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8,714 Matching Results
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1,2-HOIQO--A highly versatile 1,2-HOPO analog
A cyclic, bidentate hydroxamic acid binding unit based on an isoquinoline scaffold has been utilized for the synthesis of a hexadentate tripodal ligand based on the TREN backbone. This prototype for a new class of multidentate chelators forms mononuclear iron(III) complexes and one-dimensional coordination polymers with lanthanide(III) cations. The latter has been determined by single crystal X-ray analysis of the cerium species. The solid state structure in the monoclinic space group P2{sub 1}/c (C{sub 36}H{sub 34}CeN{sub 7}O{sub 11}, a = 12.341(2){angstrom}, b = 26.649(4){angstrom}, c = 10.621(2){angstrom}, {alpha} = {gamma} = 90{sup o}, {beta} = 96.753(3){sup o}, V = 3468.6(9) {angstrom}{sup 3}, Z = 4) exhibits a trigonal-dodecahedral environment around the cerium cation. The proof of concept for the versatility of the new scaffold has been shown by the modification of the crucial precursor 3-carboxyiso-coumarin through electrophilic aromatic substitutions to yield the corresponding chlorosulfonated and nitrated analogs.
Date:
August 7, 2006
Creator:
Seitz, Michael; Pluth, Michael D. & Raymond, Kenneth N.
System:
The UNT Digital Library
1-10 Mbar Laser-Driven Shocks Using the Janus Laser Facility
We report preliminary results using the Lawrence Livermore National Laboratory (LLNL) Janus laser facility to generate high pressure laser-driven shocks in the 1-10 Mbar regime. These experiments address various issues, including shock steadiness, planarity, uniformity and low target preheat, important for making precision EOS measurements on a small (E < 250 J) laser facility. A brief description of the experimental techniques, target design and measurements will be given.
Date:
August 10, 2001
Creator:
Dunn, J.; Price, D. F.; Moon, S. J.; Cauble, R. C.; Springer, P. T. & Ng, A.
System:
The UNT Digital Library
1-D Equilibrium Discrete Diffusion Monte Carlo
We present a new hybrid Monte Carlo method for 1-D equilibrium diffusion problems in which the radiation field coexists with matter in local thermodynamic equilibrium. This method, the Equilibrium Discrete Diffusion Monte Carlo (EqDDMC) method, combines Monte Carlo particles with spatially discrete diffusion solutions. We verify the EqDDMC method with computational results from three slab problems. The EqDDMC method represents an incremental step toward applying this hybrid methodology to non-equilibrium diffusion, where it could be simultaneously coupled to Monte Carlo transport.
Date:
August 2000
Creator:
Evans, T. M.; Urbatsch, T. J. & Lichtenstein, H.
System:
The UNT Digital Library
A 2-MeV microwave thermionic gun
A high-gradient, S-band microwave gun with a thermionic cathode is being developed in a collaborative effort by AET, Varian, and SSRL. A prototype design using an upgraded Varian dispenser cathode mounted with thermal isolation directly in the first half-cell of a 1-1/2 cell, side-coupled, standing-wave cavity has been fabricated and is being tested. Optimization of the cavity shape and beam formation was done using SUPERFISH, MASK, and PARMELA. An overview of design details, as well as the status of in-progress beam tests, will be presented. 9 refs., 6 figs.
Date:
August 1, 1989
Creator:
Tanabe, E.; Borland, M.; Green, M. C.; Miller, R. H.; Nelson, L. V.; Weaver, J. N. et al.
System:
The UNT Digital Library
N = 2 string amplitudes
In physics, solvable models have played very important roles. Understanding a simple model in detail teaches us a lot about more complicated models in generic situations. Five years ago, C. Vafa and I found that the closed N = 2 string theory, that is a string theory with the N = 2 local supersymmetry on the worldsheet, is classically equivalent to the self-dual Einstein gravity in four spacetime dimensions. Thus this string theory is solvable at the classical level. More recently, we have examined the N = 2 string partition function for spacial compactifications, and computed it to all order in the string perturbation expansion. The fact that such computation is possible at all suggests that the N = 2 string theory is solvable even quantum mechanically.
