102 research outputs found
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Removal of CDP Mandrels from Sputter Coated Beryllium Capsules for NIF Targets
Ablative targets for the National Ignition Campaign (NIC) have been fabricated by sputter coating spherical mandrels made of glow discharge polymer (GDP) with graded copper doped beryllium (Be) layers. The inner mandrel must be completely removed to meet specific ignition design requirements. The process of removing the mandrel requires elevated temperature in the presence of oxygen. However, elevating the temperature in air also oxidizes the Be and can cause blistering on the inner surface of the Be shell. This paper will discuss a refined technique, which removes the GDP mandrel without compromising the integrity of the inner Be surface. The oxygen gradient that develops during the mandrel removal and the impact of its presence will also be discussed
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Design and Fabrication of a Novel Cryogenic Laser-Driven Ignition Target
The targets used in the campaign to achieve fusion ignition at the National Ignition Facility (NIF), the world's largest laser, will be some of the most complex and precise ever built. Key to the success of the campaign is repeatable performance of the targets as components of each experiment. We have developed a target design that will achieve the necessary precision and manufacturability, and will also provide the necessary repeatability while retaining experimental flexibility
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Forensic Medicine: Age Written in Teeth by Nuclear Bomb Tests
Establishing the age of individuals is an important step in identification and a frequent challenge in forensic medicine. This can be done with high precision up to adolescence by analysis of dentition, but establishing the age of adults has remained difficult. Here we show that measuring {sup 14}C from nuclear bomb tests in tooth enamel provides a sensitive way to establish when a person was born
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In vitro high-resolution structural dynamics of single germinating bacterial spores
Although significant progress has been achieved in understanding the genetic and biochemical bases of the spore germination process, the structural basis for breaking the dormant spore state remains poorly understood. We have used atomic force microscopy (AFM) to probe the high-resolution structural dynamics of single Bacillus atrophaeus spores germinating under native conditions. Here we show that AFM can reveal previously unrecognized germination-induced alterations in spore coat architecture and topology as well as the disassembly of outer spore coat rodlet structures. These results and previous studies in other microorganisms suggest that the spore coat rodlets are structurally similar to amyloid fibrils. AFM analysis of the nascent surface of the emerging germ cell revealed a porous network of peptidoglycan fibers. The results are consistent with a honeycomb model structure for synthetic peptidoglycan oligomers determined by nuclear magnetic resonance. AFM is a promising experimental tool for investigating the morphogenesis of spore germination and cell wall peptidoglycan structure
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Studies of nondegenerate, quasi-phase-matched optical parametric amplification
We have performed extensive numerical studies of quasi-phase-matched optical parametric amplification with the aim to improve its nondegenerate spectral bandwidth. Our multi-section fan-out design calculations indicate a 35-fold increase in spectral bandwidth
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Spatial Statistical Procedures to Validate Input Data in Energy Models
Energy modeling and analysis often relies on data collected for other purposes such as census counts, atmospheric and air quality observations, economic trends, and other primarily non-energy-related uses. Systematic collection of empirical data solely for regional, national, and global energy modeling has not been established as in the above-mentioned fields. Empirical and modeled data relevant to energy modeling is reported and available at various spatial and temporal scales that might or might not be those needed and used by the energy modeling community. The incorrect representation of spatial and temporal components of these data sets can result in energy models producing misleading conclusions, especially in cases of newly evolving technologies with spatial and temporal operating characteristics different from the dominant fossil and nuclear technologies that powered the energy economy over the last two hundred years. Increased private and government research and development and public interest in alternative technologies that have a benign effect on the climate and the environment have spurred interest in wind, solar, hydrogen, and other alternative energy sources and energy carriers. Many of these technologies require much finer spatial and temporal detail to determine optimal engineering designs, resource availability, and market potential. This paper presents exploratory and modeling techniques in spatial statistics that can improve the usefulness of empirical and modeled data sets that do not initially meet the spatial and/or temporal requirements of energy models. In particular, we focus on (1) aggregation and disaggregation of spatial data, (2) predicting missing data, and (3) merging spatial data sets. In addition, we introduce relevant statistical software models commonly used in the field for various sizes and types of data sets
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New simulation capabilities of electron clouds in ion beams with large tune depression
