Optical components for the Nova laser (open access)

Optical components for the Nova laser

In addition to its other characteristics, the Nova Laser Fusion facility may well be the largest precision optical project ever undertaken. Moreover, during the course of construction, concurrent research and development has been successfully conducted, and has resulted in significant advances in various technical areas, including manufacturing efficiency. Although assembly of the first two beams of Nova is just commencing, the optical production, including construction of the special facilities required for many of the components, has been underway for over three years, and many phases of the optical manufacturing program for the first 10 beams will be completed within the next two years. On the other hand, new requirements for second and third harmonic generation have created the need to initiate new research and development. This work has been accomplished through the enormous cooperation DOE/LLNL has received from commercial industry on this project. In many cases, industry, where much of the optical component research and development and virtually all of the manufacturing is being done, has made substantial investment of its own funds in facilities, equipment, and research and development, in addition to those supplied by DOE/LLNL.
Date: May 17, 1982
Creator: Wallerstein, E.P.; Baker, P.C. & Brown, N.J.
System: The UNT Digital Library
Mixed waste treatment with a mediated electrochemical process (open access)

Mixed waste treatment with a mediated electrochemical process

The process described in this paper is intended to convert mixed waste containing toxic organic compounds (not heavy metals) to ordinary radioactive waste, which is treatable. The process achieves its goal by oxidizing hydrocarbons to CO{sub 2} and H{sub 2}O. Other atoms that may be present in the toxic organic generally are converted to nonhazardous anions such as sulfate and phosphate. This electro chemical conversion is performed at conditions of temperature and pressure that are just moderately above ambient conditions. Gaseous hydroxides and oxyhydroxides that are formed by many radionuclides during incineration cannot form in this process. 1 ref., 3 figs.
Date: May 17, 1991
Creator: Hickman, R. G.; Gray, L. W. & Chiba, Z.
System: The UNT Digital Library
Statistical characterization of dislocation ensembles (open access)

Statistical characterization of dislocation ensembles

We outline a method to study the spatial and orientation statistics of dynamical dislocation systems by modeling the dislocations as a stochastic fiber process. Statistical measures have been introduced for the density, velocity, and flux of dislocations, and the connection between these measures and the dislocation state and plastic distortion rate in the crystal is explained. A dislocation dynamics simulation model has been used to extract numerical data to study the evolution of these statistical measures numerically in a body-centered cubic crystal under deformation. The orientation distribution of the dislocation density, velocity and dislocation flux, as well as the dislocation correlations have been computed. The importance of the statistical measures introduced here in building continuum models of dislocation systems is highlighted.
Date: May 17, 2006
Creator: El-Azab, A.; Deng, J. & Tang, M.
System: The UNT Digital Library
Estimating large-scale fracture permeability of unsaturatedrockusing barometric pressure data (open access)

Estimating large-scale fracture permeability of unsaturatedrockusing barometric pressure data

We present a three-dimensional modeling study of gas flow inthe unsaturated fractured rock of Yucca Mountain. Our objective is toestimate large-scale fracture permeability, using the changes insubsurface pneumatic pressure in response to barometric pressure changesat the land surface. We incorporate the field-measured pneumatic datainto a multiphase flow model for describing the coupled processes ofliquid and gas flow under ambient geothermal conditions. Comparison offield-measured pneumatic data with model-predicted gas pressures is foundto be a powerful technique for estimating the fracture permeability ofthe unsaturated fractured rock, which is otherwise extremely difficult todetermine on the large scales of interest. In addition, this studydemonstrates that the multi-dimensional-flow effect on estimatedpermeability values is significant and should be included whendetermining fracture permeability in heterogeneous fracturedmedia.
Date: May 17, 2005
Creator: Wu, Yu-Shu; Zhang, Keni & Liu, Hui-Hai
System: The UNT Digital Library
Enchanced hohlraum radiation drive through reduction of wall losses with high-Z mixture "cocktail" wall materials (open access)

Enchanced hohlraum radiation drive through reduction of wall losses with high-Z mixture "cocktail" wall materials