Date:
August 1, 1995
Creator:
Ooguri, H.
System:
The UNT Digital Library
2$sup 0$K vacuum pumping system for Baseball II
A vacuum pumping system that provides a cryo surface for condensing and freezing of H/sub 2/ gas is described. A closed-loop vacuum system was designed and built at Lawrence Livermore Laboratory to pump down the neutralizer LH/sub e/ dewar with a volurae of 350 l and the lambda point dewar with a LH/sub e/ volume of 250 l. Both of these dewars can be pumped down simultaneously or one at a time. 100% of the H/sub e/ gas is recovered free of contaminations. The vacuum pump can handle 340 SCFM of gas. The LH/sub e/ dewars are pumped down below the lambda point. This condition reduces the LH/sub e/ container wall temperature to 2.1 deg K giving a base pressure of 10/sup -13/ torr for H/sub 2/ gas/sup 2/. To attain a stable condition the LH /sub e/ baths are puuped down to 33 torr or lower to give a surface temperatare of about 2/sup 0/K/sup 3/. The Baseball II helium factlity is a close loop system. The H/sub e/ gas is recovered from all the LH/sub e/ usage point. This gas is accumulated in one of the two 8000 cu ft inflatable gas bags. The gas from the gas …
Date:
August 20, 1973
Creator:
Denhoy, B.S.
System:
The UNT Digital Library
A 3-D adaptive mesh refinement algorithm for multimaterial gas dynamics
Adaptive Mesh Refinement (AMR) in conjunction with high order upwind finite difference methods has been used effectively on a variety of problems. In this paper we discuss an implementation of an AMR finite difference method that solves the equations of gas dynamics with two material species in three dimensions. An equation for the evolution of volume fractions augments the gas dynamics system. The material interface is preserved and tracked from the volume fractions using a piecewise linear reconstruction technique. 14 refs., 4 figs.
Date:
August 12, 1991
Creator:
Puckett, E. G. & Saltzman, J. S.
System:
The UNT Digital Library
3-D Hydrodynamic Modeling in a Geospatial Framework
3-D hydrodynamic models are used by the Savannah River National Laboratory (SRNL) to simulate the transport of thermal and radionuclide discharges in coastal estuary systems. Development of such models requires accurate bathymetry, coastline, and boundary condition data in conjunction with the ability to rapidly discretize model domains and interpolate the required geospatial data onto the domain. To facilitate rapid and accurate hydrodynamic model development, SRNL has developed a pre- and post-processor application in a geospatial framework to automate the creation of models using existing data. This automated capability allows development of very detailed models to maximize exploitation of available surface water radionuclide sample data and thermal imagery.
Date:
August 24, 2006
Creator:
Bollinger, J.; Alfred Garrett, A.; Larry Koffman, L. & David Hayes, D
System:
The UNT Digital Library
3-D Mapping Technologies for High Level Waste Tanks
This research investigated four techniques that could be applicable for mapping of solids remaining in radioactive waste tanks at the Savannah River Site: stereo vision, LIDAR, flash LIDAR, and Structure from Motion (SfM). Stereo vision is the least appropriate technique for the solids mapping application. Although the equipment cost is low and repackaging would be fairly simple, the algorithms to create a 3D image from stereo vision would require significant further development and may not even be applicable since stereo vision works by finding disparity in feature point locations from the images taken by the cameras. When minimal variation in visual texture exists for an area of interest, it becomes difficult for the software to detect correspondences for that object. SfM appears to be appropriate for solids mapping in waste tanks. However, equipment development would be required for positioning and movement of the camera in the tank space to enable capturing a sequence of images of the scene. Since SfM requires the identification of distinctive features and associates those features to their corresponding instantiations in the other image frames, mockup testing would be required to determine the applicability of SfM technology for mapping of waste in tanks. There may be …
Date:
August 31, 2010
Creator:
Marzolf, A. & Folsom, M.
