Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41454 Publications

Lateral and depth distribution of defects in ultra fine grained copper prepared by high pressure torsion

Cizek, J.; Prochazka, I.; Brauer, G.; Anwand, W.; Kuzel, R.; Cieslar, M.; Islamgaliev, R. K.

Ultra-fine grained copper prepared by high-pressure torsion has been studied by means of positron annihilation techniques (slow positron implantation spectroscopy,conventional positron lifetime and Doppler broadening measurements) combined with transmission electron microscopy, X-ray diffraction and microhardness measurements. Dislocations in distorted regions along grain boundaries and microvoids of size 3-4 vacancies inside grains were identified and their lateral distribution and depth profile were investigated in detail. The concentrationof microvoids has been found to decrease with depth and to vary slightly with the distance from specimen axis, being lowest in the centre of the specimen disc. No position dependence of the concentration of dislocations was observed.

Keywords: ultra-fine grained copper; high-pressure torsion; dislocations; microvoids; slow positron implantation spectroscopy; positron lifetime; Doppler broadening

  • J. Metastable Nanocryst. Mater. 17 (2003) 23-28

Permalink: https://www.hzdr.de/publications/Publ-6006


Sampling and Characterization of Rock Material from Uranium Mining Waste Rocks for Study and Modeling of Release and Migration of Uranium

Sachs, S.; Benes, P.; Vopalka, D.; Stamberg, K.; Mibus, J.; Bernhard, G.; Bauer, A.

To study the effects of humic substances on the leaching and migration of uranium from uranium mining waste a natural rock material was sampled from a uranium rock pile situated in the mining region Schlema/Alberoda (Saxony, Germany). This report describes the sampling and characterization of the <1 mm grain size fraction of the rock material. The main focus is on the characterization of the sampled material with regard to its elemental and mineralogical composition and its amount of uranium that is accessible from the rock material by leaching processes.

Keywords: Uranium; migration; humic substances; uranium mining; rock pile; rock material; characterization

  • Contribution to external collection
    Humic Substances in Performance Assessment of Nuclear Waste Disposal : Actinide and Iodine Migration in the Far-Field. Second Technical Progress Report, Forschungszentrum Karlsruhe, Wissenschaftliche Berichte, FZKA 6969, Karlsruhe 2004, 73-84

Permalink: https://www.hzdr.de/publications/Publ-6005


Spatial distribution of defects in ultra-fine grained copper prepared by high pressure torsion

Cizek, J.; Prochazka, I.; Brauer, G.; Anwand, W.; Kuzel, R.; Cieslar, M.; Islamgaliev, R. K.

A study of ultra-fine grained copper produced by high-pressure torsion is presented. Positron annihilation spectroscopies (slow-positron implantation, lifetime and Doppler broadening spectroscopies), transmission electron microscopy, X-ray diffraction spectroscopy and micro-hardness measurements have been employed in order to identify defects and their spatial dis-tribution, i.e. lateral distribution and depth profile, in the specimens. Two types of defects could be identified: dislocations in the distorted regions along grain boundaries and micro-voids of size of 3-4 vacancies inside the grains. No change in grain size as a function of the distance from the center of the sample disk was observed. The mean coherent domain size close to the surface was found to be 80 ± 20 nm and it slightly increases with depth. The con-centration of microvoids has been found to decrease with depth and it slightly varies with the distance from the center of the disk, being lowest in the center. No position dependence of the concentration of dislocation was observed.

Keywords: High-pressure torsion; ultra-fine grained copper; spatial distribution of defects; positron annihilation spectroscopy

  • phys.stat.sol.(a) 195 (2003) 335-349

Permalink: https://www.hzdr.de/publications/Publ-6004


Metallographical and Numerical Investigation of the EC-FOREVER-4 Test

Willschütz, H.-G.; Altstadt, E.; Mueller, G.; Boehmert, J.; Sehgal, B. R.

Assuming the hypothetical scenario of a severe accident with subsequent core meltdown and formation of a melt pool in the reactor pressure vessel (RPV) lower plenum of a Light Water Reactor (LWR) leads to the question about the behavior of the RPV. One accident management strategy could be to stabilize the in-vessel debris configuration in the RPV as one major barrier against uncontrolled release of heat and radio nuclides.
To get an improved understanding and knowledge of the melt pool convection and the vessel creep and possible failure processes and modes occurring during the late phase of a core melt down accident the FOREVER-experiments (Failure Of REactor VEssel Retention) are currently underway at the Division of Nuclear Power Safety of the Royal Institute of Technology Stockholm. These experiments are simulating the behavior of the lower head of the RPV under the thermal loads of a convecting melt pool with decay heating, and under the pressure loads that the vessel experiences in a depressurization scenario. The geometrical scale of the experiments is 1:10 compared to a common LWR.
Accompanying the experiments metallographical and numerical work is performed at the Forschungszentrum Rossendorf. An axisymmetric Finite Element model is developed based on the multi-purpose code ANSYS/Multiphysics®. First the temperature field within the melt pool and within the vessel wall is evaluated. The transient structural mechanical calculations are then performed applying a creep model which takes into account large temperature, stress and strain variations. For a failure prediction it is necessary to introduce a damage measure. This is done according to a model proposed by Lemaitre. The microstructural investigation gives an insight to the material state of the vessel wall at different positions. This can be compared with the numerical damage value calculated in the Finite Element Model.
This paper deals with the experimental, numerical, and metallographical results of the creep failure experiment EC-FOREVER-4, where the American pressure vessel steel SA533B was applied for the lower head. For comparison the results of the experiment EC-FOREVER-3B are discussed, too.

Keywords: metallographic investigations; creep; crack; RPV; vessel failure

  • Lecture (Conference)
    International Congress on Advances in Nuclear Power Plants (ICAPP '04),13.-17.06.2004, Pittsburgh, PA, United States
  • Contribution to proceedings
    International Congress on Advances in Nuclear Power Plants (ICAPP '04),13.-17.06.2004, Pittsburgh, PA, United States, Proceedings on CD-ROM, paper 4006

Permalink: https://www.hzdr.de/publications/Publ-6003


Depth resolved investigations of boron implanted silicon

Sztucki, M.; Metzger, T. H.; Milita, S.; Berberich, F.; Schell, N.; Rouviere, J. L.; Patel, J.

We have studied the depth distribution and structure of defects in boron implanted silicon (001). Silicon wafers were implanted with a boron dose of 6e15 ions/cm2 at 32 keV and went through different annealing treatments. Using diffuse X-ray scattering at grazing incidence and exit angles we are able to distinguish between different kinds of defects (point defect clusters and extrinsic stacking faults on {111} planes) and to determine their depth distribution as a function of the thermal budget. Cross-section transmission electron microscopy was used to gain complementary information.
In addition we have determined the strain distribution caused by the boron implantation as a function of depth from rocking curve measurements.

Keywords: Diffuse X-ray scattering; Transmission electron microscopy; Ion implantation; Defects

Permalink: https://www.hzdr.de/publications/Publ-6002


The nanostructure evolution during and after magnetron deposition of Au films

Schell, N.; Jensen, T.; Petersen, J. H.; Andreasen, K. P.; Bottiger, J.; Chevallier, J.

The evolution of the nanostructure of magnetron sputtered Au films has been experimentally studied. At a synchrotron-radiation beam line, during growth and subsequent annealing, in-situ X-ray diffraction has been carried out to follow the texture, the grain size, the microstrain and lattice-plane distances. With Bragg–Brentano geometry, only (111) grains, having a (111) plane parallel to the film surface, have been observed, while, with glancing incidence and exit X-ray diffraction, (111)* grains, having one of their (111) planes perpendicular to the film surface, have also been observed. Both during growth and subsequent annealing, the (111) texture changed, and some (111)* grains recrystallized and/or the orientation of the grains changed. The microstrain decreased drastically during the first few minutes of growth (300 A) while, simultaneously, the size of the coherently diffracting domains increased. Subsequently, the microstrain became constant, and the rate of increase of the size of coherently diffracting domains leveled off. Initially, during the first few minutes of annealing, a large decrease in the microstrain was observed simultaneously with a dramatic rise of the size of the coherently diffracting domains. After this initial annealing period, as during film growth, the microstrain became constant, and the rate of increase of the size of coherently diffracting domains leveled off.
The activation energy for the initial growth of the coherent diffracting domains was found to be Q=(0.25 +/- 0.03) eV, and the activation energy for normal grain growth was found to be Q=(0.99 +/- 0.04) eV.
Finally, the thin-film stress was followed during growth and subsequent annealing. A tensile contribution to the stress was observed during island coalescence.

Keywords: Nanocrystalline Au; Nanostructure; In-situ X-ray diffraction; Growth; Magnetron sputtering

  • Contribution to HZDR-Annual report
    ERSF Highlights 2003 (2004) 39-40
  • Thin Solid Films 441 (2003) 96-103

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Permalink: https://www.hzdr.de/publications/Publ-6001


On the development of texture during growth of magnetron-sputtered CrN

Schell, N.; Petersen, J.; Bottiger, J.; Mücklich, A.; Chevallier, J.; Andreasen, K. P.; Eichhorn, F.

During growth of CrN films deposited by reactive magnetron sputtering, the development of the microstructure, especially the texture, was studied.By ex-situ Bragg–Brentano X-ray diffraction measurements, the texture, the grain size and the microstrain were measured as a function of film thickness.In addition, in-situ Bragg–Brentano X-ray diffraction and reflection measurements were carried out with synchrotron radiation, including measurements where the dynamic development of the microstructure was followed in real-time. Below a transition deposition temperature of approximately 550°C, it was found that the <002> preferred orientation dominated, while a mixture of <111> and <002> preferred orientations was found above the transition temperature. The development of texture with film thickness was controlled by a recrystallization mechanism.With increasing film thickness, the grain size increased while the microstrain decreased.The real-time measurements with synchrotron radiation revealed that several different dynamic processes took place both during and after depositions.After a long-time interruption of the growth,major changes in the texture were observed.

Keywords: Texture development; CrN; Magnetron sputtering

  • Thin Solid Films 426 (2003) 100-110

Permalink: https://www.hzdr.de/publications/Publ-6000


In situ high temperature synchrotron-radiation diffraction studies of silicidation processes in nanoscale Ni layers

Rinderknecht, J.; Prinz, H.; Kammler, T.; Schell, N.; Zchech, E.; Wetzig, K.; Gessner, T.

The formation of nickel silicides has been studied by X-ray diffraction experiments using synchrotron radiation (SR). A high temperature chamber was used to investigate the phase formation and transition processes under quasi-static conditions at temperatures from 200 to 650 °C. Samples with different dopants, several metal layer thicknesses as well as samples with and without a 150 A TiN capping layer on single-crystal (001) and polycrystalline silicon substrates were examined. While n-type dopants like P and As had no significant impact on the silicidation processes, boron decreased the range of thermal stability of the low-resistivity phase NiSi. A TiN capping layer shifts both these formation and transition temperatures to higher values.

Keywords: Nickel silicide; Phase formation; Transition temperatures; Dopants; Capping layer

  • Microelectronic Engineering 70 (2003) 226-232

Permalink: https://www.hzdr.de/publications/Publ-5999


Analysis of the biaxial strain state of Al-doped c-BN films using diffraction experiments with synchrotron radiation

Linss, V.; Halm, T.; Hoyer, W.; Richer, F.; Schell, N.

Thin films of cubic-boron nitride with a small amount of aluminum were produced by rf magnetron sputtering of a h-BN target and an additional Al ring-shaped electrode. Then the strain state of the biaxially stressed films was measured using synchrotron X-ray diffraction and the lattice spacing that unstressed films would have was calculated for different amounts of aluminum. This unstressed lattice spacing gets larger with increasing Al-amount. There is much evidence that the aluminum atoms are substitutionally incorporated at boron sites. This article provides an insight into the method of determining the unstressed lattice spacing using a slightly changed sin2_psi method.

Keywords: Cubic boron nitride (c-BN); Al-doping; Unstressed lattice spacing; Synchrotron radiation; sin2_psi-method

  • Vacuum 70 (1) (2003) 1-9

Permalink: https://www.hzdr.de/publications/Publ-5998


Dynamo experiments: where we stand and where we go

Stefani, F.; Gerbeth, G.; Gailitis, A.; Lielausis, O.; Platacis, E.

It was a nice coincidence that, after years of preparations, the liquid sodium dynamo facilities in Riga and Karlsruhe had become operative nearly simultaneously at the end of 1999. Since those pioneering times, there have been many additional runs in either place, yielding a wealth of reproducible data on the kinematic as well as on the saturated regime. The accompanying numerical work has got some maturity and shows, by now, a reasonable correspondence with the experimental results. The results of the two experiments are complementary rather than redundant as they cover the paradigmatic cases of a large scale dynamo (Riga) and a mean-field dynamo (Karlsruhe). With the main focus on the results and the interpretation of the Riga dynamo experiment, we give a summary of what has been achieved so far and what is left for future dynamo experiments. In particular, we demonstrate that the saturation mechanism of the Riga dynamo experiment is already a non-trivial one as it relies heavily on the change of the flow structure due to the back-reaction of the self-excited magnetic field. We comment on the envisioned dynamo experiments in non-rotating and rotating spheres and ask what geodynamo simulation could learn from
them.

  • Abstract in refereed journal
    Geophysical Research Abstracts 6(2004), 02933
  • Invited lecture (Conferences)
    European Geosciences Union, 1st General Assembly, 25.-30.04.2004, Nice, France

Permalink: https://www.hzdr.de/publications/Publ-5996


Relaxation kinetics in amorphous carbon films: an insight from atomic scale simulation

Belov, A. Y.; Jäger, H. U.

Depending on temperature, thermodynamically favoured structural relaxations in as-deposited tetrahedral amorphous carbon (ta-C) films can either essentially retain the content of sp3 bonded atoms or result in a transition to a graphitic phase with dominating sp2 bonding. The structural relaxation occurs at low temperatures (less than ~ 600 °C) and is accompanied by reduction of the grown-in film stress. The most recent NMR spectroscopy investigation [1] shows that the structural changes in highly tetrahedral a-C films due to low-temperature annealing don't reduce to simple sp3-to-sp2 or sp3-to-sp2 conversions and have more complicated nature than it was previously believed. We present results of long-term simulated annealing studies of the relaxation processes in ta-C using molecular dynamics with a modified Brenner potential for C-C interactions and the structural models of as-deposited (unrelaxed) ta-C generated by an ion-beam film deposition simulation [2]. It is shown that during low-temperature annealing the potential energy and stress of the as-deposited ta-C films are released with only minor changes in the short-range order and density. It is demonstrated that as a result of annealing the volumes of sp3 atoms decrease, which is consistent with experiment [1]. It is also found that the change of potential energy with annealing time can be fit by an exponential function, which enables to analyze the relaxation kinetics in as-deposited ta-C, in particular, to obtain the dependence of the relaxation time on annealing temperature.
[1] T.M. Alam, T.A. Friedmann, P.A. Schultz, D. Sebastiani, Phys. Rev. B 67, 245309 (2003)
[2] H.U. Jäger, A.Yu. Belov, Phys. Rev. B 68, 024201 (2003)

  • Lecture (Conference)
    European Materials Research Society 2004 Spring Meeting, Symposium J : Synthesis, Characterisation and AdvancedApplications of Amorphous Carbon films, 24-28 May 2004, Strasbourg France, contr. J-V.6

Permalink: https://www.hzdr.de/publications/Publ-5995


Hydrogen bonding and structural order in hydrogenated amorphous silicon prepared with hydrogen-diluted silane

Danesh, P.; Pantchev, B.; Antonova, K.; Liarokapis, E.; Schmidt, B.; Grambole, D.; Baran, J.

