[en] In this thesis the creation of permanent nanostructures induced by the impact of very slow (v≤5 x 10⁵ m/s) highly charged (q≤40) ions on the ionic crystal surfaces of CaF₂ and KBr is investigated. The systematic analysis of the samples surfaces by means of atomic force microscopy supplies information on the influence of the potential as well as the kinetic projectile energy on the process of structure creation. The individual impact of highly charged ions on the KBr(001) surface can initiate the creation of mono-atomic deep pit-like structures -nanopits- with a lateral size of a few 10 nm. The volume of these pits and the corresponding number of sputtered secondary particles show a linear dependence on the projectiles potential energy. For the onset of pit formation a kinetic energy dependent threshold in the potential energy E^grenz_pot(E_kin) could be identified. Based on the defect-mediated desorption by electrons and by including effects of defect agglomeration a consistent model for the process of pit formation was drawn. In this work the recently discovered creation of hillock-like structures by impact of highly charged ions on CaF₂(111) surfaces could be verified for lowest kinetic energies (E_kin≤150 eV x q). For the first time the potential energy of impinging projectiles could be identified to be exclusively responsible for the creation of nanostructures. Furthermore, a shift of potential energy threshold for hillock formation was observed for very small projectile velocities. Within the framework of cooperation with the Vienna University of Technology simulations based on the inelastic thermal spike model were performed, which allowed to interlink the individual hillock formation with a local melting of the ionic lattice. The essential influence of electron emission during the interaction of the highly charged ions with the surface on the process of nanostructuring was taken into consideration by complementary investigations of the secondary electron statistics. Thereby, total electron yields for an insulating surface at lowest projectile velocities (v≤1 x 10⁵ m/s) were determined for the first time. For velocities v≤5 x 10⁴ m/s a significant drop of the electron yield was observed for decreasing kinetic energy on the insulator representing a large contrast to metallic surfaces. Based on different models possible reasons for this effect are discussed. (orig.)

[en] The annual report 2009 of the institute of radiochemistry covers the following topics: Part 1: Actinides (metals) in biosystems; Part 2: Actinides in waste repositories. The research projects were aimed to the basic knowledge about coordination of actinide element transport and transfer in the environment, bacteria influence on the immobilization of heavy metals in water and soils, microbial diversity in biofilms and clays, protein applications for biosensors, dominating processes of soil-liquid interfaces, sorption and surface complexation processes.

[en] A concept of a table-top accelerator, consisting of a superconducting resonator and subsequent 6 standard TESLA cells working with a frequency of 1.3 GHz, is presented. Then electron gun is based on a photocathode. Especially described are the photocathode part, the laser system, the cryostat module, the RF system, the beam extraction, and the cryogenic facility. Finally the efficiency and the costs are considered, (HSI)

[en] The following topics are dealt with: Silicon based electrically driven microcavity LED, ultraviolet electroluminescence from a Gd-implanted Si-metal-oxide-semiconductor device, semiconductor quantum-cascade lasers, ion beam synthesis and morphology of semiconductor memories, ion implantation, films, sputtering, ion-beam induced destabilization of nanoparticles. (HSI)

[en] The Institute of Radiochemistry (IRC), one of the six Institutes of the Forschungszentrum Rossendorf (FZR) performs basic and applied research in the fields of radiochemistry and radioecology. Motivation and background of our research are environmental processes relevant for the installation of nuclear waste repositories, for remediation of uranium mining and milling sites, and for radioactive contaminations caused by nuclear accidents and fallout. Because of their high radiotoxicity and long half-life the actinides are of special interest. The research is focused on a better understanding of the chemical behavior of actinides in the environment on a molecular level. We will increase our efforts to study both the speciation of actinides on bio-molecular interfaces and their transport in bio-systems. Current topics of our research work are: aquatic chemistry of actinides, actinides in bio-systems, interaction of actinides with solid phases, Reactive transport of actinides. About 60 scientists, technicians and PhD students are employed at the Institute of Radiochemistry. We accomplished many new scientific results in the past year, which are presented in this annual report. Among them only few can be highlighted in this preface. Further progress was achieved in understanding the formation and characterization of uranium containing colloids. The newly installed method of laser-induced breakdown detection was very helpful for the identification of uranium colloids under anoxic conditions. We were very successful in the determination of formation pathways and structure of various actinide complexes. These results contribute to a better understanding of actinide speciation in geo- and bio-systems, especially with respect to the chemical processes on the interfaces. The results achieved in the characterization of the properties, modification, and interaction of the S-layers of Bacillus sphaericus with uranium and some other heavy metals strengthen our hope to use this material to separate heavy metals from very low contaminated waters or to produce well-structured metal templates in future. Studies about the interaction of actinides with different bacterial strains improved our understanding about the different binding in biological systems. Our investigations about interaction, sorption, and diffusion of actinides in clay in presence of fulvic and humic acids are included in national projects and in international collaborations. Furthermore we can report that our new radiochemical experimental station on the free electron IR-Laser of the Rossendorf accelerator ELBE is now in operation. After first tests we will start our research work in 2005. (orig.)

