Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41396 Publications

Inverse Compton backscattering source driven by the multi-10 TW laser installed at Daresbury

Priebe, G.; Laundy, D.; Macdonald, M.; Diakun, G.; Jamison, S.; Jones, L.; Holder, D.; Smith, S.; Phillips, P.; Fell, B.; Sheehy, B.; Naumova, N.; Sokolov, I.; Ter-Avetisyan, S.; Spohr, K.; Krafft, G.; Rosenzweig, J.; Schramm, U.; Gruner, F.; Hirst, G.; Collier, J.; Chattopadhyay, S.; Seddon, E.

Inverse Compton scattering is a promising method to implement a high brightness, ultra-short, energy tunable X-ray source at accelerator facilities. We have developed an inverse Compton backscattering X-ray source driven by the multi-10 TW laser installed at Daresbury. Hard X-rays, with spectral peaks ranging from 15 to 30 keV, depending on the scattering geometry, will be generated through the interaction of laser pulses with electron bunches delivered by the energy recovery linac machine, initially known as energy recovery linac prototype and subsequently renamed accelerators and lasers in combined experiments. X-ray pulses containing 9 × 107 photons per pulse will be created from head-on collisions, with a pulse duration comparable to the incoming electron bunch length. For transverse collisions 8 × 106 photons per pulse will be generated, where the laser pulse transit time defines the X-ray pulse duration. The peak spectral brightness is predicted to be ~1021 photons/(s mm2 mrad2 0.1% Δλ/λ).

Keywords: ALICE; Compton scattering; Compton synchrotron radiation; Energy recovery linac; ERLP; Laser Compton scattering; Laser synchrotron radiation; Thomson scattering; Ultra-short X-ray pulses; X-ray source

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Permalink: https://www.hzdr.de/publications/Publ-12285
Publ.-Id: 12285


S-Layer basierte Forschungsarbeiten zur Eliminierung von Organika in Wasser

Raff, J.; Pollmann, K.

Vorstellung der S-Layer basierten Forschungsarbeiten am Institut für Radiochemie zur Eliminierung von Organika in Wasser über fotokatalytische Verfahren

  • Lecture (others)
    Vortrag im Rahmen des Besuchs der IBL Umwelt- und Biotechnik GmbH, 21.01.2009, Heidelberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12284
Publ.-Id: 12284


Anisotropic ion-enhanced diffusion during ion nitriding of single-crystalline austenitic stainless steel

Martinavicius, A.; Abrasonis, G.; Möller, W.; Templier, C.; Riviere, J. P.; Declemy, A.; Chumlyakov, Y.

Nitrogen diffusion is investigated in single crystalline austenitic stainless steel AISI 316L (ASS) during ion beam nitriding and subsequent annealing at different crystalline orientations. After nitriding at 400ºC and ion energy of 1 keV, the N penetration depth depends significantly on the crystalline orientation, with the highest penetration depth for (001) orientation. The experimental observations are quantitatively reproduced by fitting using the model of diffusion under the influence of traps. During subsequent isothermal annealing, the N diffusion becomes significantly slower than during nitriding and independent of the orientation. Possible mechanisms of the anisotropic ion enhanced N diffusion are discussed.

Keywords: Stainless steel; Ion nitriding; AISI316L single crystal

  • Journal of Applied Physics 105(2009)9, 093502

Permalink: https://www.hzdr.de/publications/Publ-12283
Publ.-Id: 12283


Native Sn-Pb droplets in a zeolitic amygdale (Isle of Mull, Inner Hebrides)

Dekov, V. M.; Hålenius, U.; Billström, K.; Kamenov, G. D.; Munnik, F.; Eriksson, L.; Dyer, A.; Schmidt, M.; Botz, R.

Despite the particular scientific interest in the elements with high affinity to S and O2, but found in zero-valence state in nature, the origin of these native minerals has been little explored and remains obscure. Here we describe unique Sn-Pb droplets found in a closed analcime-calcite amygdale collected from a basaltic unit cropping out at Carsaig Bay (Isle of Mull, Inner Hebrides). The droplets consist of intimate intergrowths of nearly pure Sn0 and Pb0 domains in proportion 88:12 and are enveloped in a thin, brownish, amber-like film of organic composition, which gives the impression of metallic “embryos” in organic “placenta”. The occurrence of the Sn-Pb droplets in a closed amygdale, their relationship with the host analcime+calcite and their Pb isotope composition (which does not match any known anthropogenic Pb source) rule out the possibility of anthropogenic contamination and support the natural origin of the Sn-Pb alloy.
The variable isotope (Pb, Sr, Nd) compositions in different members of the host basaltic sequence suggest that a parent basaltic magma was modified by crustal assimilation and post-emplacement alteration processes. Considering all possible scenarios, it appears that the most likely source of Pb for the Sn-Pb alloy is a discrete basaltic unit with an isotopic composition comparable to the Antrim basalts (Northern Ireland). The amygdale phases, on the other hand, show isotopic evidence for incorporation of elements from both local basaltic and sedimentary units. The apparent isotopic disequilibrium between Sn-Pb droplets and amygdale phases indicates a complex, multi-stage fluid evolution. The occurrence of Sn-Pb droplets in organic capsules suggests that the droplets and the enveloping organic substances are co-precipitates. This implies that the transportation and deposition of Sn and Pb might have occurred through organometallic compounds. We assume interaction of seawater fluids carrying metals leached from basaltic rocks with hydrocarbons from sedimentary units as a prerequisite for the formation of the organometallic complexes. The zeolites lining the basaltic vesicles might have destabilized the migrating organo- Sn and Pb compounds causing their breakdown and precipitation of Sn-Pb alloy.

Keywords: Sn-Pb alloy; organometallic compounds; Isle of Mull; Inner Hebrides

Permalink: https://www.hzdr.de/publications/Publ-12282
Publ.-Id: 12282


Tracked megawatt PV plants: Operation results 2008 in Germany and Spain

Rindelhardt, U.; Dietrich, A.; Rösner, C.

An increasing number of 2-axis tracked Megawatt PV plants have been put into operation during the last years. The higher final yield of such plants (compared to plants with fixed generator orientation) must be paid with higher plant costs and larger area consumption. The absolute yield is determined by the insolation conditions at the sites. The paper compares design and operation results of four 2-axis tracked plants operating in Germany and Spain in 2008, which are representative PV sites in Europe.

The plant locations are distributed between 37 and 50 degrees northern latitude (Fig.1), in South Spain and Central Germany. Some technical features of the investigated plants are given in the table below.

plant total power /MW tracker Plant area/m² module supplier
Borna 3.44 Solon 210000 Solon
Penig 0,2 Deger 22000 Sanyo,Sharp,SunLink
Alqueria 1.02 Solon 125000 Solon
Ventanas 1.01 Solon 102000 Solon

The used tracker systems differ in their construction and in the applied tracking principle. Whereas the Solon mover (Fig. 2) follows every 10 minutes the astronomic sun path, the Deger tracker (Fig. 3) tries to find the optimal generator position also at cloudy conditions. The tracker distance varies between the both used tracker types and the sites. The most plants started their operation in 2007. The operation of the plants was monitored by the owners or by professional service providers.

The operation results of the year 2008 are exemplarily presented. The solar irradiance in 2008 in Germany was higher than the long year average, similar to the years before. The final yield of the both plants is about 1300 kWh/kW (Fig. 4), with an advantage of 8 % for the plant using Deger trackers. The annual performance ratio was fond to be 82 %.
The yields of the Spain plants exceed the yield of the German plants with 2250 kWh/kW by more than 70 %. Only in one month (May) the yield of the German reaches the yield of the Spain plants due to the extraordinary insolation in Germany (high) and Spain (low), respectively. The performance ratios of the Spain plants were also about 82 %.
A number of operation details will be given.
Finally a long term estimation of the yield for the different plants will be given.

Keywords: PV plants; tracked systems; performance

  • Lecture (Conference)
    24th European Photovoltaic Solar Energy Conference and Exhibition, 21.-25.09.2009, Hamburg, Deutschland
  • Contribution to proceedings
    24th European Photovoltaic Solar Energy Conference and Exhibition, 21.-25.09.2009, Hamburg, Deutschland
    Proceedings CD-ROM, contribution 5AO.8.5, 3-936338-25-6

Permalink: https://www.hzdr.de/publications/Publ-12281
Publ.-Id: 12281


Beltline welding seam and base metal investigations of a WWER-440/230 reactor pressure vessel from the former Greifswald NPP

Rindelhardt, U.; Schuhknecht, J.; Viehrig, H.-W.

Nuclear plants operators must demonstrate that the structural integrity of the nuclear reactor pressure vessel (RPV) is assured during routine operations or under postulated accident conditions. Russian type WWER reactors are operated in Russia and many other European countries like Ukraine, Finland, Czech Republic and Hungary. Surveillance specimens programmes for inspection of aging of the RPV materials were implemented for the second generation (213) of WWER-440 reactors.
The paper presents results of the circumferential core weld SN0.1.4 and the base metal ring 0.3.1 of the RPV from the unit 1 of the Greifswald WWER-440/230. The investigated trepans represent the irradiated-annealed-re-irradiated (IAI) condition. The working program is focussed on the characterisation of the RPV steels through the RPV wall. The key part of the testing is aimed at the determination of the reference temperature T0 following the ASTM Test Standard E1921-05 to determine the fracture toughness in different thickness locations. It is shown that the Master Curve approach as adopted in ASTM E1921 is applicable to the investigated original WWER-440 weld and base metal.
The evaluated T0 varies through the thickness of the welding seam. The lowest T0 value was measured in the root region of the welding seam representing a uniform fine grain ferritic structure. The highest T0 of the weld seam was not measured at the inner wall surface. This is important for the assessment of ductile-to-brittle temperatures measured on sub size Charpy specimens made of weld metal compact samples removed from the inner RPV wall. Our findings imply that these samples may not represent the most conservative condition. The Charpy transition temperature TT41J estimated with results of sub size specimens after the recovery annealing was confirmed by the testing of standard Charpy V-notch specimens. The evaluated transition temperature of 51°C is close to the estimated critical embitterment temperature for the initial condition TK0 of the welding seam SN0.1.4.
The T0 from the trepan 1-4 of base metal ring 0.3.1 varies through the thickness of the welding seam. T0 decreases from -124°C at the inner surface to -90°C at a distance of 33 mm from it and again to -113°C at the outer RPV wall. The KJc values generally follow the course of the MC, although the scatter is large. The re-embrittlement during 2 campaigns operation can be assumed to be low. Hence, the variation of T0 measured through the thickness of the base metal ring 0.3.1 results basically from differences in the structure. With metallographic characterization the scatter of the MC will be investigated.
The Charpy transition temperature TT41J estimated with results of sub size specimens after the recovery annealing was confirmed by the testing of standard Charpy V-notch specimens.

Keywords: Russian WWER-type reactor; WWER; reactor pressure vessel steel; weld metal; trepans; fracture toughness; Master Curve

  • Lecture (Conference)
    6th International Scientific and Technical Conference “Safety Assurance of NPP with WWER”, 26.-29.05.2009, Podolsk, Russian Federation
  • Contribution to proceedings
    6th International Scientific and Technical Conference “Safety Assurance of NPP with WWER”, 26.-29.05.2009, Podolsk, Russian Federation
    Conference CD, Podolsk

Permalink: https://www.hzdr.de/publications/Publ-12280
Publ.-Id: 12280


Neutron fluence calculations for embrittlement surveillance specimens in VVER-1000

Konheiser, J.; Mittag, S.; Zaritsky, S.

Neutron fluence spectrum calculations have been performed for the reactor pressure vessel of a VVER-1000, applying the Monte Carlo code TRAMO. Activities measured earlier in Balakovo-1 by fluence monitors, placed in special Charpy surveillance containers, are compared to TRAMO results. The average deviation from the measurements is about 5 %. A good agreement of the fluence spectra near the RPV inner side, at the height of the core beltline, to the spectra at the Charpy probe positions on top of the radial reflector has been demonstrated.

Keywords: Neutron Fluence Calculation; Surveillance specimens; VVER-1000; Monte-Carlo; TRAMO

  • Annals of Nuclear Energy 36(2009)8, 1235-1241

Permalink: https://www.hzdr.de/publications/Publ-12279
Publ.-Id: 12279


High pressure materials for energy storage. The case of V2O5

Arroyo-De Dompablo, M. E.; Amador, U.; Gallardo–Amores, J. M.; Baehtz, C.; Biskup, N.; Morán, E.

The high pressure polymorph of V2O5 is investigated as example of a high-pressure material (HP-V2O5) with potential applications in electrochemical devices, such as lithium batteries. HP-V2O5 reversibly intercalates up to 2 lithium ions down to 1 Volt vs Li+/Li. The typical voltage-composition profile of HP-V2O5 shows distinct features than that of the ambient pressure polymorph, AP-V2O5. Remarkably, the specific capacity retention with cycling of HP-V2O5 // Li cells (250 Ah/Kg at a C/3.5 rate) is comparable to that of the ambient pressure polymorph. Furthermore, the measured resistivities at room temperature (10000 Ωcm in AP and 400 Ωcm in HP) reveal that HP-V2O5 is a better electronic conductor than AP-V2O5. The enhanced electronic conductivity of HP-V2O5 is an advantage for electrochemical applications.

Keywords: in-situ diffraction; lithium ion battery; synchrothron

Permalink: https://www.hzdr.de/publications/Publ-12278
Publ.-Id: 12278


Thermal “order-disorder” behaviour in (Na1-xKx)4B8O14 solid solutions investigated by X-ray powder diffraction

Georgievskaya, M.; Albert, B.; Bubnova, R.; Cordier, G.; Baehtz, C.; Filatov, S.

In the potassium-rich part of the binary system Na4B8O14-K4B8O14 solid solutions have been found that can be described with the formula (Na1-xKx)4B8O14 with 0.45 ≤ x < 1.0. The crystal structures of (Na0.25K0.75)4B8O14 and (Na0.45K0.55)4B8O14 were refined at room temperature by the Rietveld method. The solid solutions crystallize like K4B8O14 in the triclinic crystal system, space group P-1, with K partially substituted for Na.
An ordered distribution of the alkali atoms over the four cation sites at room temperature has been discovered. The structure of (Na0.25K0.75)4B8O14 was also refined for data collected at 300 and 500°C. The refinements show that sodium and potassium atoms are less ordered at higher temperatures.