A study of the structural development of hydrogenated amorphous silicon (a-Si :H) during plasma-enhanced chemical vapour deposition with hydrogen-diluted silane has been carried out with focus on the variations in the hydrogen bonding configuration and in the amorphous silicon network with increasing film thickness. In addition, the hypothesis of a high fraction of non-bonded (molecular) hydrogen in a-Si :H has been tested. The total hydrogen concentration and its silicon-bonded fraction have been estimated by means of nuclear reaction analysis and infrared spectroscopy, respectively. It has been shown that the presumable molecular hydrogen is not detectable within the limits of the measurement accuracy of the methods used. The hydrogen concentration is uniformly distributed along the growth direction, and the infrared absorption modes at 2000 and 2100 cm-1 are not affected by increasing the film thickness. Raman spectroscopy has been used to follow the variations in the structure of the silicon network. The increase in the film thickness leads to an improved ordering of the amorphous network on the short and medium range scale for films deposited at low substrate temperatures. In films deposited at high substrate temperatures, the tendency of structural improvement has been detected only on the medium range scale.

Keywords: H:a-Si; NRA; Raman spectroscopy; hydrogen bonding

  • Journal of Physics D 37(2004), 249-254

Permalink: https://www.hzdr.de/publications/Publ-5993


Effect of post-hydrogenation on the structural properties of amorphous silicon network

Pantchev, B.; Danesh, P.; Liarokapis, E.; Schmidt, B.; Schmidt, J.; Grambole, D.

Post-hydrogenation of magnetron sputtered amorphous silicon films has been carried out with the aim to study the effect of hydrogen interaction with amorphous silicon network on its short and medium range order. Raman spectroscopy has been used to study the variations in the amorphous structure. Nuclear reaction analysis (NRA) has been used to determine the total amount and depth distribution of the penetrated hydrogen atoms. The concentration of the silicon-bonded hydrogen and the bonding configurations have been established by means of infrared (IR) transmission measurements. The values of hydrogen concentration evaluated by NRA and IR spectroscopy coincide within the measurement accuracy, suggesting that the hydrogen diffusion proceeds via interaction with the host silicon atoms. This interaction is accompanied by a rearrangement of the strained Si-Si bonds which leads to an improvement of the amorphous network.

Keywords: amorphous silicon; post-hydrogenation; hydrogen depth distribution; Raman spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-5990


NIR Spectroscopic Study on the Influence of Phenolic OH Groups on the Neptunium(V) Humate Complex Formation

Sachs, S.; Bernhard, G.

We investigated the influence of phenolic OH groups on the Np(V) complexation by humic acids at pH 7 and pH 8. The studies were performed by near-infrared (NIR) absorption spectroscopy applying unmodified and chemically modified humic acids with blocked phenolic/acidic OH groups. The experimental data were evaluated with the metal ion charge neutralization model. For all humic acids under investigation comparable complexation constants were determined. However, compared to the original humic acids, modified humic acids with blocked phenolic/acidic OH groups show significant lower loading capacities for Np(V) under the applied experimental. This result indicates a lower amount of maximal available humic acid ligand sites for the complexation of Np(V). Thus, it can be concluded that humic acid phenolic/acidic OH groups contribute to the interaction between humic acid and Np(V) under the studied conditions.

Keywords: Humic substances; Humic acids; Actinides; Complexation; Neptunium

  • Contribution to external collection
    Humic Substances in Performance Assessment of Nuclear Waste Disposal : Actinide and Iodine Migration in the Far-Field. Second Technical Progress Report, Forschungszentrum Karlsruhe, Wissenschaftliche Berichte, FZKA 6969, Karlsruhe 2004, 61-71

Permalink: https://www.hzdr.de/publications/Publ-5989


Some metallurgical applications of magnetic fields. The role of model experiments and velocity measuring techniques.

Gerbeth, G.

Magnetic fields provide the possibility of a tailored flow control for metallurgical and crystal growth processes. Two examples will be presented: the application of a specially shaped steady magnetic field in the melt extraction process of thin metallic fibres, and the control of the flow filling process in the investment casting of aluminium alloys. The role of cold model experiments and the development of velocity measuring techniques for metallic melts will be stressed. As a final example, velocity measurements in a liquid metal switcher will be presented.

  • Lecture (Conference)
    Coventry University, 12.01.2004, Coventry, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-5988


Differentiation between recurrent tumor or radiation necrosis in a child with anaplastic ependymoma after chemotherapy and radiation therapy

Beuthien-Baumann, B.; Hahn, G.; Winkler, C.; Heubner, G.

Background: In patients after treatment for malignant brain tumors, a clear distinction between tumor recurrence and radiation necrosis can be challenging. This case report describes the diagnostic workup in child with anaplastic ependymoma and inconclusive MRI (magnetic resonance imaging) and PET (positron emission tomography) findings.
Case Report: 1.5 years after resection, hyperfractionated radiotherapy and chemotherapy of an anaplastic ependymoma in the right parietal region, the cranial MRI of an 11-year-old girl showed multiple small contrast-enhanced lesions in the frontal cortex. In the following months, these lesions increased in number and size and neurologic symptoms developed. Diagnostic workup included repeated MRI scans, PET with an 18F-amino acid and 18F-fluorodexyglucose (FDG), as well as a brain biopsy.
Results: Amino acid PET, performed when the lesions were still small, showed multiple small areas of mild uptake in close correlation to the MRI lesions. Although not typical, this result was suspicious of tumor seeding, the more since the lesions appeared in gray matter areas outside the high-dose-rate irradiation field. A biopsy, performed 6 months later when the clinical appearance worsened, showed no tumor tissue. FDG PET, performed after the size and number of the lesions has increased, showed no intensely increased glucose metabolism, a high-grade recurrent tumor was therefore very unlikely. In the following months, the clinical picture stabilized.
Conclusion: The final interpretation of the lesions was multiple focal radiation necrosis based on perfusion abnormalities after chemotherapy and conformal hyperfractionated radiotherapy, probably due to an individually enhanced of the cerebral vessels.

Keywords: Anaplastic ependymoma; Magnetic resonance imaging; Positron emission tomography; Hyperfractionated radiotherapy; Radiation necrosis

  • Strahlentherapie Onkologie (2003) 179: 819-822

Permalink: https://www.hzdr.de/publications/Publ-5987


Core response of a PWR to a slug of under-borated water

Kliem, S.; Rohde, U.; Weiß, F.-P.

A parameter study, incorporating stationary and transient core calculations, was carried out for a hypothetical boron dilution event in a pressurized water reactor, using the 3D neutron kinetics core model DYN3D in combination with a fast running semi-analytical coolant mixing model. It was assumed that a slug of deborated water was formed in one of the loops, due to a secondary-to-primary steam generator leakage during outage. It was further assumed that this slug is not recognised and that the first main coolant pump is started, in preparation to returning to power. At the initiation of pump start-up, the reactor is still in the cold and deeply sub-critical state. By varying the initial slug volume, it was found in stationary calculations that, for the given core configuration, slugs of less than 14 m³ do not lead to re-criticality. Transient core calculations with larger slug volumes show a significant reactivity insertion and over-criticality. However, according to the calculations, even an over-criticality of about 2 $ did not lead to safety-relevant consequences. The power excursion is mitigated and stopped by Doppler feedback. The influence of the cross- section library on the course of the transient was investigated, applying an alternative library. Differences in the global core parameters lead to quantitative differences in the time and height of the power excursion. In addition, it is shown that numerical diffusion has to be suppressed in order to describe the boron transport correctly, especially at low flow velocities. Otherwise the neutron kinetic core behaviour cannot be correctly modelled.

Permalink: https://www.hzdr.de/publications/Publ-5986


EXAFS Study on the Neptunium(V) Complexation by Various Humic Acids under Neutral pH Conditions

Sachs, S.; Schmeide, K.; Reich, T.; Brendler, V.; Heise, K. H.; Bernhard, G.

The structure of Np(V) humic acid (HA) complexes at pH 7 was studied by extended x-ray absorption fine structure analysis (EXAFS). For the first time, the influence of phenolic OH groups on the complexation of HA and Np(V) in the neutral pH range was investigated using modified HAs with blocked phenolic OH groups and Bio-Rex70, a cation exchange resin having only carboxyl groups as proton exchanging sites.
The formation of Np(V) humate complexes was verified by near-infrared (NIR) spectroscopy. Axial Np-O bond distances of 1.84 - 1.85 Å were determined for the studied Np(V) humate complexes and the Np(V)-Bio-Rex70 sorbate. In the equatorial plane Np(V) is surrounded by about 3 oxygen atoms with bond lengths of 2.48 - 2.49 Å. The comparison of the structural parameters of the Np(V) humates with those of Np(V)-Bio-Rex70 points to the fact that the interaction between HA and Np(V) in the neutral pH range is dominated by carboxylate groups. However, up to now a contribution of phenolic OH groups to the interaction process cannot be excluded completely. The comparison of the obtained structural data for the Np(V) humates to those of Np(V) carboxylates and Np(V) aquo ions reported in the literature indicates that humic acid carboxylate groups predominantly act as monodentate ligands. A differentiation between equatorial coordinated carboxylate groups and water molecules using EXAFS spectroscopy is impossible.

Keywords: Neptunium(V); Humic acid; Complexation; EXAFS; NIR absorption spectroscopy; Structure

  • Radiochimica Acta 93(2005), 17-25

Permalink: https://www.hzdr.de/publications/Publ-5985


Factors affecting the specific activity of [18F]fluoride from a water target

Füchtner, F.; Preusche, S.; Mäding, P.; Steinbach, J.

  • Contribution to proceedings
    15th International Symposium on Radiopharmaceutical Chemistry (ISRC), Sydney, Australia, 10.-14.08.2003; J. Label. Comds. Radiopharm. 46 (2003) S218
  • Poster
    10th Workshop on Targetry and Target Chemistry, Medison, 13.-15.08.2004
  • Lecture (Conference)
    10th Workshop on Targetry and Target Chemistry, 13.-15.08.2004, Madison, USA

Permalink: https://www.hzdr.de/publications/Publ-5983


Changes in brain metabolism associated with remission in unipolar major depression

Holthoff, V.; Beuthien-Baumann, B.; Zündorf, G.; Triemer, A.; Lüdecke, S.; Winiecki, P.; Koch, R.; Füchtner, F.; Herholz, K.

Objective: Functional brain correlates of remission in patients with major depressive disorder (MDD) are measured with positron emission tomography (PET) and 18F-fluorodeoxyglucose.
Method: Glucose metabolism was measured in patients (n = 41) with moderate to severe MDD during acute depression and in the remitted state defined as a period of asymptomatic condition over 12 weeks. Data analyses used a region-of-interest (ROI) approach and statistical parametric mapping (SPM).
Results: There were significant decreases in metabolism upon remission with respect to the baseline scan in left prefrontal, anterior temporal and anterior cingulate cortex and bilateral thalamus (SPM analysis) and bilateral putamen and cerebellum (SPM and ROI analyses). There was a significant asymmetriy in prefrontal and anterior cingulate cortex metabolism with lower metabolism in the left hemisphere that persisted despite clinical remisson.
Conclusion: These findings support the hypothesis that selective monoamine reuptake inhibition leads to an attenuation of a brain circuit that mediates depressive symptomatology.

Keywords: depressive disorder; tomography; emission-computed; limbic system; frontal lobe; cerebellum

  • Acta Psychiatrica Scandinavica 110(2004), 184-194

Permalink: https://www.hzdr.de/publications/Publ-5982


Impact of asymmetric intrauterine growth restriction on organ function in newborn piglets

Bauer, R.; Walter, B.; Brust, P.; Füchtner, F.; Zwiener, U.

  • European Journal of Obstetrics and Gynecology and Reproductive Biology 110 (2003) S40-S49

Permalink: https://www.hzdr.de/publications/Publ-5981


An accurate method for correction of head movement in PET

Bühler, P.; Just, U.; Will, E.; Kotzerke, J.; van den Hoff, J.

A method is presented to correct positron emission tomography (PET) data for head motion during data acquisition. The method is based on simultaneous acquisition of PET data in list mode and monitoring of the patient's head movements with a motion tracking system. According to the measured head motion, the line of response (LOR) of each single detected PET event is spatially transformed, resulting in a spatially fully corrected data set. The basic algorithm for spatial transformation of LORs is based on a number of assumptions which can lead to spatial artifacts and quantitative inaccuracies in the resulting images. These deficiencies are discussed, demonstrated and methods for improvement are presented. Using different kinds of phantoms the validity and accuracy of the correction method is tested and its applicability to human studies is demonstrated as well.

  • IEEE Transaction on Medical Imaging 23(2004)9, 1176-1185
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 30(2003), S174/116
  • Lecture (Conference)
    European Association of Nuclear Medicine Annual Congress 2003, Amsterdam, 23.-27.08.2003

Permalink: https://www.hzdr.de/publications/Publ-5980


Teilautomatisierte Segmentierung zur Quantifizierung von Metastasen bei der FDG-PET

Pötzsch, C.; Beuthien-Baumann, B.; van den Hoff, J.

  • Abstract in refereed journal
    Nuklearmedizin (2003) 42 p. A26

Permalink: https://www.hzdr.de/publications/Publ-5979


Nutzbarmachung der List-Mode Akquisition an der PET-Kamera ECAT EXACT HR+

Just, U.; Will, E.; Beuthien-Baumann, B.; Bühler, P.; van den Hoff, J.

  • Abstract in refereed journal
    Nuklearmedizin (2003) 42 p. A93

Permalink: https://www.hzdr.de/publications/Publ-5978


Korrektur bewegungsbedingter Fehlortung individueller Koinzidenzereignisse in der PET

Bühler, P.; Just, U.; Will, E.; Zührl, K.; Kotzerke, J.; van den Hoff, J.

