Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

32178 Publications
Thermodynamic Sorption Models: Derivation of Recommended Data Sets and Application to Performance Assessment
Brendler, V.; Richter, A.; Arnold, T.; Bernhard, G.;
This paper integrally addresses three topics: the general predictive capabilities of Surface Complexation Models (SCM) for radionuclide migration modeling, their current state of parametrization based on a respective database, and the application for performance assessment (PA).

The SCM concept is mineral-specific and can therefore also be used for additive models of more complex solid phases such as rocks or soils. It properly takes into account the physico-chemical phenomena governing the contamination source term development in time and space. One major aspect there is the substitution of conventional distribution coefficients (KD-values) for the empirical description of sorption processes, most often applied in risk assessment studies so far. Thus, the framework of a "Smart KD" is developed for complex scenarios with a detailed explanation of the underlying assumptions and theories. It helps to identify essential processes and the associated most critical parameters, easing further experimental refinement studies.

As to the knowledge of the authors, so far there is no digital thermodynamic database for surface complexation equilibria existent world-wide, despite the vast amount of available data. Therefore, the "Rossendorf Expert System for Surface and Sorption Thermodynamics" (RES³T) was developed [1]. Originally implemented as a stand-alone relational database under MS Access on a PC, now RES³T is also connected to the WWW and accessible through commonly used web browser interfaces. An integrated user interface allows to easily access selected mineral and sorption data, to convert parameter units, to extract internally consistent data sets for sorption modeling, and to export them into formats suitable for other modeling software. Data records comprise of mineral properties, specific surface area values, characteristics of surface binding sites and their protolysis, sorption ligand information, and surface complexation reactions. All relevant submodels are already implemented, extensions to other variants are straightforward. An extensive bibliography is attached, providing links not only to the above listed data items, but also to background information concerning surface complexation model theories, related software for data processing and modeling, sorption experiment techniques, and independent spectroscopic evidence of surface species. RES³T assists the identification of critical data gaps, the evaluation of existing parameter sets, consistency tests and the establishment of selected reference data sets.

High-quality experimemtal sorption data sets as provided by Phase II of the NEA Sorption Project for its fitting assessment efforts were used. The systems covered are Np(V) sorption onto hematite, U(VI) sorption onto quartz and Se sorption onto goethite. To keep the number of parameters at a minimum, the Diffuse Double Layer model was selected to account for electrostatics. All calculations were performed with the FITEQL code, version 3.2 [2]. Based on the information in the sorption database RES³T for the above minerals and chemically similar phases, first a set of relevant species was formed. Then respective surface complexation parameters were taken from RES³T: the binding site density for the minerals, the surface protolysis constants, and the brutto stability constants for all relevant surface complexes. To be able to compare and average thermodynamic constants originating from different sources, the normalization concept as introduced by Kulik [3] was applied. Lacking data was substituted by estimates exploiting chemical analogy. The only system-specific parameters directly going into the computations were the solid-liquid ratio and the specific surface area. The model prediction almost always represented the experimental values for the sorbed amount of Np, U and Se, expressed as conventional distribution coefficients KD as required by PA software, within one order of magnitude or better, provid...
  • Lecture (Conference)
    Waste Management Conference 2004, Topic 6, Tucson, Ariz., United States
  • Contribution to proceedings
    Waste Management Conference 2004, 29.02.-04.03.2004, Tucson, Ariz., United States

Publ.-Id: 5701 - Permalink


First results from subthreshold K+ production measurements with ANKE
Barsov, S.; Bechstedt, U.; Borchert, G.; Borgs, W.; Büscher, M.; Debowski, M.; Drochner, M.; Erven, W.; Eüer, R.; Fedorets, P.; Gotta, D.; Hartmann, M.; Junghans, H.; Kacharava, A.; Kamys, B.; Klehr, F.; Koch, H. R.; Komarov, V. I.; Koptev, V.; Kulessa, P.; Kulikov, A.; Kurbatov, V.; Macharashvili, G.; Maier, R.; Mikirtichyants, S.; Merzliakov, S.; Müller, H.; Mussgiler, A.; Nioradze, M.; Ohm, H.; Petrus, A.; Prasuhn, D.; Pysz, K.; Rathmann, F.; Rimarzig, B.; Rudy, Z.; Schleichert, R.; Schneider, C.; Schult, O. W. B.; Seyfahrt, H.; Sistemich, K.; Stein, H. J.; Ströher, H.; Wüstner, P.;
The new spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungszentrum Jfilich. An initial scientific goal is to study K+-production in pA collisions at subthreshold energies below the free NN-threshold of T = 1.58 GeV. First measurements of double differential cross sections in p12C collisions at emission angles around 0° have been performed at T = 1.0,1.2 and 2.0 GeV. The challenge is to identify the kaons in a huge background of pions and protons, since the signal to background ratio decreases to about 10-6 at T = 1.0 GeV. For background suppression detectors and a trigger system based on energy-loss and time-of-flight measurements have been developed.
In the analysis the decay of kaons (τ = 12.4 ns) stopped in the detection system into π+ and μ+ is exploited as well as the track information from the wire chambers.
  • Nucl. Phys. A675 (2000) 230c-233c

Publ.-Id: 5700 - Permalink


The ANKE spectrometer at COSY-Jülich and studies of the subthreshold K+ production
Barsov, S.; Bechstedt, U.; Borchert, G.; Borgs, W.; Büscher, M.; Debowski, M.; Erven, W.; Eüer, R.; Fedorets, P.; Gotta, D.; Junghans, H.; Kacharava, A.; Kamys, B.; Klehr, F.; Koch, H. R.; Komarov, V. I.; Koptev, V.; Kulessa, P.; Kulikov, A.; Kurbatov, V.; Macharashvili, G.; Maier, R.; Mikirtichyants, S.; Merzliakow, S.; Müller, H.; Mussgiller, A.; Nioradze, M.; Ohm, H.; Petrus, A.; Prasuhn, D.; Pysz, K.; Rathmann, F.; Rimarzig, B.; Rudy, Z.;
kein Abstract
  • Nucl. Phys. A 663 (2000) 1107

Publ.-Id: 5699 - Permalink


Intraindividual comparison of [11C]acetate and [11C]choline PET for detection of metastases of prostate cancer
Kotzerke, J.; Volkmer, B. G.; Glatting, G.; van den Hoff, J.; Gschwend, J. E.; Messer, P.; Reske, S. N.; Neumaier, B.;
In a pilot trial we investigated whether significant differences in prostate cancer (PCA) imaging would be observed using [11C]acetate and [11C]choline positron emission tomography (PET).
Methods: Twelve patients were studied with both radiotracers. Whole body PET without attenuation correction was performed after injection of 0.95 ± 0.15 GBq [11C]acetate and 0.84 ± 0.13 GBq [11C]choline, respectively, from 5 to 60 min p. i. Focally increased uptake in bone, below the urinary bladder or in a lymph node region was considered as tumour. Primary tumour, lymph node involvement, bone metastases, local recurrence; and no evidence of disease were known in 2, 4, 2, 2; and 2 patients, respectively.
Results: [11C]acetate uptake was highest in spleen and pancreas while [11C]choline uptake was predominant in liver and kidney parenchyma. However, interindividual variation was high. The potential of both radiotracers to detect known bone lesions, lymph node metastases, and imaging of the primary tumour was identical. However, both failed to detect a small local recurrence in two patients as well as to demonstrate lymph node involvement in one patient, which was confirmed by surgery.
Conclusion: In this preliminary study, uptake of both radiotracers in prostate cancer or its metastases was nearly identical and none of them should be favoured. At present, both radiotracers influence patient management by detection of local recurrence, lymph node, or bone metastases of PCA.
Keywords: acetate, choline, positron emission tomography, prostate cancer
  • Nuklearmedizin (2003); 42 (1): 25-30

Publ.-Id: 5698 - Permalink


Application of autocathode in a superconducting electron RF injector for the industry acclerator
Janssen, D.; Volkov, V. N.; Konstantinov, S. G.; Kudryavtsev, A. M.; Myskin, O. K.; Petrov, V. M.; Tribendis, A. G.;
Recently, publications on the development of cold field emission cathodes with current high density at rather low voltage applied are very broadly spread [1,2]. In the work presented here, the computer simulation has been performed for one of the versions of application of such cathodes in a superconducting RF cavity of the electron injector designed for the industrial accelerator.
  • Lecture (Conference)
    APAC01, September 17-21, 2001, Beijing, China

Publ.-Id: 5697 - Permalink


Infrared characterization of environmental samples by photothermal beam deflection using a free electron laser
Seidel, W.; Foerstendorf, H.; Heise, K.-H.; Ortega, J.-M.; Glotin, F.; Prazeres, R.;
The low concentration of toxic radioactive metals in environmental samples often limits the interpretation of results of infrared studies investigating the interaction processes between the metal ions and environmental compartments. For the first time, we could show that photothermal infrared spectroscopy performed with a pulsed free-electron laser can provide reliable infrared spectra throughout a distinct spectral range of interest. In this model investigation, we provide vibrational absorption spectra of a rare earth metal salt dissolved in a KBr matrix and a natural calcite sample obtained by thermal beam deflection technique and FT-IR spectroscopy, respectively. General agreement was found between all spectra of the different recording techniques.
Keywords: Keine
  • Poster
    Proc. 25th Int. Conf. on Free Electron Laser, and the 10th FEL User Workshop, Tsukuba, Ibaraki, Japan, 8 - 12 September 2003, (North-Holland, Amsterdam, 2004) ed. (eingereicht)
  • Contribution to proceedings
    Proceedings. of the 25th International. Conference on Free Electron Laser, and the 10th FEL User Workshop,08.-12.09.2003 Tsukuba, Ibaraki, Japan, (North-Holland, Amsterdam, 2004)

Publ.-Id: 5696 - Permalink


The optical resonator of the IR-FEL at ELBE
Seidel, W.; Evtushenko, P.; Gippner, P.; Grosse, E.; Jainsch, R.; Oepts, D.; Sobiella, M.; Wohlfarth, D.; Wolf, A.; Wolf, U.; Wünsch, R.; Wustmann, B.;
To allow first lasing at the ELBE FEL at the end of 2003 various efforts have been made. In particular, the optical resonator including the system which controls and stabilizes its length and alignment has been installed and tested. The resonator length is controlled by means of an interferometer beam passing diagonally from one side of the upstream mirror to a retroreflector on the opposite side of the downstream mirror.
To avoid temperature effects the mirror holders have been equiped with a special heating and cooling system which stabilizes the mirror temperature. Simulating maximum laser power the cavity detuning due to temperature changes has not exceeded 1micron.
The alignment of the resonator axis is controlled by the overlap of two He-Ne laser beams entering the resonator from each side. To predict the outcoupled laser power and the upper wavelength limit we have modeled the IR-beam propagation in the optical resonator. In particular, the vacuum chamber in the undulator, which is 10 mm high, and the outcoupling hole affect the beam power and profile significantly; respective results will be presented.
Keywords: Keine
  • Poster
    25th Int. Conf. on Free Electron Laser, Tsukuba, Ibaraki, Japan, 8 - 12 September 2003
  • Nuclear Instruments and Methods in Physics Research A 528(2004)1-2, 199-202

Publ.-Id: 5695 - Permalink


Infrared characterization of environmental samples by pulsed photothermal spectroscopy
Seidel, W.; Foerstendorf, H.; Heise, K.-H.; Nicolai, R.; Dekorsy, T.; Ortega, J.-M.; Glotin, F.; Prazeres, R.;
The low concentration of toxic radioactive metals in environmental samples often limits the interpretation of results of infrared studies investigating the interaction processes between the metal ions and environmental compartments. For the first time, we could show that photothermal infrared spectroscopy performed with a pulsed free-electron laser can provide reliable infrared spectra throughout a distinct spectral range of interest. In this model investigation, we provide vibrational absorption spectra of a rare earth metal salt dissolved in a KBr matrix and a natural calcite sample obtained by thermal beam deflection technique and FT-IR spectroscopy, respectively. General agreement was found between all spectra of the different recording techniques. Spectral deviations were observed with samples containing low concentration of the rare earth metal salt indicating a lower detection limit of the photothermal method as compared to conventional FT-IR spectroscopy. Furthermore, the photothermal method provide spatial information of a sample surface. This may result in a microspectrometric technique for determining the distribution of metal species on mineral surfaces. First experiments exploring the spatial resolution of photothermal spectroscopy were carried out by scanning the surface of a germanium substrate showing a localized region where O-ions were implanted. The border range of this region was investigated by recording time curves of the deflection signal at distinct positions of the substrate surface with a constant free-electron laser wavelength of 11.6 micrometer.
Keywords: Laser spectroscopy, thermooptical and photothermal effects
  • Poster
    International Workshop on Infrared Microscopy and Spectroscopy with Accelerator Based Sources, July 8-11, 2003, lake Tahoe, CA, USA
  • Contribution to proceedings
    International Workshop on Infrared Microscopy and Spectroscopy with Accelerator Based Sources, July 8-11, 2003, lake Tahoe, CA, USA

Publ.-Id: 5694 - Permalink


Spatial distribution of cavities in silicon formed by ion implantation generated excess vacancies
Peeva, A.; Kögler, R.; Skorupa, W.; Kuznetsov, A.; Christensen, J.;
Spatial distribution of nano-sized cavities in silicon formed by high energy Ge ion implantation and annealing was determined. The cavities were directly observed by transmission electron microscopy without any decoration. The cavities are shown to be the agglomerates of implantation-induced excess vacancies. The concentration depth profile of the vacancies bound in the cavities agrees well with the excess vacancy profile calculated for the implantation process. Almost all the generated excess vacancies agglomerate in cavities after annealing at 900 °C for 30 s. The vacancy profile coincides with the depth profile of Cu that was intentionally introduced in the cavity region. The perfect match of vacancy and Cu distribution indicates that the cavities are the determining gettering centres for Cu atoms.
Keywords: Defects in silicon, Implantation defects, Vacancies, Cavities, Gettering

Publ.-Id: 5693 - Permalink


Improved Statistical Power of the Multilinear Reference Tissue Approach to the Quantification of Neuroreceptor Ligand Binding by Regularization
Buchert, R.; Wilke, F.; van den Hoff, J.; Mester, J.;
A multilinear reference tissue approach has been widely used recently for the assessment of neuroreceptor-ligand interactions with positron emission tomography. The authors analyzed this "multilinear method" with respect to its sensitivity to statistical noise, and propose regularization procedures that reduce the effects of statistical noise. Computer simulations and singular value decomposition of its operational equation were used to investigate the sensitivity of the multilinear method to statistical noise. Regularization was performed by truncated singular value decomposition, Tikhonov-Phillips regularization, and by imposing boundary constraints on the rate constants. There was a significant underestimation of distribution volume ratios. Singular value decomposition showed that the bias was caused by statistical noise. The regularization procedures significantly increased the test-retest stability. The bias could be reduced by applying linear constraints on the rate constants based on their normal range. Underestimation of distribution volume ratios by the multilinear method is caused by its sensitivity to statistical noise. Statistical power in the discrimination of different groups of subjects can be significantly improve by regularization procedures without introducing additional bias. Correct distribution volume ratios can be obtained by imposing physiologic constraints on the rate constants.
Keywords: PET, modeling, linear regression, reference tissue method, regularization
  • Journal of Cerebral Blood Flow and Metabolism (2003) 23: 612-620

Publ.-Id: 5692 - Permalink


Experiments at COSY
Schult, O. W. B.; Bisplinghoff, J.; Müller, H.; u. a.;
A cooler synchrotron, COSY, has been built in the Research Center Jülich for the acceleration of protons to any energy between 38 and 2500 MeV and for the preparation of cooled beams for experiments, which use the circulating beam with ideal thin targets in the ring, or which benefit from smal spots of the extracted beam. At present, the accelerator is in the phase of conditioning. Internal and extracted beams have been used for testing and calibration of detectors and data acquisition systems. Production runs of physical data are expected in the very near future.
  • Contribution to proceedings
    Proceedings of the 7th international conference on nuclear reaction mechanisms, varenna, june 6-11, 1994, Milano

Publ.-Id: 5691 - Permalink


Study of medium modifications with the new spectrometer ANKE at COSY - Jülich
Barsov, S.; Koptev, V.; Mikirtychiants, S.; Bechstedt, U.; Borchert, G.; Borgs, W.; Buescher, M.; Erven, W.; Gotta, D.; Hartmann, M.; Junghans, H.; Klehr, F.; Koch, H. R.; Kulessa, P.; Maier, R.; Ohm, H.; Prasuhn, D.; Schleichert, R.; Schneider, H.; Schult, O. W. B.; Seyfahrt, H.; Sistemich, K.; Stroeher, H. J.; Debowski, M.; Müller, H.; Rimarzig, B.; Schneider, C.; Rathmann, F.; Mussgiller, A.; Kamys, B.; Pysz, K.; Rudy, Z.; Zychor, I.; Kacharava, A.; Komarov, V. I.; Kulikov, A.; Kurbatov, V.; Macharashvili, G.; Merzliakov, S.; Petrus, A.; Fedorets, P.; Nioradze, M.;
kein Abstrakt
  • Acta Phys. Pol. B31 (2000) 357

