Perspectives of Nuclear Physics in Europe: NuPECC Long Range Plan 2010

The goal of this European Science Foundation Forward Look into the future of Nuclear Physics is to bring together the entire Nuclear Physics community in Europe to formulate a coherent plan of the best way to develop the field in the coming decade and beyond.<p></p> The primary aim of Nuclear Physics is to understand the origin, evolution, structure and phases of strongly interacting matter, which constitutes nearly 100% of the visible matter in the universe. This is an immensely important and challenging task that requires the concerted effort of scientists working in both theory and experiment, funding agencies, politicians and the public.<p></p> Nuclear Physics projects are often “big science”, which implies large investments and long lead times. They need careful forward planning and strong support from policy makers. This Forward Look provides an excellent tool to achieve this. It represents the outcome of detailed scrutiny by Europe’s leading experts and will help focus the views of the scientific community on the most promising directions in the field and create the basis for funding agencies to provide adequate support.<p></p> The current NuPECC Long Range Plan 2010 “Perspectives of Nuclear Physics in Europe” resulted from consultation with close to 6 000 scientists and engineers over a period of approximately one year. Its detailed recommendations are presented on the following pages. For the interested public, a short summary brochure has been produced to accompany the Forward Look.<p></p&gt

Energy-selective neutron imaging for materials science

Common neutron imaging techniques study the attenuation of a neutron beam penetrating a sample of interest. The recorded radiograph shows a contrast depending on traversed material and its thickness. Tomography allows separating both and obtaining 3D spatial information about the material distribution, solving problems in numerous fields ranging from virtually separating fossils from surrounding rock to water management in fuel cells. It is nowadays routinely performed at PSI¿s neutron imaging facilities. Energy-selective neutron imaging studies the wavelength-dependency of the cross-section by using a beam of reduced wavelength bandwidth instead of averaging out the cross-section over the incident beam spectrum. The range of observed contrasts/image information is than extended and can largely be understood in the context of the Bragg law. Different types of monochromator (mechanical neutron velocity selector, double crystal monochromator, filter materials) are characterized for use in neutron imaging. In polycrystalline samples, sharp Bragg edges are observed as coherent elastic scattering at the (hkl) plane can occur for all wavelengths up to 2dhkl, after which a sharp increase in transmission intensity is observed. Much like diffraction peaks, they contain information on e.g. crystal phase or projected strain. The absence of coherent elastic scattering past the last Bragg edge (Bragg cut-off) allows for quantification. In samples with few grains or even single crystals, all orientations w.r.t. the beam are no longer present and rather than Bragg edges, the cross section now exhibits distinct peaks, the ensemble of which holds information on the crystallite¿s phase, orientation and shape. A spatial variation in contrast appears across the sample, between those grains fulfilling the Bragg condition ¿ scattering and decreasing the transmitted beam intensity ¿ and those that do not. After initial qualitative assessments, recent advances on the quantitative grain orientation mapping are made based on time-of-flight measurements of high energy resolution recorded at the ISIS pulsed neutron source. But where do these scattered neutrons go to? A new set-up was developed to permit simultaneous transmission and diffractive neutron imaging. Capturing the neutrons diffracted by a grain also yields a projection of that grain, with the position on the detector indicative of the orientation. These projections can in turn be used for algebraic reconstruction, which yields a grain volume as well. After feasibility studies on an iron single crystal cube the recent push towards polycrystalline samples will is illustrated with a neutron diffraction contrast tomography (nDCT) of a coarse-grained aluminium strain sample

A Measurement of Neutron Polarization and Transmission for the nEDM@SNS Experiment

The D.O.E Nuclear Science Advisory Committee Long Range Plan has called for experimental programs to explore fundamental symmetry violations and their implications in nuclear, particle and cosmological physics. The neutron electric dipole moment experiment at the Spallation Neutron Source (nEDM@SNS) aims to search for new physics in the Time-reversal (T) and Charge-Parity (CP) symmetry violating sector by setting a new limit on the nEDM down to a few x 10-28 e·cm using a novel cryogenic technique, which combines the unique properties of polarized Ultracold Neutrons (UCN), polarized 3He, and superfluid 4He. The experiment will employ a cryogenic magnet and magnetic shielding package to provide the magnetic field environment required to achieve the proposed sensitivity. This dissertation describes the design and implementation of a 3He based neutron polarimetry setup at the SNS to measure the monochromatic neutron polarization and transmission losses resulting from passage through the magnetic shielding and cryogenic windows. Results from monochromatic neutron polarization and transmission measurements will be presented