We present results from experiments, numerical simulations and analytic modeling, demonstrating enhanced hohlraum performance. Care in the fabrication and handling of hohlraums with walls consisting of high-Z mixtures (cocktails) has led to our demonstration, for the first time, of a significant increase in radiation temperature (up to +7eV at 300 eV) compared to a pure Au hohlraum, in agreement with predictions and ascribable to reduced wall losses. The data extrapolated to full NIF suggest we can expect an 18% reduction in wall loss for the current ignition design by switching to cocktail hohlraums, consistent with requirements for ignition with 1MJ laser energy.
Date: May 17, 2006
Creator: Schein, J; Jones, O; Rosen, M; Dewald, E; Glenzer, S; Gunther, J et al.
System: The UNT Digital Library
Investigation of Microwave Instability on Electron Storage Ring TLS (open access)

Investigation of Microwave Instability on Electron Storage Ring TLS

With the planned installation of a superconducting rf system, the new operation mode of TLS, the electron storage ring at NSRRC, is expected to double the beam intensity. Several accelerator physics topics need to be examined. Beam instability of single-bunch longitudinal microwave instability is one of these topics. We consider two approaches to measure the effective broad band impedance. We compare these measurement results with each other and to old data [Ref.1]. We calculate the threshold current of microwave instability with a mode-mixing analysis code written by Dr. K. Oide of KEK [Ref.2]. We also develop a multi-particle tracking code to simulate the instability. The results of simulation and measurement are compared and discussed. We conclude that doubling of beam current from 200 mA (1.5 mA/bunch) to 400 mA (3 mA/bunch) will not trigger the microwave instability even without a Landau cavity to lengthen the bunch. The benefit of Landau cavity is mainly for beam life time.
Date: May 17, 2005
Creator: Wang, M.-H. & Chao, A.
System: The UNT Digital Library
Experiments to study the feasibility of making an x-ray laser at the Novette laser facility (open access)

Experiments to study the feasibility of making an x-ray laser at the Novette laser facility

We will discuss a set of experiments which are designed to study approaches to and search for the existence of amplified spontaneous emission at photon energies of 42.3, 53.6, 119.0, and 153.0 eV. The schemes utilize pumping from the Novette laser operated with cylindrical optics at 5 TW/beam and 100 psec.
Date: May 17, 1983
Creator: Matthews, D.L.; Hagelstein, P. & Kauffman, R.
System: The UNT Digital Library
Compact Torus Compression of Microwaves (open access)

Compact Torus Compression of Microwaves

The possibility that a compact torus (CT) might be accelerated to large velocities has been suggested by Hartman and Hammer. If this is feasible one application of these moving CTs might be to compress microwaves. The proposed mechanism is that a coaxial vacuum region in front of a CT is prefilled with a number of normal electromagnetic modes on which the CT impinges. A crucial assumption of this proposal is that the CT excludes the microwaves and therefore compresses them. Should the microwaves penetrate the CT, compression efficiency is diminished and significant CT heating results. MFE applications in the same parameters regime have found electromagnetic radiation capable of penetrating, heating, and driving currents. We report here a cursory investigation of rf penetration using a 1-D version of a direct implicit PIC code.
Date: May 17, 1985
Creator: Hewett, D. W. & Langdon, A. B.
System: The UNT Digital Library
Top quark and SUSY (supersymmetric) searches at CDF (open access)

Top quark and SUSY (supersymmetric) searches at CDF

Searches for the top quark in p{bar p} collisions at {radical}s = 1.8 TeV are described. The analyses are based on data with an integrated luminosity of 4.4 pb{sup {minus}1} recorded with the Collider Detector at Fermilab in the 1988--1989 run. An upper limit on the t{bar t} cross section is obtained. The top quark with mass below 89 GeV/c{sup 2} is excluded at the 95% CL. Prospects for searches for the top quark in the future are presented. We also briefly present results on searches for supersymmetric particles. 14 refs., 10 figs.
Date: May 17, 1990
Creator: Yeh, G.P.
System: The UNT Digital Library
System modeling for the longitudinal beam dynamics control problem in heavy ion induction accelerators (open access)

System modeling for the longitudinal beam dynamics control problem in heavy ion induction accelerators