  • Abstract in refereed journal
    Nuklearmedizin (2003) 42 p. A26
  • Lecture (Conference)
    41. Jahrestagung der DGN, 2.-5. April 2003, Essen

Permalink: https://www.hzdr.de/publications/Publ-5977


Untersuchung des Glukosestoffwechsels bei Patienten mit HIV-Infektion unter hochaktiver antiretroviraler Therapie (HAART) mittels quantitativer dynamischer FDG-PET

van den Hoff, J.; Börner, A.; Behrens, G.; Meyer, G. J.; Knapp, W. H.

  • Abstract in refereed journal
    In: Nuklearmedizin als Paradigma molekularer Bildgebung, ed. I Brink, S Högerle, E Moser, p. 16, Blackwell Verlag, Berlin (2002)

Permalink: https://www.hzdr.de/publications/Publ-5976


Dynamische 15O-H2O-PET zur Erzeugung quantitativer 3D-Polar-Maps der Myokardperfusion

van den Hoff, J.; Fricke, H.; Wielepp, P.; Burchert, W.

  • Abstract in refereed journal
    Nuklearmedizin (2003) 42 p. A27

Permalink: https://www.hzdr.de/publications/Publ-5975


P0316 - Anordnung zur Röntgentomographie milt einem elektronisch abgelenkten Elektonenstrahl

Prasser, H.-M.; Hampel, U.

Aufgabe der Erfindung ist es, eine Anordung zur schnellen Tomographie mit elektronisch abgelenktem Elektronenstrahl vorzuschlagen, die es ermöglicht, Projektionen der Dichteverteilung eines zeitlich veränderlichen Messobjekts aus einer genau definierten Messebene zu ermitteln, deren Orientierung im Raum sich bei Veränderung der Durchstrahlungsrichtung während des Messzyklus nicht ändert.

  • Patent
    DE 103 56 601 A1
  • Patent
    DE 103 56 601 B4 - 2008.11.27

Permalink: https://www.hzdr.de/publications/Publ-5974


Quantenkaskadenlaser

Dekorsy, T.; Helm, M.; Georgiev, N.; Künzel, H.

Es wird ein Quantenkaskadenlaser mit einer Emissionswellenlänge unterhalb von 3,4 um und oberhalb von 1,5 um vorgeschlagen.

  • Patent
    DE 103 55 949 A1
  • Patent
    EP 1536531

Permalink: https://www.hzdr.de/publications/Publ-5973


P0313 - Verfahren zur Erzeugung verbesserter heteroepitaktischer gewachsener Siliziumkarbidschichten auf Siliziumsubstraten

Skorupa, W.; Panknin, D.; Ferro, G.; Gebel, T.; Yankow, R.

Aufgabe der Erfindung ist ein Verfahren, mit dem es möglich ist, die in der unteren Schicht vorhandenen gewünschten Eigenschaften der mit Lichtimpulsen behandelten Substrate für den weiteren Prozess verwertbar zu machen und die Welligkeit der Schicht zu verringern oder zu vermeiden.

  • Patent
    DE 103 44 986 A1
  • Patent
    WO 2005/031825 A1
  • Patent
    DE 103 44 986 B4 - 23. Okt. 2008

Permalink: https://www.hzdr.de/publications/Publ-5971


3-O-Methyl-6-[18F]Fluoro-L-DOPA and its Evaluation in Brain Tumour Imaging

Beuthien-Baumann, B.; Bredow, J.; Burchert, W.; Füchtner, F.; Bergmann, R.; Alheit, H.-D.; Reiss, G.; Hliscs, R.; Steinmeier, R.; Franke, W.-G.; Johannsen, B.; Kotzerke, J.

  • European Journal of Nuclear Medicine and Molecular Imaging (2003) 30: 1004-1008

Permalink: https://www.hzdr.de/publications/Publ-5970


Synthesis and Characterization of [11C]SMe-ADAM as a Potential Radiotracer for Imaging the Serotonin Transporter with PET

Zessin, J.; Kretzschmar, M.; Pawelke, B.; Bergmann, R.; Deuther-Conrad, W.; Brust, P.; Wüst, F.; Steinbach, J.; Johannsen, B.

  • Poster
    15th International Symposium on Radiopharmaceutical Chemistry, Sydney, Australia, 2003

Permalink: https://www.hzdr.de/publications/Publ-5969


Sex Differences in the Uptake of [18F]FMe-McN in Rat Brain

Marjamäki, P.; Eskola, O.; Haaparanta, M.; Grönroos, T.; Fagerholm, V.; Bergman, J.; Lehikoinen, P.; Savisto, N.; Zessin, J.; Solin, O.

  • Lecture (Conference)
    15th International Symposium on Radiopharmaceutical Chemistry, Sydney, Australia, 2003

Permalink: https://www.hzdr.de/publications/Publ-5968


Comparison of [11C](+)-MCN5652 and S-([18F]Fluoromethyl)-(+)-MCN5652 for PET Imaging of the Serotonin Transporter

Brust, P.; Zessin, J.; Solin, O.; Steinbach, J.

  • Lecture (Conference)
    15th International Symposium on Radiopharmaceutical Chemistry, Sydney, Australia, 2003

Permalink: https://www.hzdr.de/publications/Publ-5967


S-[18F]fluoromethyl-(+)-McN5652, a PET Tracer for the Serotonin Transporter: Evaluation in Rats

Marjamäki, P.; Zessin, J.; Eskola, O.; Grönroos, T.; Haaparanta, M.; Bergman, J.; Lehikoinen, P.; Forsback, S.; Brust, P.; Steinbach, J.; Solin, O.

The [18F]fluoromethyl analog of (+)-McN5652 ([18F]FMe-NcN) for imaging serotonin transporter (SERT) with positron emission tomography (PET) has recently been synthesized. We describe here the biological evaluation of [18F]FMe-NcN in rats. Biodistribution studies of [18F]FMe-McN in rat brain ex vivo after an intravenous injection showed a high accumulation of radioactivity in the regions rich in SERT, such as raphe nuclei, hypothalamus, thalamus, substantia nigra, locus coeruleus, and amygdala. Region-to-cerebellum ratios reached a muximum value of 9 in raphe nuclei within 3.5 h after administration. The specificity and selctivity of [18F]FMe-McN binding to SERT was studied by preinjecting blocking doses of serotonin, norepinephrine, and dopamine transporter inhibitors. Fluoxetine, a specific inhibitor for SERT, decreased the specific binding of [18F]FMe-McN in raphe nuclei by 91 plus minus 4 %; in other regions rich in SERT, similar results were obtained GBR12909 and nisoxetine, selective inhibitors for dopamine transporter (DAT) and norepinephrine transporter (NET), respectively, showed no significant effects on the uptake of [18F]FMe-McN. Our studies show that [18F]FMe-McN has a clear potential as a tracer for studies with PET or SERT function in humans.

Keywords: [18F]FMe-(+)-McN5652; serotonin transporter; positron emission tomography; 18F

  • Synapse (2003) 47: 45-53

Permalink: https://www.hzdr.de/publications/Publ-5966


18F-Labelling of the CCR1 antagonist ZK811460 for the diagnosis of the Alzheimer´s disease

Mäding, P.

  • Lecture (others)
    Technical Exchange Meeting on Alzheimer Imaging, Berlin, 30.10.2003

Permalink: https://www.hzdr.de/publications/Publ-5965


Investigation of the Complexation and the Migration Behavior of Actinides and Non-Radioactive Substances with Humic Acids under Geogenic Conditions - Complexation of Humic Acids with Actindies in the Oxidation State IV Th, U, Np

Sachs, S.; Schmeide, K.; Brendler, V.; Krepelova, A.; Mibus, J.; Geipel, G.; Heise, K.-H.; Bernhard, G.

Objective of this project was the study of basic interaction and migration processes of actinides in the environment in presence of humic acids (HA). To obtain more basic knowledge on these interaction processes synthetic HA with specific functional properties as well as 14C-labeled HA were synthesized and applied in comparison to the natural HA Aldrich. One focus of the work was on the synthesis of HA with distinct redox functionalities. The obtained synthetic products that are characterized by significantly higher Fe(III) redox capacities than Aldrich HA were applied to study the redox properties of HA and the redox stability of U(VI) humate complexes. It was confirmed that phenolic OH groups play an important role for the redox properties of HA. However, the results indicate that there are also other processes than the single oxidation of phenolic OH groups and/or other functional groups contributing to the redox behavior of HA. A first direct-spectroscopic proof for the reduction of U(VI) by synthetic HA with distinct redox functionality was obtained.
The complexation behavior of synthetic and natural HA with actinides (Th, Np, Pu) was studied. Structural parameters of Pu(III), Th(IV), Np(IV) and Np(V) humates were determined by X-ray absorption spectroscopy (XAS). The results show that carboxylate groups dominate the interaction between HA and actinide ions. These are predominant monodentately bound. The influence of phenolic OH groups on the Np(V) complexation by HA was studied with modified HA (blocked phenolic OH groups). The blocking of phenolic OH groups induces a decrease of the number of maximal available complexing sites of HA, whereas complex stability constant and Np(V) near-neighbor surrounding are not affected.
The effects of HA on the sorption and migration behavior of actinides was studied in batch and column experiments. Th(IV) sorption onto quartz and Np(V) sorption onto granite and its mineral constituents are affected by the pH value and the presence of HA. HA exhibits a significant influence on the transport of U(IV) and U(VI) in a laboratory quartz sand system.
In order to provide the basis for a more reliable modeling of the actinide transport, the metal ion complexation with HA has to be integrated into existing geochemical speciation codes. Within this project the metal ion charge neutralization model was embedded into the geochemical modeling code EQ3/6. In addition to that, a digital data base was developed which covers HA complexation data basing on the charge neutralization model.

Keywords: Humic Substances; Humic Acids; Model Substances; Redox Properties; Actoinides; Thorium; Uranium; Neptunium; Plutonium; Complexation; Structure; Sorption; Migration; Repository; Modeling; Data Base

  • Other report
    Final Report, BMWA Project No. 02 E 9299
  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf, FZR-399 2004
    ISSN: 1437-322X
  • Other report
    In: C.M. Marquardt (Ed.): Investigations on the Complexation Behaviour of Humic Acids and their Influence on the Migration of Radioactive and Non-radioactive Substances under Conditions Close to Nature. Final Report, Forschungszentrum Karlsruhe, Wissenschaftliche Berichte FZKA 6999, Karlsruhe 2004

Downloads

Permalink: https://www.hzdr.de/publications/Publ-5964


18F-markierte Corticosteroide als Liganden für die Darstellung von Glucocorticoidrezeptoren (GR) im Gehirn mittels PET

Wüst, F.

  • Lecture (others)
    Gemeinsames Institutskolloquium der Klinik und Poliklinik für Nuklearmedizin und des Instituts für Interdisziplinäre Isotopenforschung Leipzig, 23.10.2003

Permalink: https://www.hzdr.de/publications/Publ-5962


Fraktografie an radioaktiven Proben mit der Abdrucktechnik

Müller, G.

Die direkte Fraktografie auf Bruchflächen von bestrahlten oder radioaktiv kontaminierten Proben ist nur an speziell für einen solchen Einsatz dedizierten Rasterelekt-ronenmikroskopen (REM) möglich. Eine Alternative bietet die Anwendung der Abdrucktechnik, mit deren Hilfe auch fraktografische Untersuchungen an herkömmli-chen REMs durchgeführt werden können. Die Methode muss genügend Details wie-dergeben, unter den Bedingungen einer heißen Zelle handhabbar sein und im Endabdruck kontaminationsfrei arbeiten.

Abdrucktechniken werden von einschlägigen Firmen vorzugsweise auf der Basis von Folien angeboten. Für rauhe, duktile Bruchflächen sind sie ungeeignet. Auch die Verwendung von Filmmaterialien und Wachsen ist unter den gegebenen Bedingungen nicht geeignet. Am erfolgreichsten erweist sich ein einstufiger Negativ-Abdruck mit duktilen, additionsvernetzenden Silikonen.

Dieses Verfahren wurde an Bruchflächen von Proben aus Reaktordruckbehälterstäh-len und -schweißmetall erfolgreich getestet. Zielstellung war vor allem der Nachweis von interkristallinen Bruchanteilen an vorzugsweise spröd und duktil gebrochenen Charpy-Proben. An den unbestrahlten RDB-Stählen A 533-B Cl. 1 und 15 CrMoV2 sowie dem Schweißmetall 10 CrMnNiMo2 konnte ein relativ großer Anteil interkristallinen Bruchs nachgewiesen werden. Die Anwendung des Verfahrens auf bestrahlte Proben des Schweißmetalls 10 CrMnNiMo2 erbrachte, je nach der Zähig-keit der Proben, differierende Anteile an transkristallinem Spalt- und Wabenbruch und nur sehr vereinzelten interkristallinen Bruch.

Keywords: Abdrucktechnik; Bruchfläche; Provil Novo; Reaktordruckbehälterstähle; radioaktiv; kontaminiert

  • Lecture (Conference)
    Sonderbände der Praktischen Metallographie, Band 35, Fortschritte in der Metallographie, S. 371-376, Sonderdruck und Internetbericht durch Fa. Heraeus Kulzer GmbH & Co. KG
  • Contribution to external collection
    Sonderbände der Praktischen Metallographie, Band 35, Fortschritte in der Metallographie, S. 371-376, Sonderdruck und Internetbericht durch Fa. Heraeus Kulzer GmbH & Co. KG

Downloads

Permalink: https://www.hzdr.de/publications/Publ-5961


Comment on "Identification of lattice vacancies on the two sublattices of SiC"

Kuriplach, J.; Brauer, G.; Anwand, W.; Skorupa, W.

no abstract !

Keywords: silicon carbide; positron annihilation; defects

Permalink: https://www.hzdr.de/publications/Publ-5958


Percolation of Electron Tunneling between Si Nanocrystals Synthesized in Thin SiO2 Films by Ion Implantation

Müller, T.; Heinig, K.-H.

The controlled fabrication of a narrow layer of Si nanocrystals (NCs) in thin SiO2 films for multi-dot non-volatile memories (NC memory) is still a considerable materials issue, which will be addressed in this contribution. The synthesis of NCs by Si+ implantation of SiO2 followed by a thermal treatment aims at an optimum NC density. A NC density being as high as possible is required in order to achieve a substantial threshold voltage shift of the MOS transistor. On the other hand, the advantages of the NC memory, as good scalability and data retention, are lost at too high NC densities. Then NC’s charge can spread over neighboring NCs by direct e- tunneling, i.e. due to electrical in-plane percolation paths. One single oxide defect could discharge several electrically percolated NCs.
This contribution is devoted to the trade-off between these two optimization routes. The Si NC formation by nucleation, growth and Ostwald ripening in low-energy Si+ implanted SiO2 is predicted by kinetic lattice Monte Carlo simulations. On the basis of these simulations, the dependence of the Si NC density, the distribution of the NC spacing as well as the threshold for extended electron tunneling paths are predicted. Thus, process conditions could be identified, where NCs align in narrow layer at high density but are sufficiently electrically isolated.