Publ.-Id: 5690 - Permalink


A Quark Model for Hadron Production
Müller, H.;
Hadron production in nucleon-nucleon, nucleon-nucleus and nucleus-nucleus interactions is considered in the framework of the Rossendorf collision model, which aims at describing simultaneously all reaction channels in a wide energy region. An empirical matrix element based on the partonic picture of hadrons is combined with the concept of intermediate subsystems and the calculation of modified statistical weights of the various final states. In case of nuclear reactions the Glauber concept is used to calculate the partial cross sections for the interaction of various numbers of participants. It is demonstrated that a large variety of experimental data can be satisfactorile reproduced. Predictions for proposed missing-mass measurements are discussed.
  • Acta Physica Polonica B, No 11, Vol. 27 (1996)

Publ.-Id: 5689 - Permalink


Study of medium modifications with the new spectrometer ANKE at COSY - Jülich
Barsov, S.; Koptev, V.; Mikirtychiants, S.; Bechstedt, U.; Borchert, G.; Borgs, W.; Buescher, M.; Erven, W.; Gotta, D.; Hartmann, M.;
kein Abstrakt
  • Acta Phys. Pol. B31 (2000) 357

Publ.-Id: 5688 - Permalink


Kaon and antikaon production in proton nucleus collisions
Scheinast, W.;
kein Abstract
  • Acta Phys. Pol. B31 (2000) 2305

Publ.-Id: 5687 - Permalink


A Dedicated 0° Facility for Threshold Particle Production Studies at COSY
Büscher, M.; Sistemich, K.; Abaev, V.; Bechstedt, U.; Birien, P.; Borgs, W.; Cassing, W.; Dienel, S.; Dombrowski, H.; Dshemuchadze, S. V.; Ernst, J.; Müller, H.;
A universal facility is in preparation for the study of particle production in proton-nucleus reactions below the nucleon-nucleon threshold. The device will be located at the internal target position TP2 at COSY-Jülich and will consist of three dipole magnets. This 0° 'Facility will separate ejectile from the circulating proton beam and allow momentum and angle analysis both for positively and negatively charged particles. A major goal of the experimental program is the investigation of the K+-meson production at projectile energies below the NN threshold. The detector concept for these studies is described and also an overview over further planned experiments is given.
  • Physica Scripta, Vol. 48, 50-53, 1993

Publ.-Id: 5686 - Permalink


Photon Radiation from expanding gluon rich plasma
Kämpfer, B.; Pavlenko, O. P.;
Photon production in an expanding gluon plasma with initially little quark admixture is considered. Photons are created by lowest α5 order processes which include quarks. Chemical equilibration of the quarks in turn is followed by rate equations which rely on lowest α5 order gg<=>qq processes. Expansion slows down the quark cooking. Compared with the standard local qquilibrium estimates we find a drestic reduction of medium-energy photons if the initial quark admixture is below 20 % of the chemical saturation density. Higher initial temperatures increase significantly the high-energy photon yield and overcompensate this reduction.
  • Phys. Atom. Nucl. 58, 1995, 2144-2149; Yad. Fiz. 58, 1995, 2260

Publ.-Id: 5685 - Permalink


Accurate determination of metabolic rates from dynamic positron emission tomography data with very-low temporal resolution
Buchert, R.; van den Hoff, J.; Mester, J.;
Purpose: The graphical approach is widely used for the pixelwise determination of local metabolic rate of glucose from dynamic positron emission tomography (PET) data. In its conventional implementation, measured integrals over time frames are used to approximate instantaneous tracer concentrations at midframe times ("midframe approach"). This is justified in case of high temporal resolution of the PET measurement; that is, if scan protocols with a large number of short frames are used. This requires fast data handling and large amounts of memory. Cardiac gating and three-dimensional (3D) acquisition of dynamic studies is hardly possible with this approach. Therefore, a new variant of the graphical method is proposed which can be used with a very low number of rather long frames.
Methods: An operational equation of the graphical method was derived which uses measured time integrals only and, thus, avoids the systematic errors of the midframe approximation. This "integral approach" was evaluated in computer simulations based on experimental data.
Results: The integral approach enables the use of protocols with 3 frame only without compromising accuracy of the derived metabolic rates whereas the midframe approach leads to bias of about 10 % to 20 % for these protocols. Furthermore, test-retest stability can significantly be improved when using the integral approach.
Conclusion: The integral approach to the graphical evaluation of dynamic PET data yields accurate and precise results using scan protocols with down to only 3 frames. This can be relevant to gating and/or 3D acquisition of dynamic studies. The integral approach is applied most naturally whenever the input function is derived from the dynamic PET data.
Keywords: graphical analysis, positron emission tomography, sampling schedule, tracer kinetic modeling
  • Journal of Computer Assisted Tomography (2003) 27 (4): 597-605

Publ.-Id: 5684 - Permalink


Lifetime study of particle-hole excitations in the semimagig nucleus 93TC
Hausmann, M.; Jungclaus, A.; Galindo, E.; Lieb, K. P.; Yordanov, O.; Johnstone, I. P.; Schwengner, R.; Dewald, A.; Fitzler, A.; Möller, O.; de Angelis, G.; Gadea, A.; Martinez, T.; Napoli, D. R.; Ur, C.;
The recoil-distance Doppler-shift technique was employed for determining lifetimes of high-spin states in the semimagic nucleus 93Tc. The nuclei were populated using the reaction 64Zn(35Cl,b1;2p) at a beam energy of 135 MeV, and the g radiation from their decay was detected in the GASP spectrometer. A total of 26 reduced transition probabilities and limits for 19 further transitions were extracted and compared to large scale shell model calculations, considering different configuration spaces and residual interactions. The information deduced about transition strengths turned out to be essential for the correct assignment of the calculated to the experimental excited states.
  • Physical Review C68, 024309 (2003)

Publ.-Id: 5683 - Permalink


Charged hadron tumour therapy monitoring by means of PET
Enghardt, W.; Crespo, P.; Fiedler, F.; Hinz, R.; Parodi, K.; Pawelke, J.; Pönisch, F.;
Positron emission tomography (PET) imaging of radioactivity distributions induced by therapeutic irradiation is at present the only feasible method for an in-situ and non-invasive monitoring of radiooncology treatments with ion beams. Therefore, at the experimental carbon ion therapy facility at the Gesellschaft für Schwerionenforschung Darmstadt, Germany (GSI) a PET-scanner has been completely integrated into the treatment site for a quality assurance monitoring simultaneously to the therapeutic irradiation. Although the device has been assembled from components of positron emission tomographs developed for nuclear medicine applications, substantial modifications had to be made for meeting the requirements of ion therapy monitoring. these changes regard the geometrical detector configuration as well as the data acquisition and processing. Since 1997 this technique has been applied to monitoring the fractionated irradiation of more than 180 patients predominantly suffering from tumours in the head neck region. It could be demonstrated that this new PET technique is capable of assesing parameters being relevant for quality assurance of carbon ion therapy, i. e. the particle range in tissue, the position of the irradiated volume with respect to anatomical landmarks and local deviations between the planned and the applied dose distributions.
Keywords: Positron emission tomography, charged hadron therapy, ion therapy

Publ.-Id: 5682 - Permalink


Synthesis of a 11C-labelled Taxane Derivative by [1-11C]Acetylation
Mäding, P.; Zessin, J.; Pleiß, U.; Wüst, F.;
Taxans are an important class of antitumor agents. These compounds bind to the microtubuli and inhibit their depolymerization into tubulin. Subsequently, the mitosis is disrupted and the cells are not able to divide into daughter cells. Investigations with positron emission tomography (PET) are an important tool to determine the in vivo distribution and the pharmacokinetics of such drugs if they are labelled with positron-emitting radionuclides. This report describes the 11C-labelling of a taxan derivative as a new potent anticancer drug 1.
The acetyl moiety of 1 in position 10 was chosen to introduce carbon-11, because it is considered to be stable with respect to drug metabolism. For synthesis of the required precursor 2 the taxan 1 was selectively deacetylated in position 10 by treatment with sodium hydrogencarbonate and hydrogen peroxide. To avoid the known epimerization of the hydroxy group in position 7 and to stabilize the ester function in position 13 the 2’ and 7 hydroxy groups were protected with triethylsilyl moieties yielding the precursor 2.
[11C]1 was synthesized in a multi-step procedure according to the Scheme using an automated syn-thesis module. The capability of this module includes the radiosynthesis of [1﷓11C]acetyl chloride (3) and its conversion with the precursor 2 to an intermediate, which was hydrolysed to [11C]1, the HPLC purification of the final product, its solid phase extraction and formulation.
The used module was a commercially available module for 11C methylation from GE Medical Sys-tems (former Nuclear Interface), Münster, Germany.
[1﷓11C]Acetyl chloride (3) was synthesized by conversion of [11C]carbon dioxide with methyl-magnesium bromide in diethyl ether followed by quenching the resulting [11C]acetate solution with phthaloyl dichloride. After evaporation of the solvent, 3 was driven into a cooled THF solution of 2 and lithium hexamethyldisilazide. The [11C]acetylation took place at room temperature within 6 min. The solvent was evaporated and the residue was treated with a solution of hydrochloric acid in MeOH/dioxane for cleavage of the triethylsilyl protecting groups at room temperature. The crude product was purified by semipreparative RP HPLC and solid phase extraction at an RP﷓18-cartridge. The resulting ethanolic solution of [11C]1 and a saline solution was transferred succes-sively through a sterile filter to obtain the final formulation of [11C]1. The decay-corrected radio-chemical yields were in the range of 6 to 19 % (related to [11C]CO2) within a synthesis time of 45-50 min. The radiochemical purity exceeded 96 %, the chemical purity was in the range of 80-99 %.
The specific radioactivity of the final product was up to 18 GBq/µmol at 11 successful attempts with starting radioactivities of 26 GBq.
Keywords: taxan, anticancer drug, [1-11C11]acetyl chloride, automated module synthesis, PET
  • Lecture (Conference)
    11th Conference of the Central European Division e. V. of the International Isotope Society, Bad Soden, 25.-26.09.2003
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 47(2004), 263-265

Publ.-Id: 5681 - Permalink


Carbon-11 Labelled Compounds in the Development of Pharmaceuticals
Wüst, F.;
Positron emission tomography (PET) is a powerful non-invasive clinical and research imaging technique which allows in vivo measurements and quantification of biochemical processes at the molecular level. Besides the success story of PET as valuable diagnostic tool in oncology, neutrology and cardiology, PET technology has also emerged the process of drug research and development. Its strength stems from the ability to obtain directly quantitative knowledge of the distribution and bioavailability of drugs and their therapeutic and toxic effects on living systems. The direct assessment of pharmacokinetic and pharmacodynamic events in humans and animals combined with the new generation of high-resolution PET cameras place PET in a unique position to contribute significantly to the process of drug development and evaluation. PET helps to understand the molecular mechanism underlying drug action while addressing some very practical questions such as determining effective drug doses, determining the duration of drug action and examining potential drug interactions. To fully exploit PET technology in drug development, appropriately labeled compounds are needed. The drug usually must be labeled with carbon-11 (t1/2 = 20 min) to aviod changing the characteristics of the parent compound. Alternatively, fluorine-18 (t1/2 = 110 min) can be used if the drug contains a fluorine atom. The short half lives of 11C and 18F require rapid and selective labelling techniques, since time dominates all aspects of PET. In this connection the extensive performance of organic radiochemistry using 11C and 18F is fundamental but also a special challenge. This presentation will address the recent developments of organic PET radiochemistry in the synthesis of PET radiotracers with sprecial focus on the potential role of 11C-labelled compounds in the design, development and evaluation of pharmaceuticals.
  • Lecture (Conference)
    11th Conference of the International Isotope Society, Bad Soden, 25.-26.09.2003
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmceuticals 47(2004), 261-262

Publ.-Id: 5680 - Permalink


Embrittlement of Reactor Pressure Vessel Steel A508: A Look on Mesoscopic Levels
Borodin, V. A.; Böhmert, J.;
We present the results of fractographic study of standard V-notch Charpy specimens of US steel A508, tested at different temperatures ranging from the lower to upper shelf. The same fracture cross sections were studied at progressively increasing magnifications from x10 up to x20000, using both stereo optical microscopy and scanning electron microscopy. The results demonstrate that test conditions at mesoscopic and macroscopic length scale levels are important factors influencing the crack propagation.
Keywords: Fracture, steels, fractography, embrittlement
  • Lecture (Conference)
    13. International Conference on Strength of Material, 25.-30.08.2003, Budapest, Hungary, Book of Abstracts, p. 113
  • Contribution to proceedings
    13. International Conference on Strength of Material, 25.-30.08.2003, Budapest, Hungary, Book of Abstracts, p. 113

Publ.-Id: 5679 - Permalink


Generation of sub-picosecond electron bunches from superconducting 5.3 cell RF gun and coherent wiggler radiation
Volkov, V. N.; Janssen, D.; Wünsch, R.;
In this paper we discuss the possibility to gernerate subpicosecond electron bunches with a small emittance directly from the superconducting 5.3 cell rf gun by illuminating a photo-cathode in the rf cavity with a phaselocked 3 ps laser pulses. The bunch length compression caused by the RF force take place in the first TESLA cell of the rf gun. Numerical simulations of the beam dynamics in the rf gun and of the radiation of the corresponding electron bunch in a wiggler predict a coherent enhancement of radiaton for wavelength smaller than 100 micron.
  • Lecture (Conference)
    PAC 2001, June 18-22, 2001 Chicago, Illinois, USA
  • Contribution to external collection
    PAC 2001, June 18-22, 2001 Chicago, Illinois, USA

Publ.-Id: 5678 - Permalink


First operation of a superconducting RF-Gun
Janssen, D.; Büttig, H.; Evtushenko, P.; Freitag, M.; Lehnert, U.; Hartmann, B.; Michel, P.; Reppe, B.; Schamlott, A.; Schneider, C.; Schurig, R.; Teichert, J.; Gabriel, F.; Möller, K.; Quast, T.; Konstantinov, S.; Kruchkov, S.; Kudryavtsev, A.; Myskin, O.; Petrov, V.; Tribendis, A.; Volkov, V.; Sandner, W.; Will, I.; Matheisen, A.; Moeller, W.; Pekeler, M.; von Stein, P.; Haberstroh, C.;
For the first time, a superconducting RF gun where a photo cathode is inside a superconducting cavity has been working stably over a periode of seven weeks. The gun with a half cell cavity has been operated in the cryostat at 4.2K. A maximal field strength of 22MV/m in the cavity and maximal beam energy of 900keV have been obtained. Measurements of beam current, transmission, energy spread and transverse emittance are presented.