Keywords: borates; solid solutions; Rietveld refinement; structure refinement; high temperatures

Permalink: https://www.hzdr.de/publications/Publ-12277
Publ.-Id: 12277


TOPFLOW hot leg model experiments: Overview, examples, status of data analysis and future work

Vallee, C.; Seidel, T.; Lucas, D.

The presentation gives an overview about the experiments performed in the hot leg model built in in the pressure vessel of the TOPFLOW facility.
These experiments were conducted in a flat test-section representing a model of the hot leg of a pressurised water reactor. The region of the elbow and of the steam generator inlet chamber is equipped with glass side walls in order to allow high-speed video observations of the two-phase flow in this region. The used fluids were air and water at ambient temperature and pressures up to 0.5 MPa as well as steam and saturated water at pressures up to 5.0 MPa and temperatures up to 264°C. Four types of experiments were performed: experiments without water circulation, co-current flow experiments, steady counter-current flow experiments and counter-current flow limitation (CCFL) experiments. The test procedures, detailed test matrices and selected examples of the measurements are shown.
The current status of data analysis is presented. Data sheets were arranged in order to give an overview of the 191 runs. The water level measured during co-current flow experiments was analysed over probability distributions. Furthermore, the flooding characteristics of the hot leg model was determined and a new parameter is proposed to correlate the data. Finally, a first approach for the interface detection in high-speed camera images was presented.
In the next future, the acquired data will be compared with CFD calculations for validation purposes.

Keywords: hot leg; pressurised water reactor; PWR; two-phase flow; counter-current flow; counter-current flow limitation; CCFL

  • Lecture (others)
    15th Meeting of the German CFD Network, 21.-22.01.2009, Garching, Germany

Permalink: https://www.hzdr.de/publications/Publ-12276
Publ.-Id: 12276


High-temperature thermal expansion and structural behaviour of stromeyerite, AgCuS

Trots, D. M.; Senyshyn, A.; Mikhailova, D. A.; Knapp, M.; Baehtz, C.; Hoelzel, M.; Fuess, H.

Results of simultaneous thermal analysis, synchrotron and neutron powder diffraction in the range from room temperature up to the melting point at 936 K on non-superionic orthorhombic β-AgCuS as well as on superionic hexagonal α- and cubic δ-AgCuS are reported. On heating the sample is only stable in argon. The following phase transitions occur in AgCuS at elevated temperatures: β 361 K −→ α 399 K −→ α + δ 439 K −→ δ. The volume changes at the superionic β −→ α and α −→ δ phase transitions are about 2.3 and 0.6%. The volume thermal expansion coefficients are 26 × 10−6, 130 × 10−6 and 85 × 10−6 K−1 for the pure β-, α-and δ-phases, respectively. Models forthe average structures of α-and δ-AgCuS are proposed and discussed. Ionic conductivity in δ-AgCuS may originate from cation jumps in ‘skewed’ (100) directions between nearest-neighbour tetrahedral sites via the peripheries of the octahedral cavities. A correlation between the temperature dependence of the cation redistribution in δ-AgCuS and the temperature dependence of the ionic conductivity is assumed. A two-dimensional nature of the ionic conductivity due to cation jumps in slabs perpendicular to the c-direction is supposed for α-AgCuS. There is no evidence for ionic diffusion through the (1/2, 1/2, 1/2) site in (111) directions in either superionic α-or δ-phases.

Keywords: XRD phase transition AgCuS

Permalink: https://www.hzdr.de/publications/Publ-12275
Publ.-Id: 12275


Annual Report 2007 - Institute of Radiation Physics

Kämpfer, B.

activities etc. in line of previous reports. In 2007, the various research directions were organized and performed in four departments: radiation physics, biophysics (both belonging to the program Life Science), nuclear physics and hadron physics (both belonging to Structure of Matter). A substantial part of the institute’s tasks is the performance and further development of the radiation source ELBE, for which a fifth department is responsible. Besides providing secondary beams for radiation physics and biology, nuclear and hadron physics, ELBE is used by groups from other institutes of the Forschungszentrum Dresden-Rossendorf, too in parts in common projects and by external users. Beamtime is used extensively by outside users while all beam time requests have been rated by an international advisory committee.
Some highlights in 2007 related to ELBE have been: first electron beam from superconducting HF gun, first pulsed fast neutron beams from nELBE, and first experiments with single electron pulses of high bunch charge (cell irradiation for radiobiological studies). These achievements are not yet documented in this report.

  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2008
    72 Seiten
    ISSN: 1437-322X

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Permalink: https://www.hzdr.de/publications/Publ-12274
Publ.-Id: 12274


Labeling of peptides and proteins with 18F via click chemistry using a novel prosthetic group 4-[18F]fluoro-N-methyl-N-(prop-2-ynyl)benzenesulfonamide

Ramenda, T.; Knieß, T.; Steinbach, J.; Wüst, F.

Ziel/Aim:

The radiolabeling of peptides or proteins with the short-lived positron emitter 18F requires rapid and mild reaction conditions compatible with the structural and functional integrity of these biopolymers. Over the last two years several approaches have been published focusing on the application of copper(I)-mediated 1,3-dipolar [3+2]cycloaddition of azides and alkynes for labeling peptides with 18F. The peptides were functionalized with an azide- or alkyne group to be reacted with an appropriately 18F-labeled azide or alkyne, respectively. We report on the radiosynthesis of a novel alkine containing 18F-labeled prosthetic group having the advantage of a stable aromatic 18F-label and low lipophilicity caused from the sulfonamide backbone. First applications for click chemistry by labeling azide-functionalized phosphopeptides and human serum albumin (HSA) are demonstrated.

Methodik/Methods:

Two labeling precursors containing different leaving groups (nitro- and trimethylammoniumtriflate) and the reference substance were prepared by the reaction of N methylpropargylamine with the corresponding sulfonic acid chlorides. Radiofluorination was performed in a single step on an automated synthesizer. After purification on semi-preparative HPLC click reaction was performed with a phosphopeptide and the HSA protein. Peptide and protein have been modified with an azide linker. Click reaction occurs in the presence of copper(I) salts and in combination with different copper-chelating ligand systems.

Ergebnisse/Results:

The radiolabeled sulfonamide can be obtained in radiochemical yields of 19 % (d. c.) in high radiochemical purity of > 99 % after HPLC purification within 84 min. First promising results in labeling an azide modified phosphopeptide and protein via click chemistry gave labeling yields about 42 % for posphopeptides after semi-preparative HPLC and about 31 % for HSA after size exclusion chromatography.

Schlussfolgerungen/Conclusions:

The novel prosthetic group 4-[18F]fluoro-N-methyl-N-(prop-2-ynyl)benzenesulfonamide for peptide and protein labeling with 18F via click chemistry can be prepared in reasonable radiochemical yields and high radiochemical purity. Moreover, by this method for the first time click chemistry was successfully applied to the 18F-labeling of a phosphopeptide and a protein. The radiopharmacological investigation of the 18F-labeled phoshopeptides and HSA including metabolic stability, biodistribution and cell uptake studies is in progress.

  • Lecture (Conference)
    47. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 22.-25.04.2009, Leipzig, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 48(2009)2, A38
    ISSN: 0029-5566

Permalink: https://www.hzdr.de/publications/Publ-12273
Publ.-Id: 12273


Die Relevanz der Borflüchtigkeit bei Langzeittransienten in einem mit Bor vergifteten Siedewasserreaktor

Laczko, G.; Böhlke, S.; Ohlmeyer, H.; Schuster, C.; Hurtado, A.

Die Analyse der Reaktivitätswirksamkeit der Boreinspeisung am SWR erfolgt im Rahmen einer sich im Abschluss befindlichen Dissertation an der Technischen Universität Dresden. Die Finanzierung dieses Vorhabens nahm Vattenfall Europe Nuclear Energy (VENE) GmbH über den Kompetenzverbund Kerntechnik wahr. Innerhalb dieses Projektes wurde die Flüchtigkeit des Bors aus Boratlösungen in Abhängigkeit der Einflussgrößen Borkonzentration, Temperatur, pH-Wert und Volumendampfgehalt aus Zweiphasenströmungen experimentell bestimmt. Aus den Messwerten erfolgte die Ableitung empirischer Funktionen, welche für Simulationsrechnungen mit System-Codes und einfache Abschätzungen nutzbar sind [BoB08].

Keywords: Boreinspeisung am SWR; Zweiphasenströmung; Simulationsrechnung

  • Lecture (Conference)
    Jahrestagung Kerntechnik 2009, 12.-14.05.2009, Dresden, Deutschland
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2009, 12.-14.05.2009, Dresden, Deutschland
    Tagungsband der Jahrestagung Kerntechnik 2009, paper 311, Berlin: INFORUM GmbH

Permalink: https://www.hzdr.de/publications/Publ-12272
Publ.-Id: 12272


Im Kern - Energie

Weiß, F.-P.; Hurtado, A.

Weltweit sind derzeit 439 Kernkraftwerke in Betrieb, in Deutschland waren es noch 17 Anlagen. Diese 17 Anlagen haben im Jahre 2007 22,1% des gesamten in Deutschland erzeugten Stromes geliefert. An der Grundlast macht der Strom aus Kernenergie sogar 45% aus.
Die Bundesregierung hat den Ausstieg aus der Nutzung der Kernenergie zum Zwecke der Stromerzeugung beschlossen, weltweit zeichnet sich jedoch ein erheblicher Ausbau der Kernenergie ab. Im Oktober 2008 waren 36 Anlagen im Bau und 99 weitere in Planung.
Vor diesem Hintergrund geht der Vortrag auf die physikalischen und technischen Grundlagen der friedlichen Nutzung der Kernenergie, der Sicherheitsprinzipien sowie auf die mit dem Betrieb von Kernkraftwerken verbundenen Risiken im Vergleich zu anderen Formen der Stromerzeugung ein. Dabei wird auch der Beitrag der Kernenergie zu CO2-Vermeidung dargestellt. Darüber hinaus werden Aspekte der Brennstoffversorgung, insbesondere der Reichweiter des Urans, und der Abfallentsorgung beleuchtet.

Keywords: Strom aus Kernenergie; Brennstoffversorgung; CO2-Vermeidung; Abfallentsorgung

  • Invited lecture (Conferences)
    Im Kern - Energie Veranstaltungsreihe der Katholischen Akademie, 11.11.2008, Katholische Akademie Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12271
Publ.-Id: 12271


Impossibility to describe repulsion with contact interaction

Morawetz, K.; Maennel, M.

Contact interactions always lead to attractive behaviour. Arguments are presented to show why a repulsive interacting system, e.g. Bose gases, cannot be described by contact interactions and corresponding treatments are possibly obscured by the appearance of bound states.

Permalink: https://www.hzdr.de/publications/Publ-12270
Publ.-Id: 12270


Application of a step-wise verification and validation procedure to the 3D neutron kinetics code DYN3D within the European NURESIM project

Rohde, U.; Mittag, S.; Grundmann, U.; Petkov, P.; Hadek, J.

The generic strategy of core physics codes benchmarking which has been elaborated within the European NURESIM code platform development was applied to benchmarking of the 3D neutron kinetics code DYN3D for applications to VVER-type reactors. Numerical and experimental benchmark problems were considered for code verification and validation.
Mathematical problems with given cross sections are used for the verification of the mathematical methods applied e.g. in nodal codes against finite difference solutions.
After minimisation of numerical errors, modelling errors have to be considered. Diffusion approximation and homogenisation error are due to simplified physical approaches and can be estimated by comparing diffusion solutions with more accurate Monte Carlo or deterministic transport solutions.
A series of 2D whole core benchmarks for different core loadings and operational conditions for VVER-1000 reactors was defined for this purpose. Reference transport solutions were calculated by the MARIKO and APOLLO codes based on Method of Characteristics. Homogenised two-group and few-group diffusion parameters were derived from the reference solutions and used as cross section data for the nodal diffusion code DYN3D. The DYN3D solutions were compared to the reference solution. It was shown that the homogenisation error can be significantly reduced, if Assembly Discontinuity Factors (ADF) and Reference Discontinuity Factors (RDF) which are obtained from the transport solution by applying equivalence theory are used.
A study using the multi-group version of DYN3D has shown that increasing the number of groups in the considered cases has only a small effect in comparison with homogenisation error.
Experimental problems are used for code validation. Experimental data for VVER reactors, which were used for the benchmarking of the DYN3D code within NURESIM, are power distribution measurements at the full-size (VVER-1000) experimental facility V-1000, which have been well documented within the EC project VALCO, and kinetic experiments at the LR-0 zero power reactor in NRI Řež.
The code DYN3D has proved to be an effective tool for steady-state and kinetics core calculations. The high accuracy of the code is based on the advanced nodal method “HEXNEM2”, multi-group approach, applying discontinuity factors, and intra-nodal flux reconstruction.

Keywords: reactor physics; neutron kinetics; verification; validation; benchmarking; diffusion theory; homogenisation

  • Lecture (Conference)
    17th International Conference on Nuclear Engineering ICONE17, 12.-17.07.2009, Brussels, Belgium
  • Contribution to proceedings
    17th International Conference on Nuclear Engineering ICONE-17, 12.-16.07.2009, Brussels, Belgium
    CD-ROM paper 75446

Permalink: https://www.hzdr.de/publications/Publ-12269
Publ.-Id: 12269


Switching Ti Valence in SrTiO3 by a dc Electric Field

Leisegang, T.; Stöcker, H.; Levin, A. A.; Weißbach, T.; Zschornak, M.; Gutmann, E.; Rickers, K.; Gemming, S.; Meyer, D. C.

A (001) SrTiO3 wafer has been investigated in situ at room temperature under application of a static electric field of varying polarity by the fluorescence X-ray Absorption Near Edge Structure (XANES) analysis at the Sr-K and Ti-K absorption edges. The XANES spectra show a clear shift of the Ti-K absorption edge energy. The shift is attributed to a change of the Ti valence state in a volume invoked by diffusion of the oxygen ions and vacancies. No shift was observed for the Sr-K absorption edge energy. Theoretical calculations support these findings.

Keywords: functional oxide; density-functional; XANES; electric field; strontium titanate

Permalink: https://www.hzdr.de/publications/Publ-12268
Publ.-Id: 12268


On the effect of spatial discretization in integral transport calculations with HELIOS 1.9

Merk, B.; Weiß, F. P.