[en] Nucleation of dislocation loop at the crack tip in a material subjected to uniaxial loading is investigated. Analytical expression for the total energy of rectangular dislocation loop at the crack tip is found. Dependence of the nucleation energy barrier on dislocation loop shape and stress intensity factor at the crack tip is determined. It is established that the energetic barrier for nucleation of dislocation loop strongly depends on the stress intensity factor. Nucleation of dislocation loop is very sensitive to stress field modifiers (forest dislocations, precipitates, clusters of point defects, etc) in the crack tip vicinity. (orig.)

[en] Considering the hypothetical core melt down scenario for a light water reactor (LWR) a possible failure mode of the reactor pressure vessel (RPV) and its failure time has to be investigated for a determination of the loadings on the containment. Several experiments have been performed accompanied with material properties evaluation, theoretical, and numerical work. At the Institute Of Safety Research of the FZR a finite element model has been developed simulating the thermal processes and the viscoplastic behaviour of the vessel wall. An advanced model for creep and material damage has been established and has been validated using experimental data. The thermal hydraulic and the mechanical calculations are sequentially and recursively coupled. The model is capable of evaluating fracture time and fracture position of a vessel with an internally heated melt pool. The model was applied to pre- and post test calculations for the FOREVER test series representing the RPV of a PWR in the scale of 1:10. These experiments were performed at the Royal Institute of Technology in Stockholm. The results of the calculations can be summarised as follows: The creeping process is caused by the simultaneous presence of high temperature (>600 C) and pressure (>1 MPa). The hot focus region is the most endangered zone exhibiting the highest creep strain rates. The exact level of temperature and pressure has an influence on the vessel failure time but not on the failure position. The failure time can be predicted with an uncertainty of 20 to 25%. This uncertainty is caused by the large scatter and the high temperature sensitivity of the viscoplastic properties of the RPV steel. Contrary to the hot focus region, the lower centre of the vessel head exhibits a higher strength because of the lower temperatures in this zone. The lower part moves down without significant deformation. Therefore it can be assumed, that the vessel failure can be retarded or prevented by supporting this range. The development of a gap between melt crust and vessel wall could not be proofed. First calculations for a PWR geometry were performed to work out differences and commonalities between prototypic scenarios and scaled experiments. The results of the FOREVER-experiments cannot be transferred offhand to PWR geometry. The geometrical, mechanical and thermal relations cannot be scaled in the same way. Because of the significantly higher temperature level, a partial ablation of the vessel wall has to be to expected in the PWR scenario, which is not the case in the FOREVER tests. (orig.)

[en] Investigations in the technetium-99 m chemistry [1] are stimulated by the search for new radiopharmaceuticals for nuclear medical applications. To understand the coordination mode of technetium with various complexing agents, macroscopic studies of technetium coordination chemistry are often performed in the milligram level using the low energy β-emitting radionuclide radionuclide ⁹⁹Tc, which has a much longer half life (t_1/2 = 2.12 x 10⁵ years) than ^99mTc (6 hours). Investigations of rhenium coordination chemistry are done in conjunction with Tc studies because Re possesses chemical properties similar to those of Tc. For some chemical tasks, Re provides a non-radioactive alternative to work with Tc radioisotopes. In addition, ¹⁸⁶Re and ¹⁸⁸Re are of great interest to nuclear medicine as they possess nuclear properties favorable for use in therapeutic radiopharmaceuticals. Our investigations of Tc and Re coordination chemistry are toward this goal. A large series of technetium and rhenium complexes resulting from this studies have been characterized by X-ray crystal structure determinations. (orig.)

[en] Monte-Carlo estimates of the subthreshold φ meson production are performed for the reaction ¹²C + ¹²C at 2 A.GeV assuming the φ's to be emitted isotropically and distributed thermally in the center-of-mass system of the colliding nuclei. Different scenarios involving the detector installations FOPI and HADES at SIS/GSI are considered to determine the expected yields of φ(1020) mesons identified via the K⁺K^- and e⁺e^- decay channels. (orig.)

[en] The Institute of Safety Research (ISR) is one of the six Research Institutes of Forschungszentrum Rossendorf e.V. (FZR e.V.) which is a member institution of the Wissenschaftsgemeinschaft Gottfried Wilhelm Leibniz (Leibniz Association). Together with the Institute of Radiochemistry, ISR constitutes the research programme ''Safety and Environment'' which is one from three scientific programmes of FZR. In the framework of this research programme, the institute is responsible for the two subprogrammes ''Plant and Reactor Safety'' and ''Thermal Fluid Dynamics'', respectively. We also provide minor contributions to the sub-programme ''Radio-Ecology''. Moreover, with the development of a pulsed photo-neutron source at the radiation source ELBE (Electron linear accelerator for beams of high brilliance and low emittance), we are involved in a networking project carried out by the FZR Institute of Nuclear and Hadron Physics, the Physics Department of TU Dresden, and ISR. (orig.)