Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31828 Publications
Chemical stability of BioXmark® following normofractionated and single-fraction proton beam therapy
Troost, E.; Menkel, S.; Enghardt, W.; Hytry, J.; Kunath, D.; Makocki, S.; Hoffmann, A.; Jolck, R.;
Purpose/Objective
Use of solid fiducial markers in proton radiation therapy has been approached with care as their presence may cause significant local dose perturbations. Recently, a liquid carbohydrate based fiducial marker (BioXmark®) has been introduced with minimal dose perturbation (relative stopping power = 1.164) and visibility properties suitable for use in image-guided proton therapy (IGPT). The purpose of this work was to investigate the chemical stability of the marker for use in both normofractionated and single fraction proton treatment regimes.

Material/Methods
Ten identical custom-made cylindrical polymethylmethacrylate (PMMA) inserts (V = 0.95 mL, douter = 10.0 mm, dinner = 5.0 mm, l = 48 mm) were prepared. BioXmark® markers (150±30 mg) were added to the bottom of the inserts and water (700 μL) was added on top of the markers. The inserts were sealed with a rubber stopper.
A QA dosimetry phantom was modified to accommodate four PMMA inserts simultaneously by inserting these sideway into the proton irradiation field (10 × 10cm) (Figure 1). Four markers (Group A) were irradiated during daily QA for a period of 51 days with 43 fractions ranging from 1.44-1.86 Gy resulting in an accumulated dose of 67.4 Gy. Four other markers (Group B) were irradiated with a single dose of 155.4 Gy and two non-irradiated Control markers were kept on site for the duration of the experiments.
Possible chemical alterations caused by proton irradiation were evaluated by high-performance liquid chromatography (HPLC), electrospray ionization mass spectrometry (ESI-MS),thin-layer chromatography (TLC) and visual inspection of the markers and the aqueous phase above the markers.

Results
No visual alterations between markers from Group A+B and the Control markers were observed. HPLC and TLC analysis of the markers and the aqueous phase above the markers from all three groups did not indicate chemical degradation of the marker materials (Figure 2). This observation was further supported by ESI-MS analysis, which showed identical m/z fragments for all three groups (Figure 2).

Conclusion
The BioXmark®marker showed no chemical degradation after exposure to normofractionated and extremely hypofractionated proton therapy regimes and may serve as a good alternative to solid fiducial markers used for IGPT.
Keywords: BioXmark fiducial marker, proton beam irradiation

Publ.-Id: 24186 - Permalink


E1 and M1 strength functions at low energy
Schwengner, R.; Massarczyk, R.; Bemmerer, D.; Beyer, R.; Junghans, A. R.; Kögler, T.; Rusev, G.; Tonchev, A. P.; Tornow, W.; Wagner, A.;
We report on photon-scattering experiments using bremsstrahlung at the γELBE facility of Helmholtz-Zentrum Dresden-Rossendorf and using quasimonoenergetic, polarized γ beams at the HIγS facility of the Triangle Universities Nuclear Laboratory in Durham. To deduce the photoabsorption cross sections at high excitation energy and high level density, unresolved strength in the quasicontinuum of nuclear states has been taken into account. In the analysis of the spectra measured by using bremsstrahlung at γELBE, we perform simulations of statistical γ-ray cascades using the code γDEX to estimate intensities of inelastic transitions to low-lying excited states. Simulated average branching ratios are compared with model-independent branching ratios obtained from spectra measured by using monoenergetic γ beams at HIγS. E1 strength in the energy region of the pygmy dipole resonance is discussed in nuclei around mass 90 and in xenon isotopes. M1 strength in the region of the spin-flip resonance is also considered for xenon isotopes. The dipole strength function of 74Ge deduced from γELBE experiments is compared with the one obtained from experiments at the Oslo Cyclotron Laboratory. The low-energy upbend seen in the Oslo data is interpreted as M1 strength on the basis of shell-model calculations.
Keywords: photonuclear reactions, photon scattering, nuclear resonance fluorescence, photoabsorption cross section, gamma-ray strength function, shell model.
  • Invited lecture (Conferences)
    International Conference on Nuclear Data for Science and Technology, 11.-16.09.2016, Brugge, Belgien
  • Open Access LogoEuropean Physical Journal Web of Conferences 146(2017), 05001
    DOI: 10.1051/epjconf/201714605001

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Publ.-Id: 24185 - Permalink


Extension of hybrid micro-depletion model for decay heat calculation in DYN3D code
Bilodid, Y.; Fridman, E.; Kotlyar, D.; Shwageraus, E.;
Reactor dynamics code DYN3D, stand-alone or in coupling with plant thermo-hydraulic codes such as ATHLET or RELAP, is used to simulate transients and accidents scenarios. The radioactive decay heat generated by nuclear fuel after shutdown plays an important role in a number of accident scenarios. The decay heat model implemented in DYN3D so far is based on the German national standard DIN Norm 25463 (1990) and its applicability is limited to LWR fuel up to 4.1% enrichment.
This work extends the hybrid micro-depletion methodology, recently implemented in DYN3D, to the decay heat calculation by accounting explicitly for the heat contribution from the decay of each nuclide in the fuel. This method does not involve any assumptions about fuel content or operational history and therefore is valid for a wide range of fuel types. Detailed nuclide content of the fuel is calculated by DYN3D in a fuel cycle simulation, taking into account local operational history of each node. Thus, DYN3D is able to accurately calculate the axial decay heat power distribution in each fuel assembly during transients as well as in long term storage.
Keywords: DYN3D, decay heat, microscopic depletion
  • Contribution to proceedings
    26th Symposium of AER on VVER Reactor Physics and Reactor Safety, 10.-14.10.2016, Helsinki, Finland
    Proc. of the 26th Symposium of AER on VVER Reactor Physics and Reactor Safety
  • Lecture (Conference)
    26th Symposium of AER on VVER Reactor Physics and Reactor Safety, 10.-14.10.2016, Helsinki, Finland

Publ.-Id: 24184 - Permalink


Analysis of C/E results of fission rate ratio measurements in several fast lead VENUS-F cores
Kochetkov, A.; Krása, A.; Baeten, P.; Vittiglio, G.; Wagemans, J.; Bécares, V.; Bianchini, G.; Fabrizio, V.; Carta, M.; Firpo, G.; Fridman, E.ORC; Sarotto, M.
During the GUINEVERE FP6 European project (2006-2011), the zero-power VENUS water-moderated reactor was modified into VENUS-F, a mockup of lead cooled fast spectrum system with solid components that can be operated in both critical and subcritical mode.
The Fast Reactor Experiments for hybrid Applications (FREYA) FP7 project was launched in 2011 to support the designs of the MYRRHA Accelerator Driven System (ADS) and the ALFRED Lead Fast Reactor (LFR). Three VENUS-F critical core configurations, simulating the complex MYRRHA core design and one configuration devoted to the LFR ALFRED core conditions were investigated in 2015. The MYRRHA related cores simulated step by step design peculiarities like the BeO reflector and in pile sections. For all of these cores the fuel assemblies were of a simple design consisting of 30 % enriched metallic uranium, lead rodlets to simulate the coolant and Al2O3 rodlets to simulate the oxide fuel.
Fission rate ratios of minor actinides such as Np-237, Am-241 as well as Pu-239, Pu-240, Pu-242 and U-238 to U-235 were measured in these VENUS-F critical assemblies with small fission chambers in specially designed locations, to determine the spectral indices in the different neutron spectrum conditions.
The measurements have been analyzed using advanced computational tools including deterministic and stochastic codes and different nuclear data sets like JEFF-3.1, JEFF-3.2, ENDF/B7.1, ENDF/B6.8, JENDL-4.0 and TENDL-2014. The analysis of the C/E discrepancies will help to improve the nuclear data in the specific energy region of fast neutron reactor spectra.
  • Open Access LogoContribution to proceedings
    ND2016 - International Conference on Nuclear Data for Science and Technology, 11.-16.09.2016, Bruges, Belgium
    EPJ Web of ConferencesVolume 146, Article number 06007
    DOI: 10.1051/epjconf/201714606007

Publ.-Id: 24183 - Permalink


Contactless inductive flow tomography: recent developments in its application to continuous casting with electromagnetic brakes
Ratajczak, M.; Wondrak, T.; Martin, R.; Stefani, F.; Jacobs, R.;
Measuring the velocity in hot and/or aggressive melts is a challenging task. Many applications, like continuous casting of steel, would benefit even from a rough knowledge of the global flow structure of the melt, because the flow structure has a direct impact on the quality of the final product. In continuous casting, electromagnetic brakes (EMBrs) are widely used to influence the flow in the mold, as they are expected to damp undesired flow oscillations that are associated with multiple kinds of defects. Yet, without direct feedback from the mold flow, a tailored process control with EMBrs is hardly possible.
The contactless inductive flow tomography (CIFT) could help to circumvent these problems. The method relies on the induction of a secondary magnetic field if the moving fluid is exposed to a primary magnetic field. From the measurement of the induced magnetic outside the melt, the global flow structure of the melt can be inferred by solving the associated linear inverse problem. A successful application of CIFT to EMBr-influenced mold flows could enable steel producers to cast high quality steel with less rejects. In this paper we will outline the efforts to adapt CIFT to a laboratory liquid-metal mold under the influence of an EMBr.
Keywords: Contactless inductive flow tomography, continuous casting, magnetic field measurement, gradiometric sensor, electromagnetic brake
  • Contribution to proceedings
    WCIPT8 - 8th World Congress on Industrial Process Tomography, 26.-29.09.2016, Foz do Iguacu, Brasilia
  • Lecture (Conference)
    WCIPT8 - 8th World Congress on Industrial Process Tomography,, 26.-29.09.2016, Foz do Iguacu, Brasilia

Publ.-Id: 24182 - Permalink


Performance study of a Mosaic high rate MRPC
Wang, F.; Han, D.; Xie, B.; Wang, Y.; Lyu, P.; Guo, B.; Laktineh, I.; Naumann, L.; Kotte, R.; Dreyer, J.; Garcia, A. L.; Stach, D.; Fan, X.; Akindinov, A.;
A prototype of a large mosaic MRPC with low resistive glass for the future upgrade of CMS muon system is presented. This prototype is designed by jointing two pieces of glass together and separating them by fishing lines to prevent sparks. A simulation of the weighting field based on Maxwell shows that the efficiency is higher than 90% in the joint area. In a beam test at HZDR, the prototype achieved ~ 92% detection efficiency and about 60 ps time resolution in the joint area, and ~95% efficiency and 60 ps time resolution in the active area. A rate capability study shows this prototype can withstand 40 kHz/cm2 at least.

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  • Secondary publication expected

Publ.-Id: 24181 - Permalink


Spin caloritronic nano-oscillator
Safranski, C.; Barsukov, I.; Lee, H. K.; Schneider, T.; Jara, A. A.; Smith, A.; Chang, H.; Lenz, K.; Lindner, J.; Tserkovnyak, Y.; Wu, M.; Krivorotov, I. N.;
Energy loss due to ohmic heating is a major bottleneck limiting down-scaling and speed of nanoelectronic devices. Harvesting ohmic heat for signal processing is a major challenge in modern electronics. Here we demonstrate that hermal gradients arising from ohmic heating can be utilized for driving auto-oscillations of magnetization in a ferrimagnetic nanowire via the spin Seebeck effect and for generation of tunable microwave signals. Our work paves the way towards spin caloritronic microwave and magnonic nanodevices.
Keywords: nanooscillator, spincaloritronics, magnetism, spin waves, spin torque

Publ.-Id: 24180 - Permalink


SIMEX: Simulation of Experiments at Advanced Light Sources
Fortmann-Grote, C.; Andreev, A. A.; Briggs, R.; Bussmann, M.; Buzmakov, A.; Garten, M.; Grund, A.; Huebl, A.ORC; Hauff, S.; Joy, A.; Jurek, Z.; Loh, N. D.; Rüter, T.; Samoylova, L.; Santra, R.; Schneidmiller, E. A.; Sharma, A.; Wing, M.; Yakubov, S.; Yoon, C. H.; Yurkov, M. V.; Ziaja, B.; Mancuso, A. P.
Realistic simulations of experiments at large scale photon facilities, such as optical laser laboratories, synchrotrons, and free electron lasers, are of vital importance for the successful preparation, execution, and analysis of these experiments investigating ever more complex physical systems, e.g. biomolecules, complex materials, and ultra--short lived states of highly excited matter. Traditional photon science modelling takes into account only isolated aspects of an experiment, such as the beam propagation, the photon-matter interaction, or the scattering process, making idealized assumptions about the remaining parts, e.g. the source spectrum, temporal structure and coherence properties of the photon beam, or the detector response. In SIMEX, we have implemented a platform for complete start-to-end simulations, following the radiation from the source, through the beam transport optics to the sample or target under investigation, its interaction with and scattering from the sample, and its registration in a photon detector, including a realistic model of the detector response to the radiation. Data analysis tools can be hooked up to the modelling pipeline easily. This allows researchers and facility operators to simulate their experiments and instruments in real life scenarios, identify promising and unattainable regions of the parameter space and ultimately make better use of valuable beamtime.
  • Contribution to proceedings
    NOBUGS (New Opportunities for Better User Group Software), 17.-19.10.2016, Copenhagen, Denmark

Publ.-Id: 24179 - Permalink


Use of ion irradiation to tune magnetic anisotropy
Osten, J.; Greene, P.; Lenz, K.; Fassbender, J.ORC; Jenkins, C.; Arenholz, E.; Endo, T.; Iwata, N.; Liu, K.
Current challenges in magnetic storage media will be shortly discussed. In detail perpendicular magnetic recording media is addressed. Perpendicular magnetic recording media has the advantage of good data stability but the disadvantage of a high writing field. The writing field is also determined by the anisotropy of the material. To control the anisotropy ion irradiation of Co/Pd multilayers has been investigated. By adjusting the kinetic energy and fluence, the depth and lateral density of the local structural modification are controlled. First-order reversal curve analysis through X-ray magnetic circular dichroism and conventional magnetometry studies shows that the local structural damage weakens the perpendicular anisotropy near the surface, leading to a magnetization tilting towards the in-plane direction. The ion irradiation method is complementary to and may be used in conjunction with, other synthesis approaches to maximize the anisotropy gradient.
Keywords: anisotropy gradient PMR ion implantation
  • Invited lecture (Conferences)
    Ion Beams in Materials Engineering and Characterization (IBMEC), 28.09.-01.10.2016, New Dehli, Indien