In this study the consequences of the discretization effect is investigated for the full calculation chain starting with the steady state calculation continuing with the burnup calculations and finishing with the evaluation of the safety coefficients. The investigation is based on Mixed Oxide (MOX) Fuel with reactor grade Plutonium. Detailed evaluation of the convergence behavior, the influence of the discretization on the neutron spectrum and the isotopic composition during burnup is given. Finally the influence on the few group cross section preparation and an estimation of the influence of discretization on the safety coefficients is shown.

Keywords: Cell- and Lattice calculation; cross section preparation; HELIOS; Discretization; Burnup calculation; Depletion; Safety coefficients

  • Contribution to proceedings
    XXI International Conference on Transport Theory, 12.-17.07.2009, Torino, Italy

Permalink: https://www.hzdr.de/publications/Publ-12267
Publ.-Id: 12267


A three scale expansion solution for the Telegrapher’s equation with external source: development and first application

Merk, B.; Glivici, V.; Weiß, F. P.

This work presents a improved onset for the analysis of experiments by the development of an analytical approximation solution for a space-time dependent P1 neutron transport problem in a one dimensional system consisting of homogenized medium with a central external source with Green's functions. The delayed neutron production is implemented in two additional time scales with the multiple scale expansion method. The approximation solutions are developed for the switch off of the source. First applications are shown for the analysis of the YALINA Booster experiment.

Keywords: Time dependet neutron transport; Accelerator driven system; Experimental analysis; Green's funtion expansion; YALINA experiment

  • Contribution to proceedings
    XXI International Conference on Transport Theory, 12.-17.07.2009, Torino, Italy
  • Lecture (Conference)
    XXI International Conference on Transport Theory, 12.-17.07.2009, Torino, Italy

Permalink: https://www.hzdr.de/publications/Publ-12266
Publ.-Id: 12266


ATWS analysis for PWR using the coupled code system DYN3D/ATHLET

Kliem, S.; Mittag, S.; Rohde, U.; Weiß, F.-P.

The ATWS transient “Loss of main feed water supply” in a generic four-loop PWR at the nominal power of 3750 MW was analyzed using the coupled code system DYN3D/ATHLET. A variation of the MOX-fuel-assembly portion in the core has an effect on the reactivity coefficients of the fuel temperature and the moderator density. These two parameters mainly influence the behaviour of the coolant pressure, which is safety-relevant. It has been demonstrated that the pressure maximum decreases with an increasing portion of MOX. For all core loadings considered, both primary-circuit mechanical integrity and sufficient core cooling are guaranteed.

Keywords: reactor safety; MOX, reactivity; temperature-feedback; thermal-hydraulics; transient

Permalink: https://www.hzdr.de/publications/Publ-12265
Publ.-Id: 12265


Evaluation leistungsbezogener Budgetierungsmodelle

Gilge, B.; Joehnk, P.

Wird die an öffentlich finanzierten außeruniversitären Forschungseinrichtungen zunehmend wichtiger werdende Programmbudgetierung durch eine leistungsbezogene Budgetierung ergänzt, kann die durch das Neue Steuerungsmodell geforderte Wirkungsorientierung der Ressourcenallokation forciert werden. Darüber hinaus ermöglicht die Übernahme von Kriterien der externen Evaluierung in die budgetierungsrelevanten Leistungsindikatoren eine Verknüpfung zwischen externen Anforderungen der Träger der Einrichtungen und internen Leistungsanreizen. Mit dem vorliegenden Beitrag wird eine Evaluationskonzeption vorgestellt, mit welcher das leistungsbezogene Budgetierungsmodell einer öffentlich finanzierten außeruniversitären Forschungseinrichtung bewertet sowie verbessert werden kann.

  • Wissenschaftsmanagement 4(2008), 12-19

Permalink: https://www.hzdr.de/publications/Publ-12264
Publ.-Id: 12264


Preparatory Grants for Collaboratory European Research Projects

Joehnk, P.

  • Lecture (Conference)
    Bioingteh - The exploratory Workshop on Advanced Materials & Technologies in Biology and Medicine, 18.-20.09.2008, Poiana Brasov, Romania

Permalink: https://www.hzdr.de/publications/Publ-12263
Publ.-Id: 12263


High-resolution hydrogen profiling in AlGaN/GaN heterostructures grown by different epitaxial methods

González-Posada Flores, F.; Redondo-Cubero, A.; Gago, R.; Bengoechea, A.; Jiménez, A.; Grambole, D.; Braña, A. F.; Muñoz, E.

Hydrogen (H) incorporation into AlGaN/GaN heterostructures used in high electron mobility transistors, grown by different methods, is studied by high-resolution depth profiling. Samples grown on sapphire and Si(1 1 1) substrates by molecular-beam epitaxy and metal–organic vapour phase epitaxy; involving H-free and H-containing precursors, were analysed to evaluate the eventual incorporation of H into the wafer. The amount of H was measured by means of nuclear reaction analysis (NRA) using the 1H(15N,αγ )12C reaction up to a depth of ∼110 nm into the heterostructures. Interestingly, the H profiles are similar in all the samples analysed, with an increasing H content towards the surface and a negligible H incorporation into the GaN layer (0.24 ± 0.08 at%) or at the AlGaN/GaN interface. Therefore, NRA shows that H uptake is not related to the growth process or technique employed and that H contamination may be due to external sources after growth. The eventual correlation between topographical defects on the AlGaN surface and the H concentration are also discussed. (Some figures in this article are in colour only in the electronic version)

Keywords: PACS: GaN; AlGaN; Hydrogen; NRA; HEMT; AFM; MOCVD; MBE

Permalink: https://www.hzdr.de/publications/Publ-12262
Publ.-Id: 12262


Experimental studies and CFD calculations for buoyancy driven mixing phenomena

Da Silva, M. J.; Thiele, S.; Höhne, T.; Vaibar, R.; Hampel, U.

In nuclear reactor safety the mixing of borated and deborated water is a critical issue that needs investigation, assessment and prediction. Such mixing is buoyancy driven and numerical codes must correctly model momentum transfer between components of different density. To assess and develop CFD models for buoyancy driven mixing we set up a simple vertical mixing test facility (VeMix) and equipped it with a newly developed planar electrical imaging sensor. This imaging sensor acquires conductivity images of the liquid at the rear channel wall with a speed of 2,500 frames per second. By adding NaCl tracer to the denser component we were able to visualize the mixing process in high spatial and temporal detail. Furthermore, an image processing algorithm based on the optical flow concept was implemented and tested which allows the measurement of flow pattern velocities. Selected experiments at different Richardson numbers were run with two components of different density (pure water and glucose-water mixture) simulating borated and deborated water in a light water reactor scenario. These experiments were compared to CFD calculations using standard turbulence models. Good agreement between experimental data and first CFD simulations was found.

Keywords: buoyancy driven flow; mixing; deborated water; flow visualization; CFD; simulation; planar array sensor

  • Nuclear Engineering and Design 240(2010)9, 2185-2193

Permalink: https://www.hzdr.de/publications/Publ-12261
Publ.-Id: 12261


Collisional Energy Loss: A Welcoming Component for Jet Quenching Phenomenology in Heavy-Ion Collisions

Mustafa, M.

  • Lecture (others)
    Universität Gießen, 10.09.2008, Gießen, Deutschland
  • Lecture (others)
    Seminar am Max-Planck-Institut fuer extraterrestrische Physik, 11.09.2008, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12260
Publ.-Id: 12260


Strongly Coupled QGP - Equation of State

Bluhm, M.

  • Lecture (Conference)
    Workshop of the European Network SIM, 08.-12.09.2008, Villasimius, Italien

Permalink: https://www.hzdr.de/publications/Publ-12259
Publ.-Id: 12259


Nuclear data needs for transmutation of nuclear waste

Ignatyuk, A.

  • Lecture (others)
    Seminar FWK, 10.04.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12258
Publ.-Id: 12258


Quantal Rotation: Molecular view on nuclei

Frauendorf, S.

  • Lecture (others)
    Seminar FWK, 30.04.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12257
Publ.-Id: 12257


Exotic modes of rotation

Frauendorf, S.

  • Lecture (others)
    Seminar FWK, 04.06.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12256
Publ.-Id: 12256


Raman Spectrometer for monitoring Isotope Exchange Reactions and Energy Transfer in Low Temperature Plasmas

Borysow, J.

One of the major elements in tritium processing systems is hydrogen isotopes identification and separation. Work with multiple hydrogen isotopes at the is often accompanied by isotopic mixing. Maintaining isotopic purity of tritium is one of the major tasks in new generation Texas Neutrino Mass Experiment (NEXTEX). We developed unique Raman Spectrometer capable of detecting hydrogen isotopes T2, HT, H2, D2, TD and H2 at pressures near 10 Pa with signal-to-noise ratio better than 2 during minutes long observations. This spectrometer is capable of distinguishing traces of numerous isotopomers at partial concentration as low as 1:4000 and can be also used as a medical diagnostic tool. Additionally I will discuss some aspect of our Coherent Raman Spectrometer and its ability to measure molecular kinetics in low temperatures plasmas.

  • Lecture (others)
    Seminar Institut für Strahlenphysik, 01.07.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12255
Publ.-Id: 12255


Ultra-sensitive in-beam g-ray spectroscopy deep underground

Caciolli, A.

Ultra-sensitive in-beam γ-ray spectroscopy studies for nuclear astrophysics are performed at the LUNA (Laboratory for Underground Nuclear Astrophysics) 400 kV accelerator, deep underground in Italy's Gran Sasso laboratory. By virtue of a specially constructed passive shield, the laboratory γ-ray background for Eγ < 3 MeV at LUNA has been reduced to levels comparable to those experienced in dedicated offline underground γ-counting setups. The γ-ray background induced by
an incident α-beam has been studied. The data are used to evaluate the feasibility of sensitive inbeam experiments at LUNA and, by extension, at similar proposed facilities.

  • Lecture (others)
    Seminar Institut für Strahlenphysik, 05.08.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12254
Publ.-Id: 12254


Influence of system and neutron-kinetic parameter variations on an anticipated transient without SCRAM in a PWR

Kliem, S.; Mittag, S.; Rohde, U.; Weiß, F.-P.

The complete failure of the reactor scram system upon request during an operational transient is called anticipated transient without scram (ATWS). According to the German regulatory guidelines, postulated ATWS events have to be analyzed with regard to their consequences on the safety of nuclear power plants.
Since the course of ATWS transients is determined by a strong interaction of the neutron kinetics with the thermal hydraulics of the system, coupled 3D neutron kinetic/thermal hydraulic code systems are adequate tools for the analysis of such transients. The coupled code system DYN3D/ATHLET developed at FZD is applied to the analysis of an ATWS transient. The objective of the present work is to perform a best-estimate analysis with consequent use of a 3D neutron kinetic code (DYN3D) in combination with an advanced thermal hydraulic system code (ATHLET) together with a quantification of differences in the course and the results of transients, which arise from the uncertainties of thermal hydraulic and neutron-physical conditions.
Typically, the complete failure of the main feed water supply is assumed to be the bounding ATWS event with regard to the maximum primary coolant pressure, which can be reached during the transient. The limitation of the coolant pressure is a pre-condition for the integrity of the primary circuit. The situation is aggravated if the main coolant pumps remain in operation.
For this particular transient, the influence of different thermal hydraulic and neutron-physical conditions on the course of the transient was analyzed.
In a number of code runs all systems which have an influence on the course of the transient were varied. These are the auxiliary boration system and the auxiliary feed water supply. Further, the influence of the modeling of the pressurizer safety and relief valves as well as the steam bypass system on the secondary side was assessed. The variation of the pressurizer relief and safety valve behavior has the biggest influence on the primary circuit coolant pressure.
In the second part, two different core loading patterns were generated for the analyses by varying the number of MOX (mixed oxide) fuel assemblies (FA) in the core. The basic core loading contains 64 MOX FA. All these MOX FA were replaced by standard uranium oxide FA. The presence of MOX in the core has a remarkable influence on the reactivity coefficients of the fuel temperature and the moderator density. These two parameters mainly influence the behavior of the coolant pressure in the first part of the transient. It has been demonstrated that the pressure maximum decreases with growing MOX portion in the core.
The maximum pressure determined in the calculations with variation of system and neutron-physical boundary conditions does not reach the allowed limit for the primary circuit.

  • Contribution to proceedings
    17th International Conference on Nuclear Engineering, 12.-16.07.2009, Brussels, Belgium
    Proceedings of the 17th International Conference on Nuclear Engineering, CDROM, paper 75569: ASME
  • Lecture (Conference)
    17th International Conference on Nuclear Engineering, 12.-16.07.2009, Brussels, Belgium

Permalink: https://www.hzdr.de/publications/Publ-12253
Publ.-Id: 12253


Instantaneous Shape Sampling for Calculation of the Electromagnetic Dipole Strength

Zhang, S.

Electromagnetic dipole absorption cross-sections of transitional nuclei with large-amplitude shape fluctuations are calculated in a microscopic way by introducing the concept of Instantaneous Shape Sampling, which is based on the slow shape dynamics as compared to the dipole vibrations. The dipole strength is calculated by means of RPA for the instantaneous shapes, the probability of which is obtained by means of IBA-1. Very good agreement with the experimental absorption cross sections near the nucleon emission threshold is obtained. The dipole strength in this energy region is controlled by the Landau fragmentation.

  • Lecture (others)
    Seminar Institut für Strahlenphysik, 11.08.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12252
Publ.-Id: 12252


Radiation of electromagnetically and strongly interacting plasmas

Mustafa, M.

  • Lecture (others)
    Seminar Institut für Strahlenphysik, 05.09.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12251
Publ.-Id: 12251


Photoneutron measurement of Se-80, La-139: implications for the nucleosynthesis

Makinaga, A.

  • Lecture (others)
    Seminar Institut für Strahlenphysik, 08.09.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12249
Publ.-Id: 12249


phi production in hadronic processes and phi mesons in nuclear matter

Kämpfer, B.

  • Invited lecture (Conferences)
    Donnersberg Workshop 2008 - A1 Collaboration, 31.03.-03.04.2008, Donnersberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-12248
Publ.-Id: 12248


Bremsstrahlung

Kämpfer, B.

