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Parallel sphere rendering

Description: Sphere rendering is an important method for visualizing molecular dynamics data. This paper presents a parallel algorithm that is almost 90 times faster than current graphics workstations. To render extremely large data sets and large images, the algorithm uses the MIMD features of the supercomputers to divide up the data, render independent partial images, and then finally composite the multiple partial images using an optimal method. The algorithm and performance results are presented for the CM-5 and the M.
Date: October 1, 1996
Creator: Krogh, M.; Painter, J. & Hansen, C.
Partner: UNT Libraries Government Documents Department

Parallel rendering techniques for massively parallel visualization

Description: As the resolution of simulation models increases, scientific visualization algorithms which take advantage of the large memory. and parallelism of Massively Parallel Processors (MPPs) are becoming increasingly important. For large applications rendering on the MPP tends to be preferable to rendering on a graphics workstation due to the MPP`s abundant resources: memory, disk, and numerous processors. The challenge becomes developing algorithms that can exploit these resources while minimizing overhead, typically communication costs. This paper will describe recent efforts in parallel rendering for polygonal primitives as well as parallel volumetric techniques. This paper presents rendering algorithms, developed for massively parallel processors (MPPs), for polygonal, spheres, and volumetric data. The polygon algorithm uses a data parallel approach whereas the sphere and volume render use a MIMD approach. Implementations for these algorithms are presented for the Thinking Ma.chines Corporation CM-5 MPP.
Date: July 1, 1995
Creator: Hansen, C.; Krogh, M. & Painter, J.
Partner: UNT Libraries Government Documents Department

Multilayer ultra high gradient insulator technology

Description: We are investigating a novel insulator concept which involves the use of alternating layers of conductors and insulators with periods less than 1 mm. These structures perform many times better (about 1.5 to 4 times higher breakdown electric field) than conventional insulators in long pulse, short pulse, and alternating polarity applications. We present our ongoing studies investigating the degradation of the breakdown electric field resulting from surface roughness, the effect of gas pressure, and the performance of the insulator structure under bi-polar stress. Further, we present our initial modeling studies.
Date: March 27, 1998
Creator: Sampayan, S.E.; Vitello, P.A.; Krogh, M.L. & Elizondo, J.M.
Partner: UNT Libraries Government Documents Department

Characteristics of high gradient insulators for accelerator and high power flow applications

Description: The high gradient insulator has been demonstrated to operate at levels comparable or better than special geometry or coated insulators. Some patented insulator configurations allow for sophisticated accelerator structures, high power flow interfaces, and microwave applications not previously possible. Sophisticated manufacturing techniques available at AlliedSignal FM and T made this development possible. Bipolar and high power flow applications are specially suited for present insulator designs. The insulator shows a beneficial effect when used under RF fields or RF structures. These insulators can be designed, to a first approximation, from simple electron flight path equations. With a recently developed model of surface flashover physics the authors completed a set of design calculations that include effects such as layer density and dielectric/metal thickness. Experimental data, obtained in the last few years of development, is presented and reviewed. Several insulator fabrication characteristics, indicating critical design parameters, are also presented.
Date: July 1, 1997
Creator: Elizondo, J.M.; Krogh, M.L. & Smith, D.
Partner: UNT Libraries Government Documents Department

The ACL Message Passing Library

Description: This paper presents the ACL (Advanced Computing Lab) Message Passing Library. It is a high throughput, low latency communications library, based on Thinking Machines Corp.`s CMMD, upon which message passing applications can be built. The library has been implemented on the Cray T3D, Thinking Machines CM-5, SGI workstations, and on top of PVM.
Date: September 1, 1995
Creator: Painter, J.; McCormick, P.; Krogh, M.; Hansen, C. & Colin de Verdiere, G.
Partner: UNT Libraries Government Documents Department

ACLMPL: Portable and efficient message passing for MPPs

Description: This paper presents the Advanced Computing Lab Message Passing Library (ACLMPL). Modeled after Thinking Machines Corporation`s CMMD, ACLMPL is a high throughout, low latency communications library for building message passing applications. The library has been implemented on the Cray T3D, Thinking Machines CM-5, SGI workstations, and on top of PVM. On the Cray T3D, benchmarks show ACLMPL to be 4 to 7 times faster than MPI or PVM.
Date: September 19, 1995
Creator: Painter, J.; Krogh, M.; Hansen, C.; McCormick, P. & de Verdiere, G.C.
Partner: UNT Libraries Government Documents Department