We have developed a new, comprehensive set of simulation tools aimed at modeling the interaction of intense ion beams and electron clouds (e-clouds). The set contains the 3-D accelerator PIC code WARP and the 2-D ''slice'' e-cloud code POSINST [M. Furman, this workshop, paper TUAX05], as well as a merger of the two, augmented by new modules for impact ionization and neutral gas generation. The new capability runs on workstations or parallel supercomputers and contains advanced features such as mesh refinement, disparate adaptive time stepping, and a new ''drift-Lorentz'' particle mover for tracking charged particles in magnetic fields using large time steps. It is being applied to the modeling of ion beams (1 MeV, 180 mA, K+) for heavy ion inertial fusion and warm dense matter studies, as they interact with electron clouds in the High-Current Experiment (HCX) [experimental results discussed by A. Molvik, this workshop, paper THAW02]. We describe the capabilities and present recent simulation results with detailed comparisons against the HCX experiment, as well as their application (in a different regime) to the modeling of e-clouds in the Large Hadron Collider (LHC)
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Data Report on Material Ablation and Shock Pressure Measurements at ZBL
A series of tests were conducted on Z-Beamlet Laser (ZBL) to provide data that can be used to determine the laser coupling coefficient and validate code capabilities. The gauges and cables in the chamber were shielded with conduit and resulted in high fidelity signals. The stress measurements show a clear trend of peak stress attenuation with propagation distance, as would be expected. The aluminum sample stresses measured were in the 4 to 8 Kbar range. This constitutes a good data set for model validation. VISAR was considered as a diagnostic for this test series but predicted stress levels were uncertain and we had good success previously with PVDF at this test facility; plus, the aggressive test schedule and limited number of shots left little opportunity to set up this diagnostic. Shock profile measurements were made with both PVDF and Quartz gauges. The PVDF gauge and the Quartz gauge measured very similar shock pulses transmitted through 1.5-mm thick 2024-T3 samples at a nominal fluence of 400 J/cm{sup 2}. The similarity in the two profiles indicates good correlation between measurement techniques and the differences between the sensor areas allow one to evaluate different parts of the beam. The laser beam ablated the front surfaces of the samples. Surface profile measurements of the ablated surface were used to estimate the depth of material removed. Ablated sample surface and crater formation indicate a non-uniform hot spot in the center of the sample
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"Nuclear Energy - Potential to Substantially Impact California's Energy Use"
The use of nuclear power to generate electricity is very widespread today, with about 20% of all U.S. electricity coming from the nation's 103 operating reactors. Worldwide there are over 400 commercial nuclear plants that make a similar contribution percentage-wise. However, all of the current U.S. reactors and most of those elsewhere are relatively old, with no new ones having been started domestically in over two decades and only a few now being built overseas, mostly in Asia. The principal reason for this hiatus in the U.S. is that the cost of electricity from new nuclear plants has been non-competitive with other electricity sources for a long time. The U.S. nuclear-power industry has not been stagnant during this time, however. First, the existing plants themselves are running significantly better than they were twenty years ago, to the extent that the US. reactor fleet is producing about one-third more electricity annually than it was, due largely to improvements in the capacity factors: the plants run more reliably, shut down less often, and the refueling outages take less than half as long as they once did. The safety performance has also improved dramatically, with major improvements in every one of the main indicators of safety. The security of the plants against sabotage or other malevolent acts has always been very strong, and is stronger still after recent upgrades in response to the September 2001 attacks in New York and Washington. Thus the U.S. nuclear-electricity industry has remained dynamic despite the absence of new construction. The U.S. and foreign companies that design reactors and hope someday to sell more of them have also been actively at work--they have developed advanced reactor designs that promise to cost much less to build and to operate, and to have even better safety performance. Several of these advanced designs have received design-certification approvals from the U.S. Nuclear Regulatory Commission, meaning that a utility could order one of these certified designs today with confidence that the NRC approval of that design is already in place. These new reactor designs are advanced versions of the existing reactors: broadly similar in their design concept but incorporating important new safety and reliability features and cost-saving features. The term ''evolutionary'' is used to describe these designs, in contrast to several advanced reactor designs whose engineering concepts are very different
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Experimental Bench-marking of Pu Electronic Structure
Our plan is to do Ce (as a Pu surrogate) this year and be ready to do Pu next year. The Fano (Spin-resolved Photoelectron Spectroscopy) measurements are essential to testing electron correlation in the occupied 5f states. BIS (Bremstrahlung Isochromat Spectroscopy or high energy Inverse Photoelectron Spectroscopy) experiments are crucial to a quantitative determination of the 5f unoccupied density of states (5f-UDOS). The 5f UDOS is the key to differentiation between a myriad of models of 5f electronic structure. During this time, we will work to converge to a solution for the Pu safety issues, with the plan to implement these in the next FY. Acceleration of this schedule and implementation of the safety plan in this FY will require a very significant increase in funding. Ultimately, results from the Pu experiments will be fed into calculations performed by P. Soderlind, A. Landa, and others
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