Publ.-Id: 5677 - Permalink


Interaction of Polyoxotungstates with Aminosaccharides
Jelínek, L.; Matejka, Z.; Novotná, M.; Burda, R.; Sawatzki, A.-K.; Stephan, H.;
Owing to their antiviral and antitumoral properties polyoxometalates (POMs) are gaining in importance in the development of therapeutic agents. Such cluster molecules possessing a multitude of metal atoms might be took advantage in view of cancer treatment by photon activation therapy (PAT). In this nexus it is necessary to meet some requirements. So, POMs must have sufficient stability under physiological conditions. Furthermore, highly efficient transportation into cells, and finally the interaction with DNA is essential. The encapsulation of POMs by aminosaccharides seems to be a promising way to achieve that. In our previous study we reported about the possibility conditions to form complexes between various metal-oxoanions and sorbents having different diol-ligands. Now, we want to report the binding and sorption behavior of selected aminosaccharides towards polyoxotungstates.
  • Contribution to proceedings
    XVIIIth International Symposium "Ars Separatoria 2003", Z. Potok (Polen), 2003, 74-76
  • Lecture (Conference)
    XVIIIth International Symposium "Ars Separatoria 2003", Z. Potok (Polen), 02.-05.06.2003

Publ.-Id: 5676 - Permalink


A New Beam Loss Measurement System For ELBE
Schurig, R.; Evtushenko, P.; Lehnert, U.; Michel, P.; Teichert, J.;
During the commissioning of the first accelerator stage of ELBE, beam loss was measured with photomultipliers and self-testing integrating electronics. While the electronics worked flawless, the correct positioning of the monitors and finding a good trade off between sensitivity and saturation of the photomultipliers were a problem. A new BLM system, consisting of ionization chambers, acquisition electronics and monitoring software is now under construction. Coaxial cable with air dielectricum, normally used in high power applications, makes the ionization chamber and will be installed along the beamline. The outer conducter of the cable is subsectioned, the inner conductor not. The current on the inner conductor represents the total beam loss. The current from each outer conductor segment to ground is measured separately, providing position resolution of the beam loss. On each section, a RISC microcontroller (Slave) with built in ADC is used for data acquisition and continuous average calculation. One microcontroller (Master) handles the communication with the slaves via RS-485 bus and acts as an interface to a PC running monitoring software. First test have been done successfully.
  • Poster
    Beam Instrumentation Workshop 2002,Brookhaven National Laboratore, Poster Session

Publ.-Id: 5675 - Permalink


A Beam Loss Measurement System with Longitudinal Resolution
Schurig, R.; Michel, P.;
At ELBE, beamloss is measured in two different ways. Long ionization chambers (LIC) made from coaxial cable and having an air dielectric are used to detect beam loss at critical sites of the machine. In the second system, beam current is measured at three different locations. The sum signals from two stripline beam position monitors and the nuclear physics beam dump current are compared. A difference in current at these points indicates that portions of the electron beam are lost somewhere. Above a certain level the interlock is triggered and the beam is switched off. Both kinds of measurement are described in detail elsewhere in this annual report.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-375 April 2003

Publ.-Id: 5674 - Permalink


A Resonant Beam Current Monitor for ELBE
Schurig, R.; Büttig, H.; Büchner, A.;
During the first stages of commissioning ELBE, the beam current could be measured directly at the gun, the macropulser aperture and at the beam dump. Later, a package consisting of a resonant beam current monitor (RBCM) and a resonant beam position monitor was added. The result of the RBCM test are described in this paper.
  • Contribution to HZDR-Annual report
    Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-341 April 2002, 15-15

Publ.-Id: 5673 - Permalink


Application of the Normalization Method to Various Fracture Toughness Specimens
Dzugan, J.; Viehrig, H.-W.;
The objective of this paper is the evaluation of the normalization method performance compared to the conventional standard method for a broad spectrum of different materials and specimen geometries. The normalization method based critical J-integral values were summarized and compared with the results of the unloading compliance tests. The results point out the applicability of the normalization method for the J-R curve determination for the investigated materials. The normalization method provided results with up to 15 % deviation from the values obtained with the unloading compliance method.
Keywords: fracture mechanics, fracture toughness, normalization method, unloading compliance
  • Poster
    13. International Conference on the Strength of Materials, 25.-30.08.2003, Budapest, Hungary

Publ.-Id: 5672 - Permalink


A Small Angle X-ray Scattering Method to Investigate the Crack Tip in Metals
van Ouytsel, K.; Böhmert, J.; Müller, G.;
The work in this report, financed by the European Union through the Marie Curie Fellowship Association, was carried out at the FZ-Rossendorf. The subject of the research was to develop a method to investigate the damage, the high defect gradients at the tip of a ductile crack by means of Small Angle X-ray Scattering. The work explains the objectives and entails a brief introduction and background; it portrays and discusses the results which can be summarized as follows. Different damage parameters were investigated: the integral intensity, the total intensity on the detector, the anisotropy parameter and the fractal dimension. Of these, the anisotropy parameter is the most robust and most clearly depicts a damage region and the fractal dimension provides an idea of the structure of the scattering defect. The integral and total intensity provide comparable results only in some cases and are therefore not reliable.
From supportive investigations: Scanning and Transmission Electron Microscopy (S-TEM), Finite Element Analysis and X-Ray Diffraction, it is suggested that the scatterer created after deformation is related to large oriented dislocation networks.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-388 August 2003

Downloads:

Publ.-Id: 5671 - Permalink


Maßnahmen zur Sicherung der Betriebsdauer des Reaktordruckbehälters
Viehrig, H.-W.; Boehmert, J.;
Die uneingeschränkte Nutzung eines RDB bis zum Ende der Betriebsdauer des KKWs auf einem unverändert hohen Sicherheitsniveau ist nur durch ein ganzheitliches und umfassendes Programm von Maßnahmen und Instrumentarien zu gewährleisten. Entscheidend werden dafür die Weichen bereits bei der Auslegung gestellt, indem hochzähe, strahlenversprödungsresistente Werkstoffe verwendet werden, die Neutronenbelastung durch einen ausreichend breiten Wasserspalt redu-ziert wird, die fortschreitende Materialalterung durch ein gut konzipiertes repräsentatives Überwachungsprogramm erfasst und Herstellung und Konstruktion gute Prüfbarkeit ebenso wie die Vermeidung von Spannungsdiskontinuitäten absichern. Betriebliche Maßnahmen können die Bean-spruchung bei Betrieb oder im Störfall reduzieren (Transientenregime, Einspeisung von vorge-wärmten Notkühlwasser), die Neutronenflussdichte durch ein geeignetes Beladeregime senken oder mit aktualisierten Überwachungsprogrammen die Charakterisierung des Materialzustandes verbessern. Als ultimo ratio steht die Ausheilglühung zur Verfügung, deren Praktikabilität inzwi-schen bereits erwiesen ist.
Schließlich erweist sich nicht zuletzt die Einführung neuer Konzepte zur Sprödbruchsicherheitsanalyse als wertvoll. Als ein hinsichtlich seiner Einführung bereits fortgeschrittenes Beispiel dieser Art wurde das Master-Curve-Konzept vorgestellt. Dieses Konzept wird gegenwärtig zur Bestimmung einer bruchmechanisch definierten Übergangstemperatur be-nutzt, mit der die KIc-Universalkurve der Regelwerke materialspezifisch auf der Temperaturachse positioniert werden kann. Die so ermittelten Referenztemperaturen liegen ca. 40 - 60 K niedriger als die bisher verwendeten Referenztemperaturen, die auf den NDT- oder den Charpy-V-Übergangstemperaturen beruhen. Auf diese Weise kann eine unnötige Konservativität der Bewertung abgebaut werden. Das wurde bereits in realen Anwendungsfällen zweifelsfrei nachgewiesen. Langfristig könnte die statistisch definierte MC selbst als Bruchzähigkeitskurve verwendet werden. Damit erfolgt die Bestimmung der Materialparameter nach einem durchgehend physikalisch defi-nierten Konzept, welches Aussagen zur Versagenswahrscheinlichkeit ermöglicht.
Keywords: Kernreaktor, Reaktordruckbehälter, Betriebsdauer, Sprödbruchsicherheitsnachweis, Thermo-schock, Bruchzähigkeit, Referenzkurve, Master-Curve-Konzept, Neutronenversprödung, Versprödungsüberwachungsprogramm, Trendkurve, Alterung, thermische Ausheilung
  • Lecture (Conference)
    Vertiefungskurs der Schweizerischen Vereinigung für Atomenergie, Betriebsdauermanagement der Kernkraftwerke, 27. und 28. November 2003, Winterthur, Schweiz.
  • Contribution to external collection
    Vertiefungskurs der Schweizerischen Vereinigung für Atomenergie, Betriebsdauermanagement der Kernkraftwerke, 27. und 28. November 2003, Winterthur, Schweiz.

Publ.-Id: 5670 - Permalink


Washout measurement of radioisotope implanted by radioactive beams in the rabbit.
Mizuno, H.; Tomitani, T.; Kanazawa, M.; Kitagawa, A.; Pawelke, J.; Iseki, Y.; Urakabe, E.; Suda, M.; Kawano, A.; Iritani, R.; Matsushita, S.; Inaniwa, T.; Nishio, T.; Furukawa, S.; Ando, K.; Nakamura, Y. K.; Kanai, T.; Ishii, K.;
Washout of 10C and 11C implanted by radioactive beams in brain and thigh muscle of rabbits was studied. The biological washout effect in a living body is important in the range verification system or three-dimensional volume imaging in heavy ion therapy. Positron emitter beams were implanted in the rabbit and the annihilation gamma-rays were measured by an in situ positron camera which consisted of a pair of scintillation cameras set on either side of the target. The ROI (region of interest) was set as a two-dimensional position distribution and the time-activity curve of the ROI was measured. Experiments were done under two conditions: live and dead. By comparing the two sets of measurement data, it was deduced that there are at least three components in the washout process. Time-activity curves of both brain and thigh muscle were clearly explained by the three-component model analysis. The three components ratios (and washout half-lives) were 35% (2.0 s), 30% (140 s) and 35% (10191 s) for brain and 30% (10 s), 19% (195 s) and 52% (3175 s) for thigh muscle. The washout effect must be taken into account for the verification of treatment plans by means of positron camera measurements.
  • Physics in Medicine and Biology 48 (2003) 2269-2281

Publ.-Id: 5669 - Permalink


Möglichkeiten und Trends in Diagnostik und Therapie
Johannsen, B.;
Radiopharmaka werden in der nuklearmedizinischen Diagnostik und Therapie eingesetzt. Diagnostisches Ziel ist es, möglichst viele biochemische Prozesse ohne Eingriff in diese Abläufe bildgestützt zu analysieren. Der menschliche Körper soll somit biochemisch transparent werden. Trotz allen Fortschritts sind noch viele neue, spezifische, radioaktive Sondenmoleküle, sogenannte Radiotracer, nötig.
  • Pharm. Zeitg. 148, 2003, 2884-2893

Downloads:

Publ.-Id: 5668 - Permalink


Arbeiten zur Simulation prototypischer In-Vessel-Retention-Szenarien auf Basis von Vergleichsrechnungen mit mittelskaligen Experimenten
Altstadt, E.; Willschütz, H.-G.;
Bezüglich eines hypothetischen Kernschmelzeszenarios in einem Leichtwasserreaktor ist es notwendig, mögliche Versagensformen des Reaktordruckbehälters sowie Versagenszeiträume zu untersuchen, um die Belastung für das Containment bestimmen zu können. Es wurden weltweit bereits eine Reihe von Experimenten durchgeführt, welche Erkenntnisse hierüber liefern sollen. Begleitend wurden in Einzelversuchen Materialeigenschaften ermittelt, sowie theoretische und numerische Arbeiten durchgeführt.
Für die Simulation von Experimenten zum Versagen der Bodenkalotte, wie OLHF oder FOREVER, ist es notwendig, Kriechen und Plastizität zu berücksichtigen. Gleichzeitig müssen geeignete Modelle das Temperaturfeld in der Behälterwand für die mechanischen Rechnungen bereitstellen. Vom Institut für Sicherheitsforschung des FZR wird ein Finite-Elemente-Modell erstellt, das sowohl die Temperaturfeldberechnung für die Wand als auch die elasto-plastische Mechanik der Behälterwand modelliert.
Am FZR wurde ein Finite Elemente Model entwickelt, das die Verwendung von einfachen Kriechgesetzen, die mit ihren angepassten Konstanten nur für begrenzte Spannungs- und Temperaturbereiche gültig sind, umgeht. Stattdessen wird eine numerische Kriechdatenbasis angelegt, in der die Kriechdehnrate in Abhängigkeit von der Gesamtdehnung, der Temperatur und der Vergleichsspannung abgelegt ist. Eine wesentliche Aufgabe für diese Vorgehensweise besteht in der Generierung und Validierung der Kriechdatenbasis. Zusätzlich wurden alle relevanten temperaturabhängigen Materialeigenschaften mit entsprechenden Modellen in den Code eingegeben. Für die Bestimmung der Versagenszeit wurde ein Schädigungsmodel nach einem Vorschlag von Lemaitre implementiert.
Die Validierung des numerischen Models erfolgte durch die Simulation von und den Vergleich mit den skalierten Integralexperimenten der FOREVER-Reihe, in denen die Bodenkalotte eines Druckwasserreaktors mit ihrer halbkugelförmigen Geometrie wiedergegeben wird. In Zusammenarbeit mit den Experimentatoren an der KTH in Stockholm wurden Pre- und Posttest-Rechnungen für diese bisher einzigartigen Experimente durchgeführt, deren Ergebnisse qualitativ und quantitativ sehr zufriedenstellend sind.
Ausgehend von diesen Arbeiten wird die Simulation prototypischer Szenarien angestrebt, welche im Vergleich zu FOREVER um den Faktor 10 größere Abmessungen aufweisen. Hierzu sind noch Modellerweiterungen notwendig, die daraus resultieren, dass eine vollständige einheitliche Skalierung aller thermischen und mechanischen Einflussgrößen nicht möglich ist.

Keywords: Kernschmelzerückhaltung, FE-Modellierung, 2D- und 3D-Experimente
  • Lecture (Conference)
    3. Workshop KOMPETENZVERBUND KERNTECHNIK am 8.10.2003, MPA, Stuttgart, Proceedings-CD
  • Contribution to proceedings
    3. Workshop KOMPETENZVERBUND KERNTECHNIK am 8.10.2003, MPA, Stuttgart, Proceedings-CD

Publ.-Id: 5667 - Permalink


RF System and Measurements at the Superconducting RF Gun
Büttig, H.; Schurig, R.; Tribendis, A.;
The paper gives an overview on the RF-system developed for the Superconducting Photo RF Gun at FZ-Rossendorf and a brief discussion an RF-measurements at the superconducting gun-cavity.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-375 April 2002, 49

Publ.-Id: 5666 - Permalink


The ELBE- RF-Coupler
Büttig, H.;
The power-point presentation gives an overview on RF-coupler development, operational experience at the ELBE-Linac and the coupler test-equipment used at FZ-Rossendorf.
  • Lecture (Conference)
    Proc. of Workshop an 1.3 GHz couplers for cw operation at power levels between 10 and 100 kW ACCEL Instr. GmbH 09.04.2002

Publ.-Id: 5665 - Permalink


Optimizing the Antenna Tip-Length of the ELBE Main RF Coupler
Büttig, H.;
The ELBE LINAC is equipped with superconducting TESLA 9-cell cavity resonators. Its RF-coax coupler antennas are designed to operate each cavity withe 8...10 kW beam power. The paper describes a procedure on optimising the antenna- length of the RF-coupler at room temprature.
  • Contribution to HZDR-Annual report
    Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-341 April 2002, 8-9

Publ.-Id: 5664 - Permalink


Photothermal Beam Deflection Using a Free Electron Laser For Infrared Characterization of Environmental Samples
Foerstendorf, H.; Seidel, W.; Heise, K.-H.; Ortega, J.-M.; Glotin, F.; Prazeres, R.;
The low concentration of toxic radioactive metals in environmental samples often limits the interpretation of results of infrared studies investigating the interaction processes between the metal ions and environmental compartments. For the first time, we could show that photothermal infrared spectroscopy performed with a pulsed free-electron laser can provide reliable infrared spectra throughout a distinct spectral range of interest. In this model investigation, we provide vibrational absorption spectra of a rare earth metal salt dissolved in a KBr matrix and a natural calcite sample obtained by thermal beam deflection technique and FT-IR spectroscopy, respectively. General agreement was found between all spectra of the different recording techniques. Spectral deviations were observed with samples containing low concentration of the rare earth metal salt indicating a lower detection limit of the photothermal method as compared to conventional FT-IR spectroscopy. Furthermore, the photothermal method provide spatial information of a sample surface. This may result in a microspectrometric technique for determining the distribution of metal species on mineral surfaces. First experiments exploring the spatial resolution of photothermal spectroscopy were carried out by scanning the surface of a germanium substrate showing a localised region where O+-ions were implanted. The border range of this region was investigated by recording time curves of the deflection signal at distinct positions of the substrate surface with a constant free-electron laser wavelength of 11.6 micrometer.
  • Poster
    The 2nd International Conference on Advanced Vibrational Spectroscopy (ICAVS-2), Nottingham, U.K.

Publ.-Id: 5663 - Permalink


The growth of Ti(Al)N thin films studied by synchrotron radiation
Beckers, M.; Schell, N.; Möller, W.;
  • Lecture (Conference)
    DGK workshop "Characterization of thin films by x-ray scattering", Uckley, 21.-23.05.2003

Publ.-Id: 5662 - Permalink


Evolution of microstructure and preferred orientation in TiAlN thin films - an in-situ study
Beckers, M.; Schell, N.; Möller, W.;
  • Lecture (Conference)
    Frühjahrstagung der DPG, Dresden, 24.-28.03.2003

Publ.-Id: 5661 - Permalink


In-situ growth characterization of magnetron sputtered thin films by synchrotron radiation
Beckers, M.; Schell, N.; Möller, W.;
  • Lecture (Conference)
    36th IUVSTA workshop, Plzen, Czech republic, 20.-24.10.2002

Publ.-Id: 5660 - Permalink


Calculation of the Scattering Factor from the Shell Model of Nanoscale Defects
Gokhman, A.; Böhmert, J.; Ulbricht, A.;
Theoretical and experimental investigations have pointed out the formation of dilute polydisperse system of spherical particles with diffusion zones embedded in matrix in the nucleation and growth evolution stages due to quenching, irradiation and other special kinds of treatment of multicomponent materials. Small-angle neutron and X-ray scattering provide information about the chemical composition as well as about the size distribution of the nanoscale defects.
Unlike to the case of homogeneously structurized scattering objects the analytical solution for heterogeneous scattering objects has not yet well-established. The paper states that the present approaches do not account in full measure the interference between the scattering intensities from the core and shell. Therefore, a more accurate procedure to calculate the scattering factor from heterogeneous objects is worked out. It bases on the formalism of the pair distribution function and the Porod' formula.
The suggested approach is verified on homogeneous scattering objects and then is applied to the set of shell models with different parameters of structure. For the calculation a Visual-Fortran programme is worked out. It is found that the homogeneous model and shell models produce the same scattering factor.
Model of the polydisperse nanoscale defects in neutron irradiated reactor steel is considered as composites of iron core and vacancy enriched shell with different sizes. The fitting procedure to determine the parameters of the size distribution function of irradiation induced precipitates from the magnetic part of small-angle neutron scattering is worked out. The results well agree with results of investigation by other methods for VVER steels with small Cu-content.
  • Lecture (Conference)
    XV International Conference on X-ray Diffraction & Crystal Chemistry of Minerals, St. Petersburg, 15.-19.09.2003
  • Contribution to proceedings
    XV International Conference on X-ray Diffraction & Crystal Chemistry of Minerals, St. Petersburg, 15.-19.09.2003

Publ.-Id: 5659 - Permalink


Validierung des gekoppelten neutronenkinetischen-thermohydraulischen Codes ATHLET/DYN3D mit Hilfe von Messdaten des OECD Turbine Trip Benchmarks
Grundmann, U.; Kliem, S.;
Das Vorhaben bestand in der Validierung des gekoppelten neutronenkinetisch-thermohydraulischen Programmkomplexes ATHLET/DYN3D für Siedewasserreaktoren durch Teilnahme an dem OECD/NRC Benchmark zum Turbinenschnellschluss. Das von der OECD und der amerikanischen NRC definierte Benchmark basiert auf einem Experiment mit Schließens des Turbinenschnellschlussventils, das 1977 im Rahmen einer Serie von 3 Experimenten im Kernkraftwerk Peach Bottom 2 durchgeführt wurde. Im Experiment erzeugte das Schließen des Ventils eine Druckwelle, die sich unter Abschwächung bis in den Reaktorkern ausbreitete. Die durch den Druckanstieg bewirkte Kondensation von Dampf im Reaktorkern führte zu einem positiven Reaktivitätseintrag. Der folgende Anstieg der Reaktorleistung wurde durch die Rückkopplung und das Einfahren der Regelstäbe begrenzt. Im Rahmen des Benchmarks konnten die Rechenprogramme durch Vergleiche mit den Messergebnissen und den Ergebnissen der anderen Teilnehmer an dem Benchmark validiert werden.

