained from an atomic hydrogen source are compared to relevant published data.

Date: December 31, 1994

Creator: Gardner, W.L.

Object Type: Report

System: The UNT Digital Library

(open access)

Technologies for the oil and gas industry

This is the final report of a five-month, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The authors performed a preliminary design study to explore the plausibility of using pulse-tube refrigeration to cool instruments in a hot down-hole environment for the oil and gas industry or geothermal industry. They prepared and distributed a report showing that this appears to be a viable technology.

Date: December 31, 1998

Creator: Goff, S.J.; Swift, G.W. & Gardner, D.L.

Object Type: Report

System: The UNT Digital Library

(open access)

Indium dopant/defect complexes in lightly-doped ceria

Four well-defined indium-dopant/lattice-defect complexes and the non-complexed substitutional indium dopant have been observed by perturbed angular correlation (PAC) spectroscopy in cerium oxide. PAC is a nuclear hyperfine experimental method that detects interactions between a radioactive probe nucleus and nearby atoms. The magnitude and symmetry of those interactions provide a signature for the electromagnetic fields at the probe nucleus. These fields are produced by the arrangement of charges and magnetic moments in the near environment of the probe, so they provide a means of identifying defect structures.

Date: December 31, 1991

Creator: Wang, Ruiping; Gardner, J. A.; Evenson, W. E. & Sommers, J. A.

Object Type: Article

System: The UNT Digital Library

(open access)

Ion exchange properties of novel hydrous metal oxide materials

Hydrous metal oxide (HMO) materials are inorganic ion exchangers which have many desirable characteristics for catalyst support applications, including high cation exchange capacity, anion exchange capability, high surface area, ease of adjustment of acidity and basicity, bulk or thin film preparation, and similar chemistry for preparation of various transition metal oxides. Cation exchange capacity is engineered into these materials through the uniform incorporation of alkali cations via manipulation of alkoxide chemistry. Specific examples of the effects of Na stoichiometry and the addition of SiO{sub 2} to hydrous titanium oxide (HTO) on ion exchange behavior will be given. Acid titration and cationic metal precursor complex exchange will be used to characterize the ion exchange behavior of these novel materials.

Date: December 31, 1996

Creator: Gardner, T.J. & McLaughlin, L.I.

Object Type: Article

System: The UNT Digital Library

(open access)

Comparison of the folded stripline and stacked stripline concepts to the folded waveguide launcher

Two new concepts are being developed as possible upgrades to the folded waveguide launcher. The folded stripline is a folded waveguide with an additional conductor positioned inside. The term stripline refers to the resemblance of the design to microwave microstrip line. The conductor provides support for TEM mode propagation, which eliminates cutoff and the nonlinear frequency dependence of the waveguide impedance and phase velocity. A natural extension to the folded stripline is the stacked stripline, which comprises several stacked, independent TEM waveguides. Initial measurements indicate that both concepts have better magnetic flux coupling than the folded waveguide.

Date: December 31, 1993

Creator: Gardner, W. L.; Caughman, J. B. O.; Hoffman, D. J. & Probert, P. H.

Object Type: Article

System: The UNT Digital Library

(open access)

PAC spectroscopy of electronic ceramics

Dilute indium dopants in cerium oxides and YBa{sub 2}Cu{sub 3}O{sub x} have been studied by{sup 111}In/Cd Perturbed Angular Correlation (PAC) spectroscopy. By controlling oxygen vacancy concentration in the cerium oxides through doping or high-temperature vacuum annealing, we have found that indium always forms a defect complex unless the sample is doped to reduce greatly the oxygen vacancy concentration. Three different vacancy-associated complexes are found with concentrations that depend on doping and oxygen stoichiometry. Another defect complex occurs in samples having negligible vacancy concentration. At low temperatures, evidence is found of interaction with an electronic hole trapped by {sup 111}Cd after the radioactive decay of the {sup 111}In parent. In YBa{sub 2}Cu{sub 3}O{sub x} the indium substitutes preferentially at the Y site but has measurable probability of substitution in at least one of the two copper sites. A symmetry change near 650 {degree}C is consistent with the well-documented orthorhombic/tetragonal transition for samples in air or oxygen.