We address the problem of developing system models that are suitable for studying the control of the longitudinal beam dynamics in induction accelerators for heavy ions. In particular, we present the preliminary results of our efforts to devise a general framework for building detailed, integrated models of accelerator systems consisting of pulsed power modular circuits, induction cells, beam dynamics, and control system elements. Such a framework will permit us to analyze and design the pulsed power modulators and the control systems required to effect precise control over the longitudinal beam dynamics.
Date: May 17, 1993
Creator: Payne, A. N.
System: The UNT Digital Library
Wet-Etch Figuring: Optical Surfacing by Controlled Application of Etchant Solution Using the marangoni Effect (open access)

Wet-Etch Figuring: Optical Surfacing by Controlled Application of Etchant Solution Using the marangoni Effect

Wet-etch figuring (WEF), a computer-controlled method for generating arbitrarily shaped optical surfaces using wet chemical etching, has been developed. This method uses applicator geometry and surface tension gradients (the Marangoni Effect) to define and confine the footprint of a wetted etchant zone on the surface. Capillary forces attach the flowing etchant solution to the underside of the optic being figured. No mechanical or thermal stresses or residues are applied to the optic by this process. This enables interferometric measurement of the glass thickness while surfacing, which then controls the placement and dwell time of the wetted zone. The result is a truly deterministic, closed-loop figuring process with a high degree of optical precision. This process can figure sub-millimeter thickness, large-aperture plates or sheets that are very difficult to finish by conventional methods. Automated linear and circular spot etching tools were used to demonstrate surfacing on 380 micron-thick glass sheets, to Strehl better than 0.8, as specified by data array or Zernike polynomials.
Date: May 17, 2001
Creator: Rushford, M. C.; Britten, J. A.; Hoaglan, C. R.; Thomas, I. M.; Summers, L. J. & Dixit, S. D.
System: The UNT Digital Library
Comment on ''Sensitivity Analysis and Determination of Streambed Leakance and Aquifer Hydraulic Properties'' by Xunhong Chen and Xi Chen, Journal of Hydrology, 2003, v.284, 270-284 (open access)

Comment on ''Sensitivity Analysis and Determination of Streambed Leakance and Aquifer Hydraulic Properties'' by Xunhong Chen and Xi Chen, Journal of Hydrology, 2003, v.284, 270-284

Recently, studies of the Platte River watershed have gained significant attention from federal and Nebraska, USA, state agencies due to the importance of groundwater/surface-water interactions under drought conditions. Using archive data from a 1983 pumping test, Chen and Chen (2003) interpret the hydraulic properties of the alluvium and a streambed of the Platte River near Kearney, Nebraska, and compare their data with results of other studies performed over the past several years. Three important inconsistencies of this article will be highlighted here: (1) misuse of the analytical model of Hunt (1999), (2) departure of their results from previously published data, and (3) unsatisfactory explanation of these anomalous results.
Date: May 17, 2004
Creator: Kollet, S
System: The UNT Digital Library
Molecular Dynamics Simulations of Coulomb Explosion (open access)

Molecular Dynamics Simulations of Coulomb Explosion

A swift ion creates a track of electronic excitations in the target material. A net repulsion inside the track can cause a ''Coulomb Explosion'', which can lead to damage and sputtering of the material. Here we report results from molecular-dynamics (MD) simulations of Coulomb explosion for a cylindrical track as a function of charge density and neutralization/quenching time, {tau}. Screening by the free electrons is accounted for using a screened Coulomb potential for the interaction among charges. The yield exhibits a prompt component from the track core and a component, which dominates at higher excitation density, from the heated region produced. For the cases studied, the number of atoms ejected per incident ion, i.e. the sputtering yield Y, is quadratic with charge density along the track as suggested by simple models. Y({tau} = 0.2 Debye periods) is nearly 20% of the yield when there is no neutralization ({tau} {yields} {infinity}). The connections between ''Coulomb explosions'', thermal spikes and measurements of electronic sputtering are discussed.
Date: May 17, 2002
Creator: Bringa, E M
System: The UNT Digital Library
Parameters of a field-reversed mirror reactor (open access)