  • Poster
    Fall Meeting of the Materials Research Society, December 1-5, 2003, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-5957


Comparison of Kinetic MC Simulations and EFSTEM Observations of Phase Separation in Si Implanted Thin SiO2 Films

Müller, T.; Heinig, K.-H.; Bonafos, C.; Coffin, H.; Ben Assayag, G.; Schamm, S.; Zanchi, G.; Claverie, A.; Colliex, C.; Tencé, C.

Studies on the ion beam synthesis of narrow Si nanocrystal (NC) layers in thin SiO2 films are presented. Very low-energy Si+ implantation into gate oxides for MOS transistors followed by thermal annealing allows for the fabrication of novel Si NC floating gate based non-volatile charge storage devices.
Small and isolated Si NCs at high density are required to obtain a large threshold voltage shift of the memory transistor. However, former work shows that the characterization of the Si NCs embedded in SiO2 by conventional Transmission Electron Microscopy (TEM) is difficult. It requires careful con-siderations and special imaging conditions [1] due to the weak contrast be-tween Si and SiO2 .
In this contribution, Energy Filtered Scanning Transmission Electron Micros-copy (EFSTEM) investigations on the morphology of phase separated Si in SiO2 are presented, which overcome the contrast limitations of the conven-tional TEM. Furthermore, a comparison of the observed Si pattern with pre-dictions of kinetic lattice Monte Carlo (MC) simulations [2] is performed. The Si precipitates were synthesized by 1 keV Si+ implantation into 10 nm thick SiO2 and by furnace annealing in N2 (or N2 + O2). Varying fluences from 5E15 to 2E16 Si+ cm-2 were used in order to adjust the Si excess in the SiO2. For these conditions, dynamical binary collision simulations (TRIDYN) of high-fluence implantation were combined with kinetic Monte Carlo simula-tions of NC formation by phase separations. For low Si excess, NCs are pre-dicted to form by nucleation, growth and Ostwald ripening. On the other hand, at high Si excess, phase separation proceeds via spinodal decomposition, were elongated NCs are found in our computer experiment. At even higher flu-ences, structural percolation occurs and a random connected Si mesh forms. Thus, the morphology of the phase separated Si changes with increasing ion fluence from isolated, spherical NCs to percolated structures as observed by EFSTEM. The pattern of the phase separated Si predicted by kinetic Monte Carlo simulations and observed by Electron Microscopy agree remarkably well.

  • Lecture (Conference)
    Fall Meeting of the Matrials Research Society 2003, December 1-5, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-5955


Range and mixing distributions of low-energy carbon ions as a base for subplantation growth models

Dollinger, G.; Neumaier, P.; Bergmaier, A.; Görgens, L.; Eckstein, W.; Fischer, R.; Hofsäss, H.; Jäger, H. U.; Kröger, H.; Ronning, C.

Subplantation was early recognised as being the basic process in low-energy ion growth of diamondlike materials and has also to be considered for the description of bias enhanced diamond nucleation. A number of theories modelling the evolution of diamondlike phases have been proposed. However, the precise details of the subplantation and relaxation processes remain unclear. The problem in testing the complex models is that experimental information other than film structure versus ion energy is missing to a large extent. Mixing and range distributions of low-energy carbon ions are ideal data to model diamond-like film growth. Here we present measurements of range and mixing distributions for carbon ions at energies in the relevant energy range between 12 eV and 692 eV in carbon. The substrates are grown at the identical energies using 12C ions by mass separated ion beam deposition. Less than a monolayer of 13C was implanted each for the range distributions and as a marker layer for the mixing profiles. The 13C depth profiles are measured by high-resolution elastic recoil detection (ERD). These data are directly compared to calculations based on the binary collision approximation (TRIDYN) and to molecular dynamics (MD) simulations which consider atomic interactions on a time scale up to 15 ps including the thermal spike phase. Additionally, mixing distributions are derived from a transport calculation based on the measured range distributions. The measured range profiles show bimodal structures for energies below 200 eV which are significantly broader than the calculated profiles.The mixing profiles are also significantly broader than respective TRIDYN and MD calculations at these low energy. However, mixing profiles are in good agreement with transport calculations based on the measured range profiles showing the relevance of the measured range structures. Three reasons for the observed differences between the measured and theoretical range and mixing distributions are discussed in the paper: thermal induced self diffusion during thermal spike, mobility solely of the deposited ion after the collisional stage and a 3-dimensional surface structure of the carbon films on atomic scale. The experiment allows a crucial test for models of the subplantation scheme and may serve as input for improved calculations.

  • Invited lecture (Conferences)
    MRS 2003 Fall Meeting, Dec. 1 - 5, Boston, USA; Symp.R: Radiation Effects and Ion Beam Processing of Materials; contr. R12.1, invited talk

Permalink: https://www.hzdr.de/publications/Publ-5954


Conserved high-affinity ligand binding and membrane association in the native and refolded extracellular domain of the human glycine receptor alpha 1 subunit

Breitinger, U.; Breitinger, H.-G.; Bauer, F.; Fahmy, K.; Glockenhammer, D.; Becker, C.-M.

  • Journal of Biological Chemistry 279(2004)4, 1627-1636

Permalink: https://www.hzdr.de/publications/Publ-5953


Analysis of buoyancy driven coolant mixing by using the code TRIO_U

Höhne, T.; Bieder, U.

A generic investigation of the influence of density differences between the primary loop inventory and the ECC water on the mixing in the downcomer was made at the ROCOM Mixing Test Facility at Forschungszentrum Rossendorf (FZR). For the validation of the Trio_U code an experiment with 5% constant flow rate in one loop (magnitude of natural circulation) and 10% density difference between ECC and loop inventory was taken. Trio_U is a CFD code developed by the CEA France, aimed to supply an efficient computational tool to simulate transient thermal-hydraulic single -phase turbulent flows encountered in the nuclear systems as well as in the industrial processes. For this study, a LES approach was used for mesh sizes between 1–2 million control volumes. The study showed, that density effects play an important role during natural convection with ECC injection in pressurized water reactors. Further-more it was important to point out, that Trio_U is able to cope the main flow and mixing phenomena.

Keywords: Boron Dilution; COOLANT MIXING; ROCOM Test FACILITY; Computational Fluid Dynamics; LES; Trio_U

  • Lecture (Conference)
    Annual Meeting on Nuclear Technology 25.-27.05.2004, 2004, Düsseldorf, Germany
  • Contribution to proceedings
    Annual Meeting on Nuclear Technology 25.-27.05.2004, 2004, Düsseldorf, Germany, CD-ROM

Permalink: https://www.hzdr.de/publications/Publ-5952


Validation of TRIO_U – Numerical Simulations of a ROCOM Buoyancy Driven Test Case

Höhne, T.; Bieder, U.; Prasser, H.-M.; Kliem, S.

A generic investigation of the influence of density differences between the primary loop inventory and the ECC water on the mixing in the downcomer was made at the ROCOM Mixing Test Facility at Forschungszentrum Rossendorf (FZR)/Germany.
ROCOM is designed for experimental coolant mixing studies over a wide variety of possible scenarios. It is equipped with advanced instrumentation, which delivers high-resolution information characterizing either temperature or boron concentration fields in the investigated pressurized water reactor.
For the validation of the Trio_U code an experiment with 5% constant flow rate in one loop (magnitude of natural circulation) and 10% density difference between ECC and loop water was taken.
Trio_U is a CFD code developed by the CEA France, aimed to supply an efficient computational tool to simulate transient thermal-hydraulic single-phase turbulent flows encountered in the nuclear systems as well as in the industrial processes. For this study a LES approach was used for mesh sizes according to between 300000 – 2 million control volumes.
The results of the experiment as well as of the numerical calculations show, that a streak formation of the water with higher density is observed. At the upper sensor, the ECC water covers a small azimuthal sector. The density difference partly suppresses the propagation of the ECC water in circumferential direction. The ECC water falls down in an almost straight streamline and reaches the lower downcomer sensor position directly below the affected inlet nozzle. Only later, coolant containing ECC water appears at the opposite side of the downcomer.
The study showed, that density effects play an important role during natural convection with ECC injection in pressurized water reactors. Furthermore it was important to point out, that Trio_U is able to cope the main flow and mixing phenomena.

Keywords: BORON DILUTION; COOLANT MIXING; ROCOM TEST FACILITY; COMPUTATIONAL FLUID DYNAMICS; LES; TRIO_U

  • Lecture (Conference)
    12th International Conference on Nuclear Engineering, 25.-29.05.2004, Washington D.C., United States
  • Contribution to proceedings
    12th International Conference on Nuclear Engineering, 25.-29.05.2004, Washington D.C., United States, Book of Abstracts, S. 278

Permalink: https://www.hzdr.de/publications/Publ-5951


Radiation enhanced silicon self-diffusion and the silicon vacancy at high temperatures

Bracht, H.; Fage, J. P.; Zangenberg, N.; Nylandsted, A. L.; Haller, E. E.; Lulli, G.; Posselt, M.

We report proton radiation enhanced self-diffusion (RESD) studies on Si-isotope heterostructures. Self-diffusion experiments under irradiation were performed at temperatures between 780 0C and 872 0C for various times and proton fluxes. Detailed modeling of RESD provides direct evidence that vacancies at high temperatures diffuse with a migration enthalpy of HmV = (1.8±0.5 eV) significantly more slowly than expected from their diffusion at low temperatures, which is described by HmV < 0.5 eV. We conclude that this diffusion behavior is a consequence of the microscopic configuration of the vacancy whose entropy and enthalpy of migration increase with increasing temperature.

Keywords: defects; silicon; vacancy; interstitial; diffusion; ion implantation

  • Physical Review Letters 91 (2003) 245502

Permalink: https://www.hzdr.de/publications/Publ-5950


Monte-Carlo-Methoden für den Elektronentransport mit Einzelstreumodellen

Reichelt, U.; Henniger, J.; Enghardt, W.

Die Abbremsung eines Elektrons bis zu seiner vollständigen Thermalisierung ist durch eine sehr große Anzahl von Wechselwirkungen gekennzeichnet. Deshalb basieren Monte-Carlo-Algorithmen für den Elektronentransport derzeit noch fast ausschließlich auf der Anwendung von zwei Mehrfachstreumodellen. Die Vielfachstreutheorie nach MOLIERE versagt bei kleinen räumlichen Strukturen und Dichtesprüngen. Das Modell nach GOUDSMIT-SAUNDERSON führt für diese Fälle praktisch zum Einzelstreumodell und erfordert dabei aber einen enormen numerischen Aufwand.
An dieser Stelle soll ein Monte-Carlo-Algorithmus vorgestellt werden, der genuin auf Einzelstreuakten basiert. Die Strahlverfolgung (ray tracing) sowie das Erheben von Stichproben für freie Weglängen und Eigenschaften der Streuteilchen müssen mit effektiven numerischen Verfahren behandelt werden. Insbesondere die stark anisotropen Streuprozesse erschweren dieses Anliegen erheblich.
Diese Methodik ist ins Transportprogramm AMOS implementiert. Ein Vergleich mit experimentell bestimmten Daten und anderen Transportrechnungen zeigt zufriedenstellende Übereinstimmungen.

Keywords: Strahlungstransport; Einzelstreumodell; Monte-Carlo-Algorithmus

  • Lecture (Conference)
    68. Physikertagung der Deutschen Physikalischen Gesellschaft 2004, Frühjahrstagung der Arbeitskreise Atome, Moleküle, Quantenoptik und Plasmen (AMOP)

Permalink: https://www.hzdr.de/publications/Publ-5949


Measurements of gamma and neutron flux spectra in iron-water configurations

Böhmer, B.; Grantz, M.; Hansen, W.; Hinke, D.; Konheiser, J.; Noack, K.; Mehner, H.-C.; Stephan, I.; Unholzer, S.

Neutron and gamma spectra were measured behind and inside of modules consisting of variable iron and water slabs which were installed in radial beams of the zero-power training and research reactors AKR of the Technical University Dresden and ZLFR of the University of Applied Sciences Zittau/Görlitz. The applied NE-213 scintillation spectrometer allowed the measurement of gamma and neutron fluence spectra in the energy regions 0.3 - 10 MeV for photons and 1.0 - 20 MeV for neutrons. Measurements with thermoluminescence dosemeters (TLD) between slabs supplied additional information about the space distribution of energy integrated fluxes. The paper describes the experiments and presents some important results of the measurements. They will be compared with the results of transport calculations made by means of MCNP and TRAMO in another paper.

Keywords: neutron spectra; gamma spectra; spectrum measurements; coupled neutron/gamma transport calculations; NE-213 scintillation spectrometer; TLD-measurements

  • Kerntechnik 68 (2003) 5-6

Permalink: https://www.hzdr.de/publications/Publ-5948


Theorien und Experimente zum hydromagnetischen Dynamoeffekt

Stefani, F.

Die Magnetfelder von Planeten, Sternen und Galaxien entstehen hauptsächlich durch Selbsterregung in strömenden elektrisch leitfähigen Fluiden. Falls die Strömung stark genug ist und ein gewisses Mass an Schraubenförmigkeit aufweist, können die unter der Wirkung eines angenommenen Magnetfeldes induzierten elektrischen Ströme genau jenes Magneteld reproduzieren. Die Theorie hydromagnetischer Dynamos wird anhand der Induktionsgleichung sowie eines äquivalenten Integralgleichungssystems auf Basis des Biot-Savart-Gesetzes skizziert. Der Schwerpunkt des Vortrages liegt auf dem experimentellen Nachweis des Effektes, der Ende 1999 nahezu zeitgleich an zwei Natriumanlagen in Riga und Karlsruhe erfolgte. Die Ergebnisse des Rigaer Experimentes werden ausführlicher dargestellt und mit numerischen Resultaten verglichen.

  • Lecture (others)
    Physikalisches Kolloquium, Brandenburgische Technische Universität Cottbus, 13. 01.2004, Cottbus, Germany

Permalink: https://www.hzdr.de/publications/Publ-5947


Free-Electron Lasers in Physics

Dekorsy, T.

The topic of this chapter is a survey on the main applications of free-electron lasers (FELs) in physical sciences. The merits of FELs are discussed with respect to other available laser sources. For the wavelength ranges, where FELs contributed significantly to advances in physical sciences, specific examples of the research with FELs are given.

Keywords: free-electron lasers; applications of FELs; spectroscopy; time-resolved

  • Contribution to external collection
    Encyclopedia of Modern Optics, Eds. B.D. Guenther and D.G. Steel, Elsevier (2004), 164-169

Permalink: https://www.hzdr.de/publications/Publ-5946


Light-emitting silicon pn diodes

Dekorsy, T.; Sun, J.; Skorupa, W.; Schmidt, B.; Helm, M.