Hadron masses; If we would have a theory; Modelling, parametrizing, guessing

  • Lecture (Conference)
    HADES Collaboration Meeting XIX, 05.07.2008, Darmstadt, Deutschland
  • Lecture (others)
    Seminar an der TU München, 28.01.208, München, Deutschland
  • Lecture (Conference)
    Workshop on Virtual Bremsstrahlung and HADES, 12.08.2009, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12247
Publ.-Id: 12247


eta, eta' meson production in NN collisions

Kämpfer, B.

eta, eta' meson production in NN collisions

  • Lecture (Conference)
    Symposium on Meson Physics, 01.-04.10.2008, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-12246
Publ.-Id: 12246


Equation of state above T_c

Kämpfer, B.

  • Invited lecture (Conferences)
    Erice School on Nuclear Physics, 20.-25.09.2008, Erice, Italy

Permalink: https://www.hzdr.de/publications/Publ-12245
Publ.-Id: 12245


Hot 1-2 Loop QCD

Kämpfer, B.

  • Invited lecture (Conferences)
    Workshop of the European SIM Network, 08.-12.09.2008, Villasimius, Italy

Permalink: https://www.hzdr.de/publications/Publ-12244
Publ.-Id: 12244


Chiral Symmetry and Medium-Modifications of Hadrons

Kämpfer, B.

Chiral Symmetry and Medium-Modifications of Hadrons

  • Lecture (Conference)
    Hot and Dense Matter: the next few years, 17.11.2008, Rehovot, Israel

Permalink: https://www.hzdr.de/publications/Publ-12243
Publ.-Id: 12243


Medium-Modifications of Hadrons

Kämpfer, B.

  • Invited lecture (Conferences)
    International Symposium on Heavy Ion Physics 2008 (ISHIP2008), 17.-20.11.2008, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-12242
Publ.-Id: 12242


Naturwissenschaftliches Arbeiten am Forschungszentrum Dresden-Rossendorf.

Bussmann, M.

Der Vortrag soll Schülern einen Einblick in die Arbeit eines Naturwissenschaftlers geben und Ihnen helfen, sich für Ihr anstehendes Studium zu orientieren.

Keywords: physics; natural science; work; student; pupil; school

  • Lecture (others)
    Podiumsdiskussion des Gymnasiums Radeberg, 24.11.2008, Radeberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12241
Publ.-Id: 12241


Lasers and Particle Beams - From the Ultracold to the Ultrafast

Bussmann, M.

The Creation and Manipulation of Particle Beams using Lasers opens new Paths towards compact, ultrabright Radiation Sources. With the advent of high-intensity, ultrashort Laser Sources it has become possible to accelerate Electrons and Ions with table top Laser Systems in the Laboratory. Moreover, Lasers can be used to cool Ion Beams to millikelvin Temperatures. In my talk I will focus on the Study of Laser-Matter Interaction by realistic large-scale Particle Simulations which can give insight into the complex Plasma Phenomena leading to the Creation of ultrabrilliant Particle Beams. I will introduce the numerical Methods used in these Computer Experiments and draw the Connection towards recent and future Experiments planned at FZD and GSI.

Keywords: laser acceleration; electron beam; ion beam; laser cooling; molecular dynamics; simulation; strong coupling; plasma; highly charged ions; particle-in-cell; md; pic

  • Invited lecture (Conferences)
    Seminar "Materialwissenschaft/Materials Science", 16.09.2008, Dresden Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12240
Publ.-Id: 12240


Kompakte Laserbeschleuniger und ihre Anwendungen

Bussmann, M.

In diesem Vortrag werden die Prinzipien der Laserteilchenbeschleunigung sowie wichtige Anwendungen der dabei erzeugten Teilchenstrahlen vorgestellt.

Keywords: laser; particle; acceleration

  • Lecture (others)
    FZD-Vortrag für Besucher des Abendgymnasiums Bautzen, 08.07.2008, Dresden Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12239
Publ.-Id: 12239


Thermal and Chemical Freeze-out in Spectator Fragmentation

Trautmann, W.; Bassini, R.; Begemann-Blaich, M.; Ferrero, A.; Fritz, S.; Gaff-Ejakov, S. J.; Groß, C.; Imme, G.; Iori, I.; Kleinevoß, U.; Kunde, G. J.; Kunze, W. D.; Le Fevre, A.; Lindenstruth, V.; Lukasik, J.; Lynen, U.; Maddalena, V.; Mahi, M.; Möhlenkamp, T.; Moroni, A.; Müller, W. F. J.; Nociforo, C.; Ocker, B.; Odeh, T.; Orth, H.; Petruzzelli, F.; Pochodzalla, J.; Raciti, G.; Riccobene, G.; Romano, F. P.; Rubehn, T.; Saija, A.; Sann, H.; Schnittker, M.; Schüttauf, A.; Schwarz, C.; Seidel, W.; Serfling, V.; Sfienti, C.; Trzcinski, A.; Tucholski, A.; Verde, G.; Wörner, A.; Hongfei, X.; Zwieglinski, B.

Isotope temperatures from double ratios of hydrogen, helium, lithium, beryllium, and carbon isotopic yields, and excited-state temperatures from yield ratios of particle-unstable resonances in 4He, 5Li, and 8Be, were determined for spectator fragmentation, following collisions of 197Au with targets ranging from C to Au at incident energies of 600 and 1000 MeV per nucleon. A deviation of the isotopic from the excited-state temperatures is observed which coincides with the transition from residue formation to multi-fragment production, suggesting a chemical freeze-out prior to thermal freeze-out in bulk disintegrations.

  • Physical Review C 76(2007), 064606

Permalink: https://www.hzdr.de/publications/Publ-12238
Publ.-Id: 12238


Nuclear Astrophysics with real photons at ELBE

Nair, C.; Junghans, A. R.; Erhard, M.; Bemmerer, D.; Beyer, R.; Grosse, E.; Klug, J.; Kosev, K.; Rusev, G.; Schilling, K. D.; Schwengner, R.; Wagner, A.

The neutron deficient p-nuclei thought to be produced in explosive stellar environments through chains of photodisintegration reactions on heavy seed nuclei. The modelling of the nucleosynthesis for the p-nuclei is mainly based on statistical model calculations and the knowledge of the experimental cross sections for the prediction of the p-nuclei abundances is of crucial importance. To forward in this direction we have started and experimental program at the bremsstrahlung facility of the superconducting electron accelerator ELBE of FZ Dresden-Rossendorf . Photodisintegration measurements on the astrophysically relevant p-nuclei 92Mo and 144Sm have been performed via photoactivation technique with bremsstrahlung end-point energies from 10.0 to 16.5 MeV. In particular the (gamma,alpha) reactions of the mentioned nuclei were studied for the first time at different endpoint energies above and close to the threshold. The activation yields from all measurements are compared with calculations using cross sections from recent Hauser-Feshbach models .

Keywords: p-nuclei; photoactivation; bremsstrahlung

  • Invited lecture (Conferences)
    Seminar at the National Superconducting Cyclotron Laboratory, Michigan State University as a JINA (Joint Institute of Nuclear Astrophysics) visitor, 04.08.2008, Michigan, United States of America

Permalink: https://www.hzdr.de/publications/Publ-12237
Publ.-Id: 12237


Photoactivation studies on astrophysically relevant nuclei: measuring techniques for activated samples

Nair, C.; Junghans, A. R.; Erhard, M.; Bemmerer, D.; Degering, D.; Beyer, R.; Grosse, E.; Koehler, M.; Klug, J.; Kosev, K.; Rusev, G.; Schilling, K. D.; Wagner, A.; Schwengner, R.

For studying the neutron deficient p-nuclei experimentally, we have started and experimental program at the bremsstrahlung facility of the superconducting electron accelerator ELBE of FZ Dresden-Rossendorf . Photodisintegration measurements on the astrophysically relevant p-nuclei 92Mo and 144Sm have been performed via photoactivation technique with bremsstrahlung end-point energies from 10.0 to 16.5 MeV. In particular the (gamma,alpha) reactions of the mentioned nuclei were studied for the first time at different endpoint energies above and close to the threshold. The activation yields from all measurements are compared with calculations using cross sections from recent Hauser-Feshbach models. The radioactive decay of irradiated targets with very low counting statistics was studied at the low-background underground laboratory "Felsenkeller" in Dresden.

Keywords: photoactivation; p-nuclei; underground laboratory 'felsenkeller'

  • Poster
    IEEE Nuclear Science Symposium, 20.-24.10.2008, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-12236
Publ.-Id: 12236


Experimental and numerical investigations of natural circulation phenomena in passive safety systems for decay heat removal in large pools

Krepper, E.; Beyer, M.

Modern concepts of nuclear power reactor systems are equipped with passive systems for decay heat removal. Examples are the pool of the emergency condenser (BWR-1000) or the pool of the ESBWR. These systems operate without active influence from outside. The questions arise: How reliable are the based physical mechanisms? Are they understood completely? Are actual models able to describe the phenomena?
In different passive systems the energy is transferred by natural circulation into large pools which are considered as infinite heat sink. The paper deals with experiments and with CFD simulations to investigate the capability of actual CFD codes to describe these phenomena. In the FZ Dresden-Rossendorf at the facility TOPFLOW heating up tests of an emergency condenser were performed. During these tests also the temperature courses on the secondary side of the pool were recorded. The data recording comprises periods starting from single phase liquid until steam on the secondary pool side was found. During these experiments temperature stratification phenomena were observed, which were found in earlier small scale tests. In the paper also these small scale experiments are described. A detailed CFD analysis of these experiments was performed. An explanation of the observed phenomena on the basis of the small scale tests and the CFD simulations is presented.

Keywords: Passive safety systems; Experiments; CFD; natural circulation

  • Contribution to proceedings
    17th International Conference on Nuclear Engineering, ICONE-17, 12.-16.07.2009, Brussels, Belgium
  • Lecture (Conference)
    17th International Conference on Nuclear Engineering, ICONE-17, 12.-16.07.2009, Brussels, Belgium
  • Nuclear Engineering and Design 240(2010), 3170-3177
    DOI: 10.1016/j.nucengdes.2010.05.050
    ISSN: 0029-5493
    Cited 41 times in Scopus

Permalink: https://www.hzdr.de/publications/Publ-12235
Publ.-Id: 12235


Surfing the plasma wake - particle acceleration with laser light

Schramm, U.

Modern short-pulse high-power lasers can, for a few optical cycles, generate electrical field strengths strong enough to accelerate electrons to relativistic energies. Rectifying these fields by means of a laser plasma can lead to acceleration gradients that exceed conventional rf-based technology by many orders of magnitude. Recent results in this field will be discussed as well as potential applications of laser accelerated particle pulses.

Keywords: laser plasma acceleration

  • Invited lecture (Conferences)
    Tata Institute of Fundamental Research, Institute Seminar, 12.1.2009, Mumbai, India
  • Invited lecture (Conferences)
    Institute of plasma research, Seminar, 13.1.2009, Ahmenabad, India

Permalink: https://www.hzdr.de/publications/Publ-12234
Publ.-Id: 12234


Prospects of high intensity laser driven radiation sources

Schramm, U.

Recent development in table-top high-power lasers of the 100 Terawatt class combined with an improved understanding of relativistic laser matter interaction now allows for the discussion of applications of laser accelerated particle beams and secondary radiation sources. In this presentation, an introduction covering the underlying mechanisms will be given followed by a presentation of the novel combined laser-accelerator facility at FZD and its goals as, e.g., laser driven proton oncology.

Keywords: laser particle acceleration; secondary sources

  • Invited lecture (Conferences)
    Eighth DAE-BRNS National Laser Symposium (NLS-08), 07.-10.1.2009, Delhi, India
  • Invited lecture (Conferences)
    Lecture Laser and Neutron Physics Section of BARC, 14.1.2009, Mumbai, India

Permalink: https://www.hzdr.de/publications/Publ-12233
Publ.-Id: 12233


Structural investigations of ZnO thin films grown by reactive pulsed magnetron sputtering at different substrate temperatures

Redondo-Cubero, A.; Vinnichenko, M.; Krause, M.; Gago, R.

Zinc oxide (ZnO) is a promising material for electronic and optical applications [1]. As in the case of other wide bandgap compounds (i.e. GaN) grown in heteroepitaxy conditions, the final electrical properties of the film are affected by its crystal quality. Rutherford backscattering spectrometry (RBS) in channeling mode (RBS/C) is a well proved method to obtain this physical information in such structures, with the additional advantage of in-depth information [2]. In this work, we report RBS/C and Raman characterization of ZnO thin films grown onto (0001) oriented sapphire [3] by reactive pulsed magnetron sputtering at substrate temperatures (Ts) spanning from 22ºC to 550ºC .
Random and RBS/C measurements were performed along the and axes of the wurtzite lattice (P63mc) of ZnO [1] with a 3.035 MeV He+ beam. The sample position was controlled by a 3-axis goniometer. The micro-Raman spectra were collected at an excitation wavelength of 532 nm. The influence of substrate temperature onto low- and high-frequency E2 modes of the resulting film was monitored. The low-frequency E2 mode is associated with the vibration of the heavy Zn sublattice, while the high-frequency E2 mode involves only the oxygen atoms.
Stoichiometry of the oxide layer was determined from the random RBS spectra, which showed a constant composition except for an O-rich interface (associated with Zn in-diffusion). RBS/C angular scans along the axis revealed a progressive enhancement of crystal quality of wurtzite ZnO with substrate temperature, with a <0001> textured growth even for low substrate temperatures (100ºC). The film crystallinity is greatly increased for substrate temperatures above 400ºC, a behaviour also confirmed by Raman measurements. The latter shows significant decrease of the line width which in the case of low-frequency E2 mode at Ts>400 °C approaches and even becomes smaller than the values of reference single crystal sample. Also, the Raman peak positions do not change for the films grown at temperatures above 400°C. Further RBS/C analysis along the oblique axis was carried out to determine the possible influence of strain. The angular scan showed no-shift among different ZnO depths, revealing a non-strained film under the technique limits. From these measurements, it can be concluded that epitaxial ZnO films can be grown by pulsed reactive magnetron sputtering without appreciable strain on sapphire substrates at Ts ~550ºC.

