Self-similar structure and experimental signatures of suprathermal ion distribution in inertial confinement fusion implosions

The distribution function of suprathermal ions is found to be self-similar under conditions relevant to inertial confinement fusion hot-spots. By utilizing this feature, interference between the hydro-instabilities and kinetic effects is for the first time assessed quantitatively to find that the instabilities substantially aggravate the fusion reactivity reduction. The ion tail depletion is also shown to lower the experimentally inferred ion temperature, a novel kinetic effect that may explain the discrepancy between the exploding pusher experiments and rad-hydro simulations and contribute to the observation that temperature inferred from DD reaction products is lower than from DT at National Ignition Facility.Comment: Revised version accepted for publication in PRL. "Copyright (2015) by the American Physical Society.

A demographic study based upon income, age and education variables as related to the willingness or unwillingness to accept foster children

The research problem in this thesis can be briefly stated as a study of a general population to test certain demographic variables, in particular those of income, age and education, which may or may not have a significant relationship to an expressed willingness to care for foster children; and to further examine whether certain special characteristics of a child, in particular those of increased age, physical handicap, minor emotional problems or mental retardation, further increase unwillingness to care for foster children. The sample was selected by a two- stage cluster sampling taken from the Southeast catchment area of metropolitan Portland, Oregon. From this sample of 787 individuals, the survey was conducted by trained interviewers, using a questionnaire and personal interview. The data used in this research project were then extracted from the larger survey, and computed to determine the relationship of age, income and education to willingness to care for foster children. The data were extracted on the basis of the chosen variables of income, age and education and five questions relating specifically to willingness to care for foster children. As had been anticipated, the findings showed that the general population is not willing to care for foster children. However, certain significant findings were related to willingness to care for foster children. A significant relationship was found between income and willingness to care for foster children in that those respondents with incomes between $4,000-$20,000 expressed the most willingness to care for foster children while there was significant underrepresentation in both the highest and lowest income groupings to express a willingness to care for foster children with an almost lineal relationship of decreasing age with increasing willingness to care for foster children. There is no significant relationship, it was found, between education of the respondent and willingness to care for foster children. There is a lineal relationship of increasing willingness to care for foster children with increasing age of the foster child. Of those individuals expressing a willingness to care for foster children, there is no significant decrease in willingness because of physical disability, minor emotional problems or mental retardation. The results of this study have certain implication for recruitment and selection of foster parents. The findings indicate the need for further research to explore why more individuals in the population do not express a willingness to care for foster children, how such an interest can be encouraged and what criteria can be used in recruitment and selection

First record of the genus Nopachtus (Xenarthra: Cingulata: Glyptodontidae) in Uruguay

Nopachtus Ameghino is a poorly known genus of glyptodontid. The genus includes 2 species recorded in Argentina: Nopachthus coagmentatus Ameghino, from Brochero Formation (Montehermosian-Chapadmalalian, Early Pliocene-Late Pliocene) of Sierras de Córdoba/El Polvorín Formation (Upper Chapadmalalian, Pliocene) of Sierras Bayas de Olavarría, Buenos Aires province, and Nopachthus cabrerai Zamorano, Scillato-Yané, González-Ruiz and Zurita, from Monte Hermoso Formation (Montehermosian, Early Pliocene) from SO of Buenos Aires province. The knowledge about the presence of Nopachtus outside Argentina, is due to Toriño y Rinderknecht (2005), who mention one osteoderm which possesses similar characters to those of Nopachtus and Panochthus intermedius Lydekker. Later, Toriño y Perea (2008) resume this consideration. In this paper, the materials referred to Nopachtus in Uruguay are studied. There are 2 isolated osteoderms corresponding to the dorsal carapace: FC-CVF 1825 and CF-CVF 2759, both from Camacho Formation (Late Miocene) or Raigón Formation (Late Miocene-Middle Pleistocene) of the coast cliffs of San José Departament, Uruguay. Due to the great similarity of these osteoderms to those of Nopachtus, and according to the comparative analysis conducted, both are assigned to the present genus, thus expanding the geographic distribution of this taxon to Uruguay.Nopachtus Ameghino es un género de gliptodóntido poco conocido. Cuenta con 2 especies registradas para Argentina: Nopachtus coagmentatus Ameghino, de la formación Brochero (Montehermosense-Chapadmalalense, Plioceno Temprano-Plioceno Tardío) de las sierras de Córdoba/formación El Polvorín (Chapadmalalense Superior, Plioceno) de las sierras Bayas de Olavarría, provincia de Buenos Aires; y Nopachtus cabrerai Zamorano, Scillato-Yané, González-Ruiz y Zurita, de la formación Monte Hermoso (Montehermosense, Plioceno Temprano) del SO de la provincia de Buenos Aires. El conocimiento sobre la presencia de Nopachtus fuera de Argentina se debe a la mención de Torino˜ y Rinderknecht (2005) de un osteodermo que posee características semejantes a Nopachtus y a Panochthus intermedius Lydekker; posteriormente, Torino˜ y Perea (2008) retoman esta consideración. En la presente contribución se realiza un estudio de materiales referidos a Nopachtus en Uruguay. Se trata de 2 osteodermos aislados correspondientes a la coraza dorsal: FC-CVF 1825 y FC-CVF 2759, ambos proceden de la formación Camacho (Mioceno Tardío) o formación Raigón (Mioceno Tardío-Pleistoceno Medio) de las barrancas costeras del departamento de San José, Uruguay. Dada la notoria semejanza de estos osteodermos con los de Nopachtus, y por comparaciones realizadas, se asignan al citado género, ampliándose así la distribución geográfica del taxón a Uruguay.Facultad de Ciencias Naturales y Muse

Assessment of ion kinetic effects in shock-driven inertial confinement fusion implosions using fusion burn imaging

The significance and nature of ion kinetic effects in D3He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, NK) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatially resolved measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (NK3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects

Neutron time-of-flight measurements of charged-particle energy loss in inertial confinement fusion plasmas

Neutron spectra from secondary ^{3}H(d,n)α reactions produced by an implosion of a deuterium-gas capsule at the National Ignition Facility have been measured with order-of-magnitude improvements in statistics and resolution over past experiments. These new data and their sensitivity to the energy loss of fast tritons emitted from thermal ^{2}H(d,p)^{3}H reactions enable the first statistically significant investigation of charged-particle stopping via the emitted neutron spectrum. Radiation-hydrodynamic simulations, constrained to match a number of observables from the implosion, were used to predict the neutron spectra while employing two different energy loss models. This analysis represents the first test of stopping models under inertial confinement fusion conditions, covering plasma temperatures of k_{B}T≈1-4  keV and particle densities of n≈(12-2)×10^{24}  cm^{-3}. Under these conditions, we find significant deviations of our data from a theory employing classical collisions whereas the theory including quantum diffraction agrees with our data

Laser-Plasma Interactions Enabled by Emerging Technologies

An overview from the past and an outlook for the future of fundamental laser-plasma interactions research enabled by emerging laser systems