Das Benchmark wurde in 3 Phasen oder Exercises eingeteilt. Die Phase I diente der Überprüfung des thermohydraulischen Modells für das System bei vorgegebener Leistungsfreisetzung im Kern. In der Phase II wurden 3-dimensionale Berechnungen des Reaktorkerns für vorgegebene thermohydraulische Randbedingungen durchgeführt. Die gekoppelten Rechnungen für das ausgewählte Experiment und für 4 extreme Szenarien erfolgten in der Phase III. Im Rahmen des Projekts nahm FZR an Phase II und Phase III des Benchmarks teil. Die Rechnungen für Phase II erfolgten mit dem Kernmodell DYN3D unter Berücksichtigung der Heterogenitätsfaktoren und mit 764 thermohydraulischen Kanälen (1 Kanal/Brennelement). Der ATHLET-Eingabedatensatz für die Reaktoranlage wurde von der Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) übernommen und für die Rechnungen zu Phase III, die mit der parallelen Kopplung von ATHLET mit DYN3D erfolgten, geringfügig modifiziert.

Für räumlich gemittelte Parameter wurde eine gute Übereinstimmung mit den Messergebnissen und den Resultaten anderer Codes erzielt. Der Einfluss der Modellunterschiede wurde mit Hilfe von Variantenrechnungen zu Phase II untersucht. So können Unterschiede in der Leistungs- und Voidverteilung in einzelnen Brennelementen auf die unterschiedliche neutronenkinetische und thermohydraulische Modellierung des Reaktorkerns zurückgeführt werden.

Vergleiche zwischen ATHLET/DYN3D (parallele Kopplung) und ATHLET/QUABOX-CUBBOX (interne Kopplung) zeigen für räumlich gemittelte Parameter nur geringe Unterschiede. Abweichungen in den lokalen Parametern können im wesentlichen mit der unterschiedlichen Modellierung des Reaktorkerns erklärt werden (geringere Anzahl von modellierten Kühlkanälen, keine Berücksichtigung der Heterogenitätsfaktoren und ein anderes Siedemodell in der Rechnung mit ATHLET/QUABOX-CUBBOX).

Die Rechnungen für die extremen Szenarien von Phase III zeigen die Anwendbarkeit des gekoppelten Programms ATHLET/DYN3D für die Bedingungen bei Störfällen, die weit über das Experiment hinausgehen.
Keywords: nuclear reactors transients neutron kinetics three-dimesional thermal hydraulics coupled codes validation benchmark boiling water reactors turbine trip
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-384 Dezember 2003

Downloads:

Publ.-Id: 5658 - Permalink


Impact of the QCD four-quark condensate on in-medium spectral changes of light vector mesons
Zschocke, S.; Pavlenko, O. P.; Kämpfer, B.;
Within the Borel QCD sum rule approach at finite baryon density we study the role of the four-quark condensates % such as langle(overline{q} gamma_{mu} lambda^a)^2rangle_n , for the modifications of the vector mesons rho, omega and phi in nuclear matter.
We find that in-medium modifications of the rho and omega mesons are essentially dominated by the dependence of the 4-quark condensate on the nucleon density. In particular, the numerical value of a parameter (kappa_N), which describes the strength of the density dependence of the 4-quark condensate beyond the mean-field approximation, governs the decrease of the rho mass as a function of the density. For the omega meson the sign of the in-medium mass shift is changed by variations of kappa_N. To study consistently the in-medium broadening of the light vector mesons we employ rho N and omega N scattering amplitudes derived recently from a covariant unitary coupled channel approach adjusted to pion- and photo-induced reactions. In contrast to the rho and omega mesons, the in-medium mass of the phi meson is directly related to the chiral (strange) quark condensate. Measurements of the vector meson spectral change in heavy-ion collisions with HADES can shed light on the yet unknown density dependence of the 4-quark condensate.
Keywords: medium modifications, vector mesons, condensates
  • hep-ph/0308070

Publ.-Id: 5657 - Permalink


Kleinwasserkraftnutzung am Grenzfluss Lausitzer Neiße
Rindelhardt, U.; Grzelak, K.;
An der Lausitzer Neiße wird seit 100 Jahren die Wasserkraft zur Stromerzeugung genutzt. Im vorliegenden Beitrag werden - ausgehend von den hydrologischen Bedingungen und der historischen Entwicklung - der heutige Stand der Wasserkraftnutzung am Grenzfluss Lausitzer Neiße sowie mögliche Perspektiven dargestellt.
Keywords: Wasserkraft, Neiße
  • Elektrizitätswirtschaft Heft 22 (2003), S. 58

Publ.-Id: 5656 - Permalink


Origin of anomalous temperature dependence and high efficiency of silicon light-emitting diodes
Sun, J. M.; Dekorsy, T.; Skorupa, W.; Schmidt, B.; Helm, M.;
Efficient electroluminescence with power efficiency up to 0.12 % is observed from silicon pn diodes prepared by boron implantation with boron concentrations above the solubility limit at the post-implantation annealing temperature. The electroluminescence spectra exhibit a transition from two bound-exciton bands towards the free electron-hole pair recombination with an anomalous increase in the total intensity with increasing temperature. The implantation dose and temperature dependences of the relative peak intensities provide evidence for the relevance of excitonic traps as a supply for free electron-hole pairs and thus the origin of the enhanced electroluminescence at elevated temperatures.
Keywords: Electroluminescence, silicon, pn junction, implantation, boron, bound excitons

Publ.-Id: 5655 - Permalink


Slow positron beam investigations of defects caused by B implantation into epitaxial 6H-SiC
Anwand, W.; Brauer, G.; Kuriplach, J.; Skorupa, W.;
B+ implantation into epitaxial 6H-SiC has been carried out in order to create a laterally structured p-doped layer. The defects caused by the ion implantation should be minimized by implantation at higher substrate temperatures and post implantation annealing. Using Slow Positron Implantation Spectroscopy (SPIS), the distribution of vacancy-type defects after ion implantation could be evaluated and the efficiency of the annealing could be demonstrated. Furthermore, first results about the boron distribution after annealing are shown.
Keywords: 6H-SiC, B+ implantation, vacancy-type defects, defect annealing, Slow Positron Implantation Spectroscopy
  • Materials Science Forum 445-446(2004), 60-62

Publ.-Id: 5654 - Permalink


A no-go theorem for isospectral alpha^2-dynamos
Günther, U.; Stefani, F.; Gerbeth, G.;
The data analysis of current dynamo experiments and the design of new experiments led to an increasing interest in the spectral properties of MHD dynamos. In particular, the huge amount of multichannel data measured with high spectral resolution at large magnetic sensor arrays outside the liquid sodium facilities calls for the development of tomographic methods for these experiments. In general, such methods would allow for a rough reconstruction of velocity and alpha profiles inside a facility from the magnetic field data measured outside the facility. Due to the fact that viable tomographic methods are crucially based on a correct interpretation of the measured data, one has first to deeply understand the spectral properties of the experimental setup and to clarify the uniqueness of the corresponding inverse problem.

As step in this direction and in order to keep the calculations at the beginning as simple as possible, in [1] the uniqueness of spectral data was studied numerically for the toy model of a spherically symmetric alpha^2-dynamo. The results, which were obtained by combining a spectral forward solver with an inverse problem solver, indicated a possibly existing isospectrality of spherically symmetric alpha^2-dynamos with different alpha-profiles alpha_1(r) and alpha_2(r) and a corresponding non-uniqueness of the inverse problem.

The present contribution is based on Ref. [2] and reports analytical results on the isospectrality problem of spherically symmetric alpha^2-dynamo operators. First, it is shown that the 2 x 2 operator matrix of the alpha^2-dynamo possesses a fundamental (canonical) symmetry J, so that the operator itself can be naturally described as J-pseudo-Hermitian operator in a Krein space (a Hilbert space with an additional indefinite inner product structure). Then this symmetry is used to extend the operator intertwining techniques of supersymmetric quantum mechanics to the operator matrix of the alpha^2-dynamo. The intertwiners are assumed as first-order matrix differential operators with coefficients which are highly constrained by a system of nonlinear matrix differential equations. The (hidden) symmetries of this equation system are analyzed by transforming it into a set of constrained and interlinked matrix Riccati equations. As next step, the structure of the spherically symmetric alpha^2-dynamo operator is tested on its compatibility with the considered intertwining ansatz and a no-go theorem is derived which states that the structure is not compatible with an intertwining ansatz based on first-order differential operators as intertwiners. This implies, that other, more powerful techniques should be used for a clarification of the isospectrality and uniqueness problem of the dynamo operator. Finally, the linear eigenvalue problem for the 2 x 2 dynamo operator matrix is transformed to the equivalent eigenvalue problem for the associated quadratic operator pencil. From this quadratic pencil a general functional equation is derived, which will be useful in future research (extending [3]) for discriminating oscillating dynamo regimes from non-oscillating regimes and for localizing the degenerate spectral intersection points where transitions from one regime to the other occur.

[1] F. Stefani and G. Gerbeth, Astron. Nachr. 321, (2000), 235, astro-ph/0010090; Phys. Earth Planet. Inter. 128, (2001), 109.

[2] U. Günther and F. Stefani, J. Math. Phys. 44, (2003), 3097, math-ph/0208012.

[3] F. Stefani and G. Gerbeth, Phys. Rev. E 67, (2003), 027302, astro-ph/0210412.
  • Poster
    Mathematical Aspects of Natural Dynamos, Caramulo, Portugal, August 31 - September 6, 2003.

Publ.-Id: 5653 - Permalink


New Results in the Riga Dynamo Experiment
Gailitis, A.; Lielausis, O.; Platacis, E.; Gerbeth, G.; Stefani, F.;
It is widely believed that almost all magnetic fields in a natural environment are the result of the dynamo process - the field generation in a moving nearly homogeneous electroconducting fluid in the depth of celestial bodies such as Earth, most of the planets, Sun, other stars and even galaxies.
We are not going to model in the laboratory any particular celestial body. Our aim is to demonstrate the very idea that the intense motion in the large volume of a good electroconducting liquid creates a magnetic field. As the working fluid serve 2 m^3 of molten sodium, which is the best electroconducting liquid available. It is filled in a 3 m long and 0.8 m thick cylinder. By means of two thin stainless steel internal walls the cylinder is divided into three coaxial channels. The swirling sodium circulation within the two central channels is produced by a propeller at the top of the cylinder powered by two 100 kW motors. When the circulation is fast enough the magnetic field appears. The field pattern slowly rotates around the axis of the cylinder hence any field sensor produces an AC signal.
The first results were reported in the third and fifth MHD days. In the present meeting we will touch upon such details as the radial profiles of field pattern, the turbulent spectra of field, the field produced motions in sodium etc.
  • Abstract in refereed journal
    Astronomische Nachichten 324 (2003), Suppl. Issue 3, 78-79
  • Lecture (Conference)
    Jahrestagung der Astronomischen Gesellschaft, 15-20 September 2003 in Freiburg im Breisgau

Publ.-Id: 5652 - Permalink


Micro-PIXE study of gold archaeological objects
Bugoi, R.; Cojocaru, V.; Constantinescu, B.; Constantin, D.; Grambole, D.; Herrmann, F.;
Several fragments of ancient gold objects coming from an Eneolithic hoard and from Pietroasa .Clo#ca cu Puii de Aur. (.The Golden Brood Hen with Its Chickens.) hoard, unearthed on Romanian territory, and two Romanian native gold nuggets samples were analyzed using micro-PIXE technique. The purpose of the study was to clarify the metal provenance. Trace and minor elements (Cu, Te, Sn, Pb, Ti, Cr, V, Mn, Ta) and platinum group elements (PGE) concentrations were estimated. The presence of inclusions (micrometer size areas of composition different from the surroundings) was investigated. We found Si and Ca inclusions on two Eneolithic samples, and Ta inclusions on two samples from Pietroasa hoard. The measurements suggested an alluvial origin of gold for the Eneolithic samples and give indications for the possible gold ore sources of Pietroasa hoard.
Keywords: keine
  • Journal of Radioanalytical and Nuclear Chemistry,257 (2003) 375

Publ.-Id: 5651 - Permalink


Diamond formation by carbon implantation into cubic silicon carbide
Weishart, H.; Heera, V.; Eichhorn, F.; Pécz, B.; Toth, L.; Skorupa, W.;
Cubic SiC is implanted with carbon ions at 600, 900, 1100 and 1200 °C. X-ray diffraction and transmission electron microscopy revealed the influence of implantation temperature and dose rate on the formation of graphite and diamond precipitates, respectively. The high dose carbon implantation at 600 °C yields graphite already in a textured form. Spherical diamond grains, which are always epitaxial to the SiC, are found in samples implanted at 900 °C or higher. Increasing the dose rate leads to formation of graphite instead of diamond at 900 oC as well. Hence, a critical temperature for diamond evolution exists, which depends on dose rate. Size and shape of the formed diamond precipitates is not influenced by dose rate within the investigated range. Increasing the fluence results in bigger diamond nanocrystals, which are bordered by facets.
Keywords: silicon carbide (SiC), diamond crystal, ion bombardment, microstructure
  • Poster
    Diamond and Related Materials Vol 13/4-8 (2004) pp 627-632
  • Diamond and Related Materials 13(2004)4-8, 627-632

Publ.-Id: 5650 - Permalink


Time-resolved laser fluorescence spectroscopy study on the interaction of Cm(III) with Desulfovibrio äspöensis DSM 10631T
Moll, H.; Stumpf, T.; Merroun, M.; Rossberg, A.; Selenska-Pobell, S.; Bernhard, G.;
The influence of microorganisms on migration processes of actinides has to be taken into account for the assessment of potential high level nuclear waste disposal sites. Therefore it is necessary to characterize the actinide-bacteria species formed and to elucidate the reaction mechanisms involved. This work is focused on the sulfate-reducing bacterial (SRB) strain Desulfovibrio äspöensis DSM 10631T which frequently occurs in the deep granitic rock aquifers at the Äspö Hard Rock Laboratory (Äspö HRL), Sweden. We chose Cm(III) due to its high fluorescence spectroscopic sensitivity as a model system for exploring the interactions of trivalent actinides with D. äspöensis in the trace concentration range of 3 x 10-7 mol/L. A time-resolved laser fluorescence spectroscopy (TRLFS) study has been carried out in the pH range from 3.00 to 7.55 in 0.154 mol/L NaCl. We interpret the pH dependence of the emission spectra with a biosorption forming an inner-sphere surface complex of Cm(III) onto the D. äspöensis cell wall. This Cm(III)-D. äspöensis-surface complex is characterized by its emission spectrum (peak maximum at 600.1 nm) and its fluorescence lifetime (162 ± 5 µs). No evidence was found for incorporation of Cm(III) into the cells.
Keywords: Curium, Bacteria, Desulfovibrio äspöensis, TRLFS, Surface complexation

Publ.-Id: 5649 - Permalink


Corrected procedure for crack lengths calculation by the unloading compliance technique for Charpy size specimens
Dzugan, J.;
The problems with the crack length determination by the unloading compliance method are well known for Charpy size specimens. The final crack lengths calculated for bent specimens do not fulfill ASTM 1820 accuracy requirements. Some investigations have been performed to resolve this problem by correcting the compliance value, but satisfying results were not obtained. In the presented work the measured specimen compliance was taken as a correct value and the calculation procedure was modified. On the basis of experimentally obtained compliances of bent specimens and optically measured crack lengths a calculation procedure enabling accurate crack length calculation up to 5 mm of plastic deflection was developed. Applying the new procedure to a sample of 238 measured crack lengths, more than 80% of the values fulfilled the ASTM 1820 accuracy requirement, while presently used procedure provided only about 30% of valid results. The newly proposed procedure can be also prospectively used in modified form for specimens of a size being different from Charpy size.
Keywords: Unloading compliance, fracture toughness, Charpy specimen, J-R curve
  • Journal of Testing and Evaluation 33(2005)6, 433-438

