2,145 research outputs found
Transient x-ray diffraction used to diagnose shock compressed Si crystals on the Nova laser
Transient x-ray diffraction is used to record time-resolved information about the shock compression of materials. This technique has been applied on Nova shock experiments driven using a hohlraum x-ray drive. Data were recorded from the shock release at the free surface of a Si crystal, as well as from Si at an embedded ablator/Si interface. Modeling has been done to simulate the diffraction data incorporating the strained crystal rocking curves and Bragg diffraction efficiencies. Examples of the data and post-processed simulations are presented
Predicted number of peanut-allergic patients needed to treat with epicutaneous immunotherapy (EPIT) to prevent one allergic reaction: A novel approach to assessing relevance
X-ray Astronomy in the Laboratory with a Miniature Compact Object Produced by Laser-Driven Implosion
Laboratory spectroscopy of non-thermal equilibrium plasmas photoionized by
intense radiation is a key to understanding compact objects, such as black
holes, based on astronomical observations. This paper describes an experiment
to study photoionizing plasmas in laboratory under well-defined and genuine
conditions. Photoionized plasma is here generated using a 0.5-keV Planckian
x-ray source created by means of a laser-driven implosion. The measured x-ray
spectrum from the photoionized silicon plasma resembles those observed from the
binary stars Cygnus X-3 and Vela X-1 with the Chandra x-ray satellite. This
demonstrates that an extreme radiation field was produced in the laboratory,
however, the theoretical interpretation of the laboratory spectrum
significantly contradicts the generally accepted explanations in x-ray
astronomy. This model experiment offers a novel test bed for validation and
verification of computational codes used in x-ray astronomy.Comment: 5 pages, 4 figures are included. This is the original submitted
version of the manuscript to be published in Nature Physic
Scaling supernova hydrodynamics to the laboratory
Supernova (SN) 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. To test the modeling of these instabilities, we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to supernovae. Initial results were reported in J. Kane et al. [Astrophys. J. 478, L75 (1997) and B. A. Remington et al., Phys. Plasmas 4, 1994 (1997)]. The Nova laser is used to generate a 10â15 Mbar shock at the interface of a two-layer planar target, which triggers perturbation growth due to the RichtmyerâMeshkov instability, and to the RayleighâTaylor instability as the interface decelerates. This resembles the hydrodynamics of the He-H interface of a Type II supernova at intermediate times, up to a few Ă103âs.Ă103s. The scaling of hydrodynamics on microscopic laser scales to the SN-size scales is presented. The experiment is modeled using the hydrodynamics codes HYADES [J. T. Larson and S. M. Lane, J. Quant. Spect. Rad. Trans. 51, 179 (1994)] and CALE [R. T. Barton, Numerical Astrophysics (Jones and Bartlett, Boston, 1985), pp. 482â497], and the supernova code PROMETHEUS [P. R. Woodward and P. Collela, J. Comp. Phys. 54, 115 (1984)]. Results of the experiments and simulations are presented. Analysis of the spike-and-bubble velocities using potential flow theory and Ott thin-shell theory is presented, as well as a study of 2D versus 3D differences in perturbation growth at the He-H interface of SN 1987A.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69672/2/PHPAEN-6-5-2065-1.pd
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Dispersion Relationship for Solid State Instability Growth and Sensitivity to Equation of State
We have derived an approximate analytical dispersion relation for solid state instability growth following the method of Mikaelian. I He starts with the general eigenvalue equation for the velocity of a perturbation on a finite-thickness fluid layer with surface tension and viscosity, and derives an exact solution numerically from det(M)=0, where M is an 8x8 matrix. He then derives an approximate solution analytically by substituting the inviscid eigenfunctions into the exact eigenvalue equation. The integrations yield a dispersion relation which is a polynomial in the growth rate
Evaluating the efficacy of independent versus simultaneous management strategies to address ecological and genetic threats to population viability
ACKNOWLEDGMENTS We thank Sue Bignal, all land-owners and farmers and everyone who helped with fieldwork on Islay. We thank members of the Scottish Chough Forum, particularly Rae Mckenzie and Des Thompson for valuable input on management scenarios. AET was funded by Scottish Natural Heritage (SNH) and Royal Society for the Protection of Birds. SRF was funded by a Natural Environment Research Council iCASE studentship supported by SNH.Peer reviewedPublisher PD
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Laser Imprint and Implications for Direct Drive Ignition With the National Ignition Facility
For direct drive ICF, nonuniformities in laser illumination can seed ripples at the ablation front in a process called imprint. Such nonuniformities will grow during the capsule implosion and can penetrate the capsule shell impede ignition, or degrade burn. We have simulated imprint for a number of experiments on tile Nova laser. Results are in generally good agreement with experimental data. We leave also simulated imprint upon National Ignition Facility (NIF) direct drive ignition capsules. Imprint modulation amplitude comparable to the intrinsic surface finish of {approximately}40 nm is predicted for a laser bandwidth of 0.5 THz. Ablation front modulations experience growth factors up to several thousand, carrying modulation well into the nonlinear regime. Saturation modeling predicts that the shell should remain intact at the time of peak velocity, but penetration at earlier times appears more marginal
An evaluation of different provision strategies for scaled-up container-based sanitation
Container-based sanitation (CBS) is increasingly used to provide safely managed sanitation in low-income urban settlements. However, questions remain around the viability of scaling up the technology, partly because it relies on regular emptying and servicing of containers by a CBS provider. This paper investigates mechanisms by which this process can be achieved efficiently. Three separate collection strategies are evaluated for their routing efficiencies as CBS goes to scale. An open-source route optimisation solver determines the constituent driving and walking distances necessary for each strategy and has been applied in areas of Cape Town, Cap-HaĂŻtien, Lima and Nairobi. The results indicate that with fewer users (e.g. 50) transfer station models offer the shortest driving routes. However, these do require users to carry their containers (e.g. up to 170 m when stations are 100 m apart). As the number of users increases (e.g. to 5,000), visiting individual houses from a neighbourhood depot offers increasingly efficient driving distances. Overall, however, the results suggest that economies in collection distances for scaled CBS will be largely conditional on greater vehicle capacity (rather than any particular provision strategy). This highlights the importance of road access throughout low-income urban settlements in providing a viable CBS service at scale
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