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(Photo Credit: Viktor Zdrachal) With much sadness we say farewell to Helmut Rauch, who passed away on September 2, 2019. Many spectacular experiments followed in the fields of neutron optics, quantum physics, neutron interferometry and reactor physics. Further, at the Atominstitut, Helmut and his team verified the non-separability and non-locality of quantum physics and the violation of a Bell-like inequality by single neutron interferometry. [Extracted from the article]

Abstract: The influence of instrumental effects has to be taken into account in assessing various limitations to the quality of holographic images obtained with thermal neutrons. In comparison with the traditional treatment of resolution effects in the field of neutron scattering this requires a somewhat different approach. The reconstruction of the position of a nucleus from a hologram leads to a spot-like distribution of finite width in real space and the knowledge of the functional shape of this distribution is of crucial importance. In this context, the choice of the angular range covered by the recording process, the wavelength as well as the wavelength spread of the neutrons have to be considered. In planning a particular experiment, a proper choice for each of these quantities has to be worked out. Instrumental resolution also defines a limiting distance in real space up to which neighbouring object nuclei can be distinguished. The mathematical background of the above considerations is discussed. [Copyright &y& Elsevier]

A holographic image of the atomic arrangement in a PdH0.78 single crystal was recorded using spherical neutron waves generated by incoherent neutron-proton scattering (“internal source concept”). The resolution is sufficient to show the positions of single atomic nuclei on their respective lattice sites despite the delocalization of protons due to the weak bonding of hydrogen dissolved in palladium metal. Ways to overcome problems in the reconstruction of atomic positions related to the highly unfavorable sample shape are discussed. The technique offers possibilities for the investigation of various materials containing substantial amounts of hydrogen. [ABSTRACT FROM AUTHOR]

This paper reports long-term hydrogen storage experiments on MgH 2 and on the Mg alloy ZK60 following prior Severe Plastic Deformation (SPD). Although SPD processing leads to significant enhancements of hydrogen absorption and desorption rates in both materials, these are not necessarily stable with respect to repeated loading/unloading cycles. Cold rolled (CR) MgH 2 shows a reduction of capacity by 30% after 100 cycles. In contrast, in ZK60 (Mg-5Zn-0.8Zr) processed by High Pressure Torsion (HPT), both kinetics and storage capacity are stable for at least 200 absorption/desorption cycles. Analysis by means of Johnson-Mehl-Avrami theory clearly suggests that in the case of CR MgH 2 nucleation is followed by growth of extended MgH 2 domains leading to a gradual deterioration of hydrogen diffusion and storage/release characteristics. In the case of HPT ZK60, however, no further growth occurs subsequent to nucleation thus allowing for permanently enhanced hydrogen diffusion and stable storage/release properties. These results can be understood in terms of the different density and stability of SPD-induced lattice defects acting as nucleation sites in both materials studied. [ABSTRACT FROM AUTHOR]