References:

1. Ü. Özgür, Ya. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Dogan, V. Avrutin, S.-J. Cho, and H. Morkoc, J. Appl. Phys. 98, 041301 (2005).
2. L.C. Feldman, J.W. Mayer and S.T. Picraux, Material analysis by ion channeling, NY, Academic Press (1982).
3. M. Vinnichenko, N. Shevchenko, A. Rogozin, R. Grötzschel, A. Mücklich, A. Kolitsch and W. Möller, J. Appl. Phys. 102, 113505 (2007)

Keywords: ZnO; epitaxial growth; reactive pulsed magnetron sputtering

  • Poster
    Charged and neutral particles channeling phenomena (Channeling 2008), 25.10.-01.11.2008, Erice, Italy

Permalink: https://www.hzdr.de/publications/Publ-12232
Publ.-Id: 12232


Experiments on nuclear rotation

Schwengner, R.

Keywords: Nuclear structure; gamma-ray spectroscopy; collective rotation; magnetic rotation; cranking model; shell model

  • Lecture (others)
    Institutsseminar des Instituts für Strahlenphysik, 20.08.2008, Dresden-Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12231
Publ.-Id: 12231


Flavonoids – organic compounds with strong interactions towards uranium

Geipel, G.; Viehweger, K.; Bernhard, G.

Flavonoids belong to a class of secondary plant metabolites. They are most commonly known for their antioxidant activity. Next to chlorophyll flavonoids are the most important group of visible plant pigments.
We studied by use of spectrophotometric techniques the interaction of several flavonoids with uranium. The change in the spectral properties of the flavonoids was used to determine the stability constants. Spectra were evaluated with the factor analysis program Specfit. All spectra of flavonoids show strong change with increasing uranium concentration at constant pH. Stability constants were derived for quercetin, hesperetin, hesperidin, the aglycon of hesperetin. Hesperetin was obtained by hydrolytic splitting of the glycoside hesperidin.
The overall structure Isosbestic points in the absorption spectra indicate a clear interaction between the flavonoids and uranium(VI).
The most strong interaction was found for quercetin. The derived stability constant was assigned to be log β131 = 41.4 ± 0.4 at an ionic strength of 0.1 M for the reaction

UO22+ + C15H5O75- + 3 H+ → UO2C15H8O7 (1)

Hesperidin and hesperetin show much lower stability constants. For example the stability constant for the hesperetin complex at 0.1 M ionic strength was determined to be log β121 = 31.0 ± 0.6.
We assume that the complex formation occur by a ring formation, whereas quercitin forms a 6-membered ring between a phenolic group and the ketone oxygen in the benzopyran-4-one ring whereas hesperidin and hesperetin form 5-membered rings.

Keywords: Uranium; Flavonoids

  • Lecture (Conference)
    Actinides 2009, 12.-17.07.2009, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-12230
Publ.-Id: 12230


An U accumulating plant – a suitable tool for remediation?

Viehweger, K.; Geipel, G.; Bernhard, G.

Abstract. Large areas were disturbed in the southern “Erzgebirge”, Germany, due to former uranium mining activities. Great efforts were done for the remediation and restoration during the last decade. Nevertheless there are some small areas, which are not yet rehabilitated and therefore possess exalted uranium soil contents.
The first step was the evaluation of different former U mining sites. Reconstructed areas contain considerable less amounts of U compared with a leaved stock pile near Johanngeorgenstadt. To get more reliable data on the bioavailability of U in this distinct soil, a sequential chemical soil fractionation procedure was accomplished. The bioavailable U were recovered from the first 3 extraction steps (~ 30 mg*Kg-1).
Fortunately we could identify the well known heavy metal hyperaccumulator Arabidopsis halleri (also known as Cardaminopsis halleri) in this U contaminated area. A basic tool for the characterisation of metal mobility within the soil-plant system is the soil-to-plant transfer factor or accumulation factor. Arabidopsis plants growing on the mining dump achieved accumulation factors around 2.6 for roots and 1.1 for shoots, respectively.
To get more insight in mechanisms underlying plant U uptake and accumulation, a hydroponic grow system under laboratory conditions was developed. The accumulation factors in this system were around 1670 for roots and 625 for shoots. It is obvious that U is clear more bioavailable for plants in hydroponic solution than in the soil from the former mining side.
Despite this enormous U accumulation it is mandatory to evaluate the U tolerance and toxicity under hydroponic conditions. The classical root-elongation test was used for estimation of the tolerance index (TI). Plants growing permanent with U could increase their TI within 7 weeks. Nevertheless U had a negative impact on the plant fitness indicated by a significant decrease of chlorophyll a/b ratio during the growth period. Additionally, spectroscopic measurements of leaves and chlorophyll extracts revealed some disturbances of chlorophyll biosynthesis and proper function of photosystem I, respectively.
We could identify a U accumulating plant, which is able to take up enormous amounts of U in hydroponic solution. To make this plant suitable for remediation processes it is crucial getting a deeper insight in uptake, sequestration and U tolerance pathways. The described hydroponic system could be useful tool for this purpose.

Keywords: Plants; uranium

  • Lecture (Conference)
    Actinides 2009, 12.-17.07.2009, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-12229
Publ.-Id: 12229


Dipole strength in 89Y and 90Zr up to the neutron-separation energy

Schwengner, R.

Keywords: Nuclear structure; nuclear spectroscopy; photon scattering; gamma-ray strength functions; photoabsorption cross section; random-phase approximation

  • Lecture (Conference)
    DPG Frühjahrstagung, 10.-14.03.2008, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-12228
Publ.-Id: 12228


Strength-function measurements

Schwengner, R.

Keywords: Nuclear structure; gamma-ray spectroscopy; photon scattering; strength functions; absorption cross sections; random-phase approximation

  • Lecture (Conference)
    Workshop on Modern Methods Using Fast Neutrons for Research Related to the Transmutation of Nuclear Waste, 13.-15.02.2008, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-12227
Publ.-Id: 12227


NeuLAND MRPC Prototype construction and testing at Electron Linear Accelerator (ELBE)

Bemmerer, D.; Yakorev, D.; Stach, D.; Wagner, A.

Different prototypes of Multigap resistive plate chamber detector (MRPC) for the future NeuLAND detector were built and tested at the ELBE electron beam in FZD. Results and future plans are discussed.

Keywords: MRPC; RPC; Multigap resistive plate chamber; Resistive plate chamber; NeuLAND; FAIR; gas chamber; ELBE

  • Lecture (Conference)
    NeuLAND Working Group Meeting, 24.-26.09.2008, Sinaia, Romania

Permalink: https://www.hzdr.de/publications/Publ-12226
Publ.-Id: 12226


Room-temperature ferromagneticlike behavior in Mn-implanted and postannealed InAs layers deposited by Molecular Beam Epitaxy

González-Arrabal, R.; González, Y.; González, L.; García-Hernández, M.; Munnik, F.; Martín-González, M. S.

We report on the magnetic and structural properties of Ar- and Mn-implanted InAs epitaxial films grown on GaAs (100) by Molecular Beam Epitaxy (MBE) and the effect of Rapid Thermal Annealing (RTA) for 30 s at 750 °C. Channelling Particle Induced X- ray Emission (PIXE) experiments reveal that after Mn implantation almost all Mn atoms are subsbtitutional in the In site of the InAs lattice, like in a diluted magnetic semiconductor (DMS). All of these samples show diamagnetic behavior. However, after RTA treatment the Mn–InAs films exhibit room-temperature magnetism. According to PIXE measurements the Mn atoms are no longer substitutional. When the same set of experiments was performed with Ar as implantation ion, all of the layers present diamagnetism without exception. This indicates that the appearance of room-temperature ferromagneticlike behavior in the Mn–InAs-RTA layer is not related to lattice disorder produced during implantation but to a Mn reaction produced after a short thermal treatment. X-ray diffraction patterns and Rutherford backscattering measurements evidence the segregation of an oxygen-deficient MnO2 phase (nominally MnO1.94) in the Mn–InAs-RTA epitaxial layers which might be the origin of the room-temperature ferromagneticlike response observed.

Keywords: DMS; InMnAs; room temperature magnetism; PIXE; implantation; III-V semiconductors

Permalink: https://www.hzdr.de/publications/Publ-12225
Publ.-Id: 12225


Fast Digitizing and Digital Signal Processing of Detector Signals

Hannaske, R.

A fast-digitizer data acquisition system recently installed at the neutron time-of-flight experiment nELBE, which is located at the superconducting electron accelerator ELBE of Forschungszentrum Dresden-Rossendorf, is tested with two different detector types. Preamplifier signals from a high-purity germanium detector are digitized, stored and finally processed. For a precise determination of the energy of the detected radiation, the moving-window deconvolution algorithm is used to compensate the ballistic deficit and different shaping algorithms are applied. The energy resolution is determined in an experiment with γ-rays from a 22Na source and is compared to the energy resolution achieved with analogously processed signals. On the other hand, signals from the photomultipliers of barium fluoride and plastic scintillation detectors are digitized. These signals have risetimes of a few nanoseconds only. The moment of interaction of the radiation with the detector is determined by methods of digital signal processing. Therefore, different timing algorithms are implemented and tested with data from an experiment at nELBE. The time resolutions achieved with these algorithms are compared to each other as well as to reference values coming from analog signal processing. In addition to these experiments, some properties of the digitizing hardware are measured and a program for the analysis of stored, digitized data is developed. The analysis of the signals shows that the energy resolution achieved with the 10-bit digitizer system used here is not competitive to a 14-bit peak-sensing ADC, although the ballistic deficit can be fully corrected. However, digital methods give better result in sub-ns timing than analog signal processing.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZD-510 2009
    ISSN: 1437-322X
  • Poster
    Graduate Students Seminars, 27.-29.08.2008, Limbach-Oberfrohna, Deutschland
  • Lecture (others)
    IKTP Institutsseminar, 20.11.2008, Dresden, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-12224
Publ.-Id: 12224


Progress of the EPOS project: Gamma-Induced Positron Spectroscopy (GiPS)

Krause-Rehberg, R.; Anwand, W.; Brauer, G.; Butterling, M.; Cowan, T.; Jungmann, M.; Krille, A.; Schwengner, R.; Wagner, A.

Gamma-induced positron generation has been performed using the superconducting electron accelerator ELBE at the Research Center Dresden-Rossendorf.

  • Contribution to proceedings
    The XVth International Conference on Positron Annihilation (ICPA-15), 18.-23.01.2009, Kolkata, India
    Progress of the EPOS Project: Gamma-Induced Positron Spectroscopy (GiPS)
  • Lecture (Conference)
    The XVth International Conference on Positron Annihilation (ICPA-15), 18.-23.01.2009, Kolkata, India
  • Physica Status Solidi (C) 6(2009)11, 2451-2455
    DOI: 10.1002/pssc.200982076
    Cited 8 times in Scopus

Permalink: https://www.hzdr.de/publications/Publ-12223
Publ.-Id: 12223


Structural and electrochemical studies on uranyl(VI) complex with pentadentate Schiff base ligand: A guide to stable uranyl(V)

Takao, K.; Kato, M.; Takao, S.; Nagasawa, A.; Scheinost, A. C.; Bernhard, G.; Hennig, C.; Ikeda, Y.

Uranium(V) is normally instable in solution because of its disproportionation. On the other hand, U(V) has one unpaired electron in the 5f orbital, i.e., 5f1 configuration., and hence chemistry of U(V) is essential for the systematic understanding of actinide chemistry. Previously, we studied electrochemical behavior of U(VI) complexes in non-aqueous solvents, and obtained insight that multidentate ligands may stabilize U(V).1 From this point of view, we have found that two stable U(V) complexes [UVO2(salophen)DMSO]– (salophen = N,N’-disalicylidene-o-phenylenediaminate) and [UVO2(dbm)2DMSO]– (dbm = dibenzoylmethanate) are stable in DMSO.1-4 However, dissociation of a unidentate ligand (L) such as DMSO in [UVO2(salophen)L]– was also observed at lower L concentration. This prevents preparation and observation of a “pure” U(V) complex. On the basis of this knowledge, we obtained a hint that it is better to exclude L from a U(V) complex for its stability. Normally, U(VI) (UO22+) has 3–6 coordination sites in its equatorial plane, and probably most prefers 5 even in a bulky ligand.5 In this study, we selected N,N’-disalicylidenediethylenetriaminate (saldien2–)6 as a pentadentate ligand to satisfy this request. The U(VI) complex with saldien2– was characterized by single crystal X-ray analysis and X-ray absorption fine structure (XAFS) spectroscopy, and its electrochemical behavior in DMSO and N,N-dimethylformamide (DMF) was studied.
The obtained U(VI)-saldien2– complex recrystallized from DMSO was identified as orthorhombic UVIO2(saldien)•DMSO by single crystal X-ray analysis (Fig. 1). It should be noted that all coordination sites in the equatorial plane of UO22+ are occupied by saldien2–, and that any unidentate ligands are excluded as desired. A DMF solution of UVIO2(saldien) shows k3-weighted U LIII-edge EXAFS spectrum similar to that in solid state, indicating that the structure of UVIO2(saldien) remains even in the solution. This is supported by structural parameters from EXAFS curve fit.
Redox behavior of UVIO2(saldien) in DMSO and DMF was studied by using cyclic voltammetry. As a result, quasi-reversible redox waves were observed around E°’ = –1.582 ± 0.005 V vs. Fc/Fc+ (Ep = 0.080–0.170 V at v = 0.010–0.500 V•s–1) in DMSO and E°’ = –1.632 ± 0.003 V vs. Fc/Fc+ (Ep = 0.076–0.141 V at v = 0.010–0.500 V•s–1) in DMF. UV-Vis-NIR absorption spectral changes with the electrochemical reduction of UVIO2(saldien) were recorded using the spectroelectrochemical technique.1,4 The result of the DMSO solution is shown in Fig. 2. From the absorbance change, the electron stoichiometry in the reduction of UVIO2(saldien) was determined as 0.92 in DMSO and 0.82 in DMF using the Nernstian relationship. This quantity close to unity reveals that the following reaction occurs in both solutions.

UVIO2(saldien) + e– = [UVO2(saldien)]–

As we expected, it was found that UVIO2(saldien) without unidentate ligands results in the stable U(V) complex, [UVO2(saldien)]–, in DMSO and DMF. This U(V) species also shows the characteristic absorption bands of U(V) at 620, 700, 830, 1390, and 1890 nm as well as other U(V) species, [UVO2(salophen)DMSO]– and [UVO2(dbm)2DMSO]–.1,4

Keywords: U(V); Structure; Stability; Electrochemistry; Absorption Spectrum

  • Lecture (Conference)
    ACTINIDES 2009, 12.-17.07.2009, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-12222
Publ.-Id: 12222


X-ray absorption fine structures of uranyl(V) complexes in non-aqueous solutions

Takao, K.; Tsushima, S.; Takao, S.; Scheinost, A. C.; Bernhard, G.; Ikeda, Y.; Hennig, C.