Date: December 31, 1991

Creator: Gardner, J. A.; Wang, Ruiping; Schwenker, R.; Evenson, W. E.; Rasera, R. L. & Sommers, J. A.

Object Type: Report

System: The UNT Digital Library

(open access)

Harmonic analysis of the AGS Booster imperfection

The harmonic content of magnetic field imperfections in the AGS Booster has been determined through careful measurements of the required field corrections of transverse resonances. An analysis of the required correction yielded amplitude and phase information which points to possible sources of imperfections. Dipole and quadrupole imperfections, which are proportional to the field of bending magnets (B), are mainly driven by any misalignment of the magnets. Quadrupole and sextupole imperfections, which are proportional to dB/dt, are driven by imperfections of the eddy-current correction system. The observations also suggest the presence of a remnant field.

Date: December 31, 1993

Creator: Shoji, Y. & Gardner, C.

Object Type: Article

System: The UNT Digital Library

(open access)

Transient Solid Dynamics Simulations on the Sandia/Intel Teraflop Computer

Transient solid dynamics simulations are among the most widely used engineering calculations. Industrial applications include vehicle crashworthiness studies, metal forging, and powder compaction prior to sintering. These calculations are also critical to defense applications including safety studies and weapons simulations. The practical importance of these calculations and their computational intensiveness make them natural candidates for parallelization. This has proved to be difficult, and existing implementations fail to scale to more than a few dozen processors. In this paper we describe our parallelization of PRONTO, Sandia`s transient solid dynamics code, via a novel algorithmic approach that utilizes multiple decompositions for different key segments of the computations, including the material contact calculation. This latter calculation is notoriously difficult to perform well in parallel, because it involves dynamically changing geometry, global searches for elements in contact, and unstructured communications among the compute nodes. Our approach scales to at least 3600 compute nodes of the Sandia/Intel Teraflop computer (the largest set of nodes to which we have had access to date) on problems involving millions of finite elements. On this machine we can simulate models using more than ten- million elements in a few tenths of a second per timestep, and solve problems more …

Date: December 31, 1997

Creator: Attaway, S.; Brown, K.; Gardner, D.; Hendrickson, B. & Barragy, T.

Object Type: Article

System: The UNT Digital Library

(open access)

The partial Siberian snake experiment at the Brookhaven AGS

We are building a 4.7 Tesla-meter room temperature solenoid to be installed in a 10-foot long AGS straight section. This experiment will test the idea of using a partial snake to correct all depolarizing imperfection resonances and also test the feasibility of betatron tune jump in correction intrinsic resonances in the presence of a partial snake.

Date: December 31, 1992

Creator: Huang, H.; Caussyn, D. D.; Ellison, T.; Jones, B.; Lee, S. Y.; Schwandt, P. et al.

Object Type: Article

System: The UNT Digital Library

(open access)

Drilling and geohydrologic data for test hole USW UZ-1, Yucca Mountain, Nye County, Nevada

This report presents data collected to determine the hydrologic characteristics of tuffaceous rocks penetrated in test hole USW UZ-1. The borehole is the first of two deep, large-diameter, unsaturated-zone test holes dry drilled using the vacuum/reverse-air-circulation method. This test hole was drilled in and near the southwestern part of the Nevada Test Site, Nye County, Nevada, in a program conducted in cooperation with the US Department of Energy. These investigations are part of the Yucca Mountain Project (formerly the Nevada Nuclear Waste Storage Investigations) to identify a potentially suitable site for the storage of high-level radioactive wastes. Data are presented for bit and casing configurations, coring methods, sample collection, drilling rate, borehole deviation, and out-of-gage borehole. Geologic data for this borehole include geophysical logs, a lithologic log of drill-bit cuttings, and strike and distribution of fractures. Hydrologic data include water-content and water-potential measurements of drill-bit cuttings, water-level measurements, and physical and chemical analyses of water. Laboratory measurements of moisture content and matric properties from the larger drill-bit cutting fragments were considered to be representative of in-situ conditions. 3 refs., 5 figs., 10 tabs.

