Search results for "Pluto"
showing 10 items of 90 documents
The effect of titanite and other HFSE-rich mineral (Ti-bearing andradite, zircon, eudialyte) fractionation on the geochemical evolution of silicate m…
2008
Abstract We present trace element data for HFSE-rich minerals (titanite, eudialyte, Ti-bearing andradite, zircon) from plutonic rocks of the Eocene Tamazeght complex, High Atlas Mountains, Morocco. In most lithologies significant amounts of titanite are present and as such, titanite fractionation played a major role in the evolution of the HFSE budget of the whole complex. By combining our data with published titanite–melt partition coefficients we explore the effects of titanite fractionation on the evolution of geochemical parameters (Zr/Hf, Nb/Ta, La/Lu and Th/U ratios) during differentiation of silicate melts in detail. Based upon this, we further discuss the genetic relationships betwe…
Thermodynamic studies of actinide complexes. 1. A reappraisal of the solution equilibria between plutonium(IV) and ethylenediaminetetraacetic acid (E…
2007
Abstract A detailed reevaluation of the complexation equilibria of plutonium(IV) with the polyaminocarboxylic sequestering agent EDTA4− has been performed in 1 M (H,K)NO3 media at 298 K by means of visible absorption spectrophotometry and glass-electrode potentiometry at millimolar concentration levels. The high binding affinity even under strongly acidic conditions supports the exclusive formation of the neutral Pu(EDTA) complex over the range 0.01 ≤ [H+] ≤ 0.9 M with an apparent formation constant of log β110 = 25.8(1) at 0.9 M HNO3. Extrapolation to zero ionic strength using the SIT approach provides the first ever-reported NEA–TDB compliant estimate of β 110 0 ( log β 110 0 = 32.2 ( 3 )…
Zvaigžņotā Debess: 2016, Vasara (232)
2016
Contents: “ZVAIGŽŅOTĀ DEBESS” FORTY YEARS AGO: A.Balklavs. New Studies and Conclusions on Nucleus of the Galaxy (abridged) ; U.Dzērvītis. Discussion on Planetary System of Barnard’s Star Continues (abridged) ; M.Eliāss. Meeting of Solar Radio Radiation Section (abridged) ; DEVELOPMENTS in SCIENCE: O.Dumbrājs. Neutrino Oscillations: from the Outset to the Nobel Prize ; R.Misa. Conversation with Andris Ambainis on Quantum Computing Science ; DISCOVERIES: F.Gahbauer. First Direct Detection of Gravitational Waves ; I.Pundure. ATLASGAL Survey of Milky Way Completed ; SPACE RESEARCH and EXPLORATION: J.Jaunbergs. The Story of Pluto’s Satellites ; K.Schwartz. Conducting Ice and Magnetic Field of Ur…
Observation of Collisional De-Excitation Phenomena in Plutonium
2022
Proceedings for the "virtual Workshop on the Atomic Structure of Actinides & Related Topics" conference submitted to the special issue of Atoms "Atomic Structure of the Heaviest Elements". A program of research towards the high-resolution optical spectroscopy of actinide elements for the study of fundamental nuclear structure is currently ongoing at the IGISOL facility of the University of Jyväskylä. One aspect of this work is the development of a gas-cell-based actinide laser ion source using filament-based dispensers of long-lived actinide isotopes. We have observed prominent phenomena in the resonant laser ionization process specific to the gaseous envir…
In-gas-cell laser ionization studies of plutonium isotopes at IGISOL
2016
Abstract In-gas-cell resonance laser ionization has been performed on long-lived isotopes of Pu at the IGISOL facility, Jyvaskyla. This initiates a new programme of research towards high-resolution optical spectroscopy of heavy actinide elements which can be produced in sufficient quantities at research reactors and transported to facilities elsewhere. In this work a new gas cell has been constructed for fast extraction of laser-ionized elements. Samples of 238–240,242 Pu and 244 Pu have been evaporated from Ta filaments, laser ionized, mass separated and delivered to the collinear laser spectroscopy station. Here we report on the performance of the gas cell through studies of the mass spec…
Nuclear Forensics: A methodology applicable to Nuclear Security and to Non-Proliferation
2011
Nuclear Security aims at the prevention and detection of and response to, theft, sabotage, unauthorized access, illegal transfer or other malicious acts involving nuclear material". Nuclear Forensics is a key element of nuclear security. Nuclear Forensics is defined as a methodology that aims at re-establishing the history of nuclear material of unknown origin. It is based on indicators that arise from known relationships between material characteristics and process history. Thus, nuclear forensics analysis includes the characterization of the material and correlation with production history. To this end, we can make use of parameters such as the isotopic composition of the nuclear material…
Fission fragment anisotropy for the 242mAm fission isomer by spin exchange pumping with polarized rubidium vapour
1992
Abstract The foundations of an experiment have been worked out with which, in principle, the spin, hyperfine constants and the isomer shift of the 14 ms fission isomer 242mAm can be measured. Such an experiment would be based on the fission fragment anisotropy signal which has actually been observed in this work after spin exchange pumping with polarized rubidium vapour in an optical buffer gas cell. A decrease of the count rate of (12±4)% has been measured at 90% with respect to the quantization axis. From this result it is concluded that the nuclear spin of the 242mAm fission isomer must be larger than 1. The low-energy fission isomers originating from the 242Pu(d, 2n)242mAm reaction have…
Fast-neutron-induced fission cross section of Pu242 measured at the neutron time-of-flight facility nELBE
2019
The fast-neutron-induced fission cross section of $^{242}\mathrm{Pu}$ was measured at the neutron time-of-flight facility $n$ELBE. A parallel-plate fission ionization chamber with novel, homogeneous, large-area $^{242}\mathrm{Pu}$ deposits on Si-wafer backings was used to determine this quantity relative to the IAEA neutron cross-section standard $^{235}\mathrm{U}(n,f)$ in the energy range of 0.5 to 10 MeV. The number of target nuclei was determined from the measured spontaneous fission rate of $^{242}\mathrm{Pu}$. This helps to reduce the influence of the fission fragment detection efficiency on the cross section. Neutron transport simulations performed with geant4, mcnp6, and fluka2011 ar…
Production of plutonium tracers in 237Np nuclear reactions with 3He-ions in the energy range from 26 to 60 MeV
1998
Cross-sections for the reaction Np-237 + He-3 --> Pu-236,Pu-237,Pu-238 at He-3 bombarding energies from 26 to 60 MeV were measured. Thick-target yields, based on the measured and previously known cross-sections were constructed. The results are discussed and compared with Ether reactions leading to the formation of the same final nuclei. (C) 1998 Elsevier Science S.A.
Non-LTE radiation hydrodynamics in PLUTO
2019
Modeling the dynamics of most astrophysical structures requires an adequate description of the radiation-matter interaction. Several numerical (magneto)hydrodynamics codes were upgraded with a radiation module to fulfill this request. However, those among them that use either the flux-limited diffusion (FLD) or the M1 radiation moment approaches are restricted to the local thermodynamic equilibrium (LTE). This assumption may be not valid in some astrophysical cases. We present an upgraded version of the LTE radiation-hydrodynamics module implemented in the PLUTO code, originally developed by Kolb et al. (2013), which we have extended to handle non-LTE regimes. Starting from the general freq…