Actinide elements at oxidation states +5 and +6 exist as actinyl ions (AnO2n+, An = U, Np, Pu, Am) with typical trans-dioxo arrangement. Among them U(V) is quite instable due to the disproportionation. Recently, U(V) attracts special interest, because this field of actinides has been little explored despite its importance in the nuclear engineering. Especially, the U(V) solution chemistry is quite important in nuclear fuel reprocessing and environmental risks with long-term storage of radioactive waste. Structure of U(V) species is one of the essential parts of its chemistry. Actually, several crystal structures of U(V) compounds were reported previously. On the other hand, structure of U(V) species in solutions are not investigated so far except for EXAFS studies of UVO2(CO3)35– in an aqueous system.1,2 In this study, we report the structure determination of two U(V) complexes, [UVO2(salophen)DMSO]– (1V, salophen = N,N’-disalicylidene-o-phenylenediaminate) and [UVO2(dbm)2DMSO]– (2V, dbm = dibenzoylmethanate), in DMSO.3-6
The k3-weighted EXAFS spectra of 1V, 1VI, 2V, and 2VI and their Fourier transforms (FTs) are shown in Fig. 1. The structures of these U(V) and U(VI) complexes in DMSO solutions were determined by the EXAFS curve fits on the basis of the molecular structures of 1VI and 2VI from single crystal X-ray analyses.5,6 The best fit curve for each EXAFS spectrum and FTs are also displayed in Fig. 1. As a result, the interatomic distances between U and axial O (Oax) were determined as 1.84 Å for 1V and 1.85 Å for 2V, which are comparable with other U(V) complexes in crystal structures. On the other hand, the U–Oax distances of 1VI and 2VI are evaluated 1.80 and 1.78 Å, respectively. The lengthening of the U–Oax distance of 0.04–0.07 Å with the reduction of U(VI) to U(V) corroborates our previous estimation from IR spectra for 1V/1VI and 2V/2VI couples.4,5 The interatomic distances between U and coordinating atoms of salophen2– and dbm– are also lengthened 0.04–0.14 Å with the reduction from U(VI) to U(V). It should be noted that a long interatomic distance between U and O of DMSO (U–ODMSO; ca. 2.90 Å) was found in both 1V and 2V. Although these U–ODMSO distances seem unusual, those are still shorter than the sum of van der Waals radii of U and O (1.86 + 1.52 = 3.38 Å),9 indicating that such a long U–ODMSO interaction is still possible. The long U–ODMSO distance implies the very weak coordination of DMSO to U(V) in 1V and 2V. Actually, we previously observed that 1V may release DMSO at lower DMSO concentration.1 The week coordination of the unidentate ligand (L) such as DMSO might be a reason why U(V) solvates (UVO2(L)5+) is instable even in L,10,11 and provides an insight that strong multidentate ligand is required for stabilization of U(V).

Keywords: XAFS; U(V); Solution Chemistry; Structure; Stability

Related publications

  • Lecture (Conference)
    Actinides 2009, 12.-17.07.2009, San Francisco, USA
  • Inorganic Chemistry 48(2009)20, 9602-9604

Permalink: https://www.hzdr.de/publications/Publ-12221
Publ.-Id: 12221


The time-of-flight setup for inelastic scattering measurements at nELBE

Beyer, R.; Grosse, E.; Hannaske, R.; Junghans, A. R.; Matic, A.; Nolte, R.; Schilling, K.-D.; Schwengner, R.; Wagner, A.

At the nELBE facility at Forschungszentrum Dresden-Rossendorf fast neutrons with kinetic energies of 0.1 to 10 MeV will be used to deliver nuclear data on neutron induced reactions.
First experiments on neutron scattering on Fe-56 were performed using a double time-of-flight setup. This setup is based on proton recoil detectors and an array of 42 Barium-Flouride crystals. Emitted photons and neutrons are detected in coincidence to determine the inelastic neutron scattering cross section.

Keywords: nELBE; inelastic neutron scattering; double time-of-flight

  • Lecture (Conference)
    EFNUDAT progress and general assembly meeting, 01.-03.10.2008, Uppsala, Sverige

Permalink: https://www.hzdr.de/publications/Publ-12220
Publ.-Id: 12220


Transmutation with fast neutrons

Beyer, R.

Nuclear Transmutation is one way to reduce the amount nuclear waste that has to be disposed for hundred thousands of years. The idea is to convert long lived isotopes in to short lived ones by nuclear interaction with fast neutrons. This procedure will take place in future types of nuclear facilities, like generation IV reactors or accelerator driven systems. At the neutron time-of-flight setup nELBE at Forschungszentrum Dresden-Rossendorf experiments will be performed to obtain neutron induced reaction cross sections which are necessary to develop and construct such facilities.

Keywords: nuclear transmutation; nELBE; neutron time-of-flight

  • Lecture (others)
    3rd FZD Graduate Students Seminar, 27.-29.08.2008, Limbach-Oberfrohna, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12219
Publ.-Id: 12219


Experimental investigation of the residues produced in the 136Xe+Pb and 124Xe+Pb fragmentation reactions at 1A GeV

Henzlova, D.; Schmidt, K. H.; Ricciardi, M. V.; Kelic, A.; Henzl, V.; Napolitani, P.; Audouin, L.; Benlliure, J.; Boudard, A.; Casarejos, E.; Ducret, J. E.; Enqvist, T.; Heinz, A.; Junghans, A. R.; Jurado, B.; Krasa, A.; Kurtukian, T.; Leray, S.; Ordonez, M. F.; Pereira, J.; Pleskac, R.; Rejmund, F.; Schmitt, C.; Stephan, C.; Tassan-Got, L.; Villagrasa, C.; Volant, C.; Wagner, A.; Yordanov, O.

The nuclide cross sections and longitudinal velocity distributions of residues produced in the reactions of 136Xe and 124Xe at 1A GeV in a lead target were measured at the high-resolution magnetic spectrometer, the fragment separator (FRS) of GSI. The data cover a broad range of isotopes of the elements between Z=3 and Z=56 for 136Xe and between Z=5 and Z=55 for 124Xe, reaching down to cross sections of a few microbarns. The velocity distributions exhibit a Gaussian shape for masses above A=20, while more complex behavior is observed for lighter masses. The isotopic distributions for both reactions preserve a memory on the projectile N/Z ratio over the whole residue mass range.

Keywords: cross section residue high-resolution magnetic spectrometer fragment separator FRS GSI

Permalink: https://www.hzdr.de/publications/Publ-12218
Publ.-Id: 12218


Ultra-low-energy ion-beam-synthesis of Ge nanocrystals in thin ALD Al2O3 layers for memory applications

Dimitrakis, P.; Mouti, A.; Bonafos, C.; Schamm, S.; Ben Assayag, G.; Ioannou, V.; Schmidt, B.; Becker, J.; Normand, P.

Structural and electrical properties of ALD-grown 5 and 7 nm-thick Al2O3 layers before and after implantation of Ge ions (1 keV, 0.5–1 x 1016 cm-2) and thermal annealing at temperatures in the 700–1050°C range are reported. Transmission Electron Microscopy reveals the development of a 1 nm-thick SiO2-rich layer at the Al2O3/Si substrate interface as well as the formation of Ge nanocrystals with a mean diameter of ca. 5 nm inside the implanted Al2O3 layers after annealing at 800 °C for 20 min. Electrical measurements performed on metal–insulator–semiconductor capacitors using Ge-implanted and annealed Al2O3 layers reveal charge storage at low-electric fields mainly due to location of the Ge nanocrystals at a tunnelling distance from the substrate and their spatial dispersion inside the Al2O3 layers.

Keywords: Ion implantation; Ge nanocrystals; nanocrystal memory

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Permalink: https://www.hzdr.de/publications/Publ-12217
Publ.-Id: 12217


Prospects of Laser Cooling of Ion Beams at CSR

Bussmann, M.

This talk focuses on the prospects of laser cooling of ion beams at the storage rings CSRe and CSRm located at the Institute of Modern Physics in Lanzhou, China.

Keywords: laser cooling; ion beams; relativistic energies; storage ring; CSR; CSRe; CSRm

  • Invited lecture (Conferences)
    Seminar of the Institute of Modern Physics, CAS, 19.11.2008, Lanzhou, China

Permalink: https://www.hzdr.de/publications/Publ-12216
Publ.-Id: 12216


Laser Cooling of Ion Beams at PALLAS and ESR

Bussmann, M.

Recent experiments at the ESR storage ring at GSI have shown that it is possible to cool relativistics ions beams using table top laser systems. We present results from these experiments including precision laser spectroscopy measurements of the 2S1/2-2P1/2 and 2S1/2-2P3/2 transition in C3+. We compare the prospects of future laser cooling experiments at GSI and FAIR with experiments on crystalline ion beams caried out at the table top storage ring PALLAS.

Keywords: laser; laser cooling; ion beam; storage ring; PALLAS; ESR; GSI; C3+; laser spectroscopy; VUV; x-ray

  • Invited lecture (Conferences)
    Seminar of the Institute of Modern Physics, CAS, 18.11.2008, Lanzhou, China

Permalink: https://www.hzdr.de/publications/Publ-12215
Publ.-Id: 12215


Laser Cooling of Ions in Traps and Storage Rings

Bussmann, M.

Laser Cooling of Ions is an established technique for providing ultracold ions for precision experiments in traps. In this talk I will present the prospects of laser cooling of ion beams in storage rings, showing both the similarities and differences of this new cooling scheme compared to traditional in-trap laser cooling.

Keywords: laser cooling; ion beam; PALLAS; Paul trap; storage ring; ion; laser

  • Invited lecture (Conferences)
    Seminar of the Institute for Modern Physics, CAS, 17.11.2008, Lanzhou, China

Permalink: https://www.hzdr.de/publications/Publ-12214
Publ.-Id: 12214


Cooling of Ions

Bussmann, M.

Measuring the properties of heavy ions with high accuracy demands precise control of their
motional degrees of freedom in an isolated environment. Such a situation can be achieved by
combining modern cooling techniques with new means to trap and store the ions of interest. The first lecture will provide an overview of current state-of-the-art techniques to trap and store ions, including a comparison of the ion dynamics in the two most common types of ion traps, Penning and Paul traps, with the ion dynamics in storage rings.
This overview will be followed by an introduction to some widely used cooling techniques, focusing on sympathetic cooling and laser cooling. Based on this introduction the second lecture will give inside to current high accuracy experiments with ions in traps and storage rings with emphasis on sympathetic cooling of highly charged ions and laser cooling of ion beams. I will conclude with an outlook on future high accuracy measurements of heavy, unstable nuclei and accurate laser X-ray spectroscopy of Li-like and Na-like electronic transitions in heavy ions at future storage ring facilities.

Keywords: laser cooling; Paul trap; Penning trap; storage ring; ion beam; crystalline ion beam; phase transition; laser spectroscopy; x-ray; VUV

  • Invited lecture (Conferences)
    International WE-Heraeus Summer School: Atomic Properties of the Heaviest Elements, 24.08.-06.09.2008, Wittenberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12213
Publ.-Id: 12213


Laseraktivitäten am FZD in Rossendorf

Bussmann, M.

In this talk we present the scientific program of the Laser Particle Acceleration Group and the status of the DRACO laser system.

Keywords: laser; particle acceleration; ion beam; electron beam; DRACO

  • Invited lecture (Conferences)
    Gruppenseminar des Lehrstuhls für Experimentelle Kernphysik der Ludwig-Maximilians-Universität München, 16.05.2008, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12212
Publ.-Id: 12212


Laser-Cooling of Ion Beams at Relativistic Energies

Bussmann, M.

Recent Experiments at the Experimental Storage Ring at GSI have seen the successful application of laser cooling of bunched C3+ ion beams at relativistic energies of 122 MeV per nucleon. Major results of these experiments include the attainment of space-charge dominated beams, evidence for collective ion motion, three-dimensional cold beams and precision laser spectroscopy in the deep UV spectral range. The talk will review these results, showing that measurements of important beam properties such as momentum spread and bunch length are currently limited by the beam diagnostics available. Several solutions to better resolve the beam momentum spread will be presented, which can be easily included in future experiments. These experimental efforts are supplemented by extensive computer simulations of laser-cooled bunched ion beams which can provide insight into the ion-dynamics on the single-particle level. The talk will conclude with an outlook to the exciting possibilities for laser cooling of ion beams at FAIR.

Keywords: laser cooling; ion beam; crystalline beam; FAIR; ESR; GSI; laser spectroscopy; VUV; X-ray

  • Invited lecture (Conferences)
    Atomphysik-Seminar, 14.05.2008, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12211
Publ.-Id: 12211


Commissioning of the double Penning trap system MLLTRAP

Kolhinen, V. S.; Bussmann, M.; Gartzke, E.; Habs, D.; Neumayr, J. B.; Schürmann, C.; Szerypo, J.; Thirolf, P. G.

A cylindrical double Penning trap system has been installed and commissioned at the Maier-Leibnitz-Laboratory (MLL) in Garching. This trap system has been designed to isobarically purify low-energy ion beams and perform highly accurate mass measurements. Technical details of the device and the first results of the commissioning measurements will be presented. The mass resolving power achieved in the first trap for 119Rb ions is R=139(2)×103, while a relative mass uncertainty of δm/m=2.9×10−8 was reached with the second trap (no analysis of systematic uncertainties included) when using 87Rb as a reference ion for 85Rb.

Keywords: Penning trap; Mass measurement; Mass separation; Buffer gas cooling

Permalink: https://www.hzdr.de/publications/Publ-12210
Publ.-Id: 12210


Criteria for system solution in Particle Therapy Positron Emission Tomography

Shakirin, G.

Image processing in Particle Therapy Positron Emission Tomography (PT-PET) differs significantly from one in conventional nuclear medicine PET. The evaluation of dose delivery in particle therapy requires specific tasks to be solved during the analysis of the PT-PET images. Therefore, dedicated image quality criteria have been developed for PT-PET. These criteria together with a 3D configuration tool allow to construct an optimum PT-PET system for a given particle therapy facility and PET components supplier.