Publ.-Id: 24178 - Permalink


Incidental dose to cardiac subvolumes does not improve prediction of radiation pneumonitis in Stage 3 NSCLC patients
Wijsman, R.; Dankers, F.; Troost, E.; Hoffmann, A.; Bussink, J.;
Purpose: Conflicting results have been reported for the combined effect of heart and lung irradiation on the development of radiation pneumonitis (RP) [1, 2]. The reported studies based on 3D conformal radiotherapy considered the whole heart as an organ-at-risk, thereby not distinguishing between dose to the cardiac ventricles and atria. We assessed whether inclusion of incidental dose to these cardiac subvolumes improved the prediction of Grade ≥3 RP.
Material and methods: We retrospectively assessed 188 consecutive patients with stage III non-small cell lung cancer (NSCLC) having undergone (chemo-)radiotherapy (≥60 Gy) using intensity-modulated radiation therapy (until 2011) or volumetric-modulated arc therapy (starting in 2011). Most patients (n=182) received 66 Gy in 33 (once-daily) fractions to the primary tumour and involved hilar/mediastinal lymph nodes based on FDG-PET/CT. The lungs and heart (ventricles and atria separately in 156 patients that received a contrast enhanced planning CT) were re-contoured to generate accurate dose-volume histogram (DVH) data. RP was assessed using the Radiation Therapy Oncology Group scoring criteria for pulmonary toxicity. Since high multicollinearity was observed between the DVH parameters, those with the highest Spearman correlation coefficient (Rs) were selected for the modelling procedure. Using a bootstrap approach, clinical parameters (such as age, gender, performance, smoking status, forced expiratory volume in 1 second, and cardiac comorbidity, i.e., medical history of myocardial infarction, heart failure, valvular heart disease, cardiac arrhythmias and/or hypertension) and DVH parameters of lungs and heart (assessing atria and ventricles separately and combined) were evaluated for RP prediction.
Results: After a median follow-up of 18.4 months, 26 patients (13.8%) developed RP. Only the median mean lung dose (MLD) differed between groups (15.3 Gy vs 13.7 Gy for the RP and non-RP group, respectively; p=0.004). Most Rs of the lung DVH parameters exceeded those of the heart DVH parameters and only some of the lung DVH parameters were significantly correlated with RP [See Figure 1; highest Rs for MLD (0.21; p<0.01)]. Only cardiac comorbidity was borderline associated with RP (p=0.066) on univariate logistic regression analysis. After bootstrap modelling, heart DVH parameters were seldom included in the model predicting Grade ≥3 RP. The optimal model consisted of: MLD (Odds ratio (OR) 1.28 per Gy increase; p=0.03) and cardiac comorbidity (OR 2.45 in case of cardiac comorbidity; p=0.04). The area under the receiver operator characteristic curve was 0.71, with good calibration of the model.
Conclusion: Incidental dose to the cardiac atria and ventricles did not improve RP risk prediction in our cohort of stage III NSCLC patients as the DVH parameters for lung outperformed those for the heart. The multivariable model containing the variables cardiac comorbidity and MLD is the optimal model for RP prediction in this cohort.
References
1. Huang, E.X., et al., Heart irradiation as a risk factor for radiation pneumonitis. Acta Oncol, 2011. 50(1): p. 51-60.
2. Tucker, S.L., et al., Is there an impact of heart exposure on the incidence of radiation pneumonitis? Analysis of data from a large clinical cohort. Acta Oncol, 2014. 53(5): p. 590-6.

Publ.-Id: 24176 - Permalink


Shapeable magnetic sensorics
Makarov, D.;
The flourishing and eagerness of portable consumer electronics necessitates functional elements to be lightweight, flexible, and even wearable [1,2]. Next generation flexible appliances aim to become fully autonomous and will require ultra-thin and flexible navigation modules, body tracking and relative position monitoring systems. Such devices fulfill the needs of soft robotics [3], functional medical implants [4] as well as epidermal [5], imperceptible [6] and transient [7] electronics. Key building blocks of navigation and position tracking devices are the magnetic field sensors.
We developed the technology platform allowing us to fabricate high-performance shapeable magnetoelectronics [8] – namely, flexible [9-11], printable [12-14], stretchable [15-17] and even imperceptible [18] magnetosensitive elements. The technology relies on smart combination of thin inorganic functional elements prepared directly on flexible or elastomeric supports. The unique mechanical properties open up new application potentials for smart skins, allowing to equip the recipient with a “sixth sense” providing new experiences in sensing and manipulating the objects of the surrounding us physical as well as digital world [11,18].
Combining large-area printable and flexible electronics paves the way towards commercializing the active intelligent packaging, post cards, books or promotional materials that communicate with the environment and provide the respond to the customer. Realization of this vision requires fabrication of printable electronic components that are flexible and can change their properties in the field of a permanent magnet [13]. For this concept, we fabricated high performance magnetic field sensors relying on the giant magnetoresistive (GMR) effect, which are printed at pre-defined locations on flexible circuitry and remain fully operational over a temperature range from -10°C up to +95°C, well beyond the requirements for consumer electronics [14]. Our work potentially enables commercial use of high performance magneto-sensitive elements in conventional printable electronic industry, which, although highly demanded, had not yet been possible.
In this talk, I will review the recent advances in the field of shapeable magnetic sensorics and emergent applications of this novel technology.
Keywords: Shapeable magnetoelectronics, smart Skins, magnetic field sensors
  • Invited lecture (Conferences)
    Brazilian-German Frontiers of Science & Technology Symposium, 20.-23.09.2016, Campinas, Brazil

Publ.-Id: 24174 - Permalink


Advanced Neutron Dosimetry on VVER-440 Ained to Reactor Equipment Load Evaluation During Life Time Prolongation
Borodkin, P.; Khrennikov, N.; Konheiser, J.; Dzhalandinov, A.; Sidorov, A.; Tsofin, V.; Zaritskiy, S.; Egorov, A.; Kochkin, V.; Erak, D.; Panferov, P.; Makhotin, D.; Teresсhenko, A.;
Lifetime of non-restorable reactor equipment (RPV, in- and ex-vessel constructions, reactor support structures) of VVER-440 of first generation may restrict plant-life at whole. Concerning VVER, service life extension has touched the first generation of VVER-440 type reactors. Nowadays, all Russian first generation VVER-440 operated with reduced core by using dummy assemblies except reactor of Unit 4 of Novovoronezh NPP, wich are under operation more than 45 years. In comparison with other power units, the full-core loading scheme of this unit results in the highest neutron fluence accumulated over whole operation period. The analysis of degradation of material property of the equipment under irradiation are urgent in aspect of confirmation of safety of operating VVER units of similar type, and also in connection with an opportunity of further life-time prolongation. Another important aspect of dosimetry research on the Unit 4 of Novovoronezh NPP reactor is the verification and validation of calculational methods used for the prediction of the maximum neutron fluence on the VVER-440 pressure vessel.
Ex-vessel neutron dosimetry at NPP with VVER is used for a purpose of validation of calculations 3D distribution of neutron fluence on the reactor equipment. The reliability of such type validation depends on a quality of measured data and a comprehensive analysis of calculational model. The ex-vessel measurements permit to evaluate real conservatism of RPV neutron fluence evaluation, and, if possible, reduce conservative safety margins. For this purpose special advanced neutron dosimetry research were implemented at Unit 4 of Novovoronezh NPP (NV-4). Neutron activation measurement were performed in ex-vessel positions for different fuel cycles. The measurements of detectors activities also have been performed by different participants.
The purpose of the research was to perform an intercomparison of independent calculational results and comparison with reference data of the full-scale VVER-440 ex-vessel experiment. The paper deals with an analysis of a comparison of results of independent calculations by deterministic and Monte-Carlo codes between themselves and with experimental results. New and improved results of calculations analysed in the paper were run with codes and applied libraries DORT/BUGLE-96, TRAMO/ENDF/B-VII, MCNP/ENDF/B-VII, TORT/BUGLE-96, KATRIN/BGL-440, KATRIN/V7-200N47G. Calculated pure 3D or 3D synthesis multigroup neutron fluence rates in positions of experimental capsules provided by every calculator were used as basic calculational information. Based on the calculated fluence spectra the various reaction rates were computed using the dosimetry cross sections from the library IRDF-2002. The results of intercomparison of different calculation procedures and different experimental techniques give allowance to estimate of the reliable calculational and experimental uncertainties.
This verification of calculated methods provides the reliability of assessment of maximum neutron fluence on reactor equipment accumulated over whole service life period. In addition, with regard to a lifetime extension of Russian VVER-440 type reactors, advices for optimal core loading schemes will be derived. To approve the reliability and/or conservatism of calculation procedures the improved uncertainty-accounted conservative evaluation of RPV radiation loading parameters has been performed. This approach takes into account over- or underestimated C/E ratio and uncertainties of measured and calculated results. Based on such approach the analysis of end-of life-time fluence estimation has been demonstrated in the paper. The paper describes the features of the calculations, compares their results with those of the neutron activation measurements and presents neutron fluence values that were computed.
Keywords: neutron calculation, reactor pressure vessel, neutron fluence monitor, VVER-440
  • Poster
    16th International Symposium on Reactor Dosimetry (ISRD-16), 07.-12.05.2017, Santa Fe, USA
  • Contribution to proceedings
    Sixteenth International Symposium on Reactor Dosimetry (ISRD-16), 07.-12.05.2017, Santa Fe, NM, USA
    Proceedings of the 16th International Symposium on Reactor Dosimetry, West Conshohocken, USA: ASTM International, 978-0-8031-7661-4, 162-174
    DOI: 10.1520/STP160820170088

Publ.-Id: 24173 - Permalink


Update of the code intercomparison and benchmark for muon fluence and absorbed dose induced by a 18 GeV electron beam after massive iron shielding
Müller, S. E.ORC; Fassò, A.; Ferrari, A.; Ferrari, A.; Mokhov, N. V.; Nelson, W. R.; Roesler, S.; Sanami, T.; Striganov, S. I.; Versaci, R.
In 1974, Nelson, Kase, and Svensson published an experimental investigation on muon shielding around SLAC high energy electron accelerators (NIM 120 (1974) 413). They measured muon fluence and absorbed dose induced by 14 and 18 GeV electron beams hitting a copper/water beamdump and attenuated in a thick steel shielding. In their paper, they compared the results with the theoretical models available at that time.

In order to compare their experimental results with present model calculations, we use the modern transport Monte Carlo codes MARS15, FLUKA2011 and GEANT4 to model the experimental setup and run simulations. The results are then compared between the codes, and with the SLAC data. Updated results from this campaign are reported in the presentation.
  • Lecture (Conference)
    SATIF13 - 13th Meeting of the task- force on Shielding aspects of Accelerators, Targets and Irradiation Facilities, 10.-12.10.2016, Dresden, Germany
  • Open Access LogoContribution to proceedings
    SATIF13 - 13th Meeting of the taskforce on Shielding aspects of Accelerators, Targets and Irradiation Facilities, 10.-12.10.2016, Dresden, Germany
    Proceedings of the Thirteenth Meeting of the Working Group for S hielding Aspects of Accelerator, Target and Irradiation Facilities (SATIF-13) Nuclear Science NEA/NSC/R(2018)2 September 2018, 304-314

Publ.-Id: 24172 - Permalink


Transmissionselektronenmikroskopie zur Analyse anodischer Barriereschichten
Hübner, R.; Lämmel, C.; Schneider, M.;
Die vorliegende Studie stellt die vielfältigen Möglichkeiten der Transmissionselektronenmikroskopie (TEM) zur Charakterisierung dünner anodischer Barriereschichten vor. Dazu wurden magnetrongesputterte Aluminiumschichten bei unterschiedlichen Pulsfrequenzen oxidiert und mittels TEM analysiert. Unabhängig von den Herstellungsbedingungen sind die Oxidschichten porenfrei und amorph. Die Mikrostruktur des Aluminiums beeinflusst die Oxidschichten nicht. Mittels energiedispersiver Röntgenspektroskopie wurden keine Hinweise auf den Einbau von Elektrolytspezies in die Barriereschichten gefunden.
  • Lecture (Conference)
    Anodisieren - Oxidschichten von hart bis smart, 24.-25.11.2016, Dresden, Deutschland

Publ.-Id: 24170 - Permalink


X-ray microtomography of Taylor bubbles with mass transfer and surfactants in capillary two-phase flow
Boden, S.; Haghnegahdar, M.; Hampel, U.;
Development and application of techniques to measure local properties of dynamic flows is in the focus of the work of the Institute of Fluid Dynamics at HZDR and of the AREVA Endowed Chair of Imaging Techniques in Energy and Process Engineering at TU Dresden. In this paper we report on the application of enhanced X-ray microradiography and microtomography techniques to measure Taylor bubble shapes in micro- and milli-channels. Further, experiments to inves-tigate the mass transport and the influence of surfactants were conducted. The re-sulting flow structural data will foster meso- and microscalic numerical flow mod-el development for small channel multiphase flow.
  • Book chapter
    in: Advances in Mathematical Fluid Mechanics, Basel: Springer, 2017, 978-3-319-56601-6, 589-608
    DOI: 10.1007/978-3-319-56602-3

Publ.-Id: 24169 - Permalink


Advanced MRI for assessment of toxicity after photon and proton based radiation therapy in primary brain tumors.
Raschke, F.; Wesemann, T.; Petr, J.; Wahl, H.; Werner, A.; van den Hoff, J.; Krex, D.; Krause, M.; Linn, J.; Troost, E.;
In brain tumors, proton beam radiotherapy (RTx) reduces the radiation dose to healthy brain tissue outside the planning target volume compared to conventional photon based RTx. However, there is still a lack of prospective studies investigating the objective (i.e., surrogate imaging marker) and subjective (i.e., patient questionnaires) effects of photon vs. proton beam RTx for brain tumor patients. In this prospective study, primary brain tumor patients undergoing either photon- or proton-beam (chemo)RTx are being scanned using an advanced MRI protocol at 3T before RTx and at 3-monthly intervals thereafter. The MR protocol comprises conventional anatomical imaging (FLAIR, T1w, T2w, DWI) and state of the art MR sequences including quantitative T1, T2, T2* and Proton Density (PD) imaging (Figure 1), Diffusion Tensor Imaging, 2D MR spectroscopic imaging as well as ASL, T1* and T2* perfusion imaging.