Parallel sphere rendering

Description: Sphere rendering is an important method for visualizing molecular dynamics data. This paper presents a parallel divide-and-conquer algorithm that is almost 90 times faster than current graphics workstations. To render extremely large data sets and large images, the algorithm uses the MIMD features of the supercomputers to divide up the data, render independent partial images, and then finally composite the multiple partial images using an optimal method. The algorithm and performance results are presented for the CM-5 and the T3D.
Date: May 1, 1995
Creator: Krogh, M.; Hansen, C.; Painter, J. & de Verdiere, G.C.
Partner: UNT Libraries Government Documents Department

Evaluation of dynamic target options for dual axis radiography hydrotest facility II (DARHT II) and advanced hydrotest facility (AHF) programs

Description: Initial results indicate that electron beams hitting targets used to generate x-rays during multipulse operation in advanced radiography facilities will generate plasma plumes which will disturb the electron beam during subsequent pulses. This, in turn, degrades the x-ray spot quality generated by the subsequent pulses. If this concern is substantiated, new facilities such as the Dual Axia Radiography Hydrotest Facility (DARHT II) and the Advanced Hydrotest Facility (AHF) will need a provision for mitigating this effect. one such provision involves moving the target with sufficient velocity that any plasmas formed are carried adequately far from the electron beam that they do not disturb it. They report the various approaches which have been considered and present data showing the maximum target rates which can be achieved with each approach.
Date: March 1, 1999
Creator: Krogh, M; Neurath, R; Sampayan, S & Sanders, D
Partner: UNT Libraries Government Documents Department

DC CHARACTERIZATION OF HIGH GRADIENT MULTILAYER INSULATORS

Description: We have developed a novel insulator concept that involves the use of alternating layers of conductors and insulators with periods less than 1 mm. We have demonstrated that these structures perform 2 to 5 times better than conventional insulators in long pulse, short pulse, and alternating polarity applications. We present new testing results showing exceptional behavior at DC, with gradients in excess of 110kV/cm in vacuum.
Date: May 26, 2005
Creator: Watson, J A; Caporaso, G J; Sampayan, S E; Sanders, D M & Krogh, M L
Partner: UNT Libraries Government Documents Department

Vacuum Insulator Studies for the Dielectric Wall Accelerator

Description: As part of our ongoing development of the Dielectric Wall Accelerator, we are studying the performance of multilayer high-gradient insulators. These vacuum insulating structures are composed of thin, alternating layers of metal and dielectric, and have been shown to withstand higher gradients than conventional vacuum insulator materials. This paper describes these structures and presents some of our recent results.
Date: June 11, 2007
Creator: Harris, J R; Chen, Y J; Blackfield, D; Sanders, D M; Caporaso, G J & Krogh, M
Partner: UNT Libraries Government Documents Department

Vacuum Insulator Development for the Dielectric Wall Accelerator

Description: At Lawrence Livermore National Laboratory, we are developing a new type of accelerator, known as a Dielectric Wall Accelerator, in which compact pulse forming lines directly apply an accelerating field to the beam through an insulating vacuum boundary. The electrical strength of this insulator may define the maximum gradient achievable in these machines. To increase the system gradient, we are using 'High Gradient Insulators' composed of alternating layers of dielectric and metal for the vacuum insulator. In this paper, we present our recent results from experiment and simulation, including the first test of a High Gradient Insulator in a functioning Dielectric Wall Accelerator cell.
Date: March 17, 2008
Creator: Harris, J R; Blackfield, D; Caporaso, G J; Chen, Y; Hawkins, S; Kendig, M et al.
Partner: UNT Libraries Government Documents Department

Time resolved, 2-D hard X-ray imaging of relativistic electron-beam target interactions on ETA-II

Description: Advanced radiographic applications require a constant source size less than 1 mm. To study the time history of a relativistic electron beam as it interacts with a bremsstrahlung converter, one of the diagnostics they use is a multi-frame time-resolved hard x-ray camera. They are performing experiments on the ETA-II accelerator at Lawrence Livermore National Laboratory to investigate details of the electron beam/converter interactions. The camera they are using contains 6 time-resolved images, each image is a 5 ns frame. By starting each successive frame 10 ns after the previous frame, they create a 6-frame movie from the hard x-rays produced from the interaction of the 50-ns electron beam pulse.
Date: November 1998
Creator: Crist, C. E.; Sampayan, S.; Westenskow, G.; Caporaso, G.; Houck, T.; Weir, J. et al.
Partner: UNT Libraries Government Documents Department