Keywords: in-beam PET; radiation therapy

  • Invited lecture (Conferences)
    Conference on Clinical and Experimental Research in Radiation Oncology (CERRO), 17.-24.01.2009, Les Menuires, France

Permalink: https://www.hzdr.de/publications/Publ-12209
Publ.-Id: 12209


Ion Bombardment of Solids - unified simulation of damage formation and thermally activated relaxation

Liedke, B.; Heinig, K.-H.; Facsko, S.; Möller, W.

Till now, damage formation and thermally activated relaxation are calculated by different atomistic methods like Binary Collision Approximation (BCA, TRIM code) and kinetic Monte Carlo (kMC), respectively. However, frequently damage formation and relaxation happens simultaneously. Molecular Dynamics (MD), which treats both processes, can not describe them on experimental spatiotemporal scales due to insufficient computer power. Here, an unified TRIM-kMC simulation method will be presented and applied to ion-induced nanopatterning of surfaces as well as mixing and phase separation of intermetallic compounds.

Keywords: ion implantation; TRIM; Kinetic Monte-Carlo; unified description; nanopatterninig; interface mixing; phase separation

  • Lecture (others)
    Seminar at MFA of KFKI of Budapest, 11.11.2008, Budapest, Hungary

Permalink: https://www.hzdr.de/publications/Publ-12208
Publ.-Id: 12208


Simulation of defects and composition after irradiation of ultrathin Pt/Co/Pt film with Ga+

Liedke, B.; Facsko, S.; Fassbender, J.; Jaworowicz, J.; Ferre, J.; Maziewski, A.; Vernier, N.; Möller, W.

Spin reorientation transition from in-plane to out-of-plane state has been observed experimentally in Pt/tCo/Pt film (tCo=3nm) after ion irradiation with 30 keV Ga+ [1]. Theoretical studies of the collision intermixing and defects creation processes of irradiated are presented. By means of TRIDYN simulations the dependence of composition and sputtering yield on ion fluence in the range of 1014 to 5 · 1016 ions/cm2 is elucidated. Simulations show that ion fluence plays non-neglectable role in case of erosion and intermixing of the interface (which likely gives a certain strain to the system), which give rise to the new phenomena, the so-called swelling effect. On the other hand the swelling effect can relax the strain in the film and give rise to an increase of the magnetic anisotropy. However, the strain relaxation can be strongly non-uniform on the full square area providing a mixture of patches with in-plane or out-of-plane anisotropy. The presence of relatively large and quasi-uniform perpendicular anisotropy partially comes from peculiar strain states at the interface. Simulated compositions are compared with experimentally observed irradiation induced phenomena.

Keywords: TRIDYN; implantation; Monte-Carlo simulation; intermixing; swelling

  • Poster
    PHYSICS OF MAGNETISM 2008, 24.-27.06.2008, Poznan, Poland

Permalink: https://www.hzdr.de/publications/Publ-12206
Publ.-Id: 12206


Fluorescence properties of a uranyl(V)-carbonate species [U(V)O2(CO3)3]5− at low temperature

Großmann, K.; Arnold, T.; Ikeda, A.; Steudtner, R.; Geipel, G.; Bernhard, G.

Fluorescence properties of a uranyl(V)-carbonate species in solution are reported for the first time. The fluorescence characteristics of the stable aqueous uranyl(V)-carbonate complex [U(V)O2(CO3)3]5− was determined in a frozen solution (T = 153 K) of 0.5mM uranium and 1.5M Na2CO3 at pH 11.8 by time resolved laser-induced fluorescence spectroscopy (TRLFS). Two different wavelengths of 255nm and 408 nm, respectivelywere used to independently of each other excite the uranyl(V)-carbonate species. The resulting U(V) fluorescence emission bandswere detected between 380nmand 440 nm, with a maxima at 404.7nm (excitation with 255 nm) and 413.3nm (excitation with 408 nm), respectively. It was found that by using an excitation wavelength of 255nm the corresponding extinction coefficient was much higher and the fluorescence spectrum better structured than the ones excited at 408 nm. The fluorescence lifetime of the uranyl(V)-carbonate species was determined at 153K as 120s. TRLFS investigations at room temperature, however, showed no fluorescence signal at all.

Keywords: U(V); Uranyl(V)-carbonate; Fluorescence; Laser fluorescence spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-12205
Publ.-Id: 12205


Boltwoodite [K(UO2)(SiO3OH)(H2O)1.5] and Compreignacite K2[(UO2)3O2(OH)3]2 • 7 H2O Characterized by Laser Fluorescence Spectroscopy

Arnold, T.; Baumann, N.

Synthetically prepared boltwoodite and compreignacite were characterized with time-resolved laser-induced fluorescence spectroscopy (TRLFS). The obtained TRLFS emission spectra of both synthesized uranium minerals differ from each other in their positions of the vibronic peak maxima and in their fluorescence lifetimes. Also, the shapes of the spectra and their respective intensities are different. The TRLFS–spectrum of boltwoodite showed well-resolved sharp vibronic peaks at 485.1, 501.5, 521.2, 543.0, 567.4, and 591.4 nm with deep notches between them and compreignacite is characterized by two broad peaks with various shoulders. Here five emission bands were identified at 500.7, 516.1, 532.4, 554.3, and 579.6 nm. The shape of the TRLFS spectra of compreignacite is typical for uranium in a hydroxide coordination environment. For both minerals two fluorescence lifetimes were extracted. The two species of boltwoodite and compreignacite, respectively, showed the same positions of the peak maxima showing that the coordination environments are similar, but differ in the chemistry and number of possible quenchers, e.g. water molecules and hydroxide groups. For boltwoodite fluorescence lifetimes of 382 and 2130 ns, and for compreignacite shorter ones of 202 and 914 ns, respectively, were determined. The spectroscopic signatures of the two uranyl minerals reported here could be useful for identifying uranyl(VI) mineral species as colloids, as thin coatings on minerals, as minor component in soils, or as alteration products of nuclear waste.

Keywords: Boltwoodite; Compreignacite; Uranium(VI); Time-resolved Laser-induced Fluorescence Spectroscopy (TRLFS)

Permalink: https://www.hzdr.de/publications/Publ-12204
Publ.-Id: 12204


Precision measurements of the reconstructed image resolution for different PET and PET/CT scanners with the NEMA phantom.

Mix, M.; Weber, W. A.; van den Hoff, J.

Objectives:

For multicenter PET studies robust techniques are required to measure the reconstructed image resolution of different PET systems. The aim of this study was to determine the reconstructed image resolution (RIR) using a NEMA phantom as a function of count statistics and image contrast.

Methods:

Measurements with the NEMA whole-body (WB) phantom at 7 scanner systems at different signal-to-noise levels and different target to background (T/BG) ratios were analyzed. Images were reconstructed iteratively using the default scanner WB reconstruction protocol. For each sphere, the image data were transformed to spherical coordinates relative to the center of the respective sphere yielding radial profiles. The RIR was then determined by fitting the convolution of a Gaussian point spread function with the object function (sphere+wall+BG) to these profiles.

Results:

With the presented procedure the RIR can be determined easily with a high statistical accuracy (average accuracy in 593 spheres 2.8+/-0.1%). For all scanners the RIR was distinctly lower than the scanner resolution according to NEMA. Image resolution was independent from counting statistic but deteriorated with decreasing target to BG (T/BG) ratios. The average resolution degradation in relation to the background free case was ~30% for a 6:1 T/BG ratio, over 50% for 3:1 and ~80% for 1.5:1. The degradation of RIR with decreasing contrast differed between the studied scanners.

Conclusions:

The presented algorithm is a robust approach for precise measuring reconstructed image resolution (RIR). The marked contrast ratio dependence of the RIR should be considered for quantitative PET studies in a multicenter setting.

  • Lecture (Conference)
    SNM 56th Annual Meeting, 13.-17.06.2009, Toronto, Canada

Permalink: https://www.hzdr.de/publications/Publ-12203
Publ.-Id: 12203


Diffusion suppression etc. during electrical activation in implanted Ge and Si-SOI

Skorupa, W.

Recent results on diffusion suppression, electrical activation and related problems in implanted Ge and Si-SOI were reported. A prospect regarding millisecond thermal processing of high k dielectrics was given.

  • Invited lecture (Conferences)
    24. Nutzertreffen Kurzzeittemperung, 23.10.2008, Dortmund, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12202
Publ.-Id: 12202


Rare Earth Ion Beam Processing for Silicon Photonics

Skorupa, W.; Rebohle, L.; Prucnal, S.; Cherkouk, C.; Helm, M.

Combining silicon-based electronic circuits with optoelectronic functionality is one of the key challenges for the future semiconductor technology. Such work must not only be devoted to the “telecommunication” wavelength of 1.54 µm because there are much more applications requiring light sources from the UV to IR wavelength range. In our work we employed ion beam processing to embed different rare earth (RE) luminescent centers (Gd, Ce, Tm, Tb, Eu, Er) into the silicon dioxide layer of purpose-designed Metal-Oxide-Silicon-based Light Emitting Devices (MOSLEDs) with advanced electrical performance. Efficient electroluminescence was obtained from UV to infrared with a transparent top electrode made of indium-tin oxide. Several developments for improving the device stability will be proposed related to charge compensation and the elimination of defects in SiO2. The electrical and electroluminescence properties of these devices are discussed and evaluated in respect of possible applications for biosensing applications. As an example our recent effort to detect estrogens in drinking water will be discussed.

  • Invited lecture (Conferences)
    2008 MRS Fall Meeting, Symposium D: Rare-Earth Doping of Advanced Materials for Photonic Applications, 01.-05.12.2008, Boston MA, USA

Permalink: https://www.hzdr.de/publications/Publ-12201
Publ.-Id: 12201


Casting experiments and materials studies for restoring lead pipes in historical organs

Skorupa, W.; Rossner, M.; Werner, H.; Eule, A.-C.; Schucknecht, T.; Rafaja, D.; Hausmann, U.; Wegscheider, K.

We will report on a new casting technique basing on old recipes from the 17. and 18. century to produce new pipes approaching the quality of the old ones. Materials studies of old and new metal probes were performed by metallography and other methods. Different casting variants as well as the influence of hammering the casted metal plates onto the microstructure were investigated. In the course of these studies special consideration was devoted to the restoration projects at Borgentreich/Westfalen (Eule) and Stralsund/Vorpommern (Wegscheider).

  • Invited lecture (Conferences)
    25. Congress of the International Society of Organbuilders (ISO), 21.-26.09.2008, Danzig-Stralsund, Polen-Deutschland

Permalink: https://www.hzdr.de/publications/Publ-12200
Publ.-Id: 12200


A short review on Flash Lamp Annealing

Skorupa, W.

A short review on Flash Lamp Annealing

  • Invited lecture (Conferences)
    Industrie-Projekttreffen mit BASF und Zentrum für Sonnenenergie-& Wasserstoff-Forschung Baden-Württemberg (ZSW), 18.11.2008, Stuttgart, Germany

Permalink: https://www.hzdr.de/publications/Publ-12199
Publ.-Id: 12199


Old Physics for Modern Nanotechnologies - Studies of Nano-Scale Ordering by Simulations and Experiments

Heinig, K.-H.

Shaping and ordering of nanostructures is mandatory for many applications. However, top-down approaches like electron lithography have their limits and are expensive. Here, we present some bottom-up approaches like self-ordering and alignment at interfaces, which are driven by well-known thermodynamic processes like phase separation and surface energy minimization. The reaction pathways are studied by atomistic computer simulations and verified by experiments. The relevance for some applications, e.g. FLASH memories and Si-based light emitters, will be demonstrated.

Keywords: nanostructure formation; nanostructure shaping; ion irradiation; self-organisation; kinetic Monte Carlo simulation

  • Invited lecture (Conferences)
    Fizikai és Anyagtudományi Kutatóintézet Tanácstermében, 21.05.2008, Budapest, Hungary

Permalink: https://www.hzdr.de/publications/Publ-12198
Publ.-Id: 12198


Spontaneous formation of regular nanopattern on surfaces during thin film deposion and ion beam erosion

Heinig, K.-H.

Ion erosion of surface results under specific conditions to formation of dot-like or ripple-like nanopattern. These self-organized nanopattern are promising for different nanotechnologies. The presentation gives an overview of experimental techniques and results as well theoretical models and simulation work.

Keywords: ion erosion; nanopattern; experiments; theory; kinteic Monte Carlo simulations

  • Invited lecture (Conferences)
    Winter School on Nanoelectronic and Nanophotonics, 19.-25.01.2009, Ankara, Turkey

Permalink: https://www.hzdr.de/publications/Publ-12197
Publ.-Id: 12197


Formation of nanodots, nanowires, wormholes etc. driven by capillary forces-reaction pathways predicted by atomistic simulations.

Heinig, K.-H.

The use of ion irradiation methods for bulk nanostructure formation will be presented. The focus will be on the help of cappilary forces to find controllable reaction pathways for nanostructure formation. These pathways are demonstrated by kinetic Monte Carlo simulations

Keywords: nanostructure formation; ion implantation; nanodots; nanowires; kinetic Monte Carlo simulation

  • Invited lecture (Conferences)
    Winter School on Nanoelectronic and Nanophotonics, 19.-25.01.2009, Ankara, Turkey

Permalink: https://www.hzdr.de/publications/Publ-12196
Publ.-Id: 12196


Fundamentals of Ion Beam Synthesis of Nanostructures

Heinig, K.-H.

Fundamentals of ion-beam-solid-interactions will be presented. An overview over ion implantation techniques will be given. Range profile calculations, defect creation processes as well as annealing method will be treated. Finally, methods of ion beam synthesis based on phase separation of implanted species will be discussed.

Keywords: ion implantation; ion beam synthesis; kinetic Monte Carlo simulation; TRIM; lecture

  • Invited lecture (Conferences)
    Winter School on Nanoelectronic and Nanophotonics, 19.-25.01.2009, Ankara, Turkey

Permalink: https://www.hzdr.de/publications/Publ-12195
Publ.-Id: 12195


Novel LEFET with two self-aligned Si nanocrystal layers

Heinig, K.-H.; Beyer, V.; Schmidt, B.; Stegemann, K.-H.