Date: December 31, 1990

Creator: Whitfield, M.S.; Thordarson, W.; Hammermeister, D.P. & Warner, J.B.

Object Type: Report

System: The UNT Digital Library

(open access)

Inertial Confinement Fusion quarterly report, January-March 1998, volume 8, number 2

The coupling of laser light with plasmas is one of the key physics issues for the use of high-power lasers for inertial fusion, high-energy-density physics, and scientific stockpile stewardship. The coupling physics is extremely rich and challenging, particularly in the large plasmas to be accessed on the National Ignition Facility (NIF). The coupling mechanisms span the gamut from classical inverse bremsstrahlung absorption to a variety of nonlinear optical processes. These include stimulated Raman scattering (SRS) from electron plasma waves, stimulated Brillouin scattering (SBS) from ion sound waves, resonant decay into electron plasma and ion sound waves, and laser beam filamentation. These processes depend on laser intensity and produce effects such as changes in the efficiency and location of the energy deposition or generation of a component of very energetic electrons, which can preheat capsules. Coupling physics issues have an extremely high leverage. The coupling models are clearly very important ingredients for detailed calculations of laser-irradiated target behavior. Improved understanding and models enable a more efficient use of laser facilities, which becomes even more important as these facilities become larger and more expensive. Advances in the understanding also allow a more timely and cost-effective identification of new applications of high-power lasers, …

Date: March 31, 1998

Creator: Kruer, W

Object Type: Report

System: The UNT Digital Library

(open access)

A Compton camera for spectroscopic imaging from 100 keV to 1 MeV

A review of spectroscopic imaging issues, applications, and technology is presented. Compton cameras based on solid state semiconductor detectors stands out as the best system for the nondestructive assay of special nuclear materials. A camera for this application has been designed based on an efficient specific purpose Monte Carlo code developed for this project. Preliminary experiments have been performed which demonstrate the validity of the Compton camera concept and the accuracy of the code. Based on these results, a portable prototype system is in development. Proposed future work is addressed.

Date: December 31, 1998

Creator: Earnhart, J. R. D.

Object Type: Thesis or Dissertation

System: The UNT Digital Library

(open access)

The oncogenic action of ionizing radiation on rat skin. Final progress report, May 1, 1990--April 30, 1992

The multistage theory of carcinogenesis specifies that cells progress to cancer through a series of discrete, irreversible genetic alterations, but data on radiation-induced cancer incidence in rat skin suggests that an intermediate repairable alteration may occur. Data are presented on cancer induction in rat skin exposed to an electron beam (LET=0.34 keV/{mu}), a neon ion beam (LET=45) or an argon ion beam (LET=125). The rats were observed for tumors at least 78 weeks with squamous and basal cell carcinomas observed. The total cancer yield was fitted by the quadratic equation, and the equation parameters were estimated by linear regression for each type of radiation. Analysis of the DNA from the electron-induced carcinomas indicated that K-ras and/or c-myc oncogenes were activated. In situ hybridization indicated that the cancers contain subpopulations of cells with differing amounts of c-myc and H-ras amplification. The results are consistent with the idea that ionizing radiation produces stable, carcinogenically relevant lesions via 2 repairable events at low LET and via a non-repairable linked event pathway at high LET; either pathway may advance the cell by 1 stage. The proliferative response of rat epidermis following exposure to ionizing radiation was quantified by injection of {sup 14}C-thymidine. The return …

Date: December 31, 1992

Creator: Burns, F. J. & Garte, S. J.