In this NCT granted project, we will investigate qualitative and quantitative MR changes after photon and proton RTx in tumor tissue and surrounding normal appearing brain and correlate the results to the radiation dose fields as well as neurocognitive function and quality of life of the patients. The primary goal is to establish a rational for proton beam therapy in primary brain tumor patients with a long life expectancy and thus at risk of developing radiation sequelae (e.g., neurocognitive impairment, acute and late toxicity after RTx). Secondary goal is the combined analysis of the advanced multimodal MR data to identify infiltrative tumor tissue not visible on conventional MRI and predict local tumor control.
Keywords: brain tumors, proton, MRI
  • Poster
    NCT Retreat, 28.-29.11.2016, Heidelberg, Deutschland

Publ.-Id: 24168 - Permalink


Radiolabelled polymeric materials for imaging and treatment of cancer: Quo Vadis?
Pant, K.; Sedláček, O.; Nadar, R. A.; Hrubý, M.; Stephan, H.ORC
Owing to their tunable blood circulation time and suitable plasma stability, polymer-based nanomaterials hold a great potential for designing and utilising multifunctional nanocarriers for efficient cancer imaging and effective treatment of cancer. When tagged with appropriate radionuclides, they may allow for specific detection (diagnosis) as well as the destruction of tumours (therapy) or even customization of materials, aiming to both diagnosis and therapy (theranostic approach). This review provides an overview of recent developments of radiolabelled polymeric nanomaterials (natural and synthetic polymers) for molecular imaging of cancer, specifically, applying nuclear techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT). Different approaches to radiolabel polymers are evaluated from the methodical radiochemical point of view. This includes new bifunctional chelating agents (BFCAs) for radiometals as well as novel labelling methods. Special emphasis is given to eligible strategies employed to evade the mononuclear phagocytic system (MPS) in view of efficient targeting. The discussion encompasses promising strategies currently employed as well as emerging possibilities in radionuclide-based cancer therapy. Key issues involved in the clinical translation of radiolabelled polymers and future scopes of this intriguing research field are also discussed.
Keywords: polymers, cancer, radiodiagnosis, radiotherapy, targeting, nuclear medicine, theranostics

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Publ.-Id: 24167 - Permalink


Modification of semiconductor or metal nanoparticle lattices in amorphous alumina by MeV heavy ions
Bogdanovic Radovic, I.; Buljan, M.; Karlušić, M.; Jerčinović, M.; Dražič, G.; Bernstorff, S.; Boettger, R.;
In the present work we investigate effects ofMeVheavy ions (from 0.4 MeVXe to 15 MeVSi) on regularly ordered nanoparticle (NP) lattices embedded in amorphous alumina matrix. These nanostructures were produced by self-assembling growth using magnetron-sputtering deposition. From grazing incidence small-angle x-ray scattering measurements we have found that the usedMeV heavy ions do not change the NPsizes, shapes or distances among them. However, ions cause a tilt of the entire NP lattice in the direction parallel to the surface. The tilt angle depends on the incident ion energy, type and the applied fluence and a nearly linear increase of the tilt angle with the ion fluence and irradiation angle was found. This way,MeV heavy ion irradiation can be used to design custom-made NPlattices. In addition, grazing incidence small-angle x-ray scattering can be effectively used as a method for the determination of material redistribution/shift caused by the ion hammering effect. For the first time, the deformation yield in amorphous alumina was determined for irradiation performed at the room temperature.
Keywords: nanoparticles, MeV heavy ions, ion hammering, amorphous alumina, GISAXS

Publ.-Id: 24166 - Permalink


Ano-rectal wall dose-surface maps localise the dosimetric benefit of hydrogel rectum spacers in prostate cancer radiotherapy
Vanneste, B.; Buettner, F.; Pinkawa, M.; Lambin, P.; Hoffmann, A.;
Background and Purpose
To evaluate spatial differences in dose distributions of the ano-rectal wall (ARW) using dose-surface maps (DSM) between prostate cancer patients receiving intensity-modulated radiation therapy with and without implantable rectum spacer (IMRT+IRS; IMRT-IRS, respectively), and to correlate this with late gastro-intestinal (GI) toxicities using validated spatial and non-spatial normal-tissue complication probability (NTCP) models.

Materials and Methods
For 26 patients DSMs of the ARW were generated. From the DSMs various shape-based dose measures were calculated at different dose levels: lateral extent, longitudinal extent, and eccentricity. The contiguity of the ARW dose distribution was assessed by the contiguous-DSH (cDSH). Predicted complication rates between IMRT+IRS and IMRT-IRS plans were assessed using a spatial NTCP model and compared against a non-spatial NTCP model.

Results
Lateral extent, longitudinal extent and cDSH were significantly lower in IMRT+IRS than for IMRT-IRS at high-dose levels. Largest significant differences were observed for cDSH at dose levels >50Gy, followed by lateral extent at doses >57Gy, and longitudinal extent. Significant decreases (p = 0.01) in median rectal and anal NTCPs were predicted when using an IRS.

Conclusions:
Local-dose effects are predicted to significantly reduce by an IRS. Differences in predicted GI toxicity rates exist between spatial and non-spatial NTCP models.
Keywords: Prostate cancer; Radiotherapy; Rectum spacer; Dose-surface maps

Publ.-Id: 24165 - Permalink


Magnetization dynamics of a single Fe-filled carbon nanotube detected by ferromagnetic resonance
Lenz, K.; Narkowicz, R.; Reiche, C. F.; Kákay, A.; Mühl, T.; Büchner, B.; Suter, D.; Lindner, J.; Fassbender, J.ORC
Designing future spintronic devices or entities requires the knowledge of their static and dynamic properties. However, the precise magnetic characterization of a single nanostructure like a nanowire or dot, e.g. by ferromagnetic resonance, is still an experimental challenge.
Broadband ferromagnetic resonance (FMR) or cavity-based FMR usually lack the necessary sensitivity to measure single micron-sized or smaller structures. Measurements of arrays of such elements often might be no alternative due to inhomogeneity either.
Here we show that microresonator FMR [1] can overcome these limitations. By decreasing the resonator size the filling factor is increased, therefore boosting the FMR sensitivity by several orders of magnitude.
This allows for measuring even a single Fe-filled carbon nanotube (Fe-CNT) [2]. The Fe-filling inside the CNT has a diameter of 42 nm with an initial length of several micrometers (see Fig. 1). In order to understand the origin of the various resonance peaks, a focused ion beam was used to shorten little-by-little the length of the Fe-CNT after each FMR measurement.
Furthermore, angle-dependent FMR measurements were performed to extract the anisotropy contributions (like shape and magnetocrystalline anisotropy). In addition, the measured narrow linewidth suggests that the Fe-filling is a well ordered crystal, as confirmed by transmission electron microscopy. Therefore, besides the magnetic characterization of a single nanostructure, the microresonator FMR can also provide ‘indirectly’ information about the crystalline structure.
Keywords: ferromagnetic resonance, magnetization, nanostructures, microresonator, microwaves, carbon nanotubes, magnetism
  • Invited lecture (Conferences)
    5th International Conference on Microwave Magnetics, 05.-08.06.2016, Tuscaloosa, USA
  • Lecture (Conference)
    DPG Frühjahrstagung der SKM, Dresden, 19.-24.03.2017, Dresden, Deutschland
  • Invited lecture (Conferences)
    Intermag Europe 2017, IEEE International Magnetics Conference, 24.-28.04.2017, Dublin, Irland

Publ.-Id: 24164 - Permalink


The role of the internal demagnetizing field for the dynamics of a magnonic crystal
Langer, M.; Röder, F.; Gallardo, R. A.; Schneider, T.; Stienen, S.; Gatel, C.; Hübner, R.; Bischoff, L.; Lenz, K.; Lindner, J.; Landeros, P.; Fassbender, J.ORC
Magnonic crystals with locally alternating properties and specific periodicities exhibit interesting effects, such as a multitude of different spin-wave states with adjustable band gaps. This work aims for demonstrating and understanding the key role, which local demagnetizing fields play in such systems. In order to get direct access to this matter, the spin-dynamics of a magnonic crystal were reconstructed from ‘bottom-up’, i.e. the structural shape as well as the internal field landscape of the structure were experimentally reconstructed on the nanoscale using electron holography. Subsequently, both properties were utilized to perform dynamic response calculations. The simulations yield the frequency-field dependence as well as the angular dependence of spin waves in a magnonic crystal and reveal the governing role of the internal field landscape around the backward-volume geometry. Connecting the internal field landscape with the individual spin-wave mode localization, a comprehensive model is presented describing the complex angle-dependent spin-wave behavior around 360◦ rotation of an in-plane external field. A significant spin-wave propagation is reported for a broad angular range around the Damon-Eshbach geometry.
Keywords: magnonic crystal, electron holography, magnetic nanostructure, demagnetizing field, magnetization dynamics, ferromagnetic resonance, micromagnetic simulation

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Publ.-Id: 24163 - Permalink


Melanoma targeting with [99mTc(N)(PNP3)]-labeled α-melanocyte stimulating hormone peptide analogs: Effects of cyclization on the radiopharmaceutical properties
Carta, D.; Salvarese, N.; Morellato, N.; Gao, F.; Sihver, W.; Pietzsch, H.-J.; Biondi, B.; Ruzza, P.; Refosco, F.; Carpanese, D.; Rosato, A.; Bolzati, C.;
The purpose of this study was to evaluate the effect of cyclization on the biological profile of a [99mTc(N)(PNP3)]-labeled α-melanocyte stimulating hormone peptide analog. A lactam bridgecyclized H-Cys-Ahx-Ala3-c[Lys4-Glu-His-D-Phe-Arg-Trp-Glu10]-Arg11-Pro-Val-NH2 (NAP―NS2) and the corresponding linear H-Cys-Ahx-Ala-Nle-Asp-His-D-Phe-Arg-Trp-Gly-NH2 (NAP―NS1) peptide were synthetized, characterized by ESI-MS spectroscopy and their melanocortin-1 receptor (MC1R) binding affinity was determined in B16/F10 melanoma cells. The consistent [99mTc(N)(PNP3)]-labeled compounds were readily obtained in high specific activity and their stability and biological properties were assessed. As an example, the chemical identity of [99mTc(N)(NAP–NS1)(PNP3)]+ was confirmed by carrier added experiments supported by radio/UV HPLC analysis combined with ESI(+)-MS. Compared with the linear peptide, cyclization negatively affected the biological properties of NAP–NS2 peptide by reducing its binding affinity for MC1R and by decreasing the overall excretion rate of the corresponding [99mTc(N)(PNP3)]-labeled peptide from the body as well as its in vivo stability. [99mTc(N)(NAP–NS1)(PNP3)]+ was evaluated for its potential as melanoma imaging probe in murine melanoma model. Data from in vitro and in vivo studies on B16/F10 melanoma model of [99mTc(N)(NAP–NS1)(PNP3)]+ clearly evidenced that the radiolabeled linear peptide keeps its biological properties up on the conjugation to the [99mTc(N)(PNP3)]-building block. The progressive increase of the tumor-to-nontarget ratios over the time indicate a quite stable interaction between the radiocomplex and the MC1R.
Keywords: Tc-99m, alpha-MSH, melanoma, MC1R, peptides, SPECT, Imaging.

Publ.-Id: 24162 - Permalink


Radiobiological evaluation of established Glioblastoma multiforme cell lines as preclinical models in mice
Jakob, A.; Linge, A.; Löck, S.; Thames, H. D.; Baumann, M.; Krause, M.; von Neubeck, C.;
Less than 5 % of the patients diagnosed with the brain tumor Glioblastome multiforme (GBM) survive more than three years despite an intense therapy of surgery, radiation and application of the chemotherapeutic drug temozolomide (TMZ). The poor outcome underlines a need for the development of new treatment strategies which depends on the availability of suitable preclinical models. Here, we present results of the establishment and characterization of GBM models for the use in radiobiological research.
Basic in vitro investigations on the 5 GBM cell lines HGL21, LN-229, A7, U-251 MG and U-87 MG demonstrated radioresistance. The surviving fractions at a dose of 2 Gy X-rays ranged from 55 % (U-87 MG) to 85 % (A7). Administration of combined treatment with TMZ changed the cell survival in accordance to the methylation status of the MGMT promotor. Highly methylated cell lines LN-229, U-251 MG and U-87 MG showed the strongest response to TMZ.
Subcutaneous engraftment in nude mice further confirmed an aggressive character of the models.
High take rates for all cell lines were determined by means of the limiting dilution assay. Take doses 50 % , which indicate the cell number necessary to induce tumors in half of the animals, are in the range of 22 (HGL-21) to 187 (U-87 MG) cells reflecting a high content of stem-like cells. In contrast, extensive tumor control dose experiments of single dose treatment under hypoxic or ambient blood flow with or without combination with TMZ did not confirm the radioresistant phenotype. The tumor control doses 50 % (TCD50) ranked between 30 - 40 Gy under hypoxic conditions with the exception of U-87 MG (58 Gy). Additional treatment with TMZ decreased the TCD50 dramatically in 3 (LN-229, A7, U-87 MG) out of 4 models to values below 25 Gy.
Although the models partly mimic the clinical GBM characteristics, the radioresistance measured in vitro does not translate to the in vivo situation. As the models should mirror the clinical situation closely, their suitability for preclinical studies remains questionable.
  • Lecture (Conference)
    Young Scientist Forum 2016, 24.11.2016, Poznan, Poland, Poland

Publ.-Id: 24161 - Permalink


Efficient simulation of stationary multivariate Gaussian random fields with given cross-covariance
Teichmann, J.; van den Boogaart, K. G.;
The present paper introduces a new approach to simulate any stationary multivariate Gaussian random field whose cross-covariances are predefined continuous and integrable functions. Such a field is given by convolution of a vector of univariate random fields and a functional matrix which is derived by Cholesky decomposition of the Fourier transform of the predefined cross-covariance matrix.

In contrast to common methods no restrictive model for the cross-covariance is needed, it is stationary and can also be reduced to the isotropic case. The computational effort is very low since fast Fourier transform can be used for simulation. As will be shown the algorithm is computationally faster than a recently published spectral turning bands model. The applicability is demonstrated using a common numerical example with varied spatial correlation structure.

