A miniature mass analyser for in-situ elemental analysis of planetary material-performance studies

The performance of a laser ablation mass analyser designed for in-situ exploration of the chemical composition of planetary surfaces has been investigated. The instrument measures the elemental and isotopic composition of raw solid materials with high spatial resolution. The initial studies were performed on NIST standard materials using IR laser irradiance (< 1 GW cm−2) at which a high temporal stability of ion formation and sufficiently low sample consumption was achieved. Measurements of highly averaged spectra could be performed with typical mass resolution of m/Δm ≈ 600 in an effective dynamic range spanning seven decades. Sensitive detection of several trace elements can be achieved at the ~ ppm level and lower. The isotopic composition is usually reproduced with 1% accuracy, implying good performance of the instrument for quantitative analysis of the isotopic fractionation effects caused by natural processes. Using the IR laser, significant elemental fractionation effects were observed for light elements and elements with a high ionization potential. Several diatomic clusters of major and minor elements could also be measured, and sometimes these interfere with the detection of trace elements at the same nominal mass. The potential of the mass analyser for application to sensitive detection of elements and their isotopes in realistic samples is exemplified by measurements of minerals. The high resolution and large dynamic range of the spectra makes detection limits of ~100ppb possible. Figure The mass spectrum of Allende meteorite measured by a miniature laser ablation mass spectrometer. Similar mass spectra of planetary materials in-situ could be measured with spatial resolution of 10-100 μm (white circles) providing means for chemical analysis of planetary surface

Cosmogenic nuclides in the solar gas-rich H3-6 chondrite breccia Frontier Mountain 90174

We re-evaluated the cosmic-ray exposure history of the H36 chondrite shower Frontier Mountain (FRO) 90174, which previously was reported to have a simple exposure history, an irradiation time of about 7 Ma, and a pre-atmospheric radius of 80-100 cm (Welten et al. 2001). Here we measured the concentrations and isotopic compositions of He, Ne, and Ar in 8 aliquots of 6 additional fragments of this shower, and 10Be and 26Al in the stone fractions of seven fragments. The radionuclide concentrations in the stone fractions, combined with those in the metal fractions, confirm that all samples are fragments of the FRO 90174 shower. Four of the fragments contain solarwind- implanted noble gases with a solar 20Ne/22Ne ratio of ~12.0, indicating that FRO 90174 is a regolith breccia. The concentrations of solar gases and cosmogenic 21Ne in the samples analyzed by us and by Welten et al. (2001) overlap with those of the FRO H-chondrites from the 1984 season, suggesting that many of these samples are also part of the large FRO 90174 chondrite shower. The cosmogenic 21Ne concentrations in FRO 90174 show no simple correlation with 10Be and 26Al activities. We found 21Ne excesses between 0.3-1.1 x 10^(-8) cm3 STP/g in 6 of the 17 samples. Since excess 21Ne and trapped solar gases are not homogeneously distributed, i.e., we found in one fragment aliquots with and without excess 21Ne and solar 20Ne, we conclude that excess 21Ne is due to GCR irradiation of the regolith before compaction of the FRO 90174 object. Therefore, the chondrite shower FRO 90174 did not simply experience an exposure history, but some material was already irradiated at the surface of an asteroid leading to excess 21Ne. This excess 21Ne is correlated to implanted solar gases, clearly indicating that both processes occurred on the regolith.The Meteoritics & Planetary Science archives are made available by the Meteoritical Society and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Spallation reactions. A successful interplay between modeling and applications

The spallation reactions are a type of nuclear reaction which occur in space by interaction of the cosmic rays with interstellar bodies. The first spallation reactions induced with an accelerator took place in 1947 at the Berkeley cyclotron (University of California) with 200 MeV deuterons and 400 MeV alpha beams. They highlighted the multiple emission of neutrons and charged particles and the production of a large number of residual nuclei far different from the target nuclei. The same year R. Serber describes the reaction in two steps: a first and fast one with high-energy particle emission leading to an excited remnant nucleus, and a second one, much slower, the de-excitation of the remnant. In 2010 IAEA organized a worskhop to present the results of the most widely used spallation codes within a benchmark of spallation models. If one of the goals was to understand the deficiencies, if any, in each code, one remarkable outcome points out the overall high-quality level of some models and so the great improvements achieved since Serber. Particle transport codes can then rely on such spallation models to treat the reactions between a light particle and an atomic nucleus with energies spanning from few tens of MeV up to some GeV. An overview of the spallation reactions modeling is presented in order to point out the incomparable contribution of models based on basic physics to numerous applications where such reactions occur. Validations or benchmarks, which are necessary steps in the improvement process, are also addressed, as well as the potential future domains of development. Spallation reactions modeling is a representative case of continuous studies aiming at understanding a reaction mechanism and which end up in a powerful tool.Comment: 59 pages, 54 figures, Revie

Dispersion and Focusing of Cosmic Rays in Magnetospheres

imulating the irradiation of planetary atmospheres by cosmic ray particles requires, among others, the ability to understand and to quantify the interactions of charged particles with planetary magnetic fields. Here we present a process that is very often ignored in such studies: the dispersion and focusing of cosmic ray trajectories in magnetospheres. The calculations were performed using our new code CosmicTransmutation, which has been developed to study cosmogenic nuclide production in meteoroids and planetary atmospheres and which includes the computation of the irradiation spectrum on top of the atmosphere. Here we discuss effects caused by dispersion and focusing of cosmic ray particle trajectories