System:
The UNT Digital Library
A 3-dimensional theory of free electron lasers
In this paper, we present an analytical three-dimensional theory of free electron lasers. Under several assumptions, we arrive at an integral equation similar to earlier work carried out by Ching, Kim and Xie, but using a formulation better suited for the initial value problem of Coherent Electron Cooling. We use this model in later papers to obtain analytical results for gain guiding, as well as to develop a complete model of Coherent Electron Cooling.
Date:
August 23, 2010
Creator:
Webb, S. D.; Wang, G. & Litvinenko, V. N.
System:
The UNT Digital Library
N >= 4 Supergravity Amplitudes from Gauge Theory at One Loop
We expose simple and practical relations between the integrated four- and five-point one-loop amplitudes of N {ge} 4 supergravity and the corresponding (super-)Yang-Mills amplitudes. The link between the amplitudes is simply understood using the recently uncovered duality between color and kinematics that leads to a double-copy structure for gravity. These examples provide additional direct confirmations of the duality and double-copy properties at loop level for a sample of different theories.
Date:
August 19, 2011
Creator:
Bern, Z.; Boucher-Veronneau, C. & Johansson, H.
System:
The UNT Digital Library
6. 4 tesla dipole magnet for the SSC. Revision
A design is presented for a dipole magnet suitable for the proposed SSC facility. Test results are given for model magnets of this design 1 m long and 4.5 m long. Flattened wedge-shaped cables (''keystoned'') are used in a graded, two-layer ''cos theta'' configuration with three wedges to provide sufficient field uniformity and mechanical rigidity. Stainless steel collars 15 mm in radial depth, fastened with rectangular keys, provide structural support, and there is a ''cold'' iron flux return. The outer-layer cable has 30 strands of 0.648 mm diameter NbTi multifilamentary wire with Cu/S.C. = 1.8, and the inner has 23 strands of 0.808 mm diameter wire with Cu/S.C. = 1.3. Performance data are given, including training behavior, winding stresses, collar deformation, and field uniformity. 10 refs., 11 figs.
Date:
August 1, 1985
Creator:
Taylor, C.E.; Caspi, S.; Gilbert, W.; Hassenzahl, W.; Meuser, R.; Mirk, K. et al.
System:
The UNT Digital Library
A 6.7 MeV cw RFQ linac
A 6.7-MeV 350 MHz, cw Radio Frequency Quadrupole proton linac has been designed and is being fabricated for the Accelerator Production of Tritium Project at Los Alamos. This eight-meter long structure consists of four resonantly-coupled segments and is being fabricated using hydrogen furnace brazing as a joining technology. Details of the design and status of fabrication are reported.
Date:
August 1, 1997
Creator:
Schrage, D.; Young, L.; Clark, W.; Davis, T.; Martinez, F.; Naranjo, A. et al.
System:
The UNT Digital Library
The 10,000-year debate
Probabilistic Risk Assessment (PRA) has developed into a respected tool within the reactor community. Now, this PRA technique is being applied to a new arena, the distant future of the nuclear waste repository. Problems are already testing the credibility of PRA.
Date:
August 1996
Creator:
Wilson, J. R.