The model was developed to support simulation algorithms for mineral microstructures in geoscience.
Keywords: image processing, convolution, cross-covariance, Cholesky decomposition, Fourier transformation

Publ.-Id: 24160 - Permalink


Probing high-intensity laser-matter interaction at the Helmholtz International Beamline for Extreme Fields at the European XFEL
Schramm, U.ORC
Talk on Probing high-intensity laser-matter interaction at the Helmholtz International Beamline for Extreme Fields at the European XFEL
Keywords: Relativistic Laser Plasma, HIBEF
  • Invited lecture (Conferences)
    PWSC 8th Petawatt Scientific Committee and ICUIL 2016, 10.-16.09.2016, Montebello, Canada

Publ.-Id: 24159 - Permalink


Numerical Modelling of a Direct Contact Condensation Experiment using the AIAD Framework
Höhne, T.; Gasiunas, S.; Šeporaitis, M.;
The Lithuanian Energy Institute (LEI) test case deals with direct contact condensation (DCC) in the two-phase stratified steam-water flow. The main goal of CFD simulations of these experiments is to compute new models of heat and mass transport from saturated vapour to liquid over a free surface and the temperature profiles across the liquid flow in a channel. Condensation occurs mainly on free surfaces for instance at PTS scenarios. The knowledge of the accurate coolant temperature is important for nuclear safety assessment.
Three different direct contact condensation models for the heat transfer within the AIAD framework at the free surface were formulated and tested. The AIAD model describes a consistent set of model correlations for the interfacial area density, the drag, the non-resolved disturbances of a free surface and the turbulence damping the interface. The calculated surface temperature profiles agree well with the experiment. Further model development should focus on “CFD grade” experimental data and direct numerical simulations.
Keywords: CFD, CMFD, horizontal flow, PTS, PWR, AIAD, DCC, two-phase flow, two fluid flow

Publ.-Id: 24157 - Permalink


Numerical Modelling of a Direct Contact Condensation Experiment
Höhne, T.; Gasiunas, S.; Šeporaitis, M.;
The Lithuanian Energy Institute (LEI) test case deals with direct contact condensation (DCC) in the two-phase stratified steam-water flow. The main goal of CFD simulations of these experiments is to compute new models of heat and mass transport from saturated vapour to liquid over a free surface and the temperature profiles across the liquid flow in a channel. Condensation occurs mainly on free surfaces for instance at PTS scenarios. The knowledge of the accurate coolant temperature is important for nuclear safety assessment.
Three different direct contact condensation models for the heat transfer within the AIAD framework at the free surface were formulated and tested. The AIAD model describes a consistent set of model correlations for the interfacial area density, the drag, the non-resolved disturbances of a free surface and the turbulence damping the interface. The calculated surface temperature profiles agree well with the experiment. Further model development should focus on “CFD grade” experimental data and direct numerical simulations.
Keywords: CFD, CMFD, horizontal flow, PTS, PWR, AIAD, DCC, two-phase flow, two fluid flow
  • Contribution to proceedings
    2nd World Congress on Momentum, Heat and Mass Transfer (MHMT’17), 07.-08.04.2017, Barcelona, Spanien
  • Lecture (Conference)
    2nd World Congress on Momentum, Heat and Mass Transfer (MHMT’17), 07.-08.04.2017, Barcelona, Spanien

Publ.-Id: 24156 - Permalink


Nano patterns self-aligned to Ga dimer rows on GaAs surfaces
Engler, M.ORC; Škereň, T.; Facsko, S.
Ion beam irradiation of semiconductors is a method to produce regular periodic nanoscale patterns self-organized on wafer scale. At low temperatures, the surface of semiconductors is typically amorphized by the ion beam. Above a material dependent dynamic recrystallization temperature however, the surface remains crystalline and ion beam irradiation produces regular arrays of faceted ripples on III-V semiconductors. This provides a powerful single-step technique for the production of nanostructures on a large area. On (001) surfaces these ripples are parallel to the [1-10] direction without any external anisotropy. The origin of this self-alignment was not fully understood until now. A simple experiment exposing the front side and back side of a GaAs(001) wafer to the ion beam clarifies its origin and proves that the ripples align to the Ga dimer rows. As the direction of Ga dimer rows rotates by 90°on the back side, the orientation of the ripples also rotates by 90° to [110]. We discuss the experimental results in view of a model where the pattern formation is driven by creation of vacancies and ad-atoms by the ion beam and their diffusion, which is linked to the direction of dimers on the surface.
Keywords: ion beam patterning; nano patterning; GaAs; AFM; ion irradiation

Publ.-Id: 24155 - Permalink


Valuation of Uncertainty in Geometallurgical Process Optimisation
van den Boogaart, K. G.; Tolosana Delgado, R.;
Geometallurgical parameters such as block models and process response models always come with a certain (geo-)statistical uncertainty. Geometallurgical optimisation often treats these model values as if they were certain. With easy to understand model examples we demonstrate the economic effect of ignoring the uncertainty. Our stochastic optimisation method, taking it into account, uniformly outperforms the best deterministic approach, often substantially. As the method is fully aware of the underlying model uncertainty, it can quantify the value of certainty and information and thus assign economic values to geometallurgical exploration and geometallurgical processing testwork. In this way the geometallurgist can objectively justify detailed exploration and processing experiments, by computing the effect on the expected NPV upfront.
Keywords: Geometallurgy, Uncertainty, Geostatistics
  • Lecture (Conference)
    Process Mineralogy 2017, 20.-22.03.2017, Cape Town, South Africa
  • Open Access LogoContribution to proceedings
    Process Mineralogy 2017, 20.-22.03.2017, Cape Town, Sourth Africa

Publ.-Id: 24154 - Permalink


Temperature-Dependent Charge Transport through Individually Contacted DNA Origami-Based Au Nanowires
Teschome, B.; Facsko, S.; Schönherr, T.; Kerbusch, J.; Keller, A.; Erbe, A.;
DNA origami nanostructures have been used extensively as scaffolds for numerous applications such as for organizing both organic and inorganic nanomaterials, studying single molecule reactions, and fabricating photonic devices. Yet, little has been done toward the integration of DNA origami nanostructures into nanoelectronic devices. Among other challenges, the technical difficulties in producing well-defined electrical contacts between macroscopic electrodes and individual DNA origami-based nanodevices represent a serious bottleneck that hinders the thorough characterization of such devices. Therefore, in this work, we have developed a method to electrically contact individual DNA origami-based metallic nanowires using electron beam lithography. We then characterize the charge transport of such nanowires in the temperature range from room temperature down to 4.2 K. The room temperature charge transport measurements exhibit ohmic behavior, whereas at lower temperatures, multiple charge transport mechanisms such as tunneling and thermally assisted transport start to dominate. Our results confirm that charge transport along metallized DNA origami nanostructures may deviate from pure metallic behavior due to several factors including partial metallization, seed inhomogeneities, impurities, and weak electronic coupling among AuNPs. Besides, this study further elucidates the importance of variable temperature measurements for determining the dominant charge transport mechanisms for conductive nanostructures made by self-assembly approaches.
Keywords: DNA origami, gold nanoparticles, metallization, electrical contacting, charge transport

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Publ.-Id: 24153 - Permalink


Iron pnictide thin films: Synthesis and physics
Haindl, S.; Kidszun, M.; Kampert, E.;
Superconducting thin films play a prominent role in applications of superconductivity and provide an essential source for studying physical phenomena. Here, we summarize the activities for iron pnictide thin films with a focus on the German Special Priority Programme from 2009 until today. The quick availability of such films after the discovery of superconductivity in the iron-based superconductors enabled a number of experiments. After a general introduction and a brief historical overview we focus on film synthesis of iron pnictides by a two-step method and by pulsed laser deposition, the assessment of their application potential, the upper critical fields in iron oxypnictides of F-doped LaOFeAs and F-doped Sm1-xLaxOFeAs and on superconductivity in Fe/BaFe2As2 heterostructures.

Publ.-Id: 24152 - Permalink


Direct numerical simulation of an arbitrarily shaped particle at a fluidic interface
Lecrivain, G.; Yamamoto, R.; Hampel, U.; Taniguchi, T.;
A consistent formulation is presented for the direct numerical simulation of an arbitrarily shaped colloidal particle at a deformable fluidic interface. The rigid colloidal particle is decomposed into a collection of solid spherical beads and the three-phase boundaries are replaced with smoothly spreading interfaces. The major merit of the present formulation lies in the ease, with which the geometrical decomposition of the colloidal particle is implemented, yet allowing the dynamic simulation of intricate three-dimensional colloidal shapes in a binary fluid. The dynamics of a rod-like, of a plate-like, and of a ring-like particle are presently tested. It is found that plate-like particles attach more rapidly to a fluidic interface and are subsequently harder to dislodge when subject to an external force. Using the Bond number, i.e. the ratio of the gravitational force to the reference capillary force, a spherical particle with equal affinity for the two fluids breaks away from a fluidic interface at the critical value Bo = 0.75. This value is in line with our numerical experiments. It is here shown that a plate and a ring of equivalent masses detach at greater critical Bond numbers approximately equal to Bo = 1.3. Results of this study will find applications in the stabilisation of emulsions by colloids and in the recovery of colloidal particles by rising bubbles.

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Publ.-Id: 24151 - Permalink


In situ bow change of Al-alloy MEMS micromirrors during 248-nm laser irradiation
Mai, A.; Bunce, C.; Hübner, R.; Pahner, D.; Dauderstädt, U.;
Micromirror based spatial light modulators (SLMs) developed by the Fraunhofer Institute for Photonic Microsystems are well established in microlithography applications. Serving, e.g., as reflective, programmable photomasks in deep-UV mask writers, they enable highly flexible pattern generation. During operation, the micromirror bow significantly impacts contrast and the resolvable feature size of generated patterns. In some situations, MEMS micromirrors tend to change their bow during laser irradiation. A test regime including a characterization unit for the in situ analysis of MEMS micromirror topology has been developed to measure the bow change under various irradiation conditions. Experiments in which SLMs were irradiated by a 1-kHz, 248-nm pulse laser revealed that mirror bowing can occur in both directions (concave and convex). The bowing direction is dependent upon the applied irradiation parameters such as pulse-energy density, pulse number, and the deposited energy. Sustained irradiation at energy densities exceeding a certain limit can potentially become a limiting factor for the resolvable feature sizes of the patterns generated and, therefore, for the usable SLM lifespan.
Keywords: spatial light modulator; micromirror array; micro-(opto)-electro-mechanical-system device; laser; UV; in situ

Publ.-Id: 24150 - Permalink


Generation of high charge electron beams by ionization injection
Couperus, J. P.; Köhler, A.; Zarini, O.; Krämer, J.; Pausch, R.; Debus, A.; Hübl, A.; Garten, M.; Bussmann, M.; Irman, A.; Schramm, U.;
One of the most challenging aspects in Laser wakefield acceleration (LWFA) is controlled injection of electrons into the correct phase of the accelerating field. In the ionization injection scheme this is addressed by adding a small fraction of high Z gas to the accelerating medium. Electrons in the K-shell possess a high ionization threshold which is only reached around the laser maximum, close to the center of the propagation axis. Compared to wave-breaking injection, ionization injection requires relatively low laser intensities and plasma densities, allowing us to drive the wakefield in a more stable way.
We present an extensive experimental parameter study, showing the influence of Nitrogen doping concentration on beam parameters: energy spread, charge & repeatability. We discuss the influence of laser energy and plasma density on maximum reachable energy and conversion efficiency.
We show a regime where our laser system (2.5J on target, 30 fs) generates stable electron beams (252 MeV, +/- 9% shot-to-shot) with narrow bandwidth (36 MeV +/- 11MeV FWHM) and high charge (292 pC +/- 59 pC within 1/e2) electron beams, while retaining a low background.
Keywords: Laser wakefield acceleration, LWFA
  • Poster
    Advanced Accelerator Concepts Workshop (AAC 2016), 02.08.2016, National Harbor, Maryland, USA
  • Lecture (Conference)
    Novel Accelerators Workshop 2016, 24.10.2016, Paris, France

Publ.-Id: 24149 - Permalink


High temperature stable TCOs as selective transmitter for solar thermal applications
Lungwitz, F.; Schumann, E.; Guillen, E.; Escobar-Galindo, R.; Gemming, S.; Krause, M.;
Materials used in the receiver tubes of a solar thermal power plant must exhibit several properties, e.g. high temperature stability, high absorption in the solar region and low thermal emittance. Nowadays, temperatures of up to 450°C and up to 550°C are reached using parabolic trough arrays and solar tower absorbers, respectively, whereas temperatures up to 800°C or higher could be reached if the receiver materials were stable enough. Previous R&D approaches for high temperature solar receiver materials include multilayer coatings deposited by PVD or sol-gel techniques. Here, a new concept for solar-selective coating is presented. A transparent conductive oxide (TCO) is deposited as a solar selective transmitter on a black body absorber to implement both, high absorption (from the black body) in the ultraviolet, visible and near infrared spectral range (300 nm – 2500 nm) as well as high reflectivity (from the TCO) in the infrared (> 2500 nm) in a relative simple material design. Therefore SnO2:Ta and TiO2:Ta thin films are reactively magnetron co-sputtered from tantalum doped and undoped metal targets at high temperatures (400°C - 700°C). By changing dopant concentration, oxygen flux, process pressure and deposition temperature the optical properties of these films can be tailored to meet the requirements of a solar selective transmitter coating. It is also shown that the electrical properties of the TCO, namely charge carrier concentration and mobility, determine the optical behavior. The correlation between structural, optical, and electrical properties is analyzed by Raman Spectroscopy and Spectroscopic Ellipsometry (SE) both at room- and especially (in situ) at hightemperatures simulating the conditions where the functional coating is supposed to operate. Additionally, Rutherford Backscattering Spectroscopy (RBS), X-ray Diffraction (XRD), UV-VIS spectrometry, and Hall Effect measurements are performed. Financial support by the EU, grant No. 645725, project FRIENDS2, and the HGF via the W3 program (S.G.) is gratefully acknowledged.
Keywords: solar thermal, transparent conductive oxide
  • Lecture (Conference)
    15th International Conference on Plasma Surface Engineering, 14.09.2016, Garmisch-Partenkirchen, Deutschland

Publ.-Id: 24146 - Permalink


Source term and shielding calculations for the installation of a new cyclotron for medical applications at HZDR
Konheiser, J.; Ferrari, A.; Müller, S. E.; Naumann, B.;
In the presentation results for source term and shielding calculations for the installation of a new cyclotron at the Helmholtz-Zentrum Dresden-Rossendorf are given. This cyclotron will be used to produce radioisotopes for medical applications. The source terms for a proton beam hitting an18O-enriched water target were calculated with MCNP6 and FLUKA, and compared to source terms used in the literature for exclusive18O(p,n)18F production. It was found that the additional channels which are present during the cyclotron operation may not be neglected. In addition, a significant contribution from gamma-radiation produced by the proton beam in the water target was taken into account. Based on the results from the Monte Carlo simulations, theestimated dose rates in public areas around the cyclotron building are significantly below the allowed limits provided by the legal authorities.
To validate the radiation fields obtained in the simulations, an experimental program has been started using activation samples originally used in reactor dosimetry. These samples are placed at well defined positions in the radiation field, and after irradiation are analyzed for residual activation. The results can then be compared to the simulated results. We will present the status of this program.
Keywords: cycloton, 18F production, neutron source, dose rates, activation measurement
  • Poster
    SATIF-13 - 13th Meeting of the task-force on Shielding aspects of Accelerators, Targets and Irradiation Facilities, 10.-12.10.2016, Dresden, Germany
  • Contribution to proceedings
    SATIF-13 - 13th Meeting of the task-force on Shielding aspects of Accelerators, Targets and Irradiation Facilities, 10.-12.10.2016, Dresden, Germany
    Shielding Aspects of Accelerator, Target and Irradiation Facilities (SATIF),Nuclear Science NEA/NSC/R(2018)2, Wien/Paris: OECD-NEA