We report on the electrical and optical characteristics of silicon light-emitting pn diodes. The diodes are prepared by ion implantation of boron at high doses and subsequent high-temperature annealing. Under forward bias, the diodes emit infrared electroluminescence close below the bandgap of bulk Si. We present a rate equation model for bound excitons, free excitons and free carriers which successfully describes the electrical and optical behaviour of the diodes at low temperatures. Especially an electrical bistability observed below 50 K is shown to be based on the interplay of bound excitons, free excitons, and free carriers in the active area of the diodes. The ionization of bound excitons is the origin of an improved electroluminescence from the diodes
at higher lattice temperatures.

Keywords: silicon based optoelectronics; light emission; pn diode; ion implantation

  • Applied Physics A 78(2004), 471-475

Permalink: https://www.hzdr.de/publications/Publ-5945


Discussion of the Behaviour of Different RPV-Steels in Vessel Creep Failure Experiments

Willschütz, H.-G.; Müller, G.; Altstadt, E.

Considering the hypothetical core melt down scenario for a light water reactor the failure mode of the reactor pressure vessel (RPV) has to be investigated to deter-mine the loadings on the containment. Experimental and numerical work is performed worldwide to get insights about possible consequences. To validate the developed computational tools numerical simulations of Lower Head Failure experi-ments like OLHF or FOREVER are conducted.
An interesting question to be solved in this frame is the reason for the different shape of the failure site even under comparable loading conditions and for the same material: In some experiments like LHF-7 and EC-FOREVER-3B a rough crack surface was found at the failure site while in others like OLHF-1 a rather ductile behaviour was observed resulting in nearly blade-like edges on both sides of the vessel opening.

Keywords: lower head failure experiments; LHF; OLHF; FOREVER; creep failure; FEM simulation

  • Lecture (Conference)
    Annual Meeting on Nuclear Technology 2004, 25.-27.05.2004, Düsseldorf, Germany
  • Contribution to proceedings
    Annual Meeting on Nuclear Technology 2004, 25.-27.05.2004, Düsseldorf, Germany, CD-ROM 519-522

Permalink: https://www.hzdr.de/publications/Publ-5944


Fluid-Structure Interaction Investigations for Pipelines

Altstadt, E.; Carl, H.; Weiß, R.

The influence of the fluid-structure interaction on the magnitude fo the loads on pipe walls and support structures is not yet completely understood. In case of a dynamic load caused by a pressure wave, the stresses in pipe walls, especially in bends, are different from the static case.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-393 Dezember 2003
    ISSN: 1437-322X

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Permalink: https://www.hzdr.de/publications/Publ-5943


Characterization of Radiation Effects in Reactor Pressure Vessel Steels by means of Small Angle Neutron Scattering

Ulbricht, A.; Böhmert, J.

The influence of deleterious elements on the microstructural evolution in materials due to neutron irradiation was investigated by small angle neutron scattering experiments.
The study compares properties of ASTM and VVER RPV steels after different exposure levels.

Keywords: SANS; RPV steel; radiation defect

  • Lecture (Conference)
    Annual Meeting on Nuclear Technology 2004, 25.-27.05.2004, Düsseldorf, Germany
  • Contribution to proceedings
    Annual Meeting on Nuclear Technology 2004, 25.-27.05.2004, Düsseldorf, Germany, CD-ROM pp. 515-518,

Permalink: https://www.hzdr.de/publications/Publ-5942


Kolloidgetragene Schadstoffe in oxischen Bergwerkswässern

Zänker, H.; Ulrich, K.-U.; Jenk, U.; Moll, H.; Richter, W.

Ausgehend von drei grundsätzlichen Fällen werden die Konsequenzen der Vernachlässigung des kolloidgetragenen Transports von toxischen und radiotoxischen Schadstoffen in stillgelegten Bergwerken für die Prognose der Auswirkungen der Bergwerke auf die Umwelt diskutiert. Zunächst werden Messungen zur Bestimmung des Kolloidinventars in einem typischen "sauren Porenwasser" (Lettenwasser Freiberg) und einem typischen "Bulk-Wasser" (Stollenwasser Rothschönberg) beschrieben. Sodann wird ein Neutralisationsversuch vorgestellt, bei dem innerhalb von fünf Tagen 6 Liter sauerstoffarmes saures Flutungswasser aus einem Uranbergwerk mit etwa 100 Liter oxischem Grundwasser aus einem in der Nähe gelegenen Grundwasserleiter gemischt wurden, um die Flutung der Grube unter oxischen Bedingungen (Begasung mit Sauerstoff) bis in ihr Endstadium zu simulieren. Der Versuch zeigt, dass ab pH > 4 zunehmende Mengen des in dem Flutungswasser enthaltenen Urans in einen kolloidgetragenen Zustand übergehen. Die Natur der Uranbindung in den Kolloiden wird auf spektroskopischem Wege (Tieftemperatur-EXAFS an der Rossendorfer Beamline ROBL der ESRF in Grenoble) noch direkt bestimmt.

Keywords: Kolloide; Bergwerke; Uran; Flutung

  • Poster
    Jahrestagung der Wasserchemischen Gesellschaft in der GDCh, Bad Saarow, 17. - 19. Mai 2004
  • Contribution to proceedings
    Jahrestagung Wasserchemische Gesellschaft, 17.-19.05.2004, Bad Saarow, Deutschland
    Kurzreferate, Wächtersbach: PM-GrafikDesign, 3-936028-24-9, 181-185

Permalink: https://www.hzdr.de/publications/Publ-5941


Imaging Si Nanoclusters in Thin SiO_2 Layers by XTEM using Contrast Enhancing Decoration with Ge

Röntzsch, L.; Heinig, K. H.; Schmidt, B.

The Multidot Nano-flash Memory suggested by Tiwari [APL69(1996)1232] is a promissing candidate for succeeding the common Floating Gate Flash Memory.

Its most challenging configurational feature is a layer of insulated Si nanoclusters (NCs) within the oxide of a MOS-like structure.

Here, we present experimental evidence that the theoretical concept predicting the self-organization of delta-layers of Si NCs at ion irradiated interfaces is valid (cf. Heinig [APA77(2003)17]).

In this approach of ``bottom-up" structuring, unconventionally, a 15nm thin buried SiO_2 layer, which is enclosed by a 50nm poly-Si capping layer and the Si substrate, is irradiated with Si ions. Ion impact drives the system to a state far from thermodynamic equilibrium, i.e. the local composition of the target is modified to a degree unattainable in common processes. A region of SiO_x (x<2) -- where x is a function of depth -- is formed which is not stable.

During annealing, the system relaxes towards equilibrium, i.e. phase separation (via spinodal decomposition and nucleation) sets in. Within a certain time window of annealing, the structure of the system matches with a structure similar to the Multidot Memory device, the principal character of which is a 2D layer of Si nanoclusters of (d~3nm) which is embedded in a 3D SiO_2 matrix at a distance of ~3nm from the Si substrate.

The experimental handicap that tiny Si NCs (d<3nm) which are embedded in SiO_2 are not visible in common XTEM is resolved by a novel method which applies Ge as contrast enhancing element in TEM studies of tiny Si NCs.

Keywords: Ion Irradiation; Si Nanoclusters; Ge decoration; Multidot Flash Memory

  • Poster
    Conference contribution to Trends in Nanotechnology, Sept. 2003, Salamanca, Spain

Permalink: https://www.hzdr.de/publications/Publ-5939


Velocity measuring techniques at FZR and status of MULTIMAG

Galindo, V.; Cramer, A.; Eckert, S.; Gerbeth, G.

A review will be given on the present status of the facility MULTIMAG and the possibilities to measure local velocities in metal or semiconductor melts. The use of MULTIMAG or the measuring techniques for applications in crystal growth modeling will be discussed.

  • Lecture (Conference)
    Use of magnetic fields in crystal growth, Workshop, Riga (Lettland), 5.-6.12.2003

Permalink: https://www.hzdr.de/publications/Publ-5938


In vivo Measurement of the Serotonin Transporter with (S)-([18F]fluoromenthyl)-(+)-McN5652

Brust, P.; Hinz, R.; Kuwabara, H.; Hesse, S.; Zessin, J.; Pawelke, B.; Stephan, H.; Bergmann, R.; Steinbach, J.; Sabri, O.

The radiolabeled serotonin transporter (SERT) ligand 11C](+)-McN5652 has recently been used in clinical positron emission tomography (PET) studies for SERT imaging. However, this radioligand offers disadvantages in routine clinical settings because of its short radioisotope half-life (eg PET facilities within hospitals without a cyclotron need to acquire such radioligands from distant cyclotron units for clinical use). S-([18F]fluoromenthyl)-(+)-McN5652 ([18F](+)-FMe-McN5652) is an analogue which has been synthesized newly, and has a significant longer radioisotope half-life. In the porcine brain, it demonstrates the same characteristic distribution pattern of serotonin-uptake sites like the 11C-labeled congener with the highest binding in the midbrain and thalamus and the lowest in the cerebellum and occipital cortex. It shows a 30 % higher blood-brain transfer and a slower peripheral metabolism than [11C](+)-McN5652. Rather uniform brain binding was observed after injection of the pharmacologically inactive radiolabeled enantiomer, or after pretreatment with the highly selective SERT inhibitor citalopram. The norepinephrine uptake inhibitor maprotiline did not show any inhibitory effect. Using a one-tissue compartment model (K1, k´´2) or a two tissue compartment model (K1, k4) with or without constraints for calculation, the regional binding parameters of [11C](+)-McN5652 and [18F](+)-FMe-McN5652 are highly correlated among each other and with the SERT density, as determined by in vivo binding of [3H]citalopram. Using constraints to correct for the free fraction and nonspecific binding of the radiotracers, a considerable increase of the midbrain-occipital cortex ratios with higher values for [18F](+)-FMe-McN5652 compared to [11C](+)-McN5652 was revealed. It is concluded that [18F](+)-FMe-McN5652 has better features than [11C-McN5652 for SERT imaging with PET.

Keywords: serotonin transporter; receptor imaging; positron emission tomography; kinetic modeling; [18F](+)-FMe-McN5652; citalopram

  • Neuropsychopharmacology (2003) 28, 2010-2019

Permalink: https://www.hzdr.de/publications/Publ-5937


Local flow structures in liquid metals measured by ultrasonic Doppler velocimetry

Cramer, A.; Zhang, C.; Eckert, S.

Ultrasound Doppler velocimetry (UDV) has been successfully applied to measure local velocities in mercury and the eutectic alloy InGaSn. Two different kinds of magnetic fields established the fluid motion in a cylindrical vessel. For both, the rotating and the traveling field, agreement with expectations from theory and local measurements employing different techniques was achieved.
The deliverance of a profile by UDV instead of one value at one fixed co-ordinate, typical for almost any other method, allowed for the determination of the topology in a plane covered by the ultrasonic beam while the sensor was traversed. These area-wide results are, by nature, time averaged respectively mean velocities.
The range of flow regimes regarding the magnitude of velocity which is detectable by means of the Doppler procedure begins already in the turbulent region. For the case of the rotating magnetic field spectral distributions of time series of velocity signals measured at different positions in the fluid volume will be presented.

  • Flow Measurement and Instrumentation 15(2004), 145-153

Permalink: https://www.hzdr.de/publications/Publ-5936


Cathodoluminescence Decay Kinetics in Ge+, Si+, O+ Implanted SiO2 Layers

Trukhin, A. N.; Jansons, J.; Fitting, H.-J.; Barfels, T.; Schmidt, B.

Cathodoluminescence spectra shapes and respective band decay times show no similarity between luminescence centers in different crystal and amorphous modifications of SiO2 and GeO2. On the other hand, the additionally produced red luminescence centers (650 nm) by oxygen implantation into SiO2 layers are of the same nature as in stoichiometric SiO2 and are attributed to the non-bridging oxygen hole center (NBOHC). Moreover, the elevated blue (460 nm) luminescence in Si implanted SiO2 belongs to the silicon related oxygen deficient center (SiODC) as in stoichiometric layers too. Ge implantation into SiO2 and thermal post-annealing leads to a huge violet luminescence (400 nm) with a first rapid decay of t = 24 ns followed by a slow hyperbolic decay with (t)-0.15 ... (t)-0.54. The last 10% show again an exponential decay with a mean life time t = 125 µs. This complex luminescent center is related to the GeODC center formed during the thermal treatment by Ge cluster formation

Keywords: Cathodoluminesence; ion implantation; nanocluster; glass

  • Journal of Non-Crystalline Solids 331(2003) 91-99

Permalink: https://www.hzdr.de/publications/Publ-5935


DYN3D Calculations Compared to the Measurements in the V-1000 Test Facility

Grundmann, U.; Mittag, S.

The full-scale zero power facilitlity V-1000 was build at the Russian Research Centre ?Kurtschatov Institute? for the investigation of neutron-physical parameters of the VVER-1000 core[1]. Two steady-state measurements and two transient experiments at the V-1000 were made available in the frame of EU project VALCO for the valida-tion of three-dimensional neutron kinetic codes. The results of the DYN3D code [2] by using three different libraries of two group constants generated with the cell codes HELIOS [3], CASMO [4] and WIMS [5] are compared with the measurements. The C/E comparisons of the radial power distribution at the axial detector position for the two steady-states with all control rods out of core and with inserted bank 10 are pre-sented in the next section. A single control rod of bank 9 is moved in the core and reverse in the transient experiment 1. The experiment 2 consists of a scram with a delayed motion of one stuck cluster The results of the calculations with the three li-braries are compared with the incore detectors signals and the signals of two ioniza-tion chambers in section 3. The reactivity calculated by inverse point kinetics from the ionization chambers signals and from the calculated core averaged fluxes are pre-sented.

Keywords: neutron kinetics; three-dimensional; validation; codes; steady states; transients; zero power reactor; VVER-1000; experiments; nodal methods

  • Lecture (Conference)
    Annual Meeting on Nuclear Technology 2004, 25.-27.05.2004, Düsseldorf, Germany
  • Contribution to proceedings
    Annual Meeting on Nuclear Technology 25.-27.05.2004, Düsseldorf, Germany, CD-ROM 17-20

Permalink: https://www.hzdr.de/publications/Publ-5934


Stress measurements of germanium nanocrystals embedded in silicon oxide

Wellner, A.; Paillard, V.; Bonafs, C.; Coffin, H.; Claverie, A.; Schmidt, B.; Heinig, K.-H.

