| 1. |
- Titarenko, Yu. E., et al.
(författare)
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Verification of high-energy transport codes on the basis of activation data
- 2011
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 84:6, s. 064612-
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Tidskriftsartikel (refereegranskat)abstract
- Nuclide production cross sections measured at the Institute for Theoretical and Experimental Physics (ITEP) for the targets of (nat)Cr, (56)Fe, (nat)Ni, (93)Nb, (181)Ta, (nat)W, (nat)Pb, and (209)Bi irradiated by protons with energies from 40 to 2600 MeV were used to estimate the predictive accuracy of several popular high-energy transport codes. A general agreement of the ITEP data with the data obtained by other groups, including the numerous GSI data measured by the inverse kinematics method was found. Simulations of the measured data were performed with the MCNPX (BERTINI and ISABEL options), CEM03.02, INCL4.2 + ABLA, INCL4.5 + ABLA07, PHITS, and CASCADE.07 codes. Deviation factors between the calculated and experimental cross sections have been estimated for each target and for the whole energy range covered by our measurements. Two-dimensional diagrams of deviation factor values were produced for estimating the predictive power of every code for intermediate, not measured masses of nuclei targets and bombarding energies of protons. Further improvements of all tested here codes are recommended. In addition, new measurements at ITEP of nuclide yields from the (208)Pb target irradiated by 500-MeV protons are presented. A good agreement between these new data and the GSI measurements obtained by the inverse kinematics method was found.
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| 2. |
- Ming, D.W., et al.
(författare)
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Volatile and organic compositions of sedimentary rocks in Yellowknife Bay, Gale Crater, Mars
- 2014
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 343:6169
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Tidskriftsartikel (refereegranskat)abstract
- H2O, CO2, SO2, O2, H2, H2S, HCl, chlorinated hydrocarbons, NO, and other trace gases were evolved during pyrolysis of two mudstone samples acquired by the Curiosity rover at Yellowknife Bay within Gale crater, Mars. H2O/OH-bearing phases included 2:1 phyllosilicate(s), bassanite, akaganeite, and amorphous materials. Thermal decomposition of carbonates and combustion of organic materials are candidate sources for the CO2. Concurrent evolution of O2 and chlorinated hydrocarbons suggests the presence of oxychlorine phase(s). Sulfides are likely sources for sulfur-bearing species. Higher abundances of chlorinated hydrocarbons in the mudstone compared with Rocknest windblown materials previously analyzed by Curiosity suggest that indigenous martian or meteoritic organic carbon sources may be preserved in the mudstone; however, the carbon source for the chlorinated hydrocarbons is not definitively of martian origin.
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| 3. |
- Titarenko, Yu E., et al.
(författare)
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Measurement and simulation of the cross sections for nuclide production in Fe-56 and Cr-nat targets irradiated with 0.04- to 2.6-GeV protons
- 2011
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Ingår i: Physics of Atomic Nuclei. - 1063-7788 .- 1562-692X. ; 74:4, s. 523-536
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Tidskriftsartikel (refereegranskat)abstract
- The cross sections for nuclide production in thin Fe-56 and Cr-nat targets irradiated by 0.04-2.6-GeV protons are measured by direct gamma spectrometry using two gamma spectrometers with the resolutions of 1.8 and 1.7 keV for the Co-60 1332-keV gamma line. As a result, 649 yields of radioactive residual product nuclei have been obtained. The Al-27(p, x)Na-22 reaction has been used as a monitor reaction. The experimental data are compared with the MCNPX (BERTINI, ISABEL), CEM03.02, INCL4.2, INCL4.5, PHITS, and CASCADE07 calculations.
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| 4. |
- Titarenko, Yu E., et al.
(författare)
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Measurement and simulation of the cross sections for nuclide production in Nb-93 and Ni-nat targets irradiated with 0.04- to 2.6-GeV protons
- 2011
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Ingår i: Physics of Atomic Nuclei. - 1063-7788 .- 1562-692X. ; 74:4, s. 537-550
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Tidskriftsartikel (refereegranskat)abstract
- The cross sections for nuclide production in thin Nb-93 and Ni-nat targets irradiated by 0.04- to 2.6-GeV protons have been measured by direct gamma spectrometry using two gamma spectrometers with the resolutions of 1.8 and 1.7 keV in the Co-60 1332-keV gamma line. As a result, 1112 yields of radioactive residual nuclei have been obtained. The Al-27(p, x)Na-22 reaction has been used as a monitor reaction. The experimental data have been compared with the MCNPX (BERTINI, ISABEL), CEM03.02, INCL4.2, INCL4.5, PHITS, and CASCADE07 calculations.