Parameters of a field-reversed mirror reactor

Computations have been made of the parameters of a neutral-beam driven, field-reversed mirror reactor as a function of beam injection energy. Q values of 4 to 5 and a fusion power of 10 to 50 MW per cell are found at beam energies of 200 to 500 keV. Cost estimates indicate a direct capital cost of less than $1000/kW/sub e/ for multicell versions of the reactor.
Date: May 17, 1977
Creator: Devoto, R. S.; Carlson, G. A.; Condit, W. C. & Hanson, J. D.
System: The UNT Digital Library
Cantilever-Based Force Spectroscopy for Chemical and Biological Detection (open access)

Cantilever-Based Force Spectroscopy for Chemical and Biological Detection

None
Date: May 17, 2004
Creator: Sulchek, Todd; Noy, Alex; Ratto, Tim; Langry, Kevin; Colvin, Michael & Denardo, Sally
System: The UNT Digital Library
A Compact Ring Design with Tunable Momentum Compaction (open access)

A Compact Ring Design with Tunable Momentum Compaction

A storage ring with tunable momentum compaction has the advantage in achieving different RMS bunch length with similar RF capacity, which is potentially useful for many applications, such as linear collider damping ring and predamping ring where injected beam has a large energy spread and a large transverse emittance. A tunable bunch length also makes the commissioning and fine tuning easier in manipulating the single bunch instabilities. In this paper, a compact ring design based on a supercell is presented, which achieves a tunable momentum compaction while maintaining a large dynamic aperture.
Date: May 17, 2012
Creator: Sun, Y.
System: The UNT Digital Library
Tailoring properties of carbon-nanotube-based foams by ion bombardment (open access)

Tailoring properties of carbon-nanotube-based foams by ion bombardment

None
Date: May 17, 2012
Creator: Charnvanichborikarn, S.; Shin, S. J.; Worsley, M. A. & Kucheyev, S. O.
System: The UNT Digital Library
Search for Lepton-Number Violating Processes in B+ to h- l+ l+ Decays (open access)

Search for Lepton-Number Violating Processes in B+ to h- l+ l+ Decays

We have searched for the lepton-number violating processes B{sup +} {yields} h{sup -}{ell}{sup +}{ell}{sup +} with h{sup -} = K{sup -}/{pi}{sup -} and {ell}{sup +} = e{sup +}/{mu}{sup +}, using a sample of 471 {+-} 3 million B{bar B} events collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider at the SLAC National Accelerator Laboratory. We find no evidence for these decays and place 90% confidence level upper limits on their branching fractions B (B{sup +} {yields} {pi}{sup -}e{sup +}e{sup +}) < 2.3 x 10{sup -8}, {Beta}(B{sup +} {yields} K{sup -}e{sup +}e{sup +}) < 3.0 x 10{sup -8}, {Beta}(B{sup +} {yields} {pi}{sup -}{mu}{sup +}{mu}{sup +}) < 10.7 x 10{sup -8}, and {Beta}(B{sup +} {yields} K{sup -}{mu}{sup +}{mu}{sup +}) < 6.7 x 10{sup -8}.
Date: May 17, 2012
Creator: Lees, J.P.
System: The UNT Digital Library
Laser fusion overview. [Forecasting of laser fusion feasibility] (open access)

Laser fusion overview. [Forecasting of laser fusion feasibility]

Because of recent breakthroughs in the target area, and in the glass laser area, the scientific feasibility of laser fusion--and of inertial fusion--may be demonstrated in the early 1980's. Then the development in that time period of a suitable laser (or storage ring or other driving source) would make possible an operational inertial fusion reactor in this century. These are roughly the same time scales as projected by the Tokamak magnetic confinement approach. It thus appears that the 15-20 year earlier start by magnetic confinement fusion may be overcome. Because inertial confinement has been demonstrated, and inertial fusion reactors may operate on smaller scales than Tokamaks, laser fusion may have important technical and economic advantages.
Date: May 17, 1976
Creator: Nuckolls, J.
System: The UNT Digital Library
500 MHz modulation system for the 6 MeV, 700 A Astron Accelerator (open access)