Ge nanocrystals embedded in thermal SiO2 on top of a Si substrate are investigated using Raman spectroscopy and transmission electron microscopy. We observe that the Raman peak frequency of the Ge nanocrystals is strongly affected by compressive stress. In the case of large particles for which the phonon confinement-induced Raman shift can be neglected, the stress is measured taking into account isotopic composition effects induced by the ion implantation process used to produce
the nanocrystals. The stress is proposed to originate from a liquid¿solid phase transition in Ge.

Keywords: Ge nanocrystals; Raman spectroscopy; stress

Permalink: https://www.hzdr.de/publications/Publ-5933


Nanostructures by Ion Beam Synthesis

Schmidt, B.

Ion beams are widely used in research and development as well as in different fields of industrial applications, for example for doping of semiconductors in microelectronics. Furthermore, among other techniques ion beams exhibit a great potential for synthesis of new materials as well as for the self-organization of nanostructures. Two of the goals of materials research using ion beams are the ion beam synthesis (IBS) of nanocrystals (NC´s) and the self-organization of NCs under ion irradiation in a solid matrix, for example the formation of semiconducting or metallic NCs in insulating films for applications microelectronics and optoelectronics, respectively.
Semiconducting NCs embedded in the gate oxide of a MOS field effect transistor can be charged/decharged by tunnelling of electrons from/to the Si substrate, caused by an appropriate voltage pulse applied to the gate. There is a difference in the source/drain current for charged and neutral NCs which can be used for the storage of information. The basis of this memory concept is quite simple. However, the fabrication of tiny NCs (~2 nm) placed at the right position within the very thin (< 20 nm) gate oxide is a strong challenge. Different ion beam processes are being developed for realization: i) low energy ion implantation into the thin gate silicon oxide and ii) medium energy ion irradiation through the gate oxide. The two approaches will be described from the physical and technological point of view and experimental results of charge storage behaviour in NC MOS transistors fabricated by the two ion beam processes will be presented.
Another effort is currently devoted to the application of ion beam synthesized metallic NCs in optoelectronics. The fabrication of NCs by IBS requires usually a thermal treatment for phase separation of implanted impurity atoms and for damage annealing. This annealing leads inevitably to broad NC size distribution. Due to the broad size distribution of NCs fabricated by IBS, their size- depending characteristics, e.g. absorption and luminescence, can be obscured. Thus the potential for tailoring of size and size distribution of NCs by IBS is rather limited. It will be shown that size and size distribution can be tailored by high-energy ion irradiation through an ensemble of NCs.
Finally, in the outlook the lecture will address new trends of IBS for nanostructure fabrication, e.g. self-organization at ion implantation into templates and IBS of nanostructures by using focused ion beams (FIB).

Keywords: Ion beam synthesis; nanocluster; nanocluster memory

  • Lecture (Conference)
    13th International Summer School on Vacuum, Electron and Ion Technologies (VEIT 3003), September 15-19, 2003, Varna, Bulgaria

Permalink: https://www.hzdr.de/publications/Publ-5932


Local structure of Sn implanted in thin SiO2 films

Spiga, S.; Montovan, R.; Franciulli, M.; Ferretti, N.; Boscherini, F.; Schmidt, B.; Grötzschel, R.; Mücklich, A.

The formation and the structural properties of Sn nanocrystals produced by ion implantation in thin SiO2 films was investigated by 119Sn conversion electron Moessbauer spectroscopy (CEMS), x-ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM). Sn ion implantation was performed at 80 keV with a fluence of 1x1016 cm2, positioning the peak of the implantation profile in the middle of the SiO2. The annealing treatments were performed in the temperature range 800–1100 °C by rapid thermal processing. CEMS and XAS provided unique information on the local atomic and electronic environment of Sn in SiO2 allowing a detailed investigation of the effect of different annealing conditions. In the as-implanted state all Sn ions are oxidized (with both Sn2+ and Sn4+ oxidation states present), while annealing induces the formation of beta-Sn nanoclusters. TEM showed that cluster sizes are in the range 7–17 nm. For clusters with average diameter ,10 nm, XAS detected a reduction in coordination number and interatomic distances. Both XAS and CEMS indicate an increase in the static disorder in the metallic clusters. The investigated annealing treatments do not lead to a complete precipitation of Sn atoms in the metallic phase, leaving a fraction of them oxidized.

Keywords: Sn nanocluster; ion implantation; CEMS; XAS; TEM; RBS

Permalink: https://www.hzdr.de/publications/Publ-5931


Nanocrystals by ion beams - from fundamentals to application in non-volatile memories

Möller, W.; Schmidt, B.; Heinig, K.-H.

Ion beams are widely used in research and development as well as in different fields of industrial applications, for example for doping of semiconductors in microelectronics. Furthermore, among other techniques ion beams exhibit a great potential for synthesis of new materials. One of the goals of materials research using ion beams is the ion beam synthesis (IBS) of nanocrystals (NC´s) in a solid matrix, for example the synthesis of semiconducting or metallic NC´s in insulating films.
NC´s embedded in the gate oxide of a MOS field effect transistor can be charged/decharged by tunnelling of electrons from/to the Si substrate, caused by an appropriate voltage pulse applied to the gate. There is a difference in the source/drain current for charged and neutral NCs which can be used for the storage of information. The basis of this memory concept is quite simple. However, the fabrication of tiny NCs (~2 nm) placed at the right position within the very thin (< 20 nm) gate oxide is a strong challenge. Different processes are being developed for realization. Among these, only ion implantation of impurity atoms into the gate oxide followed by their precipitation during subsequent annealing is completely compatible with CMOS technology.
The lecture will first address the fundamentals governing ion beam synthesis NC´s in extremely thin SiO2 layers, with well-controlled size and position tailoring. The results of the fundamental investigations form the base for technology transfer to the production of non-volatile memories. In the frame of national and international R&D projects and in strong collaboration with local microelectronics industries, the viability of a new technology route to memory device fabrication is demonstrated.

Keywords: Ion beam synthesis; Si nancluster; nanocluster memory

  • Lecture (Conference)
    International Conference Nanofair 2003, November 20-21, 2003, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-5930


Atomistische Computersimulation von Ionenimplantation und ionenstrahlinduzierter Defektbildung und –evolution in Si und SiC

Posselt, M.

kein Abstrakt

  • Lecture (others)
    Seminar des Instituts für Materialphysik an der Universität Münster, Münster, Germany, December 1, 2003

Permalink: https://www.hzdr.de/publications/Publ-5929


Control of flow separation using electromagnetic forces

Weier, T.; Gerbeth, G.; Mutschke, G.; Lielausis, O.; Lammers, G.

Introduction

If a fluid is electrically conductive, its flow may be controlled using electromagnetic forces. Meanwhile, this technique is a recognized tool even on an industrial scale for handling highly conductive materials like liquid metals. However, also fluids of low electrical conductivity as considered in the present study, like sea--water and other electrolytes, permit electromagnetic flow control. Experimental results on the prevention of flow separation by means of a streamwise, wall parallel Lorentz force acting on the suction side of inclined flat plates and hydrofoils will be presented.

Force Configuration
The stripwise arrangement of permanent magnets and electrodes of alternating magnetization direction and polarity shown in Fig. 1 was proposed by Gailitis and Lielausis (1961). It generates a wall parallel force with a maximum value directly at the wall, decaying exponentially with the wall distance. Due to the low electrical conductivity, both electric and magnetic fields have to be applied to generate a Lorentz force of adequate strength. The width of the electrodes is equal to that of the magnets and
determines the penetration of the force into the flow. The ratio of electromagnetic to inertial force can be characterized by the interaction parameter. In analogy to the terminology used in separation control by blowing, one may also define an electrohydrodynamic momentum coefficient.

Results and Discussion
A downstream directed force adds momentum to the flow and accelerates the fluid in the vicinity of the wall. This flow acceleration may be used to counteract the energy loss due to friction and adverse pressure gradients. Actually, a streamwise Lorentz force has already been successfully applied to control the flow around a circular cylinder in Weier et al. (1998). The two inserts in Fig. 2 show the flow around an inclined flat plate. In the lower left photograph, the unforced separated flow is visible, whereas the upper subfigure depicts the fully attached flow under the action of a suction side Lorentz force. The graph indicates that the interaction
parameter, necessary to completely suppress separation, decreases with increasing chord length Reynolds number. The effect of a suction side Lorentz force on lift and drag of NACA--0017--like hydrofoils has been quantified by means of force balance measurements. Depending on the inclination angle, two different effects are observed. At small angles of incidence, a moderate lift increase due to additional circulation is observed. Simultaneously, caused by the added momentum, the drag is decreased. At higher angles of attack, where the unforced hydrofoil would normally stall, a more pronounced lift increase occurs. Fig. 3 shows the lift gained by the suction side Lorentz force at a fixed inclination angle of 17. Here delta CL is the difference of the lift coefficients of the forced and the unforced hydrofoil at the specified chord length Reynolds number. The shape of the curve as well as the total values of the lift gain and the momentum coefficient resemble the behavior found in separation control experiments with steady blowing. In the presentation, a complementary discussion on scaling issues based on experiments with a NACA 0015 hydrofoil will be given.

  • Flow, Turbulence and Combustion, Vol. 71, No. 1-4, pp. 5-17

Permalink: https://www.hzdr.de/publications/Publ-5928


Proteinoxidation und Krankheit

Pietzsch, J.; Bergmann, R.; Wüst, F.; van den Hoff, J.

Proteine zeichnen sich durch eine hohe Suszeptibilität gegenüber dem Angriff reaktiver Sauerstoffspezies (ROS) aus. Die oxidative Modifikation von Proteinen kann zur Veränderung ihrer Struktur und zur Beeinträchtigung ihrer biologischen Funktion führen. Diese Veränderungen sind beim Menschen eng mit der Ätiologie, Manifestation und Progression verschiedener Krankheiten assoziiert. Durch neue Methoden zur Charakterisierung und quantitativen Beschreibung der Bildung und des Metabolismus spezifischer Oxidationsprodukte werden Hinweise auf die Art und Weise der Schädigung sowie Schutzmöglichkeiten des Organismus gewonnen.

  • Contribution to HZDR-Annual report
    FZR-Jahresbericht 2003. In: Johannsen, B.; Joehnk, P. (Eds.) Research Center Rossendorf: Annual Report/Wissenschaftlich-Technische Berichte (Annual Report) 2003 (FZR-398). Research Centre Rossendorf, Dresden. 52-61

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Permalink: https://www.hzdr.de/publications/Publ-5926


Characterization of the unoccupied and partially occupied states of TTF-TCNQ by XANES and first-principles calculations

Fraxedas, J.; Lee, Y. J.; Jimenez, I.; Gago, R.; Nieminen, R. M.; Ordejon, P.; Canadell, E.

We report a combined experimental and theoretical study of the unoccupied electronic states of the neutral molecular organic materials TTF (tetrathiafulvalene) and TCNQ (7,7,8,8-tetracyano-p-quinodimethane) and of the one-dimensional metallic charge transfer salt TTF-TCNQ. The experimental density of states (DOS) is obtained by x-ray absorption near edge spectroscopy (XANES) with synchrotron light and the predicted DOS by means of first-principles density functional theory calculations. Most of the experimentally derived element specific XANES features can be associated to molecular orbitals of defined symmetry. Because of the planar geometry of the TTF and TCNQ molecules and the polarization of the synchrotron light, the energy dependent sigma or pi character of the orbitals can be inferred from angular dependent XANES measurements. The present work represents the state of the art analysis of the XANES spectra of this type of materials and points out the need for additional work in order to elucidate the governing selection rules in the excitation process.

Keywords: 71.20.Rv; 71.15.Mb; 61.10.Ht

Permalink: https://www.hzdr.de/publications/Publ-5925


Biologische Funktionen - ihre Aufklärung mit Hilfe von Metallkomplexverbindungen

Johannsen, B.

  • Lecture (others)
    Adlershofer Analytisches Kolloquium der BAM, Adlershof, 25.11.2003

Permalink: https://www.hzdr.de/publications/Publ-5924


Radiopharmazeutika - gestern, heute und morgen

Johannsen, B.

  • Lecture (others)
    Bad Berkaer Gespräch Nuklearmedizin, Bad Berka, 12.11.2003

Permalink: https://www.hzdr.de/publications/Publ-5923


Zur Zulassungsproblematik und spezifischen Anwendung von GMP bei PET-Radiopharmaka

Johannsen, B.

  • Lecture (Conference)
    Arbeitstagung der pharmazeutischen und veterinärmedizinischen Überwachungsbeamtinnen und -beamten der Länder, Workshop Radiopharmazeutika, Erfurt, 24.09.2003

Permalink: https://www.hzdr.de/publications/Publ-5922


CFD modelling of subcooled boiling

Krepper, E.

Heat transfer and boiling are key phenomena for power generation facilities. Whereas for 1D thermalhydraulic system codes modeling of boiling was state aof the art from the beginning of their development, the 3D modelling of boiling has not yet reached this maturity. In the paper the boiling model implemented in the CFD-code CFX-4 was applied, to analyse lots of experiments, their results were published in the literature. The validity of the implemented correlations is examined. In many cases the model yields a good agreement to experiments. The modelling of subcooled boiling in the section of a BWR fuel rod element is presented as an application example.

Keywords: CFD; boiling model; comparison with experiments; BWR fuel rod

  • Lecture (Conference)
    Annual Meeting on Nuclear Technology 2004, 25.-27.05.2004, Düsseldorf, Germany
  • Contribution to proceedings
    Annual Meeting on Nuclear Technology 2004, 25.-27.05.2004, Düsseldorf, Germany, CD-ROM

Permalink: https://www.hzdr.de/publications/Publ-5921


Novel Procedures for Preparing 99mTc(III) Complexes with Tetradentate/Monodentate Coordination of Varying Lipophilicity and Adaptation to 188Re Analogues

Seifert, S.; Künstler, J.-U.; Pietzsch, H.-J.; Pawelke, B.; Bergmann, R.; Spies, H.

Improved methods are presented for the preparation of 99mTc and 188Re mixed-ligand complexes with tetradentate and monodentate ligands of the general formula [MIII(L1)(L2)] (M = Tc, Re; L1 = NS3 or NS3-COOH; L2 = isocyanide or phosphine). To avoid the unrequested formation of reduced-hydrolyzed species of both metals the preparation of complexes is performed in a two-step procedure. At first the Tc(III)- or Re(III)-EDTA complex is formed which reacts in a second step with the tripodal NS3 ligand and the monodentate isocyanide or phosphine ligand to the so-called ‘4+1’ complex. Copper(I) isocyanide complexes are used for preparing the ‘4+1’ complexes. That facilitates storage stability and allows kit formulations. Moreover, using that stabilized form of isocyanides enables the formation of 188Re complexes in acidic solution. Only micromolar amounts of the monodentate ligand are needed and that results in high specific activity labeling of interesting molecules. The lipophilicity of complexes can be controlled by introducing a carboxyl group into the tetradentate ligand and/or derivatization of the monodentate ligands. Furthermore, the carboxyl group enables the conjugation of biomolecules. As an example, the neurotensin derivative CN-NT(8-13) was prepared and labeled with 99mTc according to the ‘4+1’ approach and its behavior in vivo was studied.