Publ.-Id: 5648 - Permalink


Quadrupole correlations and inertial properties of rotating nuclei
Almehed, D.; Dönau, F.; Nazmitdinov, R. G.;
The contribution of quantum shape fluctuations to inertial properties of rotating nuclei has been analysed for QQ-nuclear interaction using the random phase approximation (RPA). The different recipes to treat the cranking mean field plus RPA problem are considered. The effects of the dN = 2 quadrupole matrix elements and the role of the volume conservation condition are discussed.
  • J.Phys. G: Nucl. Part. Phys. 29 (9): 2193-2206 SEP 2003

Publ.-Id: 5646 - Permalink


Microstructural Characterization and Engineering of Defects in Silicon
Peeva, A.;
no abstract
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-387 Juli 2003

Downloads:

Publ.-Id: 5645 - Permalink


Uranium(VI) separation from aqueous solution by calix[6]arene modified textiles
Schmeide, K.; Heise, K.-H.; Bernhard, G.; Keil, D.; Jansen, K.; Praschak, D.;
The separation of uranium(VI) from aqueous solution by textile bound uranophile calix[6]arenes was studied as a function of pH value and uranium concentration in the absence and presence of competing ions by means of batch experiments. Furthermore, the kinetics of the uranium binding was studied as well as the possibility for remobilization of the bound uranium by solutions of various pH values.
The results showed that calixarene modified textiles are suitable for the separation of uranium from aqueous solution at pH values higher than 4. The applicability in the acidic pH range is limited. Maximal 7.6x10-7 mol uranium per 1 g of the calixarene modified textile is bound at pH 5. The influence of competing ions (sodium, potassium, calcium, magnesium, carbonate and sulfate) on the uranium separation at pH 5 is very small. However, at pH 7 in carbonate rich waters calcium ions have a competing effect due to the formation of the Ca2UO2(CO3)3 (aq) complex.
Under environmentally relevant pH conditions (near-neutral pH range) the uranium is strongly bound to the calixarene modified textile and cannot be mobilized. On the other hand, under acidic conditions an almost complete regeneration of the calixarene modified textile is feasible. The regenerated textile filter material can be utilized for further uranium separation cycles.
Keywords: Uranium, Calixarene, Complexation, Water Purification
  • Journal of Radioanalytical and Nuclear Chemistry 261(2004)1, 61-67

Publ.-Id: 5643 - Permalink


Nuclear resonance fluorescence experiments on 204, 206, 207, 208 Pb up to 6.75 MeV
Enders, J.; von Brentano, P.; Eberth, J.; Fitzler, A.; Fransen, C.; Herzberg, R.-D.; Kaiser, H.; Käubler, L.; von Neumann-Cosel, P.; Pietralla, N.; Ponomarev, V. Y.; Richter, A.; Schwengner, R.; Wiedenhöver, I.;
Dipole and electric quadrupole excitations in 204, 206, 207, 208Pb have been measured up to 6.75 MeV in resonant photon scattering experiments at the superconducting Darmstadt electron linear accelerator S-DALINAC using two Euroball-Cluster detector modules. In 208Pb, 14 excited states have been populated; in 206Pb, the decays of 41 states have been detected. Information about 45 heretofore unknown excited states in 204Pb could be measured as well as eleven known levels in 207Pb. The extracted dipole strength distributions are discussed within phenomenological ("pygmy resonance") and microscopic models (quasiparticle-phonon model). A strong fragmentation and a small shift of the detected E1 strength towards higher energies is observed with the opening of the neutron shell closure.
  • Nuclear Physics A 724 (2003) 243-273

Publ.-Id: 5642 - Permalink


Reverse painting on glass as seen by the proton beam
Neelmeijer, C.; Mäder, M.;
The combination of PIXE, RBS and PIGE proves ideal for non-destructive overall analysis of reverse paintings on glass. Simultaneous PIXE-RBS studies assist to clarify the thin-layered pigment arrangements of details painted on the reverse of the glass pane. In a second measurement, the spectra of both PIGE-PIXE taken from the pure glass front side inform on the individual glass type. This complete perception of corresponding unique objects is important and valuable regarding the knowledge of special painting techniques and the necessity of preventive conservation.

Keywords: reverse painting on glass, ion beam analysis, external beam, pigment analysis, glass composition, glass corrosion, conservation

Publ.-Id: 5641 - Permalink


Contribution of the nucleon-hyperon reaction channels to K- production in proton-nucleus collisions
Barz, H. W.; Naumann, L.;
The cross section for producing K- mesons in nucleon-hyperon collisions is estimated using the experimentally known pion-hyperon cross sections. The results are implemented in a transport model which is applied to calculation of proton-nucleus collisions. Contrarily to earlier estimates in heavy-ion collisions the inclusion of the nucleon-hyperon cross section roughly doubles the K- production in near-threshold proton-nucleus collisions.
Keywords: K- meson production, proton-nucleus collisions

Publ.-Id: 5639 - Permalink


An integral equation approach to unsteady kinematic dynamos
Xu, M.; Stefani, F.; Gerbeth, G.;
Natural and laboratory homogeneous dynamos can be modeled by supposing that the electrically conducting fluid fills a finite volume D surrounded by an insulating infinite region D'. Our considerations are restricted to the kinematic dynamo regime in which the back-reaction of the self-excited magnetic field on the flow is negligible. We also assume the velocity field to be steady. Even for such kinematic dynamo problems an analytical treatment is usually impossible, hence numerical methods have to be utilized.
A notorious problem with the usual differential equation approach is the handling of the non-local boundary conditions for the magnetic field. The integral equation approach provides a solution to the problem of non-local boundary conditions. The integral equation approach has a number of interesting features. The most important one is that it avoids the discretization of the infinite region D'. The second one is its intimate connection to inverse problems relevant not only for dynamos but also for technical applications of magnetohydrodynamics. The third one is its proven numerical robustness and stability.
We examine the integral equation approach by a few numerical examples, including the alpha^2 dynamo model with radially varying alpha, and the Bullard-Gellman model, and demonstrate its equivalence with the differential equation approach.
  • Poster
    Mathematical Aspects of Natural Dynamos, Caramulo, Portugal, August 31 - September 6 , 2003.

Publ.-Id: 5637 - Permalink


Charge storage in SiO2 layers with embedded nanoclusters studied by scanning capacitance microscopy
Beyreuther, E.; Beyer, R.; von Borany, J.; Weber, J.;
Scanning capacitance microscopy and spectroscopy (SCM/SCS) were applied to study the charge storage, the retention behaviour and the response on dynamic voltage stress of thin SiO2 layers containing Si or Ge nanoclusters. The formation of the nanoclusters was accomplished by ion beam synthesis (IBS) and verified by transmission electron microscopy (TEM). Local charge injection into the implanted layers was performed by applying a dc bias to the metallic probe tip, which was in contact with the SiO2 layer. The dC/dV-curves reveal a shift along the voltage axis compared to an equivalent curve on an unstressed control position. The curve shifts allowed a quantitative analysis of the trapped charge. Monitoring the SCM contrast between an injection spot and its unstressed surroundings over several days allows to visualize the charge decay. The retention time of the stored charge could be estimated from the measured charge decay.
  • Lecture (Conference)
    12th International Conference on Scanning Tunneling Microscopy / Spectroscopy and Related Techniques (STM 2003), July 21-25, 2003, Eindhoven, The Netherlands
  • Contribution to proceedings
    12th International Conference on Scanning Tunneling Microscopy / Spectroscopy and Related Techniques (STM 2003), July 21-25, 2003, Eindhoven, The Netherlands

Publ.-Id: 5636 - Permalink


Scanning capacitance microscopy and - spectroscopy on SiO2 films with embedded Ge and Si nanoclusters
Beyer, R.; Beyreuther, E.; von Borany, J.; Weber, J.;
Embedded nanoclusters in SiO2 films have attracted increasing interest for applications in memory devices. Charge storage effects are easily observed in MOS structures with nanoclusters, but the nature of the trap states is still unclear. In particular the implantation damage when the clusters are formed by ion beam synthesis might play a role. Spectroscopic and spatial information is required in order to examine the trapping sites responsible for the charge storage. Scanning probe techniques which detect electrical properties seem to be suitable to study the local trapping properties of implanted layers.
Scanning capacitance microscopy (SCM) and scanning capacitance spectroscopy (SCS) were developed recently to study the charging phenoma and trapping states in insulating films. Inspite of the unambiguous impact of trapped oxide charges on local dC/dV(V) curves the utilization of SCS data for a quantitative determination of local electrical properties of insulating films has not been used hitherto, due to experimental issues such as reproducibility, tip-sample effects and accuracy. We will demonstrate the suitability of the SCM / SCS method for the estimation of oxide trap densities and decay times of localized charges as well as for the implementation of local electrical stress in SiO2 films.
Nanocluster formation was accomplished by the implantation of Ge or Si into 20 nm SiO2 on (100) oriented p-type silicon and a subsequent annealing in N2 ambient at temperatures between 950°C and 1150°C, respectively. Applying a dc bias of up to +/- 10 V to the conductive tip for a certain time, a local charge injection either from the tip or the substrate into the SiO2 was performed. SCM images visualize the localized charge trapped in the injection spot area (Fig. 1).
In addition, at each spot the dC/dV signal was acquired by sweeping the dc bias between +5 V and -5 V. The shift of the peak position along the voltage axis is a measure of the trapped oxide charge (Fig. 2). Trap concentrations are derived for a set of different samples from SCS measurements and compared to results from high frequency capacitance voltage measurements on gated structures. Hysteresis effects will be discussed. Dependencies of the trap density on implantation dose and energy were detected by SCS. The decay of localized charge clusters was monitored on a timescale from a few minutes up to 14 days. At last, via tip biasing sequences local electrical stress was applied to the films. Local degradation and charge trapping is obvious from a comparison of SCS curves before and after the implementation of several stress routines.
  • Poster
    13th Bia-annual Conference on Insulating Films on Semiconductors (INFOS 2003), June 18-20, 2003, Barcelona, Spain
  • Contribution to proceedings
    13th Bia-annual Conference on Insulating Films on Semiconductors (INFOS 2003), June 18-20, 2003, Barcelona, Spain

Publ.-Id: 5635 - Permalink


A comparative study of the I-V characteristics of diodes fabricated on as-grown and thermochemically polished CVD diamond films
Weima, J. A.; von Borany, J.; Meusinger, K.; Horstmann, J.; Fahrner, W. R.;
Energies ranging between 24 and 50 keV, inclusively, are used for boron ion implantation of as-grown and thermochemically polished CVD diamond films at a total dose of 1E16 cm-2 in order to achieve p-type conductivity. N-type conductivity is acquired by lithium ion implantation of the films by a single energy of 50 keV at a dose of 2E16 cm-2. Current–voltage (I–V) characteristics reveal that leakage currents of diodes fabricated on as-grown films are approximately 2 orders of magnitude higher that those on polished films. Moreover, currents at higher voltages as less in the diodes of as-grown films in comparison to identical diodes on the polished films. The I–V characteristics of diodes on the polished films contain the trap filling, Frenkelpole emission, thermionic emission and the space charge limited current regimes but those on the as-grown films manifest a quasi-linear behavior probably due to lateral penetration of implants in the i-regions. A reduction in current of approximately 2 orders of magnitude is observed on n–i–n structures after annealing the films at 300 °C. Onset voltages of -10 V are due to the low concentration (~1E14 cm-2 ) of nitrogen centers in the diamond films.
Keywords: CVD diamond films; Ion implantation; Photolithography; Current regimes; Diode structures
  • Diamond and Related Materials 12 (2003) 1307-1314

Publ.-Id: 5633 - Permalink


Subthreshold antiproton production in proton-carbon reactions
Komarov, V. I.; Müller, H.; Sibirtsev, A.;
Data from KEK on subthreshold (p) over bar as well as on π± and K± production in proton-nucleus reactions are described at projectile energies between 3.5 and 12.0 GeV. We use a model which considers a hadron-nucleus reaction as an incoherent sum over collisions of the projectile with a varying number of target nucleons. It samples complete events and thus allows for the simultaneous consideration of ail particle species measured. The overall reproduction of the data is quite satisfactory. It is shown that the contributions from the interaction of the projectile with groups of several target nucleons are decisive for the description of subthreshold production. Since the collective features of subthreshold production become especially significant far below the threshold, the results are extrapolated down to COSY energies. It is concluded that an p measurement at ANKE-COSY should be feasible, if the high background of other particles can be efficiently suppressed.
Keywords: Nuclear reaction models and methods, Monte Carlo simulations, Nucleon-induced reactions

Publ.-Id: 5631 - Permalink


Crack lengths calculation by unloading compliance technique for Charpy size specimens
Dzugan, J.;
The problems with the crack length determination by the unloading compliance method are well known for Charpy size specimens. The final crack lengths calculated for bent specimens do not fulfil ASTM 1820 accuracy requirements. Therefore some investigations have been performed to resolve this problem. In those studies it was considered that measured compliance should be corrected for various factors, but satisfying results were not attained. In the presented work the problem was attacked from the other side, the measured specimen compliance was taken as a correct value and what had to be adjusted was the calculation procedure. On the basis of experimentally obtained compliances of bent specimens and optically measured crack lengths the investigation was carried out. Finally, a calculation procedure enabling accurate crack length calculation up to 5mm of plastic deflection was developed. Applying the new procedure, out of investigated 238 measured crack lengths, more than 80% of the values fulfilled the ASTM 1820 accuracy requirements, while presently used procedure provided only about 30% of valid results. The newly proposed procedure can be also prospectively used in modified form for the specimens of different than Charpy size.
Keywords: unloading compliance, Charpy size specimen, fracture mechanics, fracture toughness, J-R curve
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-385 Juli 2003

Downloads:

Publ.-Id: 5629 - Permalink


Syntheses of Novel Modified Acyclic Purine and Pyrimidine Nucleosides as Potential Substrates of Herpes Simplex Type-1 Thymidine Kinase for Monitoring Gene Expression
Grote, M.; Noll, S.; Noll, B.; Johannsen, B.; Kraus, W.;
Suicide gene therapy with the herpes simplex virus type-1 thymidine kinase gene (HSV-1 tk) is considered to be a promising approach to the treatment of cancer. Making use of the lower specificity of the viral enzyme compared to human thymidine kinase, the therapy involves the administration of antiviral agents (e.g. ganciclovir) as prodrugs to induce enzymatic cell death in those cells that express the transferred gene. 18F labeled derivatives have been described for monitoring location, duration and magnitude of the viral kinase enzyme activity by positron emission tomography (PET). Since an optimal radiotracer has not been developed, novel substances were synthesized for monitoring gene expression. A group of 13 nucleoside analogues were synthesized, among them N1-methyl-9-[(1,3-dihydroxy-2-propoxy)methyl]guanine 5 and N1-methyl-9-[(4-hydroxy)-3-hydroxy-methylbutyl]guanine 7 as methyl analogues of ganciclovir and penciclovir and their related fluoro compounds (6, 8). Further novel derivatives include N6-methyl-9-[(1,3-dihydroxy-2-propoxy)methyl]-, N6-methyl-9-[(4-hydroxy)-3-hydroxymethylbutyl]adenine (9, 10) as well as the uracil derivatives 5-hydroxy-1-[(1,3-dihydroxy-2-propoxy)methyl]uracil 11, 6-methyl-1-[(1,3-dihydroxy-2-propoxy)-methyl]uracil 12 and its 3-fluoro-derivative 13.
Keywords: Fluorinated Nucleoside Analogues, Gene Therapy, PET, Thymidine Kinase

Publ.-Id: 5628 - Permalink


Berührungslose Messung von Phasen- und Konzentrationsverteilungen in Blasensäulen mit positronenemittierenden Radionukliden
Zippe, C.; Hoppe, D.; Fietz, J.; Hampel, U.; Hensel, F.; Mäding, P.; Prasser, H.-M.; Zippe, W.;
Die Positronen-Emissions-Tomographie (PET) ist eine etablierte Methode zur Untersuchung von Stoffwechselvorgängen im Menschen. Sie wird als Werkzeug in der medizinischen Forschung ebenso wie klinisch als Diagnoseverfahren zur Erkennung von Metastasen eingesetzt.
Dieses Projekt beschäftigt sich mit einer nichtmedizinischen Anwendung dieses bildgebenden Verfahrens – dem Aufbau und der Anwendung eines PET-Tomographen zur Untersuchung des Verhaltens von Schaum in Blasensäulen, dem Versuchsstand SCHAUMPET. Insbesondere wird auf die technische Realisierung des Projektes und die angewendeten Verfahren zur Bildgewinnung eingegangen. Am Beispiel von Natriumcapronat wird gezeigt, dass sich die Anreicherung eines Tensids in einer Schaumschicht mit Hilfe der Positronen-Emissions-Tomographie nachweisen lässt.
Keywords: PET, Positronen-Emissions-Tomographie, Blasensäule, Schaum, Tensidanreicherung
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-389 September 2003

Downloads:

Publ.-Id: 5627 - Permalink


Institute of Nuclear and Hadron Physics, Annual Report 2002
Dönau, F.; Enghardt, W.; Fahmy, K.; Grosse, E.; Kämpfer, B.; Schneidereit, C.; (Editors)
kein Abstract
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-372

Downloads:

Publ.-Id: 5626 - Permalink


Ultra-fast x-ray tomography for multi-phase flow interface dynamic studies
Misawa, M.; Tiseanu, I.; Prasser, H.-M.; Ichikawa, N.; Akai, M.;
The present paper describes the concept of a fast scanning X-ray tomograph, the hardware development, and measurement results of gas-liquid two-phase flow in a vertical pipe. The device uses 18 pulsed X-ray sources activated in a successive order. In this way, a complete set of 18 independent projections of the object is obtained within 38 ms, i.e. the measuring rate is about 250 frames per second. Finally, to evaluate the measurement capability of the fast X-ray CT, a wire-mesh sensor was installed in the flow loop and both systems were operated for the same two-phase flow simultaneously. Comparison of the time series of the cross section averaged void fraction from both systems showed sufficient agreement for slug flow at large void fractions, while the fast CT underestimated the void fraction of bubbly flow especially in low void fraction range. For the wire-mesh sensor, coerced deformation of slug bubble interface was found. Further hardware improvement is in progress to achieve better resolution with the fast X-ray CT scanner.
Keywords: Two-phase flow, X-ray tompgraphy, mesh sensors, bubble flow, slug flow
  • Kerntechnik 68 (2003) 3, pp. 85-90.