High-performance insulator structures for accelerator applications

Description: A new, high gradient insulator technology has been developed for accelerator systems. The concept involves the use of alternating layers of conductors and insulators with periods of order 1 mm or less. These structures perform many times better (about 1.5 to 4 times higher breakdown electric field) than conventional insulators in long pulse, short pulse, and alternating polarity applications. We describe our ongoing studies investigating the degradation of the breakdown electric field resulting from alternate fabrication techniques, the effect of gas pressure, the effect of the insulator-to-electrode interface gap spacing, and the performance of the insulator structure under bi-polar stress.
Date: May 1, 1997
Creator: Sampayan, S.E.; Caporaso, G.J.; Sanders, D.M.; Stoddard, R.D.; Trimble, D.O.; Elizondo, J. et al.
Partner: UNT Libraries Government Documents Department

Experimental investigation of beam optics issues at the Bremsstrahlung converters for radiographic applications

Description: As part of the Dual Axis Radiographic Hydrodynamic Test Facility II (DARHT II) and Advanced Hydrotest Facility (AHF) programs, we have began investigation of the possible adverse effects of (1) backstreaming ion emission from the Bremsstrahlung converter target and (2) the interaction of the resultant plasma with the electron beam during subsequent pulses. These eff&s would primarily manifest themselves in the static focusing system as a rapidly varying x-ray spot. To study these effects, we are conducting beam-target interaction experiments on the ETA-II accelerator (a 6.0 MeV, 2.5 kA, 70 ns FWHM pulsed, electron accelerator). From these experiments and the multiple diagnostics we have implemented, we are able to determine spot dynamics and characterize the resultant plasma for various configurations. Our data to date shows the first effect to be minimal. We report on the details of our experiments and our preliminary experiments to study the second effect.
Date: August 21, 1998
Creator: Caporaso, G; Chen, Y J; Crist, C; Garcia, M; Houck, T; Krogh, M et al.
Partner: UNT Libraries Government Documents Department

Vacuum surface flashover and high pressure gas streamers

Description: Pre-breakdown current traces obtained during high pressure gas breakdown and vacuum surface flashover show similar signatures. The initial pre-breakdown current spike, a flat constant current phase, and the breakdown phase with voltage collapse and current surge differ mostly in magnitude. Given these similarities, a model, consisting of the initial current spike corresponding to a fast precursor streamer (ionization wave led by a photoionizing front), the flat current stage as the heating or glow phase, and the terminal avalanche and gap closure, is applied to vacuum surface flashover. A simple analytical approximation based on the resistivity changes induced in the vacuum and dielectric surface is presented. The approximation yields an excellent fit to pre-breakdown time delay vs applied field for previously published experimental data. A detailed kinetics model that includes surface and gas contributions is being developed based in the initial approximation.
Date: July 1, 1997
Creator: Elizondo, J.M.; Krogh, M.L.; Smith, D.; Stolz, D.; Wright, S.N.; Sampayan, S.E. et al.
Partner: UNT Libraries Government Documents Department

High Breakdown Strength, Multilayer Ceramics for Compact Pulsed Power Applications

Description: Advanced ceramics are being developed for use in large area, high voltage devices in order to achieve high specific energy densities (>10 6 J/m 3 ) and physical size reduction. Initial materials based on slip cast TiO2 exhibited a high bulk breakdown strength (BDS >300 kV/cm) and high permittivity with low dispersion (e�100). However, strong area and thickness dependencies were noted. To increase the BDS, multilayer dielectric compositions are being developed based on glass/TiO2 composites. The addition of glass increases the density (�99.8% theoretical), forms a continuous grain boundary phase, and also allows the use of high temperature processes to change the physical shape of the dielectric. The permittivity can also be manipulated since the volume fraction and connectivity of the glassy phase can be readily shifted. Results from this study on bulk breakdown of TiO2 multilayer structures with an area of 2cm 2 and 0.1cm thickness have measured 650 kV/cm. Furthermore, a strong dependence of breakdown strength and permittivity has been observed and correlated with microstructure and the glass composition. This paper presents the interactive effects of manipulation of these variables.
Date: July 20, 1999
Creator: Gilmore, B.; Huebner, W.; Krogh, M.L.; Lundstrom, J.M.; Pate, R.C.; Rinehart, L.F. et al.
Partner: UNT Libraries Government Documents Department