Publ.-Id: 24145 - Permalink


In-Depth Performance Analysis for OpenACC/CUDA/OpenCL Applications with Score-P and Vampir
Juckeland, G.; Henschel, R.;
Participants will work with Score-P/Vampir to learn how to dive into the execution properties of CUDA and OpenACC applications. We'll show how to use Score-P to generate a trace file and how to study it with Vampir. Additionally, we'll use the newly established OpenACC tools interface to also present how OpenACC applications can be studied for performance bottlenecks. This lab utilizes GPU resources in the cloud, you are required to bring your own laptop.
Keywords: Score-P Vampir Tracing Performance-Analysis
  • Lecture (Conference)
    GTC Europe 2016, 28.-29.09.2016, Amsterdam, Nederland

Publ.-Id: 24143 - Permalink


Introduction into Raman spectroscopy
Krause, M.;
Fundamentals and new developments in Raman spectroscopy
  • Invited lecture (Conferences)
    Friends2-Workshop: Advanced coating and characterization techniques, 19.-20.09.2016, Dresden-Rossendorf, Deutschland

Publ.-Id: 24142 - Permalink


Comparative study of the deposition of highly reflectant metal thin films by ionized PVD techniques
Rincón Llorente, G.; Guillén Rodríguez, E.; Schumann, E.; Heras Pérez, I.; Mesko, M.; Munnik, F.; Krause, M.; Escobar Galindo, R.;
The degree of ionization during Physical Vapor Deposition (PVD) plays a critical role on the final surface quality of the deposited coatings. In this work a comparative study of metal thin films (Al, Cu, Ag) deposited by conventional DC-Magnetron Sputtering (DCMS) and highly ionized techniques such as Filtered Cathodic Vacuum Arc (FCVA) and high power impulse magnetron sputtering (HiPIMS) was performed. The final scope of the study is aimed to optimize the deposition parameters to achieve higher specular reflectance as this have a critical influence in the yield of solar plants based on concentrated solar power. In this regard, the optical constants of the deposited films were modeled departing from ellipsometry data. A comparison of the experimental reflectance with that obtained after optical simulation was also carried out. The achieved optical performance of the films was further compared to the structural properties resulting from different deposition techniques. Rutherford Backscattering Spectrometry (RBS) and Elastic Recoil Detection Analysis (ERDA)was applied to explore the potential oxidation of the films during deposition. Surface morphological changes were explored by Scanning Electron Microscopy (SEM). In addition, Atomic Force Microscopy (AFM) measurements at different deposition times allowed exploring the dynamics of the growth mechanism of the films.
Keywords: PVD techniques, Optical properties, Simulation, RBS, AFM
  • Lecture (Conference)
    Plasma Surface Engineering 2016, 11.-16.09.2016, Garmisch-Partenkirchen, Deutschland

Publ.-Id: 24140 - Permalink


Impurity suppression in sputtered metallic thin films using HiPIMS
Mesko, M.; Munnik, F.; Heller, R.; Grenzer, J.; Hübner, R.; Halanda, J.; Gemming, S.; Krause, M.;
Composition and microstructure of thin films deposited by PVD are often influenced by the presence of residual gas. Therefore, it would be desirable to enable thin film growth without residuals incorporation. Strategies to avoid impurities incorporation are substrate heating, applying substrate bias, and reduction of base pressure to ultra-high vacuum (UHV) conditions. Industrial demand for low temperature and low cost processes often precludes these approaches. More recently, a very important question has been raised regarding high power impulse magnetron sputtering (HiPIMS) to form pure metallic films at low deposition rates and high values of base pressure in the deposition chamber [1].

In this study, HiPIMS was applied for room-temperature deposition of pure metallic thin films of Al, Ti, and Cu. These metals are distinguished by their oxygen affinities and melting temperatures. Deposition of carbon top layers was used to differentiate between residual gas and post-deposition contamination. Elastic recoil detection analysis (ERDA) revealed that HiPIMS produces bulk-impurity-free metallic thin films. The growth of such high-purity metallic thin films can be partly explained by gas rarefaction and the self-cleaning effect of the bombarding ions. Moreover, densification effects presumably suppress post-deposition oxidation. Proposed deposition mechanism will be explained in sufficient detail. The compositional effects are correlated with differences in the film microstructure revealed by SEM, XRD, and TEM analyses.

[1] P. Pokorný et al., Plasma Processes Polym. 12, 416 (2015)

Financial support by the EU, grant No. 645725, project FRIENDS2, and the HGF via the W3 program (S.G.) is gratefully acknowledged. This work was also funded by the ERDF, Project CAMBO, ITMS: 2622022079, and by Slovak grant agency VEGA, project no. 1/0503/15
Keywords: HiPIMS, Room temperature PVD, High-purity metallic films, ERDA
  • Poster
    Plasma Surface Engineering 2016, 11.-16.09.2016, Garmisch-Partenkirchen, Deutschland

Publ.-Id: 24139 - Permalink


In situ RBS, Raman, and ellipsometry studies of layered material systems at elevated temperatures
Wenisch, R.; Heras, I.; Lungwitz, F.; Janke, D.; Guillén, E.; Heller, R.; Gemming, S.; Escobar Galindo, R.; Krause, M.;
The detailed knowledge of composition and structure is essential for the understanding of processes and properties of functional materials at elevated temperatures. To ensure materials functionality under in operando conditions, new concepts for analysis and process monitoring are necessary. In this contribution, selected layered material systems were studied in situ at temperatures up to 830°C by Rutherford backscattering (RBS), Raman spectroscopy, and ellipsometry within a cluster tool. Metal induced crystallization (MIC) is a promising technique for hydrogen-free synthesis of two-dimensional materials. Here, Si/Ag bilayers are studied as model system. The Si/Ag layer stacks are annealed at temperatures of 380 to 700°C. simultaneously, depth profiles of the elements are investigated by RBS revealing the diffusion kinetics. The changes in the phase structure and the degree of crystallinity are analyzed by Raman spectroscopy. Both the quick initial nucleation and ensuing growth processes are investigated. MIC is observed for all temperatures under study, while layer exchange occurs only for optimized process conditions.
As an example for high-temperature functional coatings, AlTiOxN1-x thin films were investigated in order to understand the influence of the oxygen to nitrogen ratio on the optical properties and their failure mechanisms at high temperatures. Ellipsometry and RBS results showed the influence of the initial oxygen content in the sample, inward diffusion of oxygen into the coating, and the high temperature stability of AlTiOxN1-x thin films. The low emittance of AlTiOxN1-x, allowed performing in situ RBS analysis at temperature up to 830°C for the first time.
Financial support by the EU, grant No. 645725, project FRIENDS2, and the
HGF via the W3 program (S.G.) is gratefully acknowledged.
Keywords: cluster tool, in situ analysis, RBS, Raman
  • Lecture (Conference)
    Plasma Surface Engineering 2016, 11.-16.09.2016, Garmisch-Partenkirchen, Deutschland

Publ.-Id: 24136 - Permalink


The role of Ga droplets in the epitaxy of GaAs nanowires on Si substrates
Dimakis, E.;
The double role of Ga droplets in the self-catalyzed growth of GaAs nanowires on SiOx/Si substrates, as well as the droplet-confined alternate pulsed epitaxy of GaAs nanowires, are discussed.
  • Invited lecture (Conferences)
    FemtoTera Workshop, 29.09.2016, Óbuda University, Budapest, Hungary

Publ.-Id: 24135 - Permalink


Growth and applications of III-V nanowires on Si substrates
Dimakis, E.;
III-V semiconductor nanowires have been a subject of intense research over the last 10 years and a plethora of exciting nanoscale phenomena has been unveiled. The peculiar strain relaxation mechanisms in nanowire heterostructures offer the possibility to integrate epitaxially materials with large mismatch of lattice parameters and thermal expansion coefficients. Thus, one can tailor the (opto)electronic properties of nanowire heterostructures using an extended palette of materials compared to traditional thin-film heterostructures. Furthermore, the epitaxial growth of III-V nanowires on lattice mismatched Si substrates is of great interest, because the two complementary technologies can thus be integrated on single multifunctional chips combining the superior electronic and optoelectronic properties of the former with the mature CMOS technology of the latter.
This seminar will be focusing on III-As nanowires grown on Si(111) substrates by molecular beam epitaxy. Starting from the basic description of the vapor-liquid-solid growth of GaAs nanowires and the self-induced growth of InAs nanowires [1,2], the problem of structural polytypism and its effect on the nanowire optoelectronic and electrical properties will be discussed [3,4] and, finally, the droplet-confined alternate pulsed epitaxy will be proposed as a unique growth mode that offers compatibility with the Si-CMOS processing standards [5]. Finally, the growth and the structural properties of coaxial multishell (In,Al,Ga)As/GaAs nanowires will be presented, and their application in light emitting diodes or modulation doped heterostructures will be discussed [6].

[1] E. Dimakis, J. Lähnemann, U. Jahn, S. Breuer, M. Hilse, L. Geelhaar, and H. Riechert, Cryst. Growth Des. 2011, 11, 4001–4008
[2] A. Biermanns, E. Dimakis, A. Davydok, T. Sasaki, L. Geelhaar, M. Takahasi, and U. Pietsch, Nano Lett. 2014, 14, 6878−6883
[3] P. Schroth, M. Köhl, and J.-W. Hornung, E. Dimakis, C. Somaschini, L. Geelhaar, A. Biermanns, S. Bauer, S. Lazarev, U. Pietsch, T. Baumbach, Phys. Rev. Lett. 2015, 114, 055504
[4] G. Bussone, H. Schäfer-Eberwein, E. Dimakis, A. Biermanns, D. Carbone, A. Tahraoui, L. Geelhaar, P. Haring Bolívar, T. U. Schülli, and U. Pietsch, Nano Lett. 2015, 15, 981−989
[5] L. Balaghi, T. Tauchnitz, R. Hübner, L. Bischoff, H. Schneider, M. Helm, and E. Dimakis, Nano Lett. 2016, 16, 4032−4039
[6] E. Dimakis, U. Jahn, M. Ramsteiner, A. Tahraoui, J. Grandal, X. Kong, O. Marquardt, A. Trampert, H. Riechert, and L. Geelhaar, Nano Lett. 2014, 14, 2604−2609
  • Invited lecture (Conferences)
    Seminar, ANKA - Karlsruhe Institute of Technology (KIT), 15.09.2016, Eggenstein-Leopoldshafen, Germany

Publ.-Id: 24134 - Permalink


Growth and applications of III-V nanowires on Si substrates
Dimakis, E.;
III-V semiconductor nanowires have been a subject of intense research over the last 10 years and a plethora of exciting nanoscale phenomena has been unveiled. The peculiar strain relaxation mechanisms in nanowire heterostructures offer the possibility to integrate epitaxially materials with large mismatch of lattice parameters and thermal expansion coefficients. Thus, one can tailor the (opto)electronic properties of nanowire heterostructures using an extended palette of materials compared to traditional thin-film heterostructures. Furthermore, the epitaxial growth of III-V nanowires on lattice mismatched Si substrates is of great interest, because the two complementary technologies can thus be integrated on single multifunctional chips combining the superior electronic and optoelectronic properties of the former with the mature CMOS technology of the latter.
This seminar will be focusing on III-As nanowires grown on Si(111) substrates by molecular beam epitaxy. Starting from the basic description of the vapor-liquid-solid (self-induced) growth of GaAs (InAs) nanowires [1,2], the problem of structural polytypism and its effect on the nanowire optoelectronic and electrical properties will be discussed [3,4] and, finally, the droplet-confined alternate pulsed epitaxy will be proposed as a unique growth mode that offers compatibility with the Si-CMOS processing standards [5]. Finally, the growth and the structural properties of coaxial multishell (In,Al,Ga)As/GaAs nanowires will be discussed, and their application in light emitting diodes or modulation doped heterostructures will be demonstrated [6].

[1] E. Dimakis, J. Lähnemann, U. Jahn, S. Breuer, M. Hilse, L. Geelhaar, and H. Riechert, Cryst. Growth Des. 2011, 11, 4001–4008
[2] A. Biermanns, E. Dimakis, A. Davydok, T. Sasaki, L. Geelhaar, M. Takahasi, and U. Pietsch, Nano Lett. 2014, 14, 6878−6883
[3] P. Schroth, M. Köhl, and J.-W. Hornung, E. Dimakis, C. Somaschini, L. Geelhaar, A. Biermanns, S. Bauer, S. Lazarev, U. Pietsch, T. Baumbach, Phys. Rev. Lett. 2015, 114, 055504
[4] G. Bussone, H. Schäfer-Eberwein, E. Dimakis, A. Biermanns, D. Carbone, A. Tahraoui, L. Geelhaar, P. Haring Bolívar, T. U. Schülli, and U. Pietsch, Nano Lett. 2015, 15, 981−989
[5] L. Balaghi, T. Tauchnitz, R. Hübner, L. Bischoff, H. Schneider, M. Helm, and E. Dimakis, Nano Lett. 2016, 16, 4032−4039
[6] E. Dimakis, U. Jahn, M. Ramsteiner, A. Tahraoui, J. Grandal, X. Kong, O. Marquardt, A. Trampert, H. Riechert, and L. Geelhaar, Nano Lett. 2014, 14, 2604−2609
  • Invited lecture (Conferences)
    Seminar, Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas (FORTH), 05.08.2016, Heraklion, Greece

Publ.-Id: 24133 - Permalink


Droplet-confined alternate pulsed epitaxy of GaAs nanowires on Si substrates: meeting the typical MBE standards
Tauchnitz, T.; Balaghi, L.; Bischoff, L.; Hübner, R.; Schneider, H.; Helm, M.; Dimakis, E.;
We introduce a growth scheme with alternate Ga and As4 pulses for the self-catalyzed growth of free-standing GaAs nanowires on Si(111) substrates. Unlike the conventional growth mode, our scheme offers a wide growth temperature window (450 – 600 °C), low growth rates (down to 1-2 monolayers per As4 pulse), and the ability for defect-free and abrupt growth interruptions, meeting the typical MBE standards. We demonstrate the possibility to grow defect-free zinc blende nanowires in the whole temperature window and to probe the growth dynamics in specially designed experiments.
Keywords: nanowire; self-catalyzed; alternate pulsed epitaxy; GaAs; Si substrate
  • Lecture (Conference)
    International Conference on Molecular Beam Epitaxy (MBE 2016), 04.09.2016, Montpellier, France

Publ.-Id: 24130 - Permalink


Exciton recombination at crystal-phase quantum rings in GaAs/InxGa1−xAs core/multishell nanowires
Corfdir, P.; Lewis, R. B.; Marquardt, O.; Küpers, H.; Grandal, J.; Dimakis, E.; Trampert, A.; Geelhaar, L.; Brandt, O.; Phillips, R. T.;
We study the optical properties of coaxial GaAs/InxGa1-xAs core/multishell nanowires with x between 0.2 and 0.4 at 10K. The evolution of the photoluminescence energy of the InxGa1-xAs quantum well shell with x and shell thickness agrees with the result of 8-band k.p calculations, demonstrating that the shell growth is pseudomorphic. At low excitation power, the photoluminescence from the shell is dominated by the recombination of exciton states deeply localized within the shell. We show that these states are associated with crystal-phase quantum rings that form at polytype segments of the InxGa1-xAs quantum well shell.