Publ.-Id: 5625 - Permalink


Mixed-ligand complexes of Tc(III) serving as flexible tools for binding the metal to small biomolecules
Pietzsch, H.-J.;
The most frequently used technetium compounds suitable for coupling the metal to biologically active molecules are square-pyramidal complexes of the oxo ion [Tc=O]3+ based on tetradentate N2S2 ligands. Properties and thus the in vivo behaviour of such complexes are strongly influenced by the presence of the quite polar [Tc=O]3+ unit. Whether such a polarity is beneficial or not is not obvious and depends on the requirements for specific radiotracers, e.g. for receptor targeting agents or for metabolic tracers. Another crucial point in tracer design is the stability of the respective Tc chelate towards ligand exchange in vivo. So there is a considerable interest in alternative chelate systems that offer lower polarity and enhanced in vivo stability. Such systems are based on oxo-free lower oxidation states. Here we offer a new type of Tc(III) chelate 1, formed by the tripodal 2,2‘,2“-nitrilotris(ethanethiol) and a monodentate isocyanide or tertiary phosphine.
The new compounds fulfil the requirements for a non-polar building block stable against ligand exchange reaction in vivo. Belonging to the family of "n+1" mixed-ligand technetium (and rhenium) species, such a "4+1" chelate offers the advantage of high versatility in conjugating biomolecules.
Another type of neutral Tc(III) complexes, [Tc(SCH2CH2-E-CH2CH2S)(PR2S)] 2, can be obtained by association of a tridentate HS-E-SH ligand (E = N(CH3), S) with a bidentate PR2-SH chelator. This combination enables easy functionalization in order to fine-tune physico-chemical properties of the complexes as well as linking of the chelate unit to biomolecules.
99mTc analogues can be prepared at no-carrier-added level in high radiochemical yields. The complexes are stable towards ligand exchange in challenge experiments with glutathione. Furthermore, there are no indications for re-oxidation of Tc(III) to Tc(V) species or pertechnetate. There is no tendency of these complexes to bind on plasma components. The substituents at the bidentate P,S chelator significantly influence the biodistribution pattern in rats. Therefore, we propose this new type of Tc(III) complexes as a useful tool in designing of tunable 99mTc radiopharmaceuticals.
  • Lecture (Conference)
    1st Research Co-Ordination Meeting of the IAEA Co-Ordinated Research Programme on “Development of Tc-99m Based Small Biomolecules using Novel Tc-99m Cores” Ferrara, Mai 2003

Publ.-Id: 5624 - Permalink


Radiometalle in der nuklearmedizinischen Diagnostik und Therapie
Pietzsch, H.-J.;
  • Lecture (others)
    Kolloquium des GDCh-Ortsverbandes Lausitz 22.10.2003

Publ.-Id: 5623 - Permalink


A kinetic study of copper precipitates under VVER-type reactor condition
Gokhman, A.; Böhmert, J.; Ulbricht, A.;
The copper rich cluster evolution in the neutron irradiated VVER steels is investigated beginning at the nucleation stage. For this, typical VVER-type reactor conditions are considered. The cluster dynamics approach is used for calculation of the density distribution of copper precipitates related to the number of Cu- atoms or radius; mean radius, volume content, number density of precipitates and the concentration of free Cu- atoms in dependence on the irradiation time. The results for time of one year are compared with the results of small angle neutron scattering experiments which were carried out at specimens irradiated at surveillance position of VVER reactors. It is revealed the intermediated type of the evolution kinetics between diffusion and interfacial kinetics limited regimes. The duration of the nucleation and deterministic stages is estimated. The coarsening stage does not occur.
  • Radiation Effects and Defects in Solids, Vol. 158 (2003) pp. 783-792

Publ.-Id: 5622 - Permalink


Transiente Kondensationsversuche an einem Notkondensator - Einzelrohr
Böttger, A.; Gocht, T.; Prasser, H.-M.; Zschau, J.;
Die in diesem Bericht vorgestellten Experimente betreffen die Kondensation von Dampf in horizontalen bzw. leicht geneigten Rohren bei hohen auftretenden Temperaturdifferenzen bis zu über 200 K. Weitere Besonderheiten sind die detaillierte Untersuchung des transienten Verhaltens eines nichtkondensierbaren Gases mit einer neuartigen Messtechnik sowie die Ermittlung des Einflusses des Gases auf den Kondensationsvorgang. Beim Experiment wurden schnelle Übergangsvorgänge ausgelöst, indem ein in einer Kühlwanne liegendes, leicht geneigtes Wärmeübertragerrohr plötzlich mit dem Dampfraum eines unter Druck stehenden Kessels verbunden wurde. Dabei wurden im Rohr unterschiedliche Anfangsbedingungen hinsichtlich der Vorlage von nichtkondensierbaren Gasen (in diesem Falle Luft) eingestellt. Es wurden Versuche mit Atmosphärendruck, mit erhöhtem Druck, aber auch mit vorheriger Evakuierung des Versuchsrohrs durchgeführt. Durch eine Instrumentierung mit neuartigen Nadelsonden, die eine Phasendetektion kombiniert mit einer schnellen lokalen Temperaturmessung ermöglichen, konnte die Umverteilung von Dampf, Kondensat und nichtkondensierbarem Gas als Funktion der Zeit beobachtet werden. Damit bieten die erhaltenen Daten die Möglichkeit, insbesondere die in den Thermohydraulikprogrammen vorhandenen Optionen zur Berechnung der Ausbreitung von nichtkondensierbaren Gasen unter transienten Bedingungen zu validieren.
Keywords: steam condensation, non-condensable gases, two-phase flow, local void probes, mesh sensors
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-383 Juli 2003

Downloads:

Publ.-Id: 5620 - Permalink


Strömungskarten und Modelle für transiente Zweiphasenströmungen
Prasser, H.-M.; Lucas, D.; Krepper, E.; Baldauf, D.; Böttger, A.; Rohde, U.; Schütz, P.; Weiß, F.-P.; Zippe, C.; Zippe, W.; Zschau, J.;
Experimente mit neuartigen Messverfahren lieferten Daten über die Struktur von transienten Flüssig-keits-Gas-Strömungen für die Entwicklung und Validierung von mikroskopischen, d.h. geometrieunabhängigen Konstitutivbeziehungen zur Beschreibung des Impulsaustauschs zwischen Flüssig-phase und Gasblasen sowie zur Quantifizierung der Häufigkeit von Blasenkoaleszenz und -zerfall. Hierzu wurde eine vertikale Testsektion der Zweiphasentestschleife MTLoop in Rossendorf genutzt, wobei erstmals Gittersensoren mit einer Auflösung von 2-3 mm bei einer Messfrequenz von bis zu 10 kHz angewandt wurden. Dabei wurde die Evolution von Gasgehalts-, Geschwindigkeits- und Bla-sengrößenverteilungen entlang des Strömungsweges und bei schnellen Übergangsprozessen aufge-nommen und so die für die Modellbildung erforderlichen Daten bereitgestellt. Für den Test der Mo-dellbeziehungen wurde ein vereinfachtes Verfahren zur Lösung der Strömungsgleichungen entlang des Strömungswegs erstellt. Es basiert auf der Betrachtung einer größeren Anzahl von Blasengrö-ßenklassen. Die erhaltenen numerische Lösungen haben erstmals gezeigt, dass der bei Erhöhung der Gasvolumenstromdichte stattfindende Übergang von einer Blasenströmung mit Randmaximum zu einem Profil mit Zentrumsmaximum und anschließend zu einer Pfropfenströmung ausgehend von einem einheitlichen Satz physikalisch begründeter und geometrieunabhängiger Konstitutivgleichun-gen modelliert werden kann. Die Modellbeziehungen haben sich in einem abgegrenzten Gebiet der Volumenstromdichten als generalisierungsfähig erwiesen und sind für den Einbau in CFD-Modelle geeignet. Weiterhin wurden Arbeiten zur Kondensation durchgeführt, die direkten Bezug zu den Kon-densationsmodellen haben, die in Thermohydraulik-Codes enthalten sind. Die Untersuchung liefert darüber hinaus experimentelle Daten für die Modellvalidierung hinsichtlich des Verhaltens und des Einflusses nichtkondensierbarer Gase. Hierfür wurden spezielle Sonden für die Bestimmung der Konzentration und für die Lokalisierung von Pfropfen nichtkondensierbarer Gase entwickelt und bei transienten Kondensationsversuchen in einem leicht geneigten Wärmeübertragerrohr eingesetzt.
Keywords: Two-phase flow, Pipe flow, Flow pattern, Inlet length, transient processes, Gas bubbles, Bubble forces, Bubble coalescence, Bubble break-up, Bubble size distribution, Condensation
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-379 Juni 2003

Downloads:

Publ.-Id: 5619 - Permalink


Heavy-ion ERDA and spectroscopic ellipsometry characterization of a SiOC:H layered structure as functional coating on polymeric lenses
Kreissig, U.; Gago, R.; Vinnichenko, M.; Fernández-Hidalgo, P.; Martín-Palma, R. J.; Martínez-Duart, J. M.;
In order to improve the optical and mechanical performance of plastic ophthalmic lenses the use of surface coatings is necessary. However, the application of such coatings can be limited by bad adhesion to the substrate. One way to overcome this drawback is the use of a layered structure consisting in an adherent layer, an abrasion resistant hard layer and an antireflective (AR) multilayer (ML) stack. In this work we study the preparation of SiOxCy:H layered coatings to increase the mechanical durability of polymeric substrates and to accommodate gradually an external dielectric SiO2/TiO2 AR-ML. The coatings were grown by plasma assisted chemical vapor deposition (PACVD) using a mixture of hexamethyldisiloxane (HMDSO) and O2. The possibility of producing the whole layered stack by adjusting the HMDSO:O2 ratio was checked by analyzing the resulting elemental profiles obtained from ERDA. Finally, the optical properties of the different layers have been studied by spectroscopic ellipsometry in order to corroborate the adequate optical performance of the complete coating.
Keywords: Plastic ophthalmic lenses, protective coatings, ERDA, optical properties
  • Poster
    16th International Conference on Ion Beam Analysis (IBA-2003), 29 June-4 July 2003, Albuquerque, New Mexico (USA)
  • Nuclear Instruments and Methods in Physics Research B 219-220(2004), 908-913

Publ.-Id: 5618 - Permalink


AMS depth profiling of humidity in silica
Pilz, W.; Friedrich, M.; Heinig, K.-H.; Schmidt, B.; von Borany, J.;
Depth profiling measurements of light elements by Accelerator Mass Spectrometry (AMS) have been performed at the Forschungszentrum Rossendorf. Using the AMS facility at the 3 MV Tandetron accelerator, tritium depth profiles in carbon samples have been measured which had been exposed to the plasma at the first wall of the fusion experiments ASDEX-Upgrade in Garching/Germany, JET Culham/GB and TFTR Princeton/USA. Additionally, our AMS facility at the 3 MV Tandetron has been applied to depth profiling of humidity penetrated into as-implanted SiO2 layers. For this aim, Ge+ and Si+ ion implanted SiO2 layers (1014-1016 cm-2) were exposed to an artificial atmosphere with H218O humidity. AMS allows the discrimination of isobar atomic and molecular ions, thus depth profiles of O-, (OH)- and (H2O)- molecular ions could be investigated. By measuring the 18O or the H species of these molecular ions, the process of humidity penetration in as-implanted SiO2 has been studied. The high tritium inventory of the samples from the European fusion experiment JET required a dedicated AMS facility to prevent contamination of the versatile 3 MV Tandetron. Therefore, an SF6-insulated 100 kV tandem accelerator has been developed and applied to high dose tritium measurements. This facility has been also tested for depth profiling of light elements in radioactive samples.
Keywords: AMS, tritium, humidity, implantation, depth profile
  • Contribution to proceedings
    IBA-2003 Conference, Albuquerque, USA
  • Nuclear Instruments and Methods B 219-220(2004), 459-462
    DOI: 10.1016/j.nimb.2004.01.102

Publ.-Id: 5617 - Permalink


Synthesis and Enzymatic Evaluation of Nucleosides Derived from 5-Iodo-2'-deoxyuridines
Knieß, T.; Grote, M.; Noll, B.; Johannsen, B.;
The synthesis of new nucleosides by alkenylation of 5-iodo-2'-halo-2'-deoxyuridines with E-(1-tributylstannyl)-propene-1-ol via STILLE-coupline is described. The new compounds are characterized by 1H NMR and elemental analysis. All nucleosides are evaluated by an enzymatic assay to be substrates of herpes simplex virus type 1 thymidine kinase (HSV-1 TK) and compared with uridine, thymidine and (E)-5-(2-iodovinyl)-2'fluoro-2'-deoxyuridine (IVFRU).
Keywords: 5-Iodo-deoxyuridines, STILLE-coupling, HSV-1 Thymidine Kinase
  • Z. Naturforsch. 58b, 226-230 (2003)

Publ.-Id: 5615 - Permalink


CFD-Post Test Analysen der dichtegetriebenen Vermischungsexperimente an der ROCOM Versuchsanlage
Höhne, T.;
An der Anlage ROCOM wurden Experimente durchgeführt, um den Einfluss von Dichtedifferenzen und die Bedingungen des Übergangs zwischen auftriebsdominierter und impulsbetriebener Vermischung generisch zu untersuchen. In den Experimenten mit Dichteunterschieden wurden keine konkreten Störfallszenarien nachgebildet. In diesem Bericht werden nun die experimentellen Ergebnisse mit den Resultaten des Strömungsberechnungsprogrammes CFX-4 verglichen. Die Nachrechnung der Dichteexperimente an der ROCOM-Versuchsanlage ergab für die Randfälle impulsdominierte bzw. dichtedominierte Strömung als auch für Zwischenstadien eine gute qualitative Übereinstimmung mit den beobachteten, sehr unterschiedlichen Vermischungsbildern.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-386 Juli 2003

Downloads:

Publ.-Id: 5614 - Permalink


A Biot-Savart method to handle time-dependent dynamos in arbitrary domains
Stefani, F.; Xu, M.; Gerbeth, G.;
Usually, homogeneous dynamos are simulated in the framework of the differential equation approach. For purely kinematic models, the induction equation for the magnetic field has to be solved. For spherically shaped dynamo domains, such as planets and stars, the problem of implementing the non-local boundary conditions for the magnetic field is trivially solved by introducing separate boundary conditions for every degree of the spherical harmonics. However, for the simulation of other than spherically shaped dynamos, in particular for galactic and some of the recent laboratory dynamos, the handling of the boundary conditions is a notorious problem. The integral equation approach provides a solution to this problem. Basically, this approach is an application of Biot-Savart's law for dynamos. The magnetic field is produced by currents driven by an electromotive force that, in its turn, depends on the magnetic field. For the case of finite domains, the simple Biot-Savart equation has to be supplemented by a boundary integral equation for the electric potential. If the dynamo becomes time-dependent, yet another equation for the vector potential at the boundary has to be added. First numerical tests of the method for some well-investigated dynamo models in spherical domains have shown convincing agreement with the results of the differential equation method. The prospective advantage of the method, however, is its suitability to handle dynamos in other than spherical geometries.
  • Abstract in refereed journal
    Astronomische Nachrichten 324 (2003) Suppl. Issue 3, 73-74
  • Lecture (Conference)
    Jahrestagung der Astronomischen Gesellschaft, 15-20 September 2003 in Freiburg im Breisgau