COMPACT ACCELERATOR CONCEPT FOR PROTON THERAPY

Description: A new type of compact induction accelerator is under development at the Lawrence Livermore National Laboratory that promises to increase the average accelerating gradient by at least an order of magnitude over that of existing induction machines. The machine is based on the use of high gradient vacuum insulators, advanced dielectric materials and switches and is being developed as a compact flash x-ray radiography source. Research describing an extreme variant of this technology aimed at proton therapy for cancer will be presented.
Date: August 18, 2006
Creator: Caporaso, G; Sampayan, S; Chen, Y; Harris, J; Hawkins, S; Holmes, C et al.
Partner: UNT Libraries Government Documents Department

DEVELOPMENT OF A COMPACT RADIOGRAPHY ACCELERATOR USING DIELECTRIC WALL ACCELERATOR TECHNOLOGY

Description: We are developing an inexpensive compact accelerator system primarily intended for pulsed radiography. Design characteristics are an 8 MeV endpoint energy, 2 kA beam current, a cell gradient of approximately 3 MV/m (for an overall accelerator length is 2-3 m), and <$1/Volt capital costs. Such designs have been made possible with the development of high specific energy dielectrics (>10J/cm{sup 3}), specialized transmission line designs and multi-gap laser triggered low jitter (<1 ns) gas switches. In this geometry, the pulse forming lines, switches, and insulator/beam pipe are fully integrated within each cell to form a compact, stand-alone, stackable unit. We detail our research and modeling to date, recent high voltage test results, and the integration concept of the cells into a radiographic system.
Date: June 2, 2005
Creator: Sampayan, S; Caporaso, G; Chen, Y; Hawkins, S; Holmes, C; Krogh, M et al.
Partner: UNT Libraries Government Documents Department

Multilayer High-Gradient Insulators

Description: High voltage systems operated in vacuum require insulating materials to maintain spacing between conductors held at different potentials, and may be used to maintain a nonconductive vacuum boundary. Traditional vacuum insulators generally consist of a single material, but insulating structures composed of alternating layers of dielectric and metal can also be built. These ''High-Gradient Insulators'' have been experimentally shown to withstand higher voltage gradients than comparable conventional insulators. As a result, they have application to a wide range of high-voltage vacuum systems where compact size is important. This paper describes ongoing research on these structures, as well as the current theoretical understanding driving this work.
Date: November 15, 2006
Creator: Harris, J R; Anaya, R M; Blackfield, D; Chen, Y -; Falabella, S; Hawkins, S et al.
Partner: UNT Libraries Government Documents Department

HIGH GRADIENT INDUCTION ACCELERATOR

Description: A new type of compact induction accelerator is under development at the Lawrence Livermore National Laboratory that promises to increase the average accelerating gradient by at least an order of magnitude over that of existing induction machines. The machine is based on the use of high gradient vacuum insulators, advanced dielectric materials and switches and is stimulated by the desire for compact flash x-ray radiography sources. Research describing an extreme variant of this technology aimed at proton therapy for cancer will be described. Progress in applying this technology to several applications will be reviewed.
Date: June 21, 2007
Creator: Caporaso, G J; Sampayan, S; Chen, Y; Blackfield, D; Harris, J; Hawkins, S et al.
Partner: UNT Libraries Government Documents Department

Beam-target interaction experiments for Bremsstrahlung converter applications

Description: The authors are investigating the possible adverse effects of (1) backstreaming ion emission from the Bremsstrahlung converter target and (2) the interaction of the resultant plasma with the electron beam during subsequent pulses for multi-pulse radiography facilities. These effects would primarily manifest themselves in a static focusing system as a rapidly varying x-ray spot. To study these effects, they are conducting beam-target interaction experiments on the ETA-II accelerator (a 6.0 MeV, 2.5 kA, 70 ns FWHM pulsed, electron accelerator). They are measuring spot dynamics and characterizing the resultant plasma for various configurations. Thus far, their experiments show that the first effect is not strongly present when the beam initially interacts with the target. Electron beam pulses delivered to the target after formation of a plasma are strongly affected. They have also performed initial experiments to determine the effect of the beam propagating through the plasma. This data shows that the head of the beam is relatively robust, but that backstreaming ions from the plasma can still manifest itself as a dynamic focus toward the tail of the beam. They report on the details of the experimental work to suppress these effects.
Date: March 1, 1999
Creator: Buckles, R; Caparaso, G; Chen, Y-J; Crist, C; Falabella, S; Houck, T et al.
Partner: UNT Libraries Government Documents Department