System:
The UNT Digital Library
A 10 kHz Short-Stroke Rotary Fast Tool Servo
None
Date:
August 30, 2004
Creator:
Montesanti, R C & Trumper, D L
System:
The UNT Digital Library
10{times} reduction imaging at 13.4nm
A Schwarzschild imaging system has been designed to achieve 0.1 {mu}m resolution in a 0.4 mm diameter field of view when operated at a center wavelength of 13.4 nm. A decentered aperture is located on the convex primary resulting in an unobstructed numerical aperture of 0.08 and a corresponding depth of field of {plus_minus} 1 {mu}m. The Schwarzschild imaging objective is part of a five-reflection system containing the laser plasma source (LPS), condensing optics, turning mirror and reflection mask as shown in Figure 1. Extreme ultraviolet (EUV) radiation is generated by impinging a laser beam onto a copper target. The plasma source is driven by a Lambda Physik PLX 250 KrF excimer laser emitting 0.6 Joule, 20 ns pulses at a 200 Hz maximum repetition rate. Measurements of the source indicate that the full-width-half-maximum diameter is less than 100 {mu}m.
Date:
August 1, 1994
Creator:
Tichenor, D. A.; Kubiak, G. D. & Malinowski, M. E.
System:
The UNT Digital Library
11.424 Ghz Stripline Transversal Filter for Sub-Picosecond Bunch Timing Measurements
Measurement of time-of-arrival or instantaneous longitudinal position is a fundamental beam diagnostic. We present results from a stripline transversal periodic coupler structure which forms the heart of a sub-ps beam timing detector. This filter structure approximates a sinx/x response in the frequency domain which corresponds to a limited pulse length response in the time domain. These techniques have been used extensively in beam feedback systems at 3 GHz center frequencies with operational single-shot resolutions of 200 fs [1]. We present a new design, based on a 11.424 GHz center frequency, which is intended to offer a factor of four improvement in time resolution. Two-dimensional electromagnetic simulation results are shown, and the design optimization approach leading to the final circuit implementation is illustrated. The prototype circuit has been fabricated on 64mil Rogers 4003 and lab frequency domain and time domain data are compared to the 2-D simulation results. Performance of the prototype circuit is shown with applicability to sub-ps beam measurements in LINAC and FEL applications.
Date:
August 26, 2010
Creator:
Van Winkle, D.; Young, A. & Fox, J. D.
System:
The UNT Digital Library
14-MeV Neutron Generator Used as a Thermal Neutron Source
One of the most important applications of the general purpose Monte Carlo N-Particle (MCNPS and MCNPX) codes is neutron shielding design. We employed this method to simulate the shield of a 14-MeV neutron generator used as a thermal neutron source providing an external thermal neutron beam for testing large area neutron detectors developed for diffraction studies in biology and also useful for national security applications. Nuclear reactors have been the main sources of neutrons used for scientific applications. In the past decade, however, a large number of reactors have been shut down, and the importance of other, smaller devices capable of providing neutrons for research has increased. At Brookhaven National Laboratory a moderated Am-Be neutron source with shielding is used for neutron detector testing. This source is relatively weak, but provides a constant flux of neutrons, even when not in use. The use of a 14 MeV energized neutron generator, with an order of magnitude higher neutron flux has been considered to replace the Am-Be source, but the higher fast neutron yield requires a more careful design of moderator and shielding. In the present paper we describe a proposed shielding configuration based on Monte Carlo calculations, and provide calculated neutron …
Date:
August 10, 2008
Creator:
Dioszegi, I.
System:
The UNT Digital Library
15 KJ FLASH LAMP, POWER CONDITIONING UNIT DESIGNED FOR SAFTY, RELIABILITY & MANUFACTURABILITY*
A 15kJoule, Flash Lamp Power Conditioning Unit has been successfully designed, developed, and deployed in the National Ignition Facility (NIF) Preamplifier Modules (PAM). The primary design philosophy of this power conditioning unit (PCU) is safety, reliability, and manufacturability. Cost reduction over commercially equivalent systems was also achieved through an easily manufactured packaging design optimized to meet NIF requirements. While still maintaining low cost, the PCU design includes a robust control system, fault diagnostic system, and safety features. The pulsed power design includes 6 PFN modules, each including a dual series injection trigger transformer, that drive a total of 12 flash lamp loads. The lamps are individually triggered via a 20kV pulse produced by a 1kV, MCT switched capacitive discharge unit on the primary side of the trigger transformer. The remote control interface includes an embedded controller that captures flash lamp current wave forms and fault status for each shot. The embedded controller provides the flexibility of remotely adjusting both the main drive voltage from 1.6 to 2.5 kV and the trigger voltage from 0 to 20 kV.