Permalink: https://www.hzdr.de/publications/Publ-5920


TRANSIENT SIMULATIONS IN VVER-1000 – COMPARISON BETWEEN DYN3D-ATHLET AND DYN3D-RELAP5

Kozmenkov, Y.

Simulations of a real transient of an operating VVER-1000 power plant have been performed using DYN3D-ATLET and DYN3D-RELAP5 code systems in the frame of activities aimed at a validation of the coupled neutronic / thermal-hydraulic codes. The problem chosen for simulation is a main coolant pump (MCP) switching off, when three of the four MCPs of the plant are in operation (transient scenario of the VALCO project). The same nodalization models of the plant (except the core) but two different libraries of macroscopic cross-sections have been used in calculations. Additionally, the compared code systems are based on the different - external and internal - coupling techniques. This paper contains a brief description of the coupled codes and the plant model as well as a comparison between results from simulations.

Keywords: coupled code; DYN3D; RELAP5; validation; VALCO project

  • Contribution to proceedings
    Annual Meeting on Nuclear Technology 2004, 25.-27.05.2004, Düsseldorf, Germany, Proceedíngs CD-ROM paper 104

Permalink: https://www.hzdr.de/publications/Publ-5919


Analysis of MSR Benchmark by Using the Code DYN1D-MSR

Krepel, J.; Grundmann, U.; Rohde, U.

A one-dimensional code DYN1D-MSR for transient analysis of Molten Salt Reactors – MSR was developed in FZR. The code is based on the well know three-dimensional code DYN3D. The neutron kinetics routines for axial direction calculation from DYN3D are combined with new models of delayed neutrons production and thermal-hydraulic. The results from the Molten salt Reactor Experiment were used to validate the code. After the successful validation several transients typical for the liquid fuel system were analyzed using the design data of the Molten Salt Breeder Reactor. The results of all transients (overcooling of fuel at core inlet, reactivity insertion, and fuel pump coast-down) have shown that the dynamic behavior of MSR is stable when the coefficients of thermal feedback are negative.

Keywords: Molten; Salt; Reactor; Breeder; MSRE; MSBR; MSR

  • Contribution to proceedings
    Annual Meeting on Nuclear Technology 2004, 25.-27.05.2004, Düsseldorf, Germany, Proceedíngs CD-ROM paper 104 , paper 105
  • Lecture (Conference)
    Annual Meeting on Nuclear Technology 2004, 25.-27.05.2004, Düsseldorf, Germany

Permalink: https://www.hzdr.de/publications/Publ-5918


Electron beam diagnostic and the undulator field adjustment of the ELBE IR-FEL

Evtushenko, P.; Gippner, P.; Grosse, E.; Michel, P.; Seidel, W.; Wohlfahrt, D.; Wolf, A.; Wolf, U.; Wünsch, R.; Wustmann, B.; van der Geer, C. A. J.

For the electron beam diagnostic in the undulator of the ELBE FEL two systems are completed. The first one consists of insertable OTR (Optical Transition Radiation)view screens. The same view screens will be used for the FEL optical resonator alignment. This is why there are very strong requirements on the long-term positioning reproducibility of the view screens. The second system is based on a single moveable YAG (Yttrium Aluminum Garnet activated by Cerium) screen, which can travel within the undulator vacuum chamber such that the electron beam position can be measured at any place in the undulator. Both systems are completed and successfully tested. Results of the tests as well as design ideas are presented. After transporting two undulator units to Rossendorf and installing the stainless steel vacuum chamber the magnetic field has been measured again and adjusted applying the pulsed-wire method. Irregularities of the undulator magnetic field could affect gain and wavelength of the FEL. Such effects were analyzed using numerical simulations.

  • Poster
    25th International Free Electron Laser Conference, and the 10th FEL Users Workshop 2003, 08.-12.09.2003, Tsukuba, Ibaraki, Japan
  • Contribution to proceedings
    25th International Free Electron Laser Conference, and the 10th FEL Users Workshop, Part II, 08.-12.09.2003, Tsukuba, Ibaraki, Japan
    Extended Abstracts, book edition of the proceedings, 0-444-52727-8, II-29

Permalink: https://www.hzdr.de/publications/Publ-5917


Gas and liquid velocity measurements in bubble chain driven two-phase flow by means of UDV and LDA

Zhang, C.; Eckert, S.; Gerbeth, G.

The goal of our work is to apply the UDV technique for investigations of liquid metal two-phase flows. In the present paper UDV is validated for its capability of measuring both gas and liquid velocities in transparent two-phase flow. The results are discussed with references to the existing knowledge and parallel measurements by Laser Doppler Anemometry (LDA).

Keywords: UDV; LDA; bubble chain; two-phase flow; phase discrimination

  • Lecture (Conference)
    5th International Conference of Moultiphase Flow (ICMF), 30.05.-04.06.2004, Yokohama, Japan
  • Contribution to external collection
    5th International Conference of Multiphase Flow (ICMF), 30.05.-04.06.2004, Yokohama, Japan, CD-ROM ICMF2004, paper 260

Permalink: https://www.hzdr.de/publications/Publ-5916


Chromium recoil implantation into SAE 1020 steel by nitrogen bombardment

Gomes, G. F.; Ueda, M.; Reuther, H.; Richter, E.; Beloto, A. F.

Chromium recoil implantation into SAE 1020 steel by nitrogen bombardment

  • Poster
    X Latin American Workshop on Plasma Physics, São Pedro, Brasilien, 30.11. - 5.12.2003
  • Open Access Logo Brazilian Journal of Physics 34(2004)4b, 1629-1631
    ISSN: 0103-9733

Permalink: https://www.hzdr.de/publications/Publ-5915


Results from experiments on hybrid plasma immersion ion implantation / nitriding processing of materials

Ueda, M.; Kostov, K.; Gomes, G. F.; Reuther, H.; Lepienski, C. M.; Soares Jr., P. C.; Takai, O.; Silva, M. M.

Results from experiments on hybrid plasma immersion ion implantation / nitriding processing of materials

  • Lecture (Conference)
    X Latin American Workshop on Plasma Physics, São Pedro, Brasilien, 30.11. - 5.12.2003
  • Open Access Logo Brazilian Journal of Physics 34(2004)4b, 1632-1637

Permalink: https://www.hzdr.de/publications/Publ-5914


Chromium implantation into ABNT 1020 steel by nitrogen PIII and ion beam recoil

Gomes, G. F.; Ueda, M.; Beloto, A. F.; Reuther, H.

Chromium implantation into ABNT 1020 steel by nitrogen PIII and ion beam recoil

  • Lecture (Conference)
    XXIV Congresso Brasileiro de Aplicacoes de Vacuo na Industria e na Ciencia, Bauru, Brasilien, 28 - 30.7.2003

Permalink: https://www.hzdr.de/publications/Publ-5913


Annealing effects on silicon oxynitride layer synthesized by N plasma immersion ion implantation

Ueda, M.; Reuther, H.; Beloto, A. F.; Kuranaga, C.; Abramof, E.

Annealing effects on silicon oxynitride layer synthesized by N plasma immersion ion implantation

  • Lecture (Conference)
    20th International Conference on Amorphous and Microcrystalline Semiconductors - Science and Technology, Campos do Jordao, Brasilien, 25 - 29.9.2003
  • IEEE Transactions on Plasma Science 34(2006)4, 1080-1083

Permalink: https://www.hzdr.de/publications/Publ-5912


Grazing incidence X-ray diffraction of SS304 steel surfaces modified by high and low pressure ion nitriding processes

Ueda, M.; Gomes, G. F.; Abramof, E.; Reuther, H.

Grazing incidence X-ray diffraction of SS304 steel surfaces modified by high and low pressure ion nitriding processes

  • Poster
    VIIth International Workshop on Plasma-Based Ion Implantation (PBII),San Antonio, USA,16 - 19 September 2003

Permalink: https://www.hzdr.de/publications/Publ-5911


Nitrogen recoil chromium implantation into construction steel SEA 1020 steel by means of ion beam or plasma immersion ion implantation

Gomes, G. F.; Ueda, M.; Beloto, A. F.; Reuther, H.

Nitrogen recoil chromium implantation into construction steel SEA 1020 steel by means of ion beam or plasma immersion ion implantation

  • Poster
    XIIIth International Conference on Surface Modification of Materials by Ion Beams (SMMIB), San Antonio, USA, 21 - 26 September 2003

Permalink: https://www.hzdr.de/publications/Publ-5910


Beam loss detection at Radiation Source ELBE

Michel, P.; Teichert, J.; Schurig, R.

The Rossendorf superconducting Electron Linac of high Brilliance and low Emittance (ELBE) delivers an 40 MeV, 1 mA cw-beam for different applications such as bremsstrahlung production, electron channeling, free-electron lasers or secondary particle beam generation. In this energy region in case of collisions of the electron beam with the pipe nearly all beam power will be deposited into the pipe material. Therefore a reliable beam loss monitoring is essential for machine protection at ELBE. Different systems basing on photo multipliers, compton diodes and long ionisazion chambers were studied. The pros and cons of the different systems will be discussed. Ionisazion chambers based on air-isolated RF cables installed some cm away parallel to the beam line turned out to be the optimal solution. The beam shut-off threshold was adjusted to 1 µC integral charge loss during a 100 ms time interval. Due to the favourable geometry the monitor sensitivity varies less than +/- 50 % along the beam line (different shielding conditions).

  • Lecture (Conference)
    6th European Workshop on Beam Diagnostics and Instrumentation for Particle Accelerators, 05.05. – 07.05.2003, Mainz, Germany
  • Contribution to proceedings
    6th European Workshop on Beam Diagnostics and Instrumentation for Particle Accelerators, 65 - 67, 05, 05.-07.05.2003, Main, Deutschland, 65-67

Downloads

Permalink: https://www.hzdr.de/publications/Publ-5909


The temperature dependence of the energy distribution of the beam emitted by a Au82Si18 liquid metal field-ion emitter

Aidinis, C. J.; Mair, G. L. R.; Bischoff, L.; Londos, C. A.; Akhmadaliev, C.; Ganetsos, T.

The energy distribution of the monomer ion species is studied as a function of emitter temperature for a Au82Si18 eutectic liquid metal alloy ion source (LMAIS). Secondary peaks, or shoulders, in the distribution of some of the species are explained in terms of Hornsey's model, which involves the fast movement of the jet in conjunction with a space-charge energy broadening mechanism within the beam. Moreover, the results confirm an earlier conclusion that whereas Au+, Si+ and Si++ are emitted by direct field-evaporation from the liquid surface, Au++ forms by the post ionization of Au+.

Keywords: liquid metal ion source; alloy; temperature; energy distribution

Permalink: https://www.hzdr.de/publications/Publ-5908


Optische Untersuchungen an Stickstoff-implantiertem GaAs

Sinning, S.; Dekorsy, T.; Helm, M.

Seit mehreren Jahren werden verdünnte Legierungen aus III-V Halbleitern und Stickstoff intensiv untersucht. Eine hervorstechende Eigenschaft dieser Systeme ist die starke Reduktion der Bandlücke mit steigendem Stickstoffgehalt. Neben epitaktischem Wachstum ist Ionenimplantation eine weitere Methode zur Herstellung solcher Materialien.
Wir untersuchen die optischen Eigenschaften und deren Abhängigkeit von den Implantations- und Ausheilbedingungen für GaNxAs1-x (x<0,04). Es zeigt sich, dass unter entsprechenden Bedingungen der von der Implantation verursachte Schaden minimiert und die Bandkantenverschiebung maximiert werden kann. Eine in Photoreflexion beobachtete Bandlückenverschiebung von 63meV konnte bei einer implantierten N-Konzentration von 1% beobachtet werden. Der Einfluss der modifizierten Bandstruktur auf die Ladungsträgerdynamik wird in Femtosekunden zeitaufgelösten pump-probe Experimenten untersucht.

Keywords: GaNAs Stickstoff Implantation zeitaufgelöst Ladungsträgerdynamik pump-probe Reduktion Bandlücke

  • Lecture (Conference)
    DPG-Tagung, Frühjahrs-Tagung des Arbeitskreises Festkörperphysik; Dresden 2003

Permalink: https://www.hzdr.de/publications/Publ-5907


Effect of hydrodynamics on microstructure evolution of Nd-Fe-B alloys

Hermann, R.; Gerbeth, G.; Filip, O.; Priede, J.; Shatrov, V.

The influence of melt convection on the microstructure formation of Nd-Fe-B alloys, mainly the volume fraction and grain size of the a-Fe phase, has been investigated experimentally using the electromagnetic levitation technique and a specially designed floating-zone arrangement. Samples were subjected to a strong rotation during levitation and compared to fixed samples without additional sample rotation in the levitation facility. A controlled influence on the melt flow is possible via tailored magnetic fields which enable enhancement or suppression of the melt convection using the floating-zone arrangement. A specially designed magnetic two-phase stirrer offers a strong influence on the melt flow in the floating-zone facility. The microstructure pattern, mainly the volume fraction and grain size of the a-Fe phase, vary strongly with the strength of the internal flow motion in both types of experiments. The melt flow in a levitated droplet was studied numerically under the additional effect of a global sample rotation resulting in a strong suppression of internal motions. The electromagnetically driven flow in the inductively heated melt zone of the floating-zone arrangement turned out to be of strong influence on the resulting microstructure. Numerical simulations are essential in order to understand and design the various flow structures.

  • Contribution to external collection
    Dieter M. Herlach: Solidification and Crystallization, Weinheim: WILEY-VCH Verlag, 2004, 3-527-31011-8, 185-193

Permalink: https://www.hzdr.de/publications/Publ-5906


Near infrared intersubband transitions in InGaAs-AlAs-InAlAs double quantum wells

Semtsiv, M. P.; Georgiev, N.; Dekorsy, T.; Helm, M.; Masselink, W. T.

not available

Keywords: intersubband transitions; quantum wells; infrared

  • Poster
    7th Int. Conference on Intersubband Transitions in Quantum Wells, Evolene, Switzerland, Sept. 1-5, 2003 (auf CD-ROM publiziert)
  • Contribution to proceedings
    7th Int. Conference on Intersubband Transitions in Quantum Wells, Evolene, Switzerland, Sept. 1-5, 2003 (auf CD-ROM publiziert)

Permalink: https://www.hzdr.de/publications/Publ-5903


Alternated high- and low-pressure nitriding of austenitic stainless steel: Mechanisms and results

Gomes, G. F.; Ueda, M.; Reuther, H.

