[en] Ion beam analysis is a set of precise, calibration free and non-destructive methods for determining surface-near concentrations of potentially all elements and isotopes in a single measurement. For determination of concentrations the reaction cross-section of the projectile with the targets has to be known, in general at the primary beam energy and all energies below. To reduce the experimental effort of cross-section measurements a new method is presented here. The method is based on the projectile energy reduction when passing matter of thick targets. The continuous slowing down approximation is used to determine cross-sections from a thick target at projectile energies below the primary energy by backward calculation of the measured product spectra. Results for "1"2C("3He,p)"1"4N below 4.5 MeV are in rough agreement with literature data and reproduce the measured spectra. New data for reactions of "3He with "1"3C are acquired using the new technique. The applied approximations and further applications are discussed.

[en] Molecules containing conjugated π-electrons concentrate large oscillator strength into a single exciton which introduces pronounced polariton effects in the spectra of the corresponding anisotropic crystal. Coupling of excitons into a macroscopic polarization field leads to distinctly different absorption and electroabsorption spectra of a single crystal and optically isotropic nanocrystalline films as demonstrated for α-sexithiophene. We show that nevertheless the electronic states and their response to an external field are the same and all differences result from the electrodynamics of a large coherent polarization. Electroabsorption spectra resolve these electronic states which are masked in the absorption spectra by a large excess absorption attributed to scattering by anisotropic domains

[en] We illustrate a process for designing solar thermal chemical reactors for industrial applications. The process is iterative and involves developing a numerical model of the reactor that links the radiation heat transfer to the other modes of heat transfer and the kinetics of the chemical reaction. Reactors that effectively convert solar energy to chemical energy match well the solar flux entering the reactor to the rate of the reaction being effected in the reactor. The design parameters controlling this match include the reactor's geometry, the reactant feed condition, and the form of the reactants

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[en] Eurofer97, P92 and Fe samples were exposed simultaneously in the linear plasma device PSI-2 to deuterium plasma and with addition of He, Ar or Kr at elevated temperature in the range of 800–950 K. Samples were exposed to plasma with an incident ion energy of 60–80 eV and an incident ion fluence of 5 × 10²⁵ m⁻². Surface morphology investigation of exposed samples reveals formation of fuzz-like structures on the surface steels when exposed to D and D+He plasma. Tungsten enrichment on the surface of the steels was observed after all exposures, but the average tungsten concentration varied from 4 to 18 at.%, depending on plasma composition. The highest tungsten enrichment on the surface was observed for samples exposed to D+He plasma. Addition of He to the plasma increased D retention, which was attributed to near-surface bubble formation, confirmed by transmission electron microscopy studies. (topical issue article)

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[en] Highlights: • New reduced activation ferritic steel investigated for nuclear fusion applications. • PSI-2 D₂ plasma exposures up to 1150 K and modelling investigations. • ppm level of D retention and W enrichment after exposure. • Low impurity and C contents lead to low long-term activity. • Component modelling shows at least 1.5 MW/m² load limit. - Abstract: Materials are the most urgent issue in nuclear fusion research. Besides tungsten, steels are considered for unifying functional and structural materials due to their cost and mechanical advantages over tungsten. However, the fusion neutrons impose a strong constraint on the ingredients of the steel in order to avoid long lasting activation, while the material has to pertain sputtering resistance, low hydrogen retention, and long-term mechanical stability. In this proof-of-principle, we demonstrate the interesting properties of the new material HiperFer (High performance Ferrite) as a material suitable for fusion applications. The investigation covers neutron activation modelled by FISPACT-II, plasma sputtering and deuterium retention experiments in PSI-2, thermo-mechanical properties and component modelling. The material was found to feature a low nuclear inventory. Its sputtering yield reduces due to preferential sputtering by a factor 4 over the PSI-2 D₂ plasma exposure with possible reductions of up to 70 indicated by SD.Trim.SP5 modelling. The exposure temperature shows a strong influence on this reduction due to metal diffusion, affecting layers of 1 µm in PSI-2 at 1150 K exposure for 4 h. Deuterium retention in the ppm range was found under all conditions, together with ∼10 ppm C and N solubility of the ferritic material. The creep and cyclic fatigue resistance exceed the values of Eu-97 steel. As an all HiperFer component, heat loads in the order of 1.5 MW/m² could be tolerated using water-cooled monoblocks. In conclusion, the material solves several contradictions present with alternative reduced-activation steels, but its applications temperatures >820 K also introduce new engineering challenges.

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[en] EUROFER, P92 steel and iron samples were exposed in the linear plasma generator PSI-2 at a sample temperature of about 470–500 K with an incident ion flux of about 3–5 × 10²¹ m⁻² s⁻¹, an incident ion fluence of 1 × 10²⁶ m⁻² and an incident ion energy of 60–70 eV. Samples were exposed to deuterium plasma and with additional seeding impurities of He, Ar, Ne, Kr or Kr + He. Laterally averaged surface W enrichment varied between 0.6 and 6 at.%, depending on the exposure conditions, measured by energy dispersive x-ray spectroscopy with low energy electron beam and Rutherford backscattered spectroscopy. Microstructure observation revealed a complex morphology depending on the plasma composition. W enrichment was mostly located in the spike nano structures. Addition of He to the plasma rounded and enlarged the spikes on the surface whereas addition of heavier species to the plasma resulted in smoothing the steels surface. In case of steel samples exposed to D + He plasma, fine nano-bubbles with sizes below 3 nm were found near the sample surface. Sputtering rate increases by one order of magnitude by Ar and Ne seeding and by two orders of magnitude by Kr seeding for both types of steels. Measured D retention increases with He addition and decreases with higher-Z species seeding. (paper)

[en] Tungsten is a candidate material for plasma-facing components in nuclear fusion reactors. In operation it will face temperatures >800 K together with an influx of helium ions. Previously, the evolution of special surface nanostructures called fuzz was found under these conditions in a limited window of surface temperature, ion flux and ion energy. Fuzz potentially leads to lower heat load tolerances, enhanced erosion and dust formation, hence should be avoided in a fusion reactor. Here the fuzz growth is reinvestigated in situ during its growth by considering its impact on the surfaces infrared emissivity at 4 μ m wavelength with an infrared camera in the linear plasma device PSI-2. A hole in the surface serves as an emissivity reference to calibrate fuzz thickness versus infrared emissivity. Among new data on the above mentioned relations, a lower fuzz growth threshold of 815 ± 24 K is found. Fuzz is seen to grow on rough and polished surfaces and even on the hole’s side walls alike. Literature scalings for thickness, flux and time relations of the fuzz growth rate could not be reproduced, but for the temperature scaling a good agreement to the Arrhenius equation was found. (paper)