Publ.-Id: 24129 - Permalink


Functional behavior of the anomalous magnetic relaxation observed in melt-textured YBa2Cu3O7- δ samples showing the paramagnetic Meissner effect
Dias, F. T.; Vieira, V. N.; Garcia, E. L.; Wolff-Fabris, F.; Kampert, E.; Gouvea, C. P.; Schaf, J.; Obrados, X.; Puig, T.; Roa, J. J.;
We have studied the functional behavior of the field-cooled (FC) magnetic relaxation observed in melt- textured YBa2Cu3O7- δ(Y123) samples with 30 wt% of Y2Ba1Cu1O5 (Y211) phase, in order to investigate anomalous paramagnetic moments observed during the experiments. FC magnetic relaxation experiments were performed under controlled conditions, such as cooling rate and temperature. Magnetic fields up to 5T were applied parallel to the ab plane and along the c-axis. Our results are associated with the para-magnetic Meissner effect (PME), characterized by positive moments during FC experiments, and related to the magnetic flux compression into the samples. After different attempts our experimental data could be adequately fitted by an exponential decay function with different relaxation times. We discuss our results suggesting the existence of different and preferential flux dynamics governing the anomalous FC paramagnetic relaxation in different time intervals. This work is one of the first attempts to interpret this controversial effect in a simple analysis of the pinning mechanisms and flux dynamics acting during the time evolution of the magnetic moment. However, the results may be useful to develop models to explain this interesting and still misunderstood feature of the paramagnetic Meissner effect.

Publ.-Id: 24128 - Permalink


Magneto-acoustic study near the quantum critical point of the frustrated quantum antiferromagnet Cs2CuCl4
Cong, P. T.; Postulka, L.; Wolf, B.; van Well, N.; Ritter, F.; Assmus, W.; Krellner, C.; Lang, M.;
Magneto-acoustic investigations of the frustrated triangular-lattice antiferromagnet Cs2CuCl4 were performed for the longitudinal modes c11 and c33 in magnetic fields along the a axis. The temperature dependence of the sound velocity at zero field shows a mild softening at low temperature and displays a small kink-like anomaly at TN. Isothermal measurements at T < TN of the sound attenuation a reveal two closely spaced features of different characters on approaching the material’s quantum-critical point (QCP) at Bs = 8.5 T for B II a. The peak at slightly lower fields remains sharp down to the lowest temperature and can be attributed to the ordering temperature TN(B). The second anomaly, which is rounded and which becomes reduced in size upon cooling, is assigned to the material’s spin-liquid properties preceding the long-range antiferromagnetic ordering with decreasing temperature. These two features merge upon cooling suggesting a coincidence at the QCP. The elastic constant at lowest temperatures of our experiment at 32 mK can be well described by a Landau free energy model with a very small magnetoelastic coupling constant G/kB = 2.8 K. The applicability of this classical model indicates the existence of a small gap in the magnetic excitation spectrum which drives the system away from quantum criticality.

Publ.-Id: 24127 - Permalink


A monomeric copper-phosphoramide complex: Synthesis, structure, and electronic properties
Henriques, M. S.; Gorbunov, D. I.; Ponomaryov, A. N.; Saneei, A.; Pourayoubi, M.; Dusek, M.; Zvyagin, S.; Uhlarz, M.; Wosnitza, J.;
We report on a novel phosphoramide complex with formula Cu(NO3)2([C5H10N]3PO)2. This complex is the first example of a copper monomeric phosphoric triamide having an octahedral Cu[O]6 coordination environment. Cu(NO3)2([C5H10N]3PO)2 crystallizes in the monoclinic space group P21/n with the Cu atom located at an inversion center, as determined by single-crystal X-ray diffraction. Magnetic measurements along the principal crystallographic directions of the single crystal indicate that the complex is a paramagnet with very low magnetic anisotropy. Electron paramagnetic resonance spectra reveal the presence of two Cu2+ sites and make it possible to extract the hyperfine coupling.

Publ.-Id: 24126 - Permalink


Evaluation of E-Waste Processing through Secondary Copper Smelting
Rhamdhani, M. A.; Ghodrat, M.; Brooks, G.; Masood, S.; Corder, G.; Haque, N.; Reuter, M. A.;
Wastes of electronics and electrical equipment (WEEE) or simply e-wastes contain many valuable elements that include base metals (Cu, Fe, Pb, Al), precious metals (Au, Ag, Pt, Pd), other metals (Sn, Se, Te, Ta, Co, In, Ru, etc); as well as hazardous elements. Sustainable extraction of the valuable elements from e-waste is challenging due to the complexities of the materials and associated processing routes. There have been a number of processing and extraction techniques developed at laboratory level and few are implemented in industrial practices [1]. The processes implemented at industrial scale are mainly based on an improved combination of traditional extractive metallurgy processes (for example a combined pyrometallurgy, hydrometallurgy and electrometallurgy processes). Although practiced at industry scale, these processes and processing routes are far from optimised. Development of new technologies and/or improvement of the existing practices are still needed. Some of the barriers for improvement include: lack of fundamental knowledge (behaviour of all of these elements, which are governed by their solution thermodynamics); limited sound technoeconomic analyses; as well as limited understanding on the environmental impact of the different processing routes.
Keywords: E-Waste, E-Waste processing, WEEE recycling, precious metals, secondary copper
  • Lecture (Conference)
    8th Annual High Temperature Processing Symposium 2016, 01.-02.02.2016, Melbourne, Australien

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Publ.-Id: 24125 - Permalink


Recycling Indices Visualizing the Performance of the Circular Economy
Reuter, M. A.; van Schaik, A.;
The EU has adopted an ambitious Circular Economy (CE) package. This action plan aims to "close" the loop of product lifecycles through improved product design, improved collection, recycling, remanufacture and re-use. Through this the EU envisages to bring benefits both environmentally as well as economically. Recycling forms the heart of the CE system; metal and material recycling and metallurgical processing are key enablers. Maximizing the recovery of materials from End-of-Life (EoL) products, while simultaneously lowering the environmental footprint, is a vital outcome. Therefore, designing greener products while also optimizing organisational and technology infrastructures of industrial recycling processing flow sheets are vital. This enables the maximal recovery of materials and also especially strategic elements from EoL products, requiring a deep understanding of the fundamental opportunities and limits and the dynamics of the evolving and agile system. In order to inform the consumer, this paper presents the developed Recycling Index (RI) (analogous to the EU Energy Labels) that includes a new Material-RI.These are based on simulation models that have their roots in minerals and metallurgical processing. It builds on previous work by the authors that visualises and communicate the recycling performance of a product as well as of the individual materials in a clear, easy and transparent manner. It will help to empower the consumer to make informed purchasing decisions. Furthermore, RIs are essential for communicating greener design and efforts to improve resource efficiency by producers and state-of-the art recycling and (metallurgical) processing technology by industry. The RI is an excellent tool to provide insight into possibilities and improvements as well as barriers and limits for CE to policy makers and to close the missing links in the CE.
Keywords: Recycling – Design for Recycling – Recycling Index – Simulation – Calculation methods for recycling rates – Circular Economy
  • World of Metallurgy - Erzmetall 69(2016)4, 201-216

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Publ.-Id: 24124 - Permalink


Strategic metal recycling: adaptive metallurgical processing infrastructure and technology are essential for a Circular Economy
Reuter, M. A.; van Schaik, A.;
Recycling forms the heart of the Circular Economy (CE) system. Ultimately all products will have to be recycled at their End-of-Life (EoL). Maximizing the recovery of materials and also especially strategic elements from EoL products requires a deep understanding of the fundamental limits and the dynamics of the evolving system, thus an adaptive processing and metallurgical infrastructure is critical to recover all metals and materials. Paramount is the quantification of the “mineralogy”, the complex and interlinked composition of products, to trace and quantify specifically all the losses of materials, metals, alloys, etc. due to thermodynamic and other non-linear interactions. We named this product centric recycling. The recycling potential and performance must be quantified and demonstrated for products, collection systems, waste separation and recovery technologies, and material supply. Emphasis is also placed on informing the consumer through iRE i.e. informing Resource Efficiency in an easy-to-understand way. System Integrated Metal Processing (SIMP) using big-data, multi-sensors, simulation models, metallurgy, etc. links all stakeholders through Circular Economy Engineering (CEE), an important enabler to maximize Resource Efficiency and thus iRE.
Keywords: EoL, CE, CEE
  • Annales des Mines - Responsiabilité & Environnement (2016)82, 62-66

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Publ.-Id: 24123 - Permalink


Gold - A Key Enabler of a Circular Economy: Recycling of Waste Electric and Electronic Equipment
Reuter, M. A.; van Schaik, A.;
Metals are an essential and critical component of today's society: a moment's reflection on their ubiquitous presence in virtually all energy and material production processes is sufficient to confirm this. Metals play a key role in enabling sustainability through various high-tech applications in society. However, the resources of our planet are limited, as is the strain to which we can subject it in terms of emissions, pollution, and disposal of waste. For these reasons, finding ways to lower the environmental footprint of our collective existence and therefore lowering greenhouse gas and other emissions is a vital priority. The principal theme of this contribution is the maximization of resource efficiency as well as enabling a circular economy (CE) through the recycling of waste electric and electronic equipment, with a focus on precious metals (PMs) (incorporating gold, silver, and the platinum group metals [PGMs]) and the base-metal industry that enables their recycling. The detailed and deep knowledge that is required to systemically fully understand resource efficiency in the context of a CE are discussed and the concepts of design for resource efficiency and design for recycling elaborated on. Specifically, the understanding of product-centric recycling is highlighted, setting it apart from the usual material-centric recycling approaches. The latter focus more on bulk materials and therefore inherently limit the maximal recovery of technologically critical elements in particular, as well as PMs and PGMs. The base metals – principally, copper, cobalt, lead, nickel, tin, and zinc – all play a crucial part in the present society. Increasingly, these are linked in concert to form the crucial carrier metals for the sustainable CE society termed the “web of metals” and “web of products” or, in a more modern paradigm, system integrated metal production–in other words, the process metallurgical Internet of things. This chapter also examines the special and crucial role base metals have in acting as enablers in any recycling efforts, as they also play a key role during recycling, such as copper and lead being the solvent of gold and other PMs and PGMs and release them during refining. Above all, the PMs are key economic enablers for the economic viability of recycling as well as the metallurgical infrastructure (system integrated metal production/Internet of things) that makes it possible to recover PMs and PGMs and their other associated elements.
Keywords: Critical metals; Design for recycling; Furnace technology; Gold; Hydrometallurgy; Internet-of-things; Precious metals; Process metallurgy; Pyrometallurgy; Recycling; System integrated Metal production; WEEE

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Publ.-Id: 24122 - Permalink


Digitalizing the Circular Economy: Circular Economy Engineering Defined by the Metallurgical Internet of Things
Reuter, M. A.;
Metallurgy is a key enabler of a circular economy (CE), its digitalization the metallurgical Internet of Things (m-IoT). In short: Metallurgy is at the heart of a CE, as metals all have strong intrinsic recycling potentials. Process metallurgy, as a key enabler for a CE, will help much to deliver its goals. The first-principles models of process engineering help quantify the resource efficiency (RE) of the CE system, connecting all stakeholders via digitalization. This provides well-argued and first-principles environmental information to empower a tax paying consumer society, policy, legislators, and environmentalists. It provides the details of capital expenditure and operational expenditure estimates. Through this path, the opportunities and limits of a CE, recycling, and its technology can be estimated. The true boundaries of sustainability can be determined in addition to the techno-economic evaluation of RE. The integration of me tallurgical reactor technology and systems digitally, not only on one site but linking different sites globally via hardware, is the basis for describing CE systems as dynamic feedback control loops, i.e., the m-IoT.
Keywords: digitalization the metallurgical Internet of Things (m-IoT)

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Publ.-Id: 24121 - Permalink


Fast neutron-induced fission at the time-of-flight facility nELBE
Kögler, T.; Beyer, R.; Junghans, A. R.; Müller, S.;
The fast neutron-induced fission cross section of Pu(242) was determined the range of 0.5 MeV and in 10 MeV relative to U(235)(n,f) at the neutron time-of-flight facility nELBE. Using the high spontaneous fission rate of Pu(242) to determine the number of target atoms makes the cross section independent from the detection. Sophisticated neutron transport simulations with Geant 4 and MCNP 6 are used to correct the neutron scattering. The determined relative cross section is in good agreement with current experimental and evaluated data sets.
Keywords: neutron-induced fission cross section, neutron scattering corrections, fast neutrons, nELBE
  • Lecture (Conference)
    ND2016 - International Conference on NUCLEAR DATA FOR SCIENCE AND TECHNOLOGY, 11.-16.09.2016, Bruges, Belgien
  • Open Access LogoContribution to proceedings
    ND 2016 - International Conference on NUCLEAR DATA FOR SCIENCE AND TECHNOLOGY, 11.-16.09.2016, Bruges, Belgien
    EPJ Web of Conferences, Les Ulis Cedex A
    DOI: 10.1051/epjconf/201714611023

Publ.-Id: 24120 - Permalink


Temperature Quenching in LAB based liquid scintillator
Sörensen, A.; Junghans, A. R.; Kögler, T.; Wagner, A.; Zuber, K.;
This work investigated the effect of temperature changes on the light output of LAB based liquid scintillator in a range from -5°C to 30°C with a-particles and electrons in a small scale setup. Assuming a linear behaviour, a combined negative temperature coefficient of (-0.29+-0.01) % / °C is found. Considering hints for a particle type dependency, electrons show (-0.17+-0.02) % / °C, whereas the temperature dependency seems stronger for a-particles, with (-0.35+-0.03) % / °C. A pulse shape analysis shows increased strength of a slow decay component at lower temperatures, pointing to reduced non-radiative triplet state de-excitations at lower temperatures.
Keywords: lineare Alcyl benzene, temperature quenching