A light emitting feld-effect transistor (LEFET) which is based on self-aligned silicon nanocrystal delta-layers in the gate oxide of a nMOSFET device with an active gate area of 20x20 µm2 is demonstrated. Two layers of Si NCs were prepared in the gate oxide close to both Si/SiO2 interfaces by ion irradiation through the 50 nm poly-Si/15 nm SiO2/(001)Si substrate LEFET stack and subsequent annealing. An AC voltage was applied to the gate in order to inject charges of both polarities in the Si NCs. AC voltage and frequency dependent electroluminescence spectra were recorded as a function of the annealing conditions.

Keywords: nanotechnology; ion irradiation; electroluminescence; field effect transistor; modelling; kinetic Monte Carlo simulation

  • Invited lecture (Conferences)
    Workshop on Nanoelectronics and Nanophotoniocs, 26.-28.01.2009, Ankara, Turkey

Permalink: https://www.hzdr.de/publications/Publ-12194
Publ.-Id: 12194


Mapping of two-plus-one-dimensional KPZ growth onto driven lattice gas model of dimers

Ódor, G.; Liedke, B.; Heinig, K.-H.

We show that a 2+1 dimensional discrete surface growth model exhibiting KPZ class scaling can be mapped onto a two dimensional conserved lattice gas model of directed dimers. In case of KPZ height anisotropy the dimers follow driven diffusive motion. We confirm by numerical simulations that the scaling exponents of the dimer model are in agreement with those of the 2+1 dimensional KPZ class. This opens up the possibility of analyzing growth models via reaction-diffusion models, which allow much more efficient computer simulations.

Keywords: KPZ class scaling; lattice gas model; Monte Carlo simulation

  • Poster
    International Workshop on Nonequilibrium Nanostructures, 01.-06.12.2008, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-12193
Publ.-Id: 12193


Swift-heavy-ion-induced shaping of spherical nanoparticles into disks and rods

Schmidt, B.; Heinig, K.-H.; Mücklich, A.; Akhmadaliev, C.

The swift heavy ion induced deformation of SiO2 and metal nanoparticles were studied intensively in the last years. Recently, we reported on ion beam shaping of Ge nanospheres [1]. Surprisingly, Ge nanospheres in silica form oblate ellipsoids, what is opposite to prolate ellipsoids found for metal spheres.
This presentation reports on the experimental features of the shaping of Ge nanospheres and our theoretical search for the shaping mechanism(s). A stack of alternating Ge and SiO2 layers was sputtered on an oxidized Si wafer. The Ge layer thickness varied from 2.5 to 7.5 nm with 100 nm SiO2 in-between. Heating this layer stack to 950 °C for 300 s transformed each Ge layer into a layer of Ge nanospheres. With growing Ge layer thickness the mean diameter increases from 10 to 40 nm. After irradiation with (1-10)x1014 I7+cm-2 at 38 MeV, cross-section TEM images of as-prepared and irradiated samples showed that the largest Ge nanospheres kept spherical, whereas medium-size Ge spheres became oblates, and smaller ones shaped diamond-like. The different shaping of metal and semiconducting spheres is explained by their differences in thermodynamic properties.

Keywords: swift heavy ions; irradiation; nanostructure; shaping; modelling; simulation

  • Lecture (Conference)
    16th International conference on Ion Beam Modification of Materials (IBMM 08), 31.08.-05.09.2008, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-12192
Publ.-Id: 12192


Surface modification using Binary Collision Approximation and 3D Lattice Kinetic Monte Carlo simulation

Liedke, B.; Facsko, S.; Heinig, K.-H.; Möller, W.

Periodic pattern formation during low energetic ion-beam bombardment has been observed for many different surfaces. Two different kinds of approaches have been used to explain and simulate the pattern formation and evolution in time: (i) continuum theories, which are based on the Bradley and Harper model, and (ii) Kinetic Monte Carlo method (KMC) for surface diffusion coupled with Sigmund’s theory to incorporate sputtering. Both of them have been developed in terms of surface processes induced by ion sputtering, although without including microscopic effects, i.e. defect creation and diffusion of vacancies in the bulk.
We present a new approach using Binary Collision Approximation for simulating collision cascades during ion bombardment coupled with 3D Lattice KMC Ising model, to simulate surface and bulk diffusion of defects and vacancies. The combination of these two models gives an advantage on the simple Gaussian approximation of the deposited energy proposed by Sigmund, because it includes detailed collision cascades into the discrete lattice system. In addition, information about the relation between atomistic features, i.e. vacancies and defects creation and annihilation, sputtering yield distribution, bulk and surface diffusion, and pattern formation is obtained. We will present the time evolution of surface morphology for different initial system parameters and compare it with continuum theories. Moreover, the influence of substrate temperature on the pattern evolution is studied.

Keywords: ion irradiation; collision cascade; binary collision approximation; kinetic Monte Carlo; surface pattern; nanostructure

  • Poster
    16th International Conference on Ion Beam Modification of Materials (IBMM 08), 31.08.-05.09.2008, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-12191
Publ.-Id: 12191


Surface patterning by ion erosion – atomistic computer simulations

Heinig, K.-H.; Numazawa, S.

Surface ripple formation by low-energy ion erosion is a far-from-equilibrium process for which standard thermodynamics have to be put into question. Thus, an effective negative surface tension can be found under low-energy ion irradiation of surfaces [1] and ion beam mixing of interfaces [2]. This negative surface tension tends to increase the surface by inverse Ostwald ripening or surface patterning [2]. Here, for very low energy ion irradiation of surfaces patterning is predicted to evolve even without sputtering, resulting solely from defect creation and annihilation kinetics. Self-organisation of surface pattern by irradiation with ions in the region of keV-energies is strongly affected by sputtering, but even in that case far-from-equilibrium surface defect kinetic can play a major role. This will be underlined by a theoretical study of the temperature-dependent ripple formation found recently on Ag(110) [3]. In agreement with the experiment, kinetic Monte-Carlo calculations show that under ion irradiation at low temperatures (111) facets become unstable, resulting in a ripple rotation from (111) facets to (100) facets.

Keywords: ion erosion; surface pattern; nanostructure; modelling; kinetic Monte Carlo

  • Poster
    16th International Conference on Ion Beam Modification of Materials (IBMM 08), 31.08.-05.09.2008, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-12190
Publ.-Id: 12190


Nanocomposite Au-SiO2 thin film deposition by co-sputtering: comparison of experiments with atomistic simulations

Khan, S.; Heinig, K.-H.; Avasthi, D.

Fast atom beam co-sputtering has been found to be an excellent technique for producing metal nanoclusters in variety of matrices without the need of any post-deposition annealing. The films thus prepared show homogeneous distribution of nanoclusters having rather narrow size distributions. The average size of these embedded nanoclusters can be effectively controlled by varying the ratio of sputtered metal and matrix species. In this contribution, we present results from the computer simulation of the deposition process to investigate the structural evolution and growth of Au nanoclusters embedded in silica matrix during co-sputtering. A three dimensional kinetic Monte Carlo technique has been used here to study the growth kinetics of nanoparticles taking into consideration the effect of the energetic sputtered species reaching the surface of the film during deposition. Nucleation and subsequent growth of Au nanoclusters has been simulated under different deposition conditions. As a result, the simulation has been shown to be useful for deposition parameters optimization in the process of nanocomposite thin film growth by fast atom beam co-sputtering.

Keywords: layer deposition; co-sputtering; nanostructure; kinetic Monte Carlo

  • Poster
    16th International Conference on Ion Beam Modification of Materials (IBMM 08), 31.08.-05.09.2008, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-12189
Publ.-Id: 12189


Facetting Morphology of Crystallites under Ion Irradiation – a 3D Kinetic Lattice Monte Carlo Study

Heinig, K.-H.; Röntzsch, L.

The orientation-dependent surface energies of crystal facets determine the shape of crystallites via Wulff’s theorem. Thus, in the framework of a nearest neighbor Ising model, the equilibrium shape of a fcc crystallite is a truncated octahedron. This crystallite shape is found frequently, e.g. for A-type CoSi2 crystallites embedded in silicon.
In this contribution we show that crystallites change their shape under intense ion irradiation. A first indication for a crystallite shape change under ion irradiation was reported several years ago [1]. In a Monte Carlo simulation the continuing vacancy production transformed the equilibrium fcc crystallite shape of a truncated octahedron into the steady-state shape of a cube. Here we present a systematic study of ion-irradiation-induced crystallite shape changes for different crystal structures and different irradiation intensities and temperatures. For the first time, an explanation of the shape changes based on the surface defect kinetics will be given: Whereas in thermodynamics the equilibrium concentration of surface defects is determined by energetics (“detailed balance”), under ion irradiation its steady-state value is controlled by the geometry of atomic displacements. Consequently, facets with a high atomic area density become unstable. It will be shown that this facet instability might be the reason for temperature dependent pattern formation on metal surfaces under ion erosion [2].
[1] P. Bellon, Phys. Rev. Letters 81, 4176 (1998).
[2] U. Valbusa et al., J. Phys.: Condens. Matter 14, 8153 (2002).

Keywords: ion irradiation; surface energy; crystal shape; kinetic Monte Carlo

  • Poster
    16th International Conference on Ion Beam Modification of Materials (IBMM 08), 31.08.-05.09.2008, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-12188
Publ.-Id: 12188


Mapping of 2 + 1 dimensional KPZ growth onto driven lattice gas model of dimers

Odor, G.; Liedke, B.; Heinig, K.-H.

We show that a 2+1 dimensional discrete surface growth model exhibiting KPZ class scaling can be mapped onto a two dimensional conserved lattice gas model of directed dimers. In case of KPZ height anisotropy the dimers follow driven diffusive motion. We confirm by numerical simulations that the scaling exponents of the dimer model are in agreement with those of the 2+1 dimensional KPZ class. This opens up the possibility of analyzing growth models via reaction-diffusion models, which allow much more efficient computer simulations.

Keywords: crystal growth; KPZ equation; Edward-Wilkinson equation; scaling behavior; Monte-Carlo simulation

Permalink: https://www.hzdr.de/publications/Publ-12187
Publ.-Id: 12187


Ion mass dependence of irradiation-induced local creation of ferromagnetism in Fe60Al40 alloys

Fassbender, J.; Liedke, M. O.; Strache, T.; Moeller, W.; Menendez, E.; Sort, J.; Rao, K. V.; Deevi, S. C.; Nogues, J.

Ion irradiation of Fe60Al40 alloys results in the phase transformation from the paramagnetic, chemically ordered B2 phase to the ferromagnetic, chemically disordered A2 phase. The magnetic phase transformation is related to the number of displacements per atom (dpa) during the irradiation. For heavy ions (Ar+, Kr+, and Xe+), a universal curve is observed with a steep increase in the fraction of the ferromagnetic phase that reaches saturation, i.e., a complete phase transformation, at about 0.5 dpa. This proves the purely ballistic nature of the disordering process. If light ions are used (He+ and Ne+), a pronounced deviation from the universal curve is observed. This is attributed to bulk vacancy diffusion from the dilute collision cascades, which leads to a partial recovery of the thermodynamically favored B2 phase. Comparing different noble gas ion irradiation experiments allows us to assess the corresponding counteracting contributions. In addition, the potential to create local ferromagnetic areas embedded in a paramagnetic matrix is demonstrated.

  • Physical Review B 77(2008), 174430

Permalink: https://www.hzdr.de/publications/Publ-12186
Publ.-Id: 12186


Application of self-actuated 32 cantilever array in atomic force surface measurements

Gotszalk, T.; Zawierucha, P.; Woszczyna, M.; Zielony, M.; Ivanov, T.; Ivanova, K.; Volland, B. E.; Sarov, Y.; Persaud, A.; Dontzov, D.; Schmidt, B.; Nikolov, N.; Kostic, I.; Engl, W.; Sulzbach, T.; Mielczarski, J.; Kolb, S.; Pedreau, R.; Huq, S. E.; Edinger, K.; Fortagne, O.; Blom, H. O.; Rangelow, I. W.

Main industry requirement for applying scanning probe microscopy in surface measurements is the high
scan speed, which allow the microelectronics producers to obtain the information about the technological
process quality in-situ on the semiconductor wafer. Common single topography measurement consume few
minutes for scanning area about 100 μm2 because of limited cantilever dynamic properties. To overcome
this problem one may utilize the cantilever with resonance frequency above 1 MHz but in this case,
cantilever suffer from wear and it requires complicated, large bandwidth measurement system. Different
approach to high speed topography measurement is to apply massive array of cantilevers, where the
surface topography image is taken simultaneously from every probe.
In the contribution present the application of the one dimensional VLSI NEMS-chip (Very Large Scale
Integrated Nano Electro Mechanical System) incorporating 32 proximal probes for high speed atomic force
microscopy measurements will be presented. Each array cantilever integrates a thermal deflection actuator, a
piezoresistor acting as a deflection detector and a microtip with radius of 10 nm.

Keywords: NEMS; proximal AFM probe array; piezoresistive deflection sensing; thermal deflection actuation

  • Poster
    34th Micro and Nano Engineering Conference MNE08, 15.-18.09.2008, Athens, Greece

Permalink: https://www.hzdr.de/publications/Publ-12183
Publ.-Id: 12183


Acceleration of irradiation hardening of low-copper reactor pressure vessel steel observed by means of SANS and tensile testing

Bergner, F.; Ulbricht, A.; Viehrig, H.-W.

Neutron irradiation of low-copper reactor pressure vessel steels containing manganese and nickel gives rise to microstructural changes and a deterioration of mechanical properties apparently progressing slower than in steels containing more than or about 0.1 wt% Cu. An acceleration of this process after accumulation of a threshold fluence caused by so-called late blooming phases is a matter of debate. We report results of small angle neutron scattering (SANS) experiments and tensile tests for two low-Cu model RPV steels irradiated at 255°C. Motivation for the use of the integrated magnetic scattering as a microstructural parameter combining the volume fraction and magnetic contrast of nanometre-sized irradiation-induced features is given. The results indicate one of the rare cases of acceleration of both the change of a microstructural parameter and the yield stress increase. The issues of the nature of the irradiation-induced features, the role of phosphorus, and the observed strong correlation of integrated magnetic scattering and yield stress increase are addressed.

Keywords: neutron irradiation; SANS; tensile testing; pressure vessel steel

Permalink: https://www.hzdr.de/publications/Publ-12182
Publ.-Id: 12182


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