A combined surface modification treatment consisting of ion nitriding at high pressure and high temperature, followed by a cycle at low pressure, both cycles using a gas mixture of (N-2/H-2):(50/50) in pressure, was applied to stainless-steel AISI 304. In the first cycle, in a glow discharge at 4x10(-1) mbar and temperatures of 400- 450 degreesC, high-pressure nitriding was applied to the samples. In the second cycle, in a glow discharge at 8x10(-4) mbar, low-pressure nitriding was applied to the samples. Applying this sequential hybrid treatment alternately, good nitriding was obtained. X-ray diffraction (XRD) measurements showed the effects of this hybrid ion nitriding in the AISI 304 surface, indicating thick nitrided layers, confirmed by Auger electron spectroscopy (AES). Conversion electron Mossbauer spectroscopy, combined with AES and XRD, showed phases and compounds induced by such treatments. Vickers hardness measurements showed great enhancement in the surface hardness. Applying other combinations of gas mixtures and cycles, produced diverse results in the surface, like the induction of alpha- and epsilon-phases.

Permalink: https://www.hzdr.de/publications/Publ-5902


Facility Management in Forschungseinrichtungen - Anforderungen, Umsetzung, Erfahrungen

Joehnk, P.

  • Lecture (Conference)
    Workshop Facility-Management, Slowakische Technische Universität, Bratislava, 29.9.2003 Smolenice, Slowakische Republik

Permalink: https://www.hzdr.de/publications/Publ-5901


The bremsstrahlung facility at the ELBE accelerator

Rusev, G.; Schwengner, R.; Schilling, K. D.; Wagner, A.; Käubler, L.; Dönau, F.; Mallion, S.; Grosse, E.; Junghans, A. R.; Erhard, M.; Schulze, W.; Hartmann, A.

A superconducting electron linear accelerator of high brilliance and low emittance has been constructed in the Forschungszentrum Rossendorf in order to deliver cw electron beams with a maximum average current of 1 mA. The accelerator will be used to produce different kinds of secondary radiation, neutrons and positrons. Bremsstrahlung produced at ELBE will be used for nuclear-structure and nuclear-astrophysics experiments employing photon-induced reactions such as (y,y) (nuclear-resonance-fluorescence), (y,n), (y,p) (nuclear photo effect) and photon-induced fission. These experiments will be carried out with electron energies up to 20 MeV at a specially designed bremsstrahlung facility. In order to optimize the design of components of the bremsstrahlung facility and to reduce background radiation, simulations using the code GEANT were performed. We describe the main elements of the bremsstrahlung facility, such as the thin water-cooled radiator, the beam hardener, the photon beam collimator, the HPGe-detector setup. Furthermore, we present a comparison of simulations with measurements and report on first experiments with the new facility.

  • BgNS Transactions 9(2004), 173

Permalink: https://www.hzdr.de/publications/Publ-5900


Diagnostics of a N2/Ar direct current magnetron discharge for reactive sputter deposition of fullerene-like carbon nitride thin films

Neidhardt, J.; Hultman, L.; Abendroth, B.; Gago, R.; Moeller, W.

Plasma probe measurements and energy selective mass spectrometry were used to characterize the composition and energetic conditions of the ion flux of a direct current, N2 /Ar, unbalanced magnetron sputtering plasma in front of a graphite target, depending on the total pressure and gas composition. It is shown that the flux of ionized film-forming species consist predominantly of CxNy (x,y<2) species. The total number of C-containing ions strongly depends on the N2 fraction in the discharge and can be increased by almost one order of magnitude scaling with the availability of N2 as the discharge gas. This finding suggests that besides C and N atoms and ions, other species, like preformed CxNy particles, play an important role during growth of fullerene-like (FL) carbon nitride (CNx) thin films. It is proposed that such clusters have a direct effect as growth templates or nucleation sites on the evolution of curved and cross-linked FL structures. The carbon target was identified as the main source of preformed C-containing species, following from the pressure dependence of the ion energy distributions of the most abundant CxNy (x,y<2) ions.

  • Journal of Applied Physics 94/11 (2003) 7059
    DOI: 10.1063/1.1625091
    Cited 48 times in Scopus
  • Virtual Journal of Nanoscale Science & Technology 8/21 (Compilation of links to selected articles covering a focused area of frontier research published by the American Institute of Physics and the American Physical Society)

Permalink: https://www.hzdr.de/publications/Publ-5899


High-Fluence C-Implantation into 3C-SiC: Synthesis of Buried Diamond-Nanocrystals

Weishart, H.; Heera, V.; Pécz, B.; Tóth, L.; Skorupa, W.

Their outstanding properties, such as wide band gap, high thermal conductivity and saturated electron drift velocity, make silicon carbide and diamond useful semiconductors for applications under harsh conditions. A combination of both materials on a microscopic scale may be a promising way to novel devices.
Ion Beam Synthesis (IBS) is an excellent method for creating precipitates inside any matrix without thermodynamic constraints. We previously demonstrated the synthesis of nanocrystalline 3C-SiC inside diamond by high-fluence Si implantation. In this work we investigate phase formation in carbon-implanted 3C-SiC substrates. Implantations were performed with different fluences ranging form 3x1017 cm-2 to 3x1018 cm-2. Additionally, the influence of implantation temperature and dose rate was studied using X-ray diffraction (XRD), Raman spectrometry and high-resolution cross-sectional transmission electron microscopy (HRTEM).
Low implantation temperatures and high dose rates favor the formation of graphite precipitates in a textured form, while in all other cases epitaxial diamond nanocrystals grow. Hence, a critical temperature for diamond formation exists, which depends on dose rate. Increasing the fluence leads to bigger nanocrystals. Diamond platelets of up to 20 nm length were found.

Keywords: Ion Beam Synthesis; silicon carbide; diamond

  • Lecture (Conference)
    Verhandlungen der Deutschen Physikalischen Gesellschaft 2004, Fachverband Dünne Schichten, Sitzung DS 18.2, Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 8.-12.03.2004, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-5898


VALIDATION OF COUPLED CODES IN VALCO WP1 USING MEASURED VVER DATA

Hämäläinen, A.; Vanttola, T.; Weiss, F.-P.; Mittag, S.; Kliem, S.; Kozmenkov, Y.; Keresztúri, A.; Hádek, J.; Strmensky, C.; Stefanova, S.; Kuchin, A.; Hlbocky, P.; Siko, D.; Danilin, S.

The collection of measured data from transients in VVER type NPPs has been used for the validation of coupled thermal hydraulics / neutron kinetics codes in the previous PHARE project SRR1/95 and continuing now in the Work Package 1 of the VALCO project with new types of transients and new data. Firstly, a collection of five transients was made, then two transients; ‘Drop of control rod at nominal power at Bohunice-3’ for VVER-440 reactors and ‘Coast-down of 1 from 3 working MCPs at Kozloduy-6’ for VVER-1000 reactors, were used in code validation. Eight institutes participated with ten calculations for the code validation with five different combinations of coupled codes. Used thermal hydraulic codes were ATHLET, SMABRE and RELAP5 and the neutron kinetic codes DYN3D, HEXTRAN, KIKO3D and BIPR8.

The amount of collected data in WP1 was excessive. Simultaneous calculation of the selected transients brought up additional specification needs for data, which improved its quality. Further, the ability to interpret plant data has increased among the participants. The general behaviour of both transients was quite well calculated with all the codes and as a result more information in some special phenomena was received. The differences between the calculations pave the way for future needs of more accurate fuel models in the coupled codes.

  • Lecture (Conference)
    13. Symposium of AER, Dresden, 22-26 September, 2003, pp. 555-576
  • Contribution to proceedings
    13. Symposium of AER, Dresden, 22-26 September, 2003, pp. 555-576

Permalink: https://www.hzdr.de/publications/Publ-5897


Self-Organization of Nanocluster delta-Layers at Ion-Beam-Mixied Si-SiO2 Interfaces

Röntzsch, L.; (Editor)

This diploma thesis presents experimental evidence of a theoretical concept which predicts the self-organization of delta-layers of silicon nanoclusters in the buried oxide of a MOS-like structure. This approach of "bottom-up" structuring might be of eminent importance in view of future semiconductor memory devices.

Unconventionally, a 15nm thin SiO2 layer, which is enclosed by a 50nm poly-Si capping layer and the Si substrate, is irradiated with Si+ ions. Ion impact drives the system to a state far from thermodynamic equilibrium, i.e. the local composition of the target is modified to a degree unattainable in common processes. A region of SiOx (x<2) - where x is a function of depth - is formed which is not stable.

During annealing, the system relaxes towards equilibrium, i.e. phase separation (via spinodal decomposition and nucleation) sets in. Within a certain time window of annealing, the structure of the system matches with a structure similar to the multidot non-volatile memory device, the principal character of which is a 2D layer of Si nanoclusters of ~3nm in diameter which is embedded in a 3D SiO2 matrix at a distance of ~3nm from the Si substrate.

The physical mechanisms of ion mixing of the two Si-SiOx interfaces and subsequent phase separation, which result in the desired sample structure, are elucidated from the viewpoint of computer simulation. In addition, experimental evidence is presented based on various methods, including TEM, RBS, and SIMS. Of particular importance is a novel method of Si nanocluster decoration which applies Ge as contrast enhancing element in TEM studies of tiny Si nanoclusters.

Keywords: ion-mixing; self-organization; phase separation; Si nanocluster; non-volatile memory; Si-SiO2 interface; Ge decoration

  • Open Access Logo Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-392 Oktober 2003
    ISSN: 1437-322X

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Permalink: https://www.hzdr.de/publications/Publ-5896


Redox and electrocatalytic activity of Ni ion-implanted Ti

Pham, M. T.; Maitz, M. F.; Reuther, H.; Richter, E.; Matz, W.; Muecklich, A.; Chevtchenko, N.; Prokert, F.

Ni-Ti surface alloy was prepared by ion-implanting Ni into Ti. The surface film was amorphous having a Ni surface content of 10 - 40 at. %. The material was compared with a Ni-Ti bulk alloy (44.08:55.9) regarding their redox and electrocatalytic behaviour in NaOH by cyclic voltammetry. The surface was characterized by X-ray photoelectron spectroscopy, X-ray and electron diffraction, and electron and atomic force microscopy. The ion-implantated material revealed an enhanced activity toward the redox conversion of Ni(OH)2 " NiOOH and the anodic oxidation of glucose. The effect was discussed considering the enhanced generation of active Ni surface sites from amorphous Ni and the stabilization of higher valence Ni by Ti.

Keywords: Ni-Ti alloy electrodes; electrocatalysis; glucose; surface alloying; ion implantation

  • Journal of Materials Research 19(2004), 1249-1256

Permalink: https://www.hzdr.de/publications/Publ-5895


Modifications in cell cycle kinetics and in expression of G1 phase-regulating proteins in human amniotic cells after exposure to electromagnetic fields and ionizing radiation

Lange, S.; Viergutz, T.; Simkó, M.

Low-frequency electromagnetic fields are suspected of being involved in carcinogenesis, particularly in processes that could be related to cancer promotion. Since development of cancer is associated with deregulated cell growth and we previously observed a MF-induced decrease in DNA synthesis (Lange et al. 2002), this study aims to document the influence of 50 Hz, 1 mT magnetic fields (MF), with or without initial gamma-ionizing radiation (IR), on the following cell proliferation-relevant parameters in AFC cells: cell cycle distribution, expression of the G1 phase-regulating proteins Cdk4, cyclin D1, p21CIP1, and p16INK4a, and Cdk4 kinase activity. While IR induced a G1 delay as well as a dose-dependent G2 arrest, no discernible changes in cell cycle kinetics were observed due to MF exposure. Significant alterations in the protein expression of cyclin D1, p21CIP1, and p16INK4a could be detected after exposure to MF and/or IR, respectively, whereas only a slight diminution of Cdk4 kinase activity was noticed. Consequently, Cdk4 appears not to act as mediator of MF- or IR-induced changes in the cell cycle of AFC cells. Combined exposure to MF/IR affected neither cell cycle distribution nor protein expression or kinase activity additionally or synergisticly and, therefore, MF seems not to modify the mutagenic potency of IR.

Keywords: electromagnetic field; ionizing radiation; cell cycle regulation; Cdk4; cyclin D1; p16INK4a; p21CIP1

  • Cell Proliferation 37(2004)5, 337-349

Permalink: https://www.hzdr.de/publications/Publ-5894


Reactor Dosimetry: Accurate Determination and Benchmarking of Radiation Field Parameters, relevant for Pressure Vessel Monitoring (REDOS)

Ballesteros, A.; Garcia, G.; Böhmer, B.; OšMera, B.; Keresztúri, A.; Ilieva, K.; Acosta, B.; Smutný, V.; Polke, E.; Zaritsky, S.; Ortego, P.

Radiation embrittlement of reactor pressure vessel (RPV) steels is a degradation mechanism that requires crucial consideration for the safe operation of aged nuclear power plants. Plant life management needs a reliable estimation of radiation field parameters, including their uncertainty, to avoid the use of conservative approaches.
The particular objectives of the REDOS project are the improvements of the RPV monitoring, the improvement of the neutron-gamma calculation methodologies through the LR-0 engineering benchmarks for VVER-1000 and VVER-440, and the accurate determination of radiation field parameters in the vicinity and over the thickness of the RPV.
The REDOS project started in November 2001 and has a duration of three years. At its mid term stage in the project, all the required NPP experimental data have been collected. A review of the available experimental data of Kozloduy RPV unit 1 has been performed and the attenuation coefficients through the vessel wall have been estimated. The collection of the available revised data for VVER-440 Mock-up have been completed. Furthermore, the existing data for the VVER-1000 Mock-up have been reviewed and the preparatory work for subsequent measurement and experimental data analysis was carried out.

Measurements of the space-energy distribution of the mixed neutron-gamma field in the VVER-1000 model have been performed over the RPV simulator. The photon and neutron spectra have being measured simultaneously with the stilbene scintillator and the multiparameter technique, and the thermal neutron flux has been measured in several points with a He-3 miniature chamber. The most important improvements in the experimental techniques used are the multiparameter spectrometer and a new low noise precise monitoring system in the LR-0 reactor, developed for this type of measurements. The calculational models of the benchmark exercise were prepared by the project participants using their respective codes.

Keywords: Radiation embrittlement; reactor pressure vessel; VVER-1000; VVER-440; LR-0; reactor mock-up; neutron-gamma calculation; radiation field parameters; photon and neutron spectra measurements; stilbene scintillator; multiparameter spectrometer; He-3 miniature chamber

  • Lecture (Conference)
    FISA-2003 - Symposium on EU Research in Reactor Safety, 10-13 November 2003, Luxembourg
  • Contribution to proceedings
    FISA-2003 - Symposium on EU Research in Reactor Safety, 10-13 November 2003, Luxembourg

Permalink: https://www.hzdr.de/publications/Publ-5892


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