500 MHz modulation system for the 6 MeV, 700 A Astron Accelerator

An rf system is described for the 500-MHz cylindrical resonator that is coupled to the Astron beam to modulate its energy by +- 1.5 percent.
Date: May 17, 1976
Creator: Reginato, L. L. & Smith, B. H.
System: The UNT Digital Library
Distinguishing Pu Metal from Pu Oxide Using Fast Neutron Counting (open access)

Distinguishing Pu Metal from Pu Oxide Using Fast Neutron Counting

None
Date: May 17, 2013
Creator: Verbeke, J M; Chapline, G C; Nakae, L F & Sheets, S A
System: The UNT Digital Library
Formal Specification of the OpenMP Memory Model (open access)

Formal Specification of the OpenMP Memory Model

OpenMP [1] is an important API for shared memory programming, combining shared memory's potential for performance with a simple programming interface. Unfortunately, OpenMP lacks a critical tool for demonstrating whether programs are correct: a formal memory model. Instead, the current official definition of the OpenMP memory model (the OpenMP 2.5 specification [1]) is in terms of informal prose. As a result, it is impossible to verify OpenMP applications formally since the prose does not provide a formal consistency model that precisely describes how reads and writes on different threads interact. This paper focuses on the formal verification of OpenMP programs through a proposed formal memory model that is derived from the existing prose model [1]. Our formalization provides a two-step process to verify whether an observed OpenMP execution is conformant. In addition to this formalization, our contributions include a discussion of ambiguities in the current prose-based memory model description. Although our formal model may not capture the current informal memory model perfectly, in part due to these ambiguities, our model reflects our understanding of the informal model's intent. We conclude with several examples that may indicate areas of the OpenMP memory model that need further refinement however it is specified. …
Date: May 17, 2006
Creator: Bronevetsky, G & de Supinski, B R
System: The UNT Digital Library
Fast Neutron Damage Studies on NdFeB Materials (open access)

Fast Neutron Damage Studies on NdFeB Materials

Many materials and electronics need to be tested for the radiation environment expected at linear colliders (LC) since both accelerator and detectors will be subjected to large fluences of hadrons, leptons and {gamma}'s over the life of the facility [1]. While the linacs will be superconducting, there are still many uses for NdFeB in the damping rings, injection and extraction lines and final focus. Our understanding of the situation for rare earth, permanent magnet materials was presented at PAC03 [2]. Our first measurements of fast neutron, stepped doses at the UC Davis McClellan Nuclear Reactor Center (UCD MNRC) were presented at EPAC04 [3]. We have extended the doses, included other manufacturer's samples, and measured induced radioactivities which are discussed in detail.
Date: May 17, 2005
Creator: Anderson, S.; Spencer, J.; Wolf, Z.; /SLAC; Baldwin, A.; Pellett, D. et al.
System: The UNT Digital Library
Zero Energy Windows (open access)

Zero Energy Windows

Windows in the U.S. consume 30 percent of building heating and cooling energy, representing an annual impact of 4.1 quadrillion BTU (quads) of primary energy. Windows have an even larger impact on peak energy demand and on occupant comfort. An additional 1 quad of lighting energy could be saved if buildings employed effective daylighting strategies. The ENERGY STAR{reg_sign} program has made standard windows significantly more efficient. However, even if all windows in the stock were replaced with today's efficient products, window energy consumption would still be approximately 2 quads. However, windows can be ''net energy gainers'' or ''zero-energy'' products. Highly insulating products in heating applications can admit more useful solar gain than the conductive energy lost through them. Dynamic glazings can modulate solar gains to minimize cooling energy needs and, in commercial buildings, allow daylighting to offset lighting requirements. The needed solutions vary with building type and climate. Developing this next generation of zero-energy windows will provide products for both existing buildings undergoing window replacements and products which are expected to be contributors to zero-energy buildings. This paper defines the requirements for zero-energy windows. The technical potentials in terms of national energy savings and the research and development (R&D) status …
Date: May 17, 2006
Creator: Arasteh, Dariush; Selkowitz, Steve; Apte, Josh & LaFrance, Marc
System: The UNT Digital Library