Publ.-Id: 5613 - Permalink


The Radiation Source ELBE at the Research Center Rossendorf
Lehnert, U.; Büchner, A.; Büttig, H.; Enghardt, W.; Evtushenko, P.; Gabriel, F.; Gippner, P.; Grosse, E.; Guratzsch, H.; Michel, P.; Naumann, B.; Neubert, W.; Prade, H.; Schamlott, A.; Schilling, K. D.; Schwengner, R.; Seidel, W.; Teichert, J.; Voigtländer, J.; Wagner, A.; Wagner, W.; Wolf, A.; Wolf, U.; Wünsch, R.;
At the Forschungszentrum Rossendorf (FZR) the new facility ELBE for research with various kinds of radiation is presently under construction. ELBE is centered around a superconductiong Electron Linac which will produce quasi-continuous beams of high Brillance and low Emittance. Preliminary results of the first stage accelerator tests will be shown. The 40 MeV / 1 mA electron beam will be used to drive free-electron lasers for the production of infrared light in the 5-510µm wavelength range. X-ray beams in the 5-50 keV energy range will be generated using channeling radiation. Additionally, the ELBE facility will provide bremsstrahlung and photoneutron beams for investigations in nuclear physics and technology.
  • Contribution to external collection
    Electron-Photon Interaction in Dense Mediaed. H. Wiedemann NATO Science Series II Vol. (2002) 49 p. 313

Publ.-Id: 5612 - Permalink


First Operation of the ELBE Linear Accelerator
Lehnert, U.; Evtushenko, P.; Michel, P.; Teichert, J.;
The new radiation source "Strahlungsquelle ELBE" at the Forschungszentrum Rossendorf (FZR) will us the high brilliance electron beam from a linac with superconducting rf-cavities to porduce various secondary beams for experiments in nuclear science, solid state physics, materials research, environmental chemisty and in the life sciences. During the year 2001 all components belonging to the first stage of ELBE (20 MeV) were successfully put into operation. The main beam properties were measured and it was shown that all major design parameters could be reached with the ELBE accelerator. In the low bunch charge mode of operation intended for radiation physics applications a transversal emittance of 3 mm mrad was measured. At the 77 pC maximum bunch charge the emittance is still better than 10 mm mrad, well sufficient for driving the ELBE free-electron lasers. The longitudinal phase space properties are mainly determined by the capture process of the electron bunches into the first accelerator cavity and could, thus, be characterized by measuring the energy spectrum of the beam while scanning the rf-phase of the second cavity. These measurements at 3 pC bunch charge vielded an emittance of 57 keV ps and a bunchlength of 2 ps, in good agreement with theoretical predictions and with bunch length measurements using an autocorrelation technique.
  • Poster
    The XXI International Linac ConferenceGyeongju, Korea Auguest 19 - 23, 2002

Publ.-Id: 5611 - Permalink


Integral equation approach to time-dependent kinematic dynamos in finite domains
Xu, M.; Stefani, F.; Gerbeth, G.;
The homogeneous dynamo effect is at the root of cosmic magnetic field generation. With only a very few exceptions, the numerical treatment of homogeneous dynamos is carried out in the framework of the differential equation approach. The present paper tries to facilitate the use of integral equations in dynamo research. Apart from the pedagogical value to illustrate dynamo action within the well-known picture of Biot-Savart's law, the integral equation approach has a number of practical advantages. The first advantage is its proven numerical robustness and stability. The second and perhaps most important advantage is its applicability to dynamos in arbitrary geometries. The third advantage is its intimate connection to inverse problems relevant not only for dynamos but also for technical applications of magnetohydrodynamics. The paper provides the first general formulation and application of the integral equation approach to time-dependent kinematic dynamos in finite domains. For the spherically symmetric alpha^2 dynamo model it is shown how the general formulation is reduced to a coupled system of two radial integral equations for the defining scalars of the poloidal and the toroidal field components. The integral equation formulation for spherical dynamos with general velocity fields is also derived. Two numerical examples, the alpha^2 dynamo model with radially varying alpha, and the Bullard-Gellman model illustrate the equivalence of the approach with the usual differential equation method.

Publ.-Id: 5610 - Permalink


Laserinduzierte Spektroskopie: Von der Speziesdetektion zur Fluoreszenzspektroskopie an Mineralien
Geipel, G.;
ohne Abstract
  • Lecture (Conference)
    Geowissenschaftl. Kolloquium in Freiberg 2.7.2003

Publ.-Id: 5609 - Permalink


Investigation of emission instabilities of liquid metal alloy ion sources
Akhmadaliev, C.; Bischoff, L.; Mair, G. L. R.; Aidinis, C. J.; Ganetsos, T.;
A detailed investigation of the emission instabilities and their frequency spectra for Ga, AuGeSi and AuGe Liquid Metal Alloy Ion Sources (LMAIS) was carried out. The ion sources with an extracting electrode (triode scheme) as well as without an extractor (diode scheme) were applied. The ion current coming from the collector electrode was amplified and converted into a voltage. The amplifier has a -3 dB edge at 40 MHz and converting factor of 200 mV/µA. The frequency spectra from 0 to 50 MHz were measured using a HP8591 spectrum analyzer with a resolution of 300 kHz. Simultaneously the corresponding oscillograms of the emission current were obtained using a digital oscilloscope. The measured spectra are correlated with these oscillograms. The current for which pulses appear superimposed on the d.c. level of current is well predicted by existing theory. The pulses are believed to be the result of droplet emission, and their terminal frequency appears to coincide with the frequency of vibrations of the sides of the liquid cone at high currents. The emitted droplets screen the source tip. This leads to decreasing of the effective electric field and fluctuation of the emission process. The following disintegration of the droplets into smaller ones aggravate the noise. The fluctuation depends nonlinearly on the emission current. This dependence shows an S shape, at low emission current the noise is negligible, at 40-60 µA the fluctuation goes up rapidly and higher than 70 µA it comes to a saturation. The onset of the pulses (at about 30 µA) is also predictable from a criterion developed by Mair for the critical current. At 100 µA emission current the typical fluctuation is about 5 µA(rms). The alloy sources were investigated also at temperatures from 400 to 1100 °C and the dependence of the fluctuations of the emission on the temperature were obtained. With increasing temperature a stronger fluctuation was registered. Better understanding of the instabilities that develop on the liquid anode can be useful for deposition purposes.
Keywords: Liquid metal ion source, ion emission instabilities
  • Microelectronic Engineering 73-74(2004), 120-125

Publ.-Id: 5608 - Permalink


Simultanbestimmung von237Np, 233U und 226Ra mittels Flüssigszintillations-Spektroskopie (LS)
Nebelung, C.; Baraniak, L.;
In Umweltproben sind verschiedene langlebige Actinide von Bedeutung. In Wässern oder Salzlösungen mobilisierte Actinide sind mittels LS auch in Multielementspektren ohne chemische Trennung zuverlässig und schnell nachzuweisen. Die Energien müssen allerdings mindestens eine Halbwertsbreite auseinander liegen, um eine Trennung der Einzelnuklide mittels Spektrenentfaltung [1] zu erreichen. Für die Nuklide 226Ra (4,78 MeV), 237Np (4,79 MeV) und 233U (4,82 MeV) liegen die Energielinien zur einfachen Bestimmung mittels Peakfitting zu dicht beieinander. Bei der Bestimmung dieser Nuklide werden die Gleichgewichte von 226Ra und 237Np mit ihren radioaktiven Zerfallsprodukten ausgenutzt. Das 226Ra ist Glied der Uran-Radium-Familie. Es entsteht aus 238U durch Zerfall über Th und Pa. 226Ra zerfällt in der Reihe: 1600 a 226Ra (alpha: 4,78 MeV) 3,82 d 222Rn (alpha: 5,49 MeV) 3,05 min218Po (alpha: 6,00 MeV) 26,8 min 214Pb (beta) 19,8 min 214Bi (beta) 164 µs 214Po (alpha: 7,69 MeV) 22,3 a 210Pb (beta) 5,02 d 210Bi (beta) 138 d 210Po (alpha: 5,31 MeV) st. 206Pb. Im alpha-LS-Spektrum treten folglich mit aufsteigender Energie die Peaks des 226Ra, des 222Rn, des 218Po und des 214Po auf. Mit zunehmenden Alter des 226Ra-Präparates bildet sich eine Spur des beta-Stahlers 210Pb, aus der dann etwas 210Po (5,31 MeV) hervorgeht. Die beta-Strahler erscheinen im LS-Spektrum, werden aber durch beta-Diskriminierung eliminiert, so dass ein reines alpha-Spektrum resultiert. Da das Tochterprodukt 222Rn gasförmig ist, kann ein Teil bei der Probenahme entweichen, so dass das radioaktive Gleichgewicht innerhalb der Zerfallskette gestört ist. Nach 8-10 Halbwertszeiten des 222Rn, also 5-6 Wochen, ist das Gleichgewicht wieder hergestellt. Die Probe wird also nach etwa 6 Wochen Wartezeit gemessen, wobei die Gesamtimpulsrate der alpha-Aktivität des 226Ra im Gleichgewicht mit seinen Folgeprodukten entspricht. Der 226Ra-Anteil wird aus den Peaks der 226Ra-Folgeprodukte bestimmt, die im Spektrum auf den 237Np/234U/226Ra-Summenpeak, der bei 4,8 MeV liegt, folgen und mittels Peakfitting zugänglich sind. Diese machen im radioaktiven Gleichgewicht mit dem 226Ra genau 74,9% der alpha-Counts aus, so dass 25,1% auf das 226Ra entfallen [2,3]. Das 237Np (2,144·106 a) ist im Gleichgewicht mit seiner Tochter 233Pa (26,976 d), das durch alpha-beta-Trennung gut von den alpha-strahlenden Nukliden abgetrennt werden kann. Auf Grund von Einzelmessungen bzw. Berechnungen ist das Aktivitätsverhältnis von 237Np zu 233Pa bekannt. So kann aus dem beta-Peak des 233Pa die 237Np-alpha-Aktivität berechnet werden. Durch Subtraktion des 226Ra und 237Np-Anteils des Summenpeaks bei 4,8MeV erhält man den Anteil des 233U.

[1] Nebelung, C., Nitsche, H.: Stillegung und Rückbau Direktmessung alpha-aktiver Nuklide in Bauschutt zur Freigabeentscheidung Schlussbericht, BMBF Förder-vorhaben 02S7655, 1999
[3] Baraniak, L., Nebelung, C., Thieme, M.: Report FZR-343 (2002) 48
[4] Nebelung, C.: Report FZR-373 (2003) 53

Keywords: 226Ra ,237Np, 233U, Multielementspektren, Spektrenentfaltung, Flüssigszintillations-Spektroskopie
  • Poster
    GDCh-Tagung, München, 06.10.-11.10.2003
  • Contribution to proceedings
    GDCh-Tagung, München, 06.10.-11.10.2003

Publ.-Id: 5607 - Permalink


Modellierung der Kühlmittelvermischung in Druckwasserreaktoren
Höhne, T.;
Ziel dieser Arbeit war die experimentelle und numerische Beschreibung der Kühlmittelvermischung in Druckwasserreaktoren (DWR). Die Kühlmittelvermischung ist für zwei Klassen von Störfällen relevant: Borverdünnungsstörfälle und Kaltwassertransienten. Ausgehend von den Vermischungsphänomenen, die für diese Szenarien bedeutsam sind, wurde die Versuchs-anlage ROCOM (Rossendorf Coolant Mixing Facility) konzipiert und aufgebaut. Die Untersuchung der Vermischung erfolgt anhand eines Tracers (verdünnte Salzlösung) und der Messung der Leitfähigkeit des Fluids. Die numerische Simulation der Kühlmittelvermischung wurde mit dem CFD-Code CFX-4 durchgeführt. Vergleichende CFD-Rechnungen für das Modell und die Geometrie des Originalreaktors vom Konvoi-Typ belegten, dass eine Skalierung im Maßstab 1:5 die Übertragbarkeit der Ergebnisse gewährleistet. An ROCOM wurden umfangreiche Geschwindigkeitsmessungen im Ringspalt des Reaktordruckbehälters (RDB) für verschiedene Schleifendurchsätze und bei Teilschleifenbetrieb durchgeführt und mit CFX-4 Rechnungen verglichen. Bei Vollschleifenbetrieb konnte im Modell eine Unabhängigkeit der Geschwindigkeitsprofile von der Reynoldszahl im Bereich des Nominaldurchsatzes nachgewiesen werden. Besonders aufschlussreich waren, in Übereinstimmung mit CFX-4 Rechnungen, die Messungen transienter Geschwindigkeitsfelder mittels Hochleistungs-LDA-Technik. Damit konnte die Phänomenologie der beschleunigten Strömung aufgeklärt werden, wobei zunächst das Fluid als Ganzes beschleunigt wird, sich später aber große Wirbel im Ringraum herausbilden. Die Experimente an der ROCOM-Anlage zur stationären Kühlmittel-zirkulation bei Betrieb aller Schleifen zeigen übereinstimmend mit CFX-4 Berechnungen eine Beschränkung der Verteilung des eingespeisten Tracers am Kerneintritt überwiegend auf den Quadranten der mit dem Tracer beaufschlagten Schleife. Bei der Simulation von transienten Strömungsvorgängen, wie z.B. dem Anlaufen der Kühlmittelzirkulation, ergibt sich dagegen im Experiment und der korrespondierenden Rechnung ein vollständig anderes Vermischungsbild. Die Strömung teilt sich in eine linke und rechte Komponente um den Kernbehälter auf, so dass die Störung zuerst den Sektor des Reaktorkerns erfasst, der der Schleife gegenüberliegt, über die der Tracer eingespeist wird. Ergänzend wurden Berechnungen zum WWER-440 bei stationärem Durchsatz durchgeführt, die die Anwendbarkeit eines analytischen Ver-mischungsmodells für WWER-440 Reaktoren bestätigen. Für turbulente Strömungen konnte CFX-4 somit anhand von Experimenten validiert werden und steht für weitere Untersuchungen in der Reaktorsicherheitsforschung zur Verfügung. Weiterhin konnte gezeigt werden, dass die Vermischungsmittelwerte im DWR mit Hilfe einer Lösung der eindimensionalen konvektiv-diffusiven Transportgleichung längs des Strömungsweges abbildbar sind. Die Ergebnisse der Experimente, CFD-Rechnungen und des analytischen Modells fließen in ein Modul ein, welches in Computercodes für Störfallanalysen integriert wird. Über eine verbesserte Beschreibung der Vermischung wird dadurch eine realistische Störfallsimulation erreicht.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-382 Juni 2003

Downloads:

Publ.-Id: 5606 - Permalink


Gerätesystem zur Laser-induzierten Breakdown-Detektion aquatischer Kolloide
Hübener, S.; Opel, K.; Zänker, H.;
Zur hochempfindlichen in situ Detektion aquatischer Kolloide mit Partikeldurchmessern < 50 nm wurde im Institut für Radiochemie ein modulares Gerätesystem zur Laser-induzierten Breakdown-Detektion (LIBD) aufgebaut, orientiert an den im Institut für Nukleare Entsorgung des FZK entwickelten LIBD-Systemen. [1-2]
Als gepulste 532 nm-Lichtquelle wird ein diodengepumpter Nd:YAG-Laser eingesetzt. Die Laserpulsenergie wird mit einer Kombination aus Fresnelrhomben und Calcitpolarisator variiert und einem pyroelektrischen Detektor gemessen. Zur Strahlcharakterisierung wird ein kommerzielles Laserstrahlanalysesystem verwendet, das eine 14 Bit-CCD-Kamera, Abschwächungsoptik, PCI-Einschubkarte und Software umfasst. Durchfluss-Küvetten aus Quarzglas werden als Probengefäße benutzt. Die Breakdown-Ereignisse werden akustisch mit einem piezoelektrischen Sensor detektiert und gleichzeitig mit einem Kamerasystem ortsaufgelöst registriert. Systemsteuerung, Datenerfassung und –verarbeitung erfolgen über ein digitales Oszilloskop sowie zwei PC.
Test- und Kalibriermessungen erfolgten an wässrigen Dispersionen von Polystyrolpartikeln. Erste Anwendungen befassten sich mit der Charakterisierung von realen Wässern.
Das Gerätesystem wird ausführlich vorgestellt, die Ergebnisse der Kalibriermessungen, der Messungen an realen Wässern sowie erster Untersuchungen zur Kolloidbildung von U(IV) werden mitgeteilt und diskutiert.