Publ.-Id: 24119 - Permalink


Plutonium interaction studies with the Mont Terri Opalinus Clay isolate Sporomusa sp. MT-2.99: changes in the plutonium speciation by solvent extractions.
Moll, H.; Cherkouk, A.; Bok, F.; Bernhard, G.;
Since plutonium could be released from nuclear waste disposal sites, the exploration of the complex interaction processes between plutonium and bacteria is necessary for an improved understanding of the fate of plutonium in the vicinity of such a nuclear waste disposal site. In this basic study the interaction of plutonium with cells of the bacterium, Sporomusa sp. MT-2.99, isolated from Mont Terri Opalinus Clay, was investigated anaerobically (in 0.1 M NaClO4) with or without adding Na-pyruvate as an electron donor. The cells displayed a strong pH dependent affinity for Pu. In the absence of Na-pyruvate a strong enrichment of stable Pu(V) in the supernatants was discovered, whereas Pu(IV)-polymers dominated the Pu oxidation state distribution on the biomass at pH 6.1. A pH-dependent enrichment of the lower Pu oxidation states (e.g. Pu(III) at pH 6.1 which is considered to be more mobile than Pu(IV) formed at pH 4) was observed in the presence of up to 10 mM Na-pyruvate. In all cases, the presence of bacterial cells enhanced removal of Pu from solution and accelerated Pu interaction reactions, e.g. biosorption and bioreduction.
Keywords: plutonium; bacteria; Sporomusa sp.; biosorption; bioreduction; solvent extractions

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Publ.-Id: 24118 - Permalink


The case of a rough potential energy surface: Discrepancies between results of NEB and MD calculations
Posselt, M.;
Vacancy migration is studied in a silicon crystal with atomic interactions described by the Kumagai potential [1]. The basic functional form of this potential is very similar to the Tersoff potential. The main improvements concern the values of the elastic constants and the melting temperature. However, the potential energy surface is as rough as in the case of the Tersoff potential. In the ground state the vacancy has the “normal” tetrahedral configuration. The migration in the rugged potential energy landscape leads to peculiarities. Extensive Molecular Dynamics (MD) calculations show that the atomic mechanism of the migration process depends on temperature. The vacancy migration energy changes at about 1000 K: At lower and higher temperatures it is about 0.71 and 0.41 eV, respectively. Investigations on the dominating defect structure show that below about 1000 K the tetrahedral vacancy prevails whereas at higher temperature a modified version of the tetrahedral vacancy, the split vacancy and other configurations become dominant.
Applying the Nudged Elastic Band (NEB) method to the potential energy surface in the ground state, the transition between neighboring tetrahedral vacancy structures was studied. A number of intermediate metastable states were found, amongst them the modified version of the tetrahedral vacancy and the split vacancy. The maximum barrier for the migration between one ground state configuration to another is about 0.9 eV, whereas a barrier of about 0.3 eV is found for the transition from the split to the modified tetrahedral structure. Comparing with the results of MD simulations one may assume that in the high temperature range the vacancy moves mainly between high-energy configurations such as the split and the modified tetrahedral structure. The reason why the vacancy is not very often found in the ground state is not completely clear. Obviously, the free energy landscape at elevated temperature differs strongly from the ground-state energy landscape. Vibrational degrees of freedom may lead to the narrowing of the path to the tetrahedral state while the path between the high energy states may become much broader.
[1] T. Kumagai et al., Comput. Mater. Sci. 39, 457 (2007)
Keywords: molecular dynamics, nudged elastic band method, potential energy surface
  • Poster
    Int. Focus Workshop on Bridging-Time Scale Techniques and their Application in Atomistic Computational Science, 12.-15.09.2016, Dresden, Germany

Publ.-Id: 24117 - Permalink


Local Scale-Invariance of the 2+1 dimensional Kardar-Parisi-Zhang model
Kelling, J.; Ódor, G.; Gemming, S.;
Local Scale-Invariance theory is tested by extensive dynamical simulations of the driven dimer lattice gas model, describing the surface growth of the 2+1 dimensional Kardar–Parisi–Zhang surfaces. Very precise measurements of the universal autoresponse function enabled us to perform nonlinear fitting with the scaling forms, suggested by local scale-invariance (LSI). While the simple LSI ansatz does not seem to work, forms based on logarithmic extension of LSI provide satisfactory description of the full (measured) time evolution of the autoresponse function.
Keywords: Kardar-Parisi-Zhang, Local Scale-Invariance, Monte-Carlo, GPU
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Publ.-Id: 24116 - Permalink


Inter-sublevel dynamics in single InAs/GaAs quantum dots probed by strong terahertz excitation
Stephan, D. R.;
In this thesis, the response of single self-assembled quantum dots to strong terahertz pulses is investigated by measuring the emitted photoluminescence spectrally as well as in a time-resolved manner, revealing the dynamics of the system. Experimentally, this is realized by combining the micro-photoluminescence technique with illumination from a free-electron laser, which provides intense, tunable narrow-band terahertz pulses. The photoluminescence is triggered by spectrally tunable near-infrared illumination with a synchronized, mode-locked titanium sapphire laser. The measured transients are evaluated with a rate-equation model, taking into account the precise detector response. These measurements reveal three distinct effects, which appear or are obscured depending on the excitation conditions. Firstly, the conduction band inter-sublevel s-p transition is excited by the THz pulses. However, for strong terahertz intensities, a loss of photoluminescence is observed, which can lead to total depletion at very high intensities. This is attributed to the transfer of charge carriers into the wetting layer. Thirdly, for certain near-infrared energies, the opposite behavior is observed, in which the terahertz pulse causes an increase of photoluminescence. The cause of this effect is the release of previously trapped charge carriers, which is also visible in the photoluminescence spectrum. The source of the additional charge carriers is unambiguously identified as the wetting layer. The obtained data is compared to previous studies, and an overview of the relevant theory is presented. In addition, a description of the custom built experimental setup is given.
Keywords: InAs/GaAs semiconductor quantum dot, time-resolved photoluminescence, micro-photoluminescence, free-electron laser, terahertz excitation, carrier dynamics
  • Book (Authorship)
    München: Verlag Dr. Hut, 2016
    122 Seiten

Publ.-Id: 24115 - Permalink


Nodal recurrence after stereotactic body radiotherapy for early stage non-small cell lung cancer: incidence and proposed risk factors
Wink, K. C. J.; van Baardwijk, A.; Troost, E. G. C.; de Ruysscher, D.;
Stereotactic body radiotherapy (SBRT) is an alternative to surgery for patients with early stage non-small cell lung cancer (NSCLC) who are inoperable due to comorbid disease or who refuse surgery. SBRT results in an excellent local control rate of more than 90%, which is comparable to surgery, while short and long-term overall toxicity is low. Surgically treated patients are often more extensively staged pre-operatively, e.g. with EBUS, and undergo intra-operative lymph node dissection or sampling. Occult nodal metastases (ONM) detected by lymph node dissection have been shown to increase the incidence of regional recurrence (RR) after surgery, which is associated with poor outcome. In patients undergoing SBRT, however, definite pathological nodal staging is lacking. Therefore, other ways to identify patients at high risk for ONM and RR might be thought for.
The aim of this systematic review is to summarize the incidence of and risk factors for RR after SBRT and compare these to those after surgery.
Keywords: SBRT, SABR, NSCLC, regional recurrence, lymph node, early stage

Publ.-Id: 24114 - Permalink


Cyclotron resonance and photoluminescence studies of dilute GaAsN in magnetic fields up to 62 Tesla
Eßer, F.;
In this thesis, we investigate optical and electrical properties of dilute nitride semiconductors GaAsN in pulsed magnetic fields up to 62 T. For the most part, the experiments are performed at the Dresden High Magnetic Field Laboratory (HLD).
In the first part of this thesis, the electron effective mass of GaAsN is determined with a direct method for the first time. Cyclotron resonance (CR) absorption spectroscopy is performed in Si-doped GaAsN epilayers with a nitrogen content up to 0.2%. For the CR absorption study, we use the combination of the free-electron laser FELBE and pulsed magnetic fields at the HLD, both located at the Helmholtz-Zentrum Dresden-Rossendorf. A slight increase of the CR electron effective mass with N content is obtained. This result is in excellent agreement with calculations based on the band anticrossing model and the empirical tight-binding method. We also find an increase of the band nonparabolicity with increasing N concentration in agreement with our calculations of the energy dependent momentum effective mass.
In the second part of this thesis, the photoluminescence (PL) characteristics of intrinsic GaAsN and n-doped GaAsN:Si is studied. The PL of intrinsic and very dilute GaAsN is characterized by both GaAs-related transitions and N-induced features. These distinct peaks merge into a broad spectral band of localized excitons (LEs) when the N content is increased. This so-called LE-band exhibits a partially delocalized character because of overlapping exciton wave functions and an efficient interexcitonic population transfer. Merged spectra dominate the PL of all Si-doped GaAsN samples. They have contributions of free and localized excitons and are consequently blue-shifted with respect to LE-bands of intrinsic GaAsN. The highly merged PL profiles of GaAsN:Si are studied systematically for the first time with temperature-dependent time-resolved PL. The PL decay is predominantly monoexponential and has a strong energy dispersion. In comparison to formerly reported values of intrinsic GaAsN epilayers, the determined decay times of GaAsN:Si are reduced by a factor of 10 because of enhanced Shockley-Read-Hall and possibly Auger recombinations.
In the third part of this thesis, intrinsic and Si-doped GaAsN are investigated with magneto-PL in fields up to 62 T. A magneto-PL setup for pulsed magnetic fields of the HLD was built for this purpose. The blue-shift of LE-bands is studied in high magnetic fields in order to investigate its delocalized character. The blue-shift is diminished in intrinsic GaAsN at higher temperatures, which indicates that the interexcitonic population transfer is only active below a critical temperature 20 K < T < 50 K. A similar increase of the temperature has no significant impact on the partially delocalized character of the merged spectral band of GaAsN:Si. We conclude that the interexcitonic transfer of Si-doped GaAsN is more complex than in undoped GaAsN. In order to determine reduced masses of undoped GaAsN and GaAs:Si, the field-induced shift of the free exciton transition is studied in the high-field limit. We find an excellent agreement of GaAs:Si with a formerly published value of intrinsic GaAs which was determined with the same method. In both cases, the reduced mass values are enhanced by 20% in comparison to the accepted reduced mass values of GaAs. The determined GaAsN masses are 1.5 times larger than in GaAs:Si and match the rising trend of formerly reported electron effective masses of GaAsN.
Keywords: dilute nitride, recombination dynamics, effective mass, pulsed magnetic fields, magneto-photoluminescence
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-072 2016
    ISSN: 2191-8708

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Publ.-Id: 24113 - Permalink


Rohstoffe für die Energieversorgung der Zukunft
Angerer, G.; Buchholz, P.; Gutzmer, J.; Hagelten, C.; Herzig, P.; Little, R.; Trauer, R. K.; Welker, F.-W.;
  • Book (Authorship)
    München: Acatech, 2016
    198 Seiten

Publ.-Id: 24112 - Permalink


Self-Supporting Hierarchical Porous PtAg Alloy Nanotubular Aerogels as Highly Active and Durable Electrocatalysts
Liu, W.; Haubold, D.; Rutkowski, B.; Oschatz, M.; Hübner, R.; Werheid, M.; Ziegler, C.; Sonntag, L.; Liu, S.; Zheng, Z.; Herrmann, A.-K.; Geiger, D.; Terlan, B.; Gemming, T.; Borchardt, L.; Kaskel, S.; Czyrska-Filemonowicz, A.; Eychmüller, A.;
Developing electrocatalysts with low cost, high activity, and good durability is urgently demanded for the wide commercialization of fuel cells. By taking advantage of nanostructure engineering, we fabricated PtAg nanotubular aerogels (NTAGs) with high electrocatalytic activity and good durability via a simple galvanic replacement reaction between the in situ spontaneously gelated Ag hydrogel and the Pt precursor. The PtAg NTAGs have hierarchical porous network features with primary networks and pores from the interconnected nanotubes of the aerogel and secondary networks and pores from the interconnected thin nanowires on the nanotube surface, and they show very high porosities and large specific surface areas. Due to the unique structure, the PtAg NTAGs exhibit greatly enhanced electrocatalytic activity toward formic acid oxidation, reaching 19 times higher metal-based mass current density as compared to the commercial Pt black. Furthermore, the PtAg NTAGs show outstanding structural stability and electrochemical durability during the electrocatalysis. Noble metal-based NTAGs are promising candidates for applications in electrocatalysis not only for fuel cells, but also for other energy-related systems.