Date:
August 7, 2007
Creator:
James, G.; Merritt, B.; Dreifuerst, G.; Strickland, S. & Tse, E.
System:
The UNT Digital Library
N-15 SIGNALS OF NITROGEN SOURCE AND FATE IN A SEMI-ARID WETLANDS
None
Date:
August 1, 2001
Creator:
Heikoop, J. M. & Hickmott, D. D.
System:
The UNT Digital Library
O(18) revived
We present an O(18) theory which is pertubatively unifiable and which accounts for the absence of right-handed families in the low-energy world. The model gives rise to dramatic predictions for proton decay and for the Z/sup 0/ width.
Date:
August 1, 1984
Creator:
Bagger, J.; Dimopoulos, S. & Masso, E.
System:
The UNT Digital Library
20-100 keV K(alpha) X-Ray Source Generation by Short Pulse High Intensity Lasers
We are studying the feasibility of utilizing K{alpha} x-ray sources in the range of 20 to 100 keV as a backlighters for imaging various stages of implosions and high areal density planar samples driven by the NIF laser facility. The hard x-ray K{alpha} sources are created by relativistic electron plasma interactions in the target material after a radiation by short pulse high intensity lasers. In order to understand K{alpha} source characteristics such as production efficiency and brightness as a function of laser parameters, we have performed experiments using the 10 J, 100 fs JanUSP laser. We utilized single-photon counting spectroscopy and x-ray imaging diagnostics to characterize the K{alpha} source. We find that the K{alpha} conversion efficiency from the laser energy is {approx} 3 x 10{sup -4}.
Date:
August 22, 2003
Creator:
Park, H. S.; Koch, J. A.; Landen, O. L.; Phillips, T. W. & Goldsack, T.
System:
The UNT Digital Library
A 20 ampere shunt regulator for controlling individual magnets in a seriesed string
At the CEBAF accelerator, groups of dipole magnets are often connected together in series and powered from a single large constant-current regulated D-C supply, referred to locally as a {open_quotes}box{close_quotes} supply. Besides the economy realized, this configuration promotes correct field tracking of all elements of a beam transport channel. However, it is often desirable to vary the current in one element of a string independently of the others, particularly at the entrance and exits of transport channels. A 20 ampere programmable current shunt is described. Installed in parallel with the desired magnet, it permits shunting (bypassing) up to 5% of the string current around that magnet. The shunt regulator consists of a bank of MOSFET power transistors operated in linear mode. Regulation of current through the passbank is obtained by feedback from a manganin shunt maintained at a constant temperature for stability. The module is designed for remote operation and provides readbacks of various parameters useful for maintenance. To achieve complete electrical isolation, an onboard microprocessor provides remote communications via an opto-isolated serial data link. Constructional details and initial operating experience with the plug-in shunt are described.
Date:
August 1, 1996
Creator:
Martin, E. J.; Dobeck, N.; Jones, G. S. & O`Sullivan, M. K.
System:
The UNT Digital Library
20 TeV collider lattices with low-. beta. insertions
A lattice containing insertions designed for collisions of 20 TeV proton beams at crossing points having beta values of two meters or less is presented. The machine would use high-field double bore superconducting magnets, with opposite focusing action on the two beams passing through each quadrupole. Hence the focusing pattern in the insertions is antisymmetric about the crossings. The beams, separated by 16 cms in the arcs are made colinear by dipoles common to both beams and then focused to the low-..beta.. collision points by quadrupole triplets. A similar machine design for pp collisions is also included.
Date:
August 1, 1983
Creator:
Garren, A.A.
System:
The UNT Digital Library