Literatur:

[1] T. Bundschuh, W. Hauser, J.I. Kim, R. Knopp, F.J. Scherbaum, Colloid. Surf. A 180, 285, (2001)
[2] C. Walther, C. Bitea, W. Hauser, J.I. Kim, F.J. Scherbaum, Nucl. Instr. and Meth. B 195, 374, (2002)

Keywords: Kolloide, Laser, U(IV)
  • Poster
    GDCh-Jahrestagung Chemie 2003, Jahrestagung der Fachgruppe Nuklearchemie, 6. - 11. Oktober 2003, München

Publ.-Id: 5605 - Permalink


Particle Flux Calculations for a Pulsed Photoneutron Source at the Radiation Source ELBE
Beckert, C.; Freiesleben, H.; Grosse, E.; Naumann, B.; Weiß, F.-P.;
Die Parameter des Elektronenstrahls an der Strahlungsquelle ELBE des Forschungszentrums Rossendorf sind u.a. eine variable Elektronenenergie zwischen 12 und 40 MeV, 1 mA maximaler Strom, eine maximale Frequenz von 13 MHz, eine Pulslänge kleiner als 10 ps und eine geringe Emittanz. Dies führte zu der Idee, die kurzen und intensiven Elektronenpulse in kurze Neutronenpulse umzuwandeln, um an einem Flugzeitspektrometer energieabhängige Neutronenwirkungsquerschnitte zu messen bei einem kurzen Flugweg von nur einigen Metern. Hauptziel ist dabei die Messung solcher Querschnitte für Konstruktionsmaterialien von Fusions- und Spaltreaktoren und für Abfälle aus solchen Reaktoren. Aufgrund der sehr hohen Energiedeposition durch die Elektronen im Neutronenradiator wurde flüssiges Metall (Blei) als Neutronenradiator gewählt. Für das Wandmaterial ist Molybdän der Hauptkandidat, für den thermomechanische und neutronenphysikalische Rechnungen vollständig gemacht wurden. Mit den Monte Carlo Codes MCNP und FLUKA wurden die Teilchentransportrechnungen ausgeführt. U.a. wurden aus Berechnungen des Neutronenstrahls und des Untergrunds am geplanten Messplatz Schlussfolgerungen für die Konstruktion und Materialauswahl der Photoneutronenquelle gezogen. Die Berechnung des Neutronenpulses am Messplatz zeigt, dass die Neutronen von den Photonen separiert werden können, sich die Neutronenpulse jedoch stark überlappen. Wird z.B. nur jeder vierte Elektronenpuls verwendet, so beträgt der Neutronenfluss am Messplatz zirka 2.5×106 n/cm2/s und der nutzbare Energiebereich 660 keV bis 6 MeV bei den Parametern 3.6 m Flugweg, 11.2×11.2 mm2 Querschnitt des Radiators, 30 MeV Elektronenenergie und 1 mA Elektronenstrom. Das FZR arbeitet an einer Elektronenquelle mit kleinerer Pulsfrequenz bei gleichem mittleren Strom von 1 mA. Die Energieauflösung am Messplatz liegt unter 1%.
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2003, Berlin, 20.-22. Mai 2003, Tagungsbericht S. 47-51
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2003, Berlin, 20.-22. Mai 2003, Tagungsbericht S. 47-51

Publ.-Id: 5604 - Permalink


Small angle neutron scattering analysis of the radiation susceptibility of reactor pressure vessel steels
Ulbricht, A.; Böhmert, J.;
The irradiation induced microstructure for two reactor pressure vessel (RPV) steel types after irradiation at different neutron exposure levels and annealing treatments were investigated by means of small-angle neutron scattering (SANS).
The radiation susceptibility changes with the type of steel. Therefore the role of particular material parameters in defect evolution was worked out. The characteristics of the irradiation-induced defects such as number density, size distribution, and volume content were determined and potential defect compositions were estimated. The type of RPV steel influences the volume content but hardly the size distribution. The evolution of the defect content for a particular steel is not linear in response to the irradiation damage described in displacements per atom. The defect type is not uniform. The average composition of defects is partly changed with increasing dpa-doses. Additionally, the redissolving behaviour of irradiation induced defect clusters was studied after gradual thermal treatments.
The analysis bases on the hypothesis that the radiation defects are not-ferromagnetic. The consistency of the results supports the correctness of the hypothesis.
Keywords: Radiation damage; Radiation hardening; Reactor pressure vessel steel; SANS
  • Physica B 350(2004), E483-E486

Publ.-Id: 5603 - Permalink


Synergism effects of hydrogen and radiation defects in steel
Ulbricht, A.; Heinemann, A.;
There is a hypothesis which postulates the microstructural radiation defects as effective traps for hydrogen and this deposited hydrogen as a stabilizer of these features. Thus, the higher the content of hydrogen the stronger is the embrittlement. The H-trap hypothesis should be examined by a SANS experiment.

The measurement has shown that we can detect H-deposition (> 1x10-4 wt.-%) by SANS.
Keywords: small angle neutron scattering; hydrogen; steel
  • Contribution to external collection
    BENSC Experimental Reports 2002 (eds. Y. Kirschbaum, M. Tovar, D. Bischoff, R. Michaelsen), HMI-B 590, p. 220, Hahn-Meitner Institut Berlin, April 2003.

Publ.-Id: 5602 - Permalink


Silylated mixed-ligand rhenium complexes with the [PNS/S] donor atom set
Knieß, T.; Fernandes, C.; Santos, I.; Kraus, W.; Spies, H.;
New oxorhenium complexes with 2-(diphenylphosphanyl)-N-(2-thioethyl)benzamide (H2PNS) and trimethyl-, triethyl- and triphenyl-hydroxyl silylated monodentate thiols are reported. These new complexes have been prepared by reacting [NnBu4][R-e(O)Cl4] with the tridentate H2PNS and the corresponding silylated thiol at room temperature. The characterization of the complexes involved elemental analysis, 31P and 1H NMR spectroscopies and X-ray crystallographic analysis for the triethyl-silylated Re complex.
Keywords: Crystal structure; Rhenium oxo mixed-ligands complexes
  • Inorganica Chimica Acta 348 (2003) 237-241

Publ.-Id: 5601 - Permalink


Laser Induced Spectroscopy of Actinides - A Tool to Study Interaction with Various Ligands at Low Concentrations
Geipel, G.;
Heavy metals like actinides in the aquatic environment are normally transported as a complexed species. Knowledge about the complex formation is therefore essential for prediction of the migration of these elements.
Spectroscopic methods have the advantage to be non-invasive and non-destructive. The high intensity of laser light sources allows the excitation of all species in the illuminated volume. Therefore laser-based methods reach low detection limits.
Mainly Laser-induced Photoacoustic Spectroscopy (LIPAS) and Time-resolved Laser-induced Fluorescence Spectroscopy (TRLFS) were used for such speciation studies. The introduction of lasers with pulse durations in the pico- and femtosecond range in combination with short gated CCD-cameras enables studies of fluorescing species with fluorescence lifetimes of some nanoseconds.
As uranium, americium and curium show fluorescence properties time-resolved laser-induced fluorescence spectroscopy enables the determination of species up to detection limits of 10-8 M and less. Besides the study of the complex formation of uranium (sulfate, phosphate, arsenate) we determined the formed species in several mining related waters as function of pH. The change in the speciation of uranium(VI) is shown to be in agreement with calculations.
Absorption spectroscopy can be used as tool for direct determination of actinide species. However the concentration of actinides in the natural environment is much lower than the detection limit of conventional UV-VIS spectroscopy. Using laser-induced photoacoustic spectroscopy the detection limit can be decreased by about three orders of magnitude. Studies of the complex formation of uranium(IV) with phosphate and arsenate will be presented, demonstrating the advantage of direct speciation methods.
Polyelectrolytic organic macromolecules, like humic substances, are important complexing agents towards actinide metal ions. The investigation of simple model ligands would give a more detailed description of the binding behavior of humic substances. Especially the different bonding of carboxylic and phenolic group and the discrimination between them is of interest to get more detailed information about the complex formation. The various hydroxy benzoic acids allow the investigation of these differences.
To study the complex formation of actinides with such organic ligands we used the new, recently developed femtosecond laser-induced time-resolved fluorescence spectroscopy. The method uses the fluorescence properties of organic ligands with p-electron systems and their change by interaction with actinide ions to study the complex formation of these systems.
  • Lecture (Conference)
    5. Internationale Konferenz on f-Elements in Geneva, 24.-29.8.2003, Switzerland
  • Contribution to proceedings
    5. Internationale Konferenz on f-Elements, 24.-29.08.2003, Geneva, Switzerland

Publ.-Id: 5600 - Permalink


Design, Construction and Test of Stripline BPM Electronics
Schurig, R.; Evtushenko, P.; Gabriel, F.; Büttig, H.;
Commisioning and operating the ELBE accelerator requires exact knowledge and easy, reproduceable control of various parameters. Important parameters like beam position and beam current are measured with a system consisting of a stripline BPM (beam position monitor), conversion electronics, data acquisition and monitoring software. The design of the electronics is described in this paper
  • Contribution to HZDR-Annual report
    Wissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-341 April 2002, 14-14

Publ.-Id: 5599 - Permalink


Stripline beam position monitors for ELBE
Evtushenko, P.; Büttig, H.; Büchner, A.; Jordan, K.; Michel, P.; Schurig, R.;
The ELBE accelerator needs a non-destructive system for measurement of the electron beam position at about 30 location. To obtain the required resolution about 100mm a system of stripline beam position monitors (BPM) is under design. The stripline BPM can work in full power mode almost without influence on the beam. To study the basic operational principle of the stripline BPM and to get information about BPM signal behavior we did a set of measurements on the ELBE injector. The resolution of the BPM was measured as a function of the electron beam current; at an electron beam current of 1mA the resolution is about 30mm. One of the BPMs will be installed upstream the cryomodule. Since the power spectrum of the beam depends on the bunch length, measurements in the frequency domain give us information about the length of the bunch entering the cryomodule with RF cavities. The BPM will serve for setting correct phase and power of both bunchers of the injector and for measurements of the electron beam position at the entrance of the cryomodule. There are two alternative schemes of the BPM electronics under development. The first one is based on the logarithmic amplifier AD8313, another one on the an rms-responding true power detector AD8361. Both of them can process RF signals with frequencies up to 2.5GHz. The BPM electronics will operate at the fundamental frequency of the accelerator which is 1.3GHz.


1 FZR, , Germany
2 TJNAF, Newport News, Virginia, USA

  • Lecture (Conference)
    Talk at DPG 2001 Erlangen

Publ.-Id: 5598 - Permalink


Performance of the ELBE BPM Electronics
Evtushenko, P.; Schurig, R.;
The radiation source ELBE is based on a superconducting LINAC. Initially it was designed to operate in CW mode with repetition rates either 13 MHz either 260 MHz. Later it was decided to operate the accelerator with reduced repetition rates for diagnostic reasons and for certain users. Now it is possible to operate with bunch frequency 13/n MHz, where n can be 2,4,8,16,32,64 and 128. It is required that the BPM system supports any of these operation modes. A core element of the BPM electronics is a logarithmic detector AD8313 made by Analog Devices Inc. The logarithmic detector is a direct RF to DC converter rated up to 2.5 GHz. Initial design of the BPM electronic was sophisticated only for CW operation with repetition rate more than 10 MHz, since bandwidth of the AD8313 is about of 10 MHz. Additionally a sample and hold amplifier is built in to provide enough time for an ADC to make measurements. The sample and hold amplifier is synchronized with a bunch frequency. In the paper we present results of the modified BPM electronics test.
  • Poster
    6th European Workshop on Beam Diagnostics and Instrumentation for Particle Accelerators, 202 – 204, 05.05. – 07.05.2003, Mainz, Germany
  • Contribution to proceedings
    6th European Workshop on Beam Diagnostics and Instrumentation for Particle Accelerators, 05.-07.05.2003, Mainz, Germany

Downloads:

Publ.-Id: 5597 - Permalink


Results of the ELBE superconducting Electron Linac Comissioning
Evtushenko, P.; Michel, P.; Lehnert, U.; Teichert, J.;
The radiation source ELBE at Forschungszentrum Rossendorf is based on a superconducting linear accelerator that produces a CW electron beam up to 40 MeV and 1 mA. In 2001 the first stage of the ELBE LINAC was put into operation. The main electron beam parameters like energy, transverse emittance, bunch length and energy spread were determined. Moreover, optimal machine parameters were specified and several online diagnostics were tested, such as beam position monitors and beam-loss detectors.
  • Lecture (Conference)
    Univ. of Erlangen-Nürnberg, May 31 and June 1, 2002

Publ.-Id: 5596 - Permalink


Electron Beam Diagnostics at the Radiation Source ELBE
Evtushenko, P.; Lehnert, U.; Michel, P.; Schneider, C.; Schurig, R.; Teichert, J.;
n the research center Rossendorf, the radiation source ELBE based on a super conducting LINAC is under construction. In the year 2001 the first accelerating module was commissioned. The electron beam parameters like emittance, bunch length, energy spread weremeasured. Here we present results of the measurements as well as the methodics used to make the measurements. In the ELBE injector, where electron beam energy is 250 keV, the emittance was measured with the help of multislit device. Emittance of the accelerated beam was measured by means of quadrupole scan method and is 8 mm×mrad at 77 pC bunch charge. Electron bunch length was measured using coherent transition radiation technique. At the maximum design
bunch charge of 77 pC the RMS bunch length was measured to be 2 ps. A set of online diagnostic systems is also under development. One of them a system of stripline beam position monitors is also described here. A BPM resolution of about 10 µm was achieved using logarithmic amplifier as the core element of the BPM electronics. A system of beam loss monitors based on the RF Heliax cable working as an ionization chamber is intended to be another online diagnostic system.
  • Poster
    10th Beam Instrumentation Workshop, Brookhaven National Laboratory, Upton, NY, May 6 - 9, 2002

Publ.-Id: 5595 - Permalink


Stripline Beam Position Monitors for ELBE
Evtushenko, P.; Büchner, A.; Büttig, H.; Michel, P.; Schurig, R.; Wustmann, B.; Jordan, K.;
At the Forschungszentrum Rossendorf (FZR), the superconducting electron linear accelerator ELBE is under construction. It will deliver an electron beam with an energy of up to 40 MeV at an average beam current of up to 1mA. The accelerator uses standing wave DESY type RF cavities operating at 1.3 GHz. A non-destructive system for the measurement of the beam position at about 30 locations is needed. To obtain the required resolution of 100 mm, a system of stripline beam position monitors (BPM) is under design.
  • Poster
    5th European Workshop on Diagnostics and Beam Instrumentation Sunday 13th to Tuesday 15th May, 2001 ESRF, Grenoble, France

Publ.-Id: 5593 - Permalink


Comparison between wire-mesh sensor and ultra-fast X-ray tomograph for an air-water flow in a vertical pipe
Prasser, H.-M.; Misawa, M.; Tiseanu, I.;
A comparison between ultra-fast X-ray CT and a wire-mesh sensor is presented. The measurements were carried out in a vertical pipe of 42 mm inner diameter, which was supplied with an air-water mixture. Both gas and liquid superficial velocities were varied. The X-ray CT delivered 263 frames per second, while the wire-mesh sensor was operated at a frequency four times higher. Two different gas injectors were used: 4 orifices of 5 mm diameter for creating large bubbles and gas plugs and a sintered plate with a pore size of 100 µm for generating a bubbly flow. It was found that the wire-mesh sensor has a significantly higher resolution than the X-ray CT. Small bubbles, which are clearly shown by the wire-mesh sensor, cannot be found in the CT images, because they cross the measuring plane before a complete scan can be performed. This causes artifacts in the reconstructed images, instead. Furthermore, there are large deviations between the quantitative information contained in the reconstructed tomographic 2D distributions and the gas fractions measured by the sensor, while the agreement is very good, when the gas fraction is obtained by a direct evaluation of the X-ray attenuation along the available through-transmission chords of the tomography setup. This shows that there are still potentials for an improvement of the image reconstruction method. Concerning the wire-mesh sensor it was found, that the gas fraction inside large bubbles is slightly underestimated. Furthermore, a significant distortion of large Taylor bubbles by the sensor was found for small liquid velocities up to 0.24 m/s. This effect vanished with growing superficial water velocity.
Keywords: Two-phase flow, X-ray tomography, Wire-mesh sensor, Gas fraction distribution, Bubble flow, Slug flow
  • Flow Measurement and Instrumentation 16(2005), 73-83

Publ.-Id: 5592 - Permalink


Pages: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80] [81] [82] [83] [84] [85] [86] [87] [88] [89] [90] [91] [92] [93] [94] [95] [96] [97] [98] [99] [100] [101] [102] [103] [104] [105] [106] [107] [108] [109] [110] [111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] [127] [128] [129] [130] [131] [132] [133] [134] [135] [136] [137] [138] [139] [140] [141] [142] [143] [144] [145] [146] [147] [148] [149] [150] [151] [152] [153] [154] [155] [156] [157] [158] [159] [160] [161] [162] [163] [164] [165] [166] [167] [168] [169] [170] [171] [172] [173] [174] [175] [176] [177] [178] [179] [180] [181] [182] [183] [184] [185] [186] [187] [188] [189] [190] [191] [192] [193] [194] [195] [196] [197] [198] [199] [200] [201] [202] [203] [204] [205] [206] [207] [208] [209] [210] [211] [212] [213] [214] [215] [216] [217] [218] [219] [220] [221] [222] [223] [224] [225] [226] [227] [228] [229] [230] [231] [232] [233] [234] [235] [236] [237] [238] [239] [240] [241] [242] [243] [244] [245] [246] [247] [248] [249] [250] [251] [252] [253] [254] [255] [256] [257] [258] [259] [260] [261] [262] [263] [264] [265] [266]