Characterization of 81P/Wild 2 Particles C2067,1,111,6.0 and C2067,1,111,8.0

The concentrations of C and N in cometary particles are of interest in characterizing the regions where comets formed. One aim of this work is to analyze enough Stardust particles to draw meaningful statistical conclusions about their inventories of C and N. Toward that end we report recent studies of Stardust particles and related materials

C/N and other Elemental Ratios of Chondritic Porous IDPS and a Fluffy Concordia Micrometeorite

Chondritic porous interplanetary dust particles (CP-IDPs) may be cometary in origin [1], as may ultracarbona-ceous (UCAMMs) [2] and 'fluffy' [3] micrometeorites from the Concordia collection. They are all rich in organics, which can rim grains and may have helped glue grains together during accretion [4]. The organics also contain nitrogen the input of which to Earth has potential biological importance. We report C/N ratios, and other properties of CP-IDPs and a Concordia fluffy microme-teorite

The use of NRA to study thermal diffusion of helium in (U,Pu)O-2

International audienceA lot of work has been already done on helium atomic diffusion in UO2 samples, but information is still lacking about the fate of helium in high level damaged UOX and MOX matrices and more precisely their intrinsic evolutions under alpha self irradiation in disposal/storage conditions. The present study deals with helium atomic diffusion in actinide doped samples versus damage level. The presently used samples allow a disposal simulation of about 100 years of a UOX spent fuel with a 60 MW d kg−1 burnup or a storage simulation of a MOX spent fuel with a 47.5 MW d kg−1 burnup. For the first time, nuclear reaction analysis of radioactive samples has been performed in order to obtain diffusion coefficients of helium in (U, Pu)O2. Samples were implanted with 3He+ and then annealed at temperatures ranging from 1123 K to 1273 K. The evolution of the 3He depth profiles was studied by the mean of the non-resonant reaction: 3He(d, p)4He. Using the SIMNRA software and the second Fick's law, thermal diffusion coefficients have been measured and compared to the 3He thermal diffusion coefficients in UO2 found in the literature

Extraterrestrial materials examined by mean of nuclear microprobe

Comet fragments, micrometeorites, and Interplanetary Dust Particles (IDPs) are small objects (<1 mm) of high scientific interest in cosmochemistry. More particularly, the determination of light element concentrations, such as C and N, in cometary samples is of interest since it gives information on the regions where such materials formed. Analyses of such objects should be performed so as to extract as much information as possible while preserving sample integrity. For this purpose, we need instruments and methods that provide both microanalysis and detailed imaging. In these respects, the nuclear microprobe offers many potential advantages: (i) the spatial resolution, ∼ 1μm is well-matched to the typical object dimensions, (ii) with some reservations, it is non-destructive when carefully conducted, (iii) it is quantitative, and especially sensitive for light elements. At the Saclay nuclear microprobe, we have been performing analyses of extraterrestrial objects for many years. We review some of these studies, emphasizing the specific requirements for successful analyses. We also discuss the potential pitfalls that may be encountered

ion beam analysis of light elements in thin films: common uses and capabilities

International audienc

l-Erdadevelopmentsinordertoimprovethewatercontent determinationinhydrousandnominallyanhydrousmantlephases

International audienceThepreciseknowledgeof thewater content ingeological samples suchas mantleminerals, volcanicglasses andglassyinclusions provestobecrucial informationfortheEarthSciencesbecausewaterhasaconsiderableinfluenceonphysical andchemical properties of Earth'smantleandcrust. Amongthenuclearmicrobeamtechniques, elasticrecoil detectionanalysis(ERDA) hasbeenusedat the nuclearmicroprobeof thePierreSu ̈eLaboratory(LPS) withaverygoodreliabilityforalongtimetodeterminethewatercontent of various materials. Previous ERDAmeasurements gavethetotal Hcontent at amicrometricscaleinthebulkof hydrous geologic samples. However, itwasmoredifficulttocharacterizenominallyanhydrousphases. Recenteffortsallowedustosignificantlyimprove thedifferent steps of theERDAanalysis, fromthesamplepreparationtothedeterminationof theuncertainties of theresultingH concentration. Alargeseriesof verydifferent geological sampleshasbeenmeasured: volcanicglassesandglassyinclusions, synthetic andnatural nominallyanhydrousminerals. Ournewsamplepreparationprotocol limitedthethicknessof thesurfacelayerof H-pol- lution, leadingtoaneasierdifferentiationofthebulkcontribution. SimultaneousPIXEandRBSmeasurementsallowthepreciseloca- tionoftheinterestingareasandalsogiveinformationonthechemical characterizationoftheinvestigatedsamples, withrespecttothe major andminor elements. Theprocessingof thelist-modeacquisitionfiles is madeusingtheRISMINsoftware, allowingamong other interestingfeatures tochecktheabsenceof water loss under thebeam. Wewill present theresults of theH-content measure- ments andshowthe goodagreement betweenour present results andthose obtainedbyFourier transforminfraredspectroscopy (FTIR) for thesameset of samples. Thedetectionlimit was measuredonadehydratednatural SanCarlos olivine((Mg,Fe)2SiO4) equal to130wt ppmH2O(15wt ppmHor 300at ppmH) andthe relative uncertainties onthe water concentrationrange from 10%to15%

Neutron Resonance Spectrometry of 99-Tc from 3 eV to 150 keV.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

Dehydration Melting Below the Undersaturated Transition Zone

International audienceA reflector 70-130 km below the base of the transition zone beneath Tibet is observed in receiver functions and underside seismic reflections, at depths consistent with the transition of garnet to bridgmanite. Contrast in water storage capacity between the minerals of the Earth's transition zone and lower mantle suggests the possibility for dehydration melting at the top of the lower mantle. First-principles calculations combined with laboratory synthesis experiments constrain the mantle water capacity across the base of the transition zone and into the top of the lower mantle. We interpret the observed seismic signal as consistent with 3-4 vol % hydrous melt resulting from dehydration melting in the garnet to bridgmanite transition. Should seismic signals evident in downwelling region result from water contents representative of upper mantle water globally, this constrains the water stored in nominally anhydrous minerals in the mantle to <30% the mass of the surface oceans. Plain Language Summary The dynamic mantle circulates material between the upper and lower mantle. At 70-130 km below the upper-to-lower mantle boundary, seismic waves indicate an abrupt change in the material properties of the mantle at that depth. We offer a new interpretation of these seismic signals through the calculation of the effects of water on the materials moving from the upper into the lower mantle, which suggests that the decrease in water storage upon pressure-induced breakdown of garnet can explain the observations through the generation of deep melt. Together with the synthesis of water-bearing garnet at the relevant pressures, we demonstrate that the synthesis of the observations suggest that the mantle may be significantly limited in water storage, with as little as 30% of the water that is found at the surface of the Earth