Object Type: Report

System: The UNT Digital Library

(open access)

Inversion of Head Wave Traveltimes for Three-Dimensional Planar Structure

Inversion of head wave arrival times for three-dimensional (3D) planar structure is formulated as a constrained parameter optimization problem, and solved via linear programming techniques. The earth model is characterized by a set of homogeneous and isotropic layers bounded by plane, dipping interfaces. Each interface may possess arbitrary strike and dip. Predicted data consists of traveltimes of critically refracted waves formed on the plane interfaces of the model. The nonlinear inversion procedure is iterative; an initial estimate of the earth model is refined until an acceptable match is obtained between observed and predicted data. Inclusion of a priori constraint information, in the form of inequality relations satisfied by the model parameters, assists the algorithm in converging toward a realistic solution. Although the 3D earth model adopted for the inversion procedure is simple, the algorithm is quite useful in two particular contexts: (i) it can provide an initial model estimate suitable for subsequent improvement by more general techniques (i.e., traveltime tomography), and (ii) it is an effective analysis tool for investigating the power of areal recording geometries for detecting and resolving 3D dipping planar structure.

Date: March 31, 1999

Creator: Aldridge, D. F. & Oldenburg, D. W.

Object Type: Article

System: The UNT Digital Library

(open access)

Ultra-High Intensity Proton Accelerators and their Applications

The science and technology of proton accelerators have progressed considerably in the past three decades. Three to four orders of magnitude increase in both peak intensity and average flux have made it possible to construct high intensity proton accelerators for modern applications, such as: spallation neutron sources, kaon factory, accelerator production of tritium, energy amplifier and muon collider drivers. The accelerator design focus switched over from intensity for synchrotrons, to brightness for colliders to halos for spallation sources. An overview of this tremendous progress in both accelerator science and technology is presented, with special emphasis on the new challenges of accelerator physics issues such as: H(-) injection, halo formation and reduction of losses.

Date: December 31, 1997

Creator: Weng, W. T.

Object Type: Article

System: The UNT Digital Library

(open access)

The Clifton Record (Clifton, Tex.), Vol. 102, No. 88, Ed. 1 Friday, October 31, 1997

Semi-weekly newspaper from Clifton, Texas that includes local, state, and national news along with advertising.

Date: October 31, 1997

Creator: Smith, W. Leon

Object Type: Newspaper

System: The Portal to Texas History

(open access)

Hydrodynamic instability modeling for ICF

The intent of this paper is to review how instability growth is modeled in ICF targets, and to identify the principal issues. Most of the material has been published previously, but is not familiar to a wide audience. Hydrodynamic instabilities are a key issue in ICF. Along with laser-plasma instabilities, they determine the regime in which ignition is possible. At higher laser energies, the same issues determine the achievable gain. Quantitative predictions are therefore of the utmost importance to planning the ICF program, as well as to understanding current Nova results. The key fact that underlies all this work is the stabilization of short wavelengths.

Date: March 31, 1993

Creator: Haan, S. W.

Object Type: Article

System: The UNT Digital Library

(open access)

Performance and measurements of the AGS and Booster beams

Analyses of Hot Gas Stream Cleanup (HGSC) ashes and descriptions of filter performance were made to address the problems with filter operation that are apparently linked to the collected ash. This task is designed to generate data base of the key properties of ashes collected from operating advanced particle filters and to relate these ash properties to the operation and performance of these filters. Activities including initial formatting of the data base and entry, modification of the permeability model, and initial design of a high-temperature test device for measuring uncompacted bulk porosity of ash aggregates (indicator of relative cohesivity of the ash, filter cake porosity/permeability). Chemical analyses of hopper and filter cake ashes from Tidd showed that the consolidation degree could not be accounted for by condensation/adsorption from the flue gas; the mechanism is likely physical rearrangement of the ash particles.

Date: December 31, 1995

Creator: Weng, W. T.

Object Type: Article

System: The UNT Digital Library