Development and evaluation of the elastic recovery concept for expandable space structures

Elastic recovery of expandable space structure

Investigations on polystyrene sulfonates and polyacrylates in the presence of specifically interacting cations

In der vorliegenden Arbeit werden die Wechselwirkungen zwischen Polyelektrolyten (PE) und spezifisch wechselwirkenden Kationen (SIC) in verdünnter wässriger Lösung mit unterschiedlichen Streumethoden und der isothermalen Titrationskalorimetrie (ITC) untersucht. Der Fokus liegt auf der Kombination Al3+-Polystyrolsulfonat (AlPSS) und Ba2+-Polystyrolsulfonat (BaPSS).Es konnte gezeigt werden, dass das Phasendiagramm von Polystyrolsulfonat in Gegenwart von Al3+ eine Phasengrenze besitzt, die eine ansteigende kritische Al3+ Konzentration mit ansteigender Polymerkonzentration aufweist. Unterhalb der Phasengrenze sind die AlPSS Lösungen stabil, während oberhalb der Phasengrenze eine Fällung der Ketten auftritt. Das Phasendiagramm von Polystyrolsulfonat mit Ba2+ weist ebenfalls einen stabilen Bereich bei niedrigen und einen instabilen Bereich bei hohen Ba2+ Konzentrationen auf, die über eine Phasengrenze mit einem ungewöhnlichen horizontalen Verlauf voneinander getrennt sind. Bei beiden Kombinationen kommt es mit zunehmender Al3+ und Ba2+ Konzentration zu einer Schrumpfung der PSS Ketten, wobei im Fall von AlPSS die Struktur bis kurz vor der Phasengrenze knäuelartig bleibt, während im Falle von BaPSS die Ketten kompakter werden, ohne aber zu einer kompakten Kugel zu kollabieren. In beiden Fällen führt eine Einführung oder die Konzentrationserhöhung eines Inertsalzes zu einer Verschiebung der Phasengrenzen zu höheren SIC Konzentrationen. ITC Messungen an verschiedenen SIC-PE Kombinationen zeigen, dass in nahezu allen untersuchten Kombinationen die Anbindung der SIC an das Polymer entropiegetrieben ist. Lediglich im Fall von BaPSS kann von einer exothermen Anbindung ausgegangen werden.Mit Hilfe der gewonnenen Resultate werden Vergleiche zu Studien gezogen, die mit SIC-Polyacrylaten Komplexen durchgeführt wurden.Interactions between polyelectrolytes (PE) and specifically interacting cations (SIC) in dilute aqueous solutions were investigated in the present work by various scattering methods and isothermal titration calorimetry. The focus lies on the combination of Al3+-polystyrene sulfonate (AlPSS) and Ba2+-polystyrene sulfonate (BaPSS).It could be shown that the phase diagram of polystyrenesulfonate in the presence of Al3+ exhibits a phase boundary, which shows a linear correlation between the amount of salt necessary to precipitate the polyelectrolyte and the molar concentration of the negative residues of the polyelectrolyte. Below the threshold the AlPSS samples are stable, while precipitation of the AlPSS chains can be observed at states located beyond the threshold. The phase diagram of polystyrenesulfonate in the presence of Ba2+ exhibits also a stable regime at low barium and an instable regime at higher Ba2+ concentrations. Both regimes are separated from each other by an unusual horizontal threshold. In both combinations a shrinking of the PSS chains can be observed with an increasing concentration of Al3+ or Ba2+. The structure of AlPSS stays coil-like even at points close to the phase boundary, while the BaPSS chains become more compact, but without collapsing to a compact sphere. An implementation or an increase of an inert salt concentration, leads to a shift of the threshold to higher SIC concentrations. ITC measurements on various SIC-PE combinations underlines that the binding of the SICs to the PE is in nearly all cases, which were investigated, an entropically driven process. Just in case of BaPSS it can be concluded that the binding process is exothermic.The present results on AlPSS and BaPSS make available a detailed comparison with corresponding studies performed with complexes of SIC-polyacrylates.von Markus Hansch, M.Sc. ; [1. Gutachter: Prof. Dr. Klaus Huber, 2. Gutachter: Prof. Dr. Wolfgang Bremser]Tag der Verteidigung: 27.04.2017Universität Paderborn, Dissertation, 201