Spallation, cosmic rays, meteorites, and planetology

In this review article we present some of the major applications for cosmogenic nuclide studies; extraterrestrial applications on meteorites, lunar surface samples but also on interstellar grains and terrestrial applications ranging from ages for exposure and burial over erosion and denudation rates to uplift and soil dynamics. For all the applications a good knowledge of the cosmogenic nuclide production rates is indispensable. Since it is neither possible nor feasible measuring production rates for all possible set-ups and geometries they are usually calculated using the particle spectra for primary and secondary particles and the cross sections for the relevant nuclear reactions. Considering the reacting particles we also discuss in some detail the basic properties of solar and galactic cosmic rays, especially we focus on the temporal variability. With a good understanding of the projectile types, a very relevant step is to understand and model the induced nuclear reactions. In doing so, we will briefly discuss the basic properties of spallation reactions and we especially focus on the recent very impressive improvements. We finish with a short outlook of the next possible steps for further improvements

The predictable collateral consequences of nucleosynthesis by spallation reactions in the early solar system

Ever since their first discovery in 1960, the origin of the relatively short-lived radionuclides, now extinct but alive in the early solar system, has been under debate. Possible scenarios are either nucleosynthetic production in stellar sources, e.g., asymptotic giant branch stars, Wolf-Rayet stars, novae, and supernovae, with subsequent injection into the solar nebula, or the production by spallation reactions in the early solar system. Here we present model calculations for the second scenario, the production of the relatively short-lived radionuclides by solar energetic particle events at the start of the solar system. The model is based on our current best knowledge of the nuclear reaction probabilities. In addition, the modeling depends on the relative fluence contribution of protons, 3He, and 4He in the solar particle events as well as on their energy distribution. The relative fluence contribution is the only free parameter in the system. Finally, the modeling depends on the chemical composition assumed for the irradiated target. The model simultaneously describes the observed solar system initial ratios 7Be/9Be, 10Be/9Be, 26Al/27Al,41Ca/40Ca, 53Mn/55Mn, and 92Nb/93Nb. In the framework of the local production scenario, the concordance of measured and modeled data for nuclides with half-lives ranging from 53 days up to 36 Myr enables us to put some stringent constraints on possible calcium-aluminum-rich refractory inclusion (CAI) production and its timing. One important requirement in such a scenario is that the material forming most of the CAIs must have experienced a surprisingly homogenous particle fluence. CAIs showing evidence for live 10Be, 26Al, 41Ca, 53Mn, and 92Nb close to the inferred solar system initial ratios would have to have been irradiated within ∼1 Myr. Much more stringent would be the time constraint for the one CAI for which formerly live 7Be has been reported. Such CAIs would have to have been irradiated for less than about 1 yr. Such a short timescale requires flux densities as high as ∼10 16 cm-2 s-1. To allow further tests of the local production scenario, we also predict solar system initial ratios for 14C/12C, 22Na/23Na, 36Cl/35Cl, 44Ti/48Ti, 54Mn/55Mn, 63Ni/60Ni, and 91Nb/93Nb, whose correlated shifts in the daughter isotopes would help to further test the local production scenario

The predictable collateral consequences of nucleosynthesis by spallation reactions in the early solar system

Ever since their first discovery in 1960, the origin of the relatively short-lived radionuclides, now extinct but alive in the early solar system, has been under debate. Possible scenarios are either nucleosynthetic production in stellar sources, e.g., asymptotic giant branch stars, Wolf-Rayet stars, novae, and supernovae, with subsequent injection into the solar nebula, or the production by spallation reactions in the early solar system. Here we present model calculations for the second scenario, the production of the relatively short-lived radionuclides by solar energetic particle events at the start of the solar system. The model is based on our current best knowledge of the nuclear reaction probabilities. In addition, the modeling depends on the relative fluence contribution of protons, 3He, and 4He in the solar particle events as well as on their energy distribution. The relative fluence contribution is the only free parameter in the system. Finally, the modeling depends on the chemical composition assumed for the irradiated target. The model simultaneously describes the observed solar system initial ratios 7Be/9Be, 10Be/9Be, 26Al/27Al,41Ca/40Ca, 53Mn/55Mn, and 92Nb/93Nb. In the framework of the local production scenario, the concordance of measured and modeled data for nuclides with half-lives ranging from 53 days up to 36 Myr enables us to put some stringent constraints on possible calcium-aluminum-rich refractory inclusion (CAI) production and its timing. One important requirement in such a scenario is that the material forming most of the CAIs must have experienced a surprisingly homogenous particle fluence. CAIs showing evidence for live 10Be, 26Al, 41Ca, 53Mn, and 92Nb close to the inferred solar system initial ratios would have to have been irradiated within ∼1 Myr. Much more stringent would be the time constraint for the one CAI for which formerly live 7Be has been reported. Such CAIs would have to have been irradiated for less than about 1 yr. Such a short timescale requires flux densities as high as ∼10 16 cm-2 s-1. To allow further tests of the local production scenario, we also predict solar system initial ratios for 14C/12C, 22Na/23Na, 36Cl/35Cl, 44Ti/48Ti, 54Mn/55Mn, 63Ni/60Ni, and 91Nb/93Nb, whose correlated shifts in the daughter isotopes would help to further test the local production scenario