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| 5. |
- Titarenko, Yu E., et al.
(författare)
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Measurement and simulation of the cross sections for nuclide production in W-nat and Ta-181 targets irradiated with 0.04- to 2.6-GeV protons
- 2011
-
Ingår i: Physics of Atomic Nuclei. - 1063-7788 .- 1562-692X. ; 74:4, s. 551-572
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Tidskriftsartikel (refereegranskat)abstract
- The cross sections for nuclide production in thin (nat)Wand Ta-181 targets irradiated by 0.04-2.6-GeV protons have been measured by direct gamma spectrometry using two gamma spectrometers with the resolutions of 1.8 and 1.7 keV in the Co-60 1332-keV gamma line. As a result, 1895 yields of radioactive residual product nuclei have been obtained. The Al-27(p, x)Na-22 reaction has been used as a monitor reaction. The experimental data have been compared with the MCNPX (BERTINI, ISABEL), CEM03.02, INCL4.2, INCL4.5, PHITS, and CASCADE07 calculations.
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| 6. |
- Titarenko, Yu E., et al.
(författare)
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Measurement and simulation of the cross sections for the production of Gd-148 in thin W-nat and Ta-181 targets irradiated with 0.4- to 2.6-GeV protons
- 2011
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Ingår i: Physics of Atomic Nuclei. - 1063-7788 .- 1562-692X. ; 74:4, s. 573-579
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Tidskriftsartikel (refereegranskat)abstract
- The cross sections for the production of Gd-148 in W-nat and Ta-181 targets irradiated by 0.4-, 0.6-, 0.8-, 1.2-, 1.6-, and 2.6-GeV protons at the ITEP accelerator complex have been measured by direct alpha spectrometry without chemical separation. The experimental data have been compared with the data obtained at other laboratories and with the theoretical simulations of the yields on the basis of the BERTINI, ISABEL, CEM03.02, INCL4.2, INCL4.5, CASCADE07, and PHITS codes.
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| 7. |
- Farley, K.A., et al.
(författare)
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In situ radiometric and exposure age dating of the martian surface
- 2014
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 343:6169
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Tidskriftsartikel (refereegranskat)abstract
- We determined radiogenic and cosmogenic noble gases in a mudstone on the floor of Gale Crater. A K-Ar age of 4.21 ± 0.35 billion years represents a mixture of detrital and authigenic components and confirms the expected antiquity of rocks comprising the crater rim. Cosmic-ray-produced 3He, 21Ne, and 36Ar yield concordant surface exposure ages of 78 ± 30 million years. Surface exposure occurred mainly in the present geomorphic setting rather than during primary erosion and transport. Our observations are consistent with mudstone deposition shortly after the Gale impact or possibly in a later event of rapid erosion and deposition. The mudstone remained buried until recent exposure by wind-driven scarp retreat. Sedimentary rocks exposed by this mechanism may thus offer the best potential for organic biomarker preservation against destruction by cosmic radiation.
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| 8. |
- Conrad, P.G., et al.
(författare)
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Environmental Dynamics and the Habitability Potential at Gale Crater, Mars
- 2013
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Konferensbidrag (refereegranskat)abstract
- The assessment of environmental habitability potential involves measurement of the chemical and physical attributes of the system as well as their dynamic interplay. The environmental dynamics describe the availability of both energy sources and raw materials for meeting the requirements of organisms and for altering the environment. Energetic exchange can also determine the preservation potential for organic materials in the rock record. During its first year at Gale Crater, the Mars Science Laboratory payload has directly measured the chemistry and physical attributes, e.g., temperature, humidity, radiation, pressure, etc. of the martian atmosphere. Curiosity has also acquired chemical and mineralogical data, both from a wind drift deposit of fines and from two examples of a sedimentary rock formation in a region of Gale Crater called Yellowknife Bay, some 445 meters to the east of Bradbury Landing, where Curiosity initially touched down. These data enabled inferences to be made regarding depositional environment and past habitability potential at Gale Crater. The rock chemistry data reveal signs of aqueous interaction i.e., H2O, OH and H2 and sufficient elemental basis (C, H, O, S and possibly N) for plausible nutrient supply, should Mars have ever had autotrophic prokaryotes to exploit it, and a range of redox conditions tolerable to Earth microbes is indicated by the presence of clay minerals. Curiosity’s observations of the chemical, physical and geologic features of Yellowknife Bay point to a formerly habitable environment.
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