Publ.-Id: 24111 - Permalink


Parallel assessment of hypoxia in tumor and LN metastases increases prognostic value of hypoxia-specific PET imaging in locally advanced head-and-neck cancer - secondary analysis of the DDFMISO-trial
Bandurska-Luque, A.; Löck, S.; Haase, R.; Zöphel, K.; Abolmaali, N.; Seidlitz, A.; Perrin, R.; Richter, C.; Troost, E.; Steinbach, J.;
Background: Primary tumor (Tu) hypoxia based on hypoxia-specific PET-imaging is a known prognostic parameter for locally-advanced head-and-neck cancer patients. A secondary analysis of the prospective clinical trial on repeated pre- and per-treatment [18F]fluoromisonidazole (FMISO) PET/CT imaging aimed to assess whether parallel evaluation of the oxygenation status in lymph node metastases (LN) and the Tu increases its prognostic value.
Patients and methods: Patients with LN-positive disease from the trial (NCT00180180, Zips et al. 2012, Seidlitz et al. 2015) were included in this analysis (n=45). The patients were treated with curatively intended radiochemotherapy (RCT). The imaging protocol consisted of FMISO PET/CT at four time points: baseline, week 1, 2 and 5. Delineation of the Tu and LNs was based on pre-treatment FDG PET/CT. Qualitative hypoxia analysis was performed for each Tu and LN using a visual binary scale: hypoxic or normoxic being FMISO uptake higher than or equal to background respectively. Based on this scale two prognostic parameters were defined: Tu hypoxia (patients with a hypoxic Tu, independently of LN oxygenation status) and synchronous Tu- and LN-hypoxia (Tu&LN-hypoxia). In the patients with a large LN (n=15) a quantitative analysis of FMISO PET/CT was performed to validate the qualitative hypoxia scale. The log-rank test and multivariate Cox-regression were used to evaluate the prognostic impact of hypoxia on local control (LC) and loco-regional control (LRC).
Results: Qualitative FMISO assessment (Table 1) confirmed poor LC in patients with Tu hypoxia in week 2 and 5. Detection of synchronous Tu- and LN-hypoxia had a strong negative impact on LC and LRC at all measured time-points. These results were supported by multivariate analysis (for LRC: HR=14.8, p=0.016; HR=8.3, p=0,003 and HR=5.5, p=0,005 at baseline, in week 2 and 5, respectively). Moreover, there was a significant correlation between the qualitative and quantitative FMISO PET/CT parameters (p<0.001; R>0.6-0.8).
Conclusions: Parallel evaluation of tumor and LN hypoxia improved the prognostic information in comparison to primary tumor assessment alone, based on secondary analysis of the Dresden FMISO PET/CT trial. If this prognostic value of synchronous tumor- and LN-hypoxia is confirmed in ongoing prospective clinical trials and show to outperform tumor assessment only, it may become a powerful decision-making parameter useful for dose escalation or combined modality trials.
Keywords: FMISO, tumor and lymph node hypoxia

Publ.-Id: 24110 - Permalink


Downscaling Effect on the Superconductivity of Pd3Bi2X2 (X = S or Se) Nanoparticles Prepared by Microwave-Assisted Polyol Synthesis
Roslova, M.; Opherden, L.; Veremchuk, I.; Spillecke, L.; Kirmse, H.; Herrmannsdörfer, T.; Wosnitza, J.; Doert, T.; Ruck, M.;
PdBi2S2 and Pd3Bi2Se2 have been successfully prepared in the form of nanoparticles with diameters of ∼50 nm by microwave-assisted modified polyol synthesis at low temperatures. The composition and morphology of the samples have been studied by means of powder X-ray diffraction as well as electron microscopy methods, including X-ray intensity mapping on the nanoscale. Superconducting properties of the as-prepared samples have been characterized by electrical resistivity measurements down to low temperatures (∼0.2 K). Deviations from the bulk metallic behavior originating from the submicrometer nature of the samples were registered for both phases. A significant critical-field enhancement up to 1.4 T, i.e., 4 times higher than the value of the bulk material, has been revealed for Pd3Bi2Se2. At the same time, the critical temperature is suppressed to 0.7 K from the bulk value of ∼1 K. A superconducting transition at 0.4 K has been observed in nanocrystalline Pd3Bi2S2. Here, a zero-temperature upper critical field of ∼0.5 T has been estimated. Further, spark plasma-sintered Pd3Bi2S2 and Pd3Bi2Se2 samples have been investigated. Their superconducting properties are found to lie between those of the bulk and nanosized samples.

Publ.-Id: 24109 - Permalink


Field-stepped broadband NMR in pulsed magnets and application to SrCu2(BO3)2 at 54 T
Kohlrautz, J.; Haase, J.; Green, E. L.; Zhang, Z. T.; Wosnitza, J.; Herrmannsdörfer, T.; Dabkowska, H. A.; Gaulin, B. D.; Stern, R.; Kühne, H.;
Pulsed magnets generate the highest magnetic fields as brief transients during which the observation of NMR is difficult, however, this is the only route to unique insight into material properties up to the regime of 100 T. Here, it is shown how rather broad NMR spectra can be assembled in a pulsed magnet during a single field pulse by using the inherent time dependence of the field for the recording of field-stepped free induction decays that cover a broad frequency range. The technique is then applied to 11B NMR of the spin-dimer system SrCu2(BO3)2, a magnetic insulator known to undergo a series of field-driven changes of the magnetic ground state. At peak fields of about 54 T at the Dresden High Magnetic Field Laboratory, 11B NMR spectra spanning a total of about 9 MHz width are reconstructed. The results are in good accordance with a change from a high-temperature paramagnetic state to a low-temperature commensurate superstructure of field-induced spin-dimer triplets.

Publ.-Id: 24108 - Permalink


Quantum phase transitions and multicriticality in Ta(Fe1-xVx)2
Brando, M.; Kerkau, A.; Todorova, A.; Yamada, Y.; Khuntia, P.; Förster, T.; Burkhard, U.; Baenitz, M.; Kreiner, G.;
We present a comprehensive study of synthesis, structure analysis, transport and thermodynamic properties of the C14 Laves phase Ta(Fe1-xVx)2. Our measurements confirm the appearance of spin-density wave (SDW) order within a dome-like region of the x-T phase diagram with vanadium content 0.02 < x < 0.3. Our results indicate that on approaching TaFe2 from the vanadium-rich side, ferromagnetic (FM) correlations increase faster than the antiferromagnetic (AFM) ones. This results in an exchange-enhanced susceptibility and in the suppression of the SDW transition temperature for x < 0.13 forming the dome-like shape of the phase diagram. This effect is strictly related to a significant lattice distortion of the crystal structure manifested in the c / a ratio. At x = 0.02 both FM and AFM energy scales have similar strength and the system remains paramagnetic down to 2 K with an extremely large Stoner enhancement factor of about 400. Here, spin fluctuations dominate the temperature dependence of the resistivity ρ ∝ T3/2 and of the specific heat C/T ∝-log(T) which deviate from their conventional Fermi liquid forms, inferring the presence of a quantum critical point of dual nature.

Publ.-Id: 24107 - Permalink


Can enhanced feedback effects and improved breeding coincide in a metal fueled, sodium cooled fast reactor?
Merk, B.; Devan, K.; Bachchan, A.; Paul, D.; Puthiyavinayagam, P.; Srinivasan, G.;
Different strategies for the improvement of in core breeding on fuel assembly level are investigated using the HELIOS 2.1 code. An additional key boundary condition is the conservation of the safety related feedback effects of the assembly. It is demonstrated that the insertion of 1/3 of fertile fuel rods into the fuel assembly, while the overall Pu content of the assembly is kept constant, can improve the breeding of fresh Plutonium. A second proposal is the reduction of the Pu content of the assembly compensated by eliminating one ring of the fertile blanket around the core. This method proofs to be very efficient to improve the in core breeding. The consequences on the fuel assembly multiplication factor, the fissile material content, and the pin wise power as well as burnup distribution is analyzed. Additionally, the effect of fine distributed material on breeding as well as on the safety related feedback effects is investigated for both proposals. A clear enhancement of the feedback effects could be proven.
Keywords: nuclear reactors, fast reactors, plutonium breeding, enhanced feedback effects, moderating material

Publ.-Id: 24106 - Permalink


Multiscale modeling of bacterial colonies: How pili mediate the dynamics of single cells and cellular aggregates
Pönisch, W.; Weber, C.; Juckeland, G.; Biais, N.; Zaburdaev, V.;
Neisseria gonorrhoeae is the causative agent of one of the most common sexually transmitted diseases, gonorrhea. An vital step during the infection process is the formation of microcolonies, agglomerates of up to thousands of cells. The assembly of these colonies is driven by type IV pili, filamentaeous polymers protruding from the surface of the colonies, undergoing cycles of elongation and retraction and forming bonds with each other and a substrate. Here, we present a computer model of individual cells interacting via each other solely by pili. This model allows us to study a wide range of processes, from the motion of individual cells and colonies on a surface, over the dynamics within colonies and how they drive the coalescence of two microcolonies, up to the self-assembly of cells.

Publ.-Id: 24105 - Permalink


Structure, composition and magnetism in FeAl alloys
Menendez, E.; Surinach, S.; Baro, M. D.; Liedke, M. O.; Fassbender, J.ORC; Nogues, J.; Sort, J.
Fe1–xAlx alloys with x ranging from roughly 0.35 to 0.5 at. % show an interesting combination of room temperature magnetic and structural properties. Atomically ordered Fe1–xAlx (0.35 ≤ x ≤ 0.5 at. %) alloys are paramagnetic, while atomically disordered Fe1–xAlx (0.35 ≤ x ≤ 0.5 at. %) alloys become ferromagnetic [1]. The transition from the paramagnetic to the ferromagnetic state can be accomplished by different means (e.g., deformation or ion irradiation) and, remarkably, fully reversed upon thermal treatment [2]. Fabrication of Fe1–xAlx (0.35 ≤ x ≤ 0.5 at. %) thin films with controlled microstructure, composition and thickness would turn them into potential candidates to be magnetically patterned for the functioning of devices, such as magnetic storage media or magnetoresistive random access memories [3]. An overwiew of this order-disorder transition by either deformation or ion irradiation in bulk samples will be presented. Particular emphasis will be given to magnetic patterning routes by both local deformation and selective ion irradiation. Finally, our recent results on the preparation of thin films with controlled microstructure, composition and thickness will be outlined.

[1] E. Menéndez et al. New J. Phys. 10 (2008) 103030
[2] E. Menéndez et al. Small 5 (2009) 229
[3] R. Bali et al. Nano Lett. 14 (2014) 435

Keywords: magnetism, FeAl, binary alloys
  • Invited lecture (Conferences)
    Frontiers in Materials Processing Applications, Research and Technology, 09.-12.07.2017, Bordeaux, Frankreich

Publ.-Id: 24104 - Permalink


Effects of Substrate and Post-Growth Treatments on the Microstructure and Properties of ZnO Thin Films Prepared by Atomic Layer Deposition
Haseman, M.; Saadatkia, P.; Winarski, D. J.; Selim, F. A.; Leedy, K. D.; Tetlak, S.; Look, D. C.; Anwand, W.; Wagner, A.;
Aluminum doped zinc oxide (ZnO:Al) thin films were synthesized by atomic layer deposition on silicon, quartz and sapphire substrates and characterized by X-ray diffraction (XRD), high-resolution scanning electron microscopy (SEM), optical spectroscopy, conductivity mapping, Hall-effect measurements and positron annihilation spectroscopy (PAS). XRD showed that the as-grown films are of single-phase ZnO wurtzite structure and do not contain any secondary or impurity phases. The type of substrate was found to affect the orientation and degree of crystallinity of the films but had no effect on the defect structure or the transport properties of the films. High conductivity of 10-3 Ohm cm, electron mobility of 20 cm2/Vs and carrier density of 1020 cm-3 were measured in most films. Thermal treatments in various atmospheres induced a large effect on the thickness, structure and electrical properties of the films. Annealing in a Zn and nitrogen environment at 400 oC for one hour led to a 16% increase in the thickness of the film; this indicates that Zn extracts oxygen atoms from the matrix and forms new layers of ZnO. On the other hand, annealing in a hydrogen atmosphere led to the emergence of an Al2O3 peak in the XRD pattern, which implies that hydrogen and Al atoms compete to occupy Zn sites in the ZnO lattice. Only ambient-air anneal had an effect on film defect density and electrical properties, generating reduction in conductivity and electron mobility. Depth resolved measurements of positron annihilation revealed short positron diffusion lengths and high concentration of defects in all as-grown films. However these defects did not diminish the electrical conductivity in the films.
Keywords: ZnO defects positron annihilation annealing

Publ.-Id: 24103 - Permalink


Out-of-plane magnetized cone-shaped magnetic nanoshells
Ball, D. K.; Günther, S.; Fritzsche, M.; Lenz, K.; Varvaro, G.; Laureti, S.; Makarov, D.; Mücklich, A.; Facsko, S.; Albrecht, M.; Fassbender, J.ORC
The geometry of a magnetic nanoobject, namely its shape and dimension determines the complex electromagnetic responses. Here, we address the geometry-induced changes of the magnetic properties of thin ferromagnetic Co/Pd multilayers with out-of-plane magnetic anisotropy deposited on 3-dimensionally curved templates. For this pourpose, arrays of self-assembled cone-shaped nanoobjects with a chracteristic size of either 30 or 70 nm were created in GaSb(001) by the ion erosion technique. The templates are designed in the way that the shape of the cone remains the same for all the samples; namely, we keep the opening angle at about 55º by adjusting the ratio between the cone height and its base diameter to be about 1. In this case, we are able to address the impact of the linear dimensions of the object on the magnetic properties and exclude the impact of the shape from the consideration. Deposition of 15-nm-thick Co/Pd multilayers on top of the cone templates results in the formation of a close-packed array of 2-dimensional magnetic cone-shaped shells. Integral angle-dependent magnetometry measurements demonstrate that local curvature results in the spread of the easy axes of magnetization following the shape of nanocones independent of the linear dimensions of the cone. At the same time different local magnetic domain patterns are observed for samples prepared on 30 and 70 nm large cones. When the thickness of the magnetic shell is only half of the linear dimension of a cone, a clear multidomain state is observed. Remarkably, we find that the neighboring magnetic cone-shaped shells are exchange decoupled when the linear dimension of a cone is 4 times larger compared to the thickness of the magnetic shell. These findings are relevant for the further development of tilted bit patterned magnetic recording media as well as for the emergent field of magnetism in curved geometries.
Keywords: curvilinear magnetism, 2D magnetic shells, self-assembled nanostructures, Co/Pd multilayers, magnetic properties, exchange coupling

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Publ.-Id: 24101 - Permalink


Magnetic anisotropy peculiarities of high-temperature ferromagnetic MnxSi1−x (x ≈ 0.5) alloy films
Drovosekov, A. B.; Kreines, N. M.; Savitsky, A. O.; Kapelnitsky, S. V.; Rylkov, V. V.; Tugushev, V. V.; Prutskov, G. V.; Novodvorskii, O. A.; Cherebilo, E. A.; Kulatov, E. T.; Wang, Y.; Zhou, S.;
Thin films of MnxSi1-xalloys with different Mn concentration x ≈ 0.44-0.63 grown by the pulsed-laser deposition (PLD) method onto the Al2O3(0001) substrate were investigated in the temperature range 4-300 K using ferromagnetic resonance (FMR) measurements in the wide range of frequencies and magnetic fields . For samples with x ≈ 0.52-0.55, FMR data show clear evidence of ferromagnetism (FM) with high Curie temperatures Tc ∼ 300K. These samples demonstrate the complex and unusual character of magnetic anisotropy described in the frame of phenomenological model as a combination of the essential second-order easy-plane anisotropy contribution and the additional fourth-order anisotropy contribution with the easy direction normal to the film plane. We explain the obtained results by a polycrystalline (mosaic) structure of the films caused by the film-substrate lattice mismatch

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Publ.-Id: 24100 - Permalink


Formation of silicon nanocrystals in silicon carbide using flash lamp annealing
Weiss, C.; Schnabel, M.; Prucnal, S.; Hofmann, J.; Reichert, A.; Fehrenbach, T.; Skorupa, W.; Janz, S.;
During the formation of Si nanocrystals (Si NC) in SixC1-x layers via solid-phase crystallization, the unintended formation of nanocrystalline SiC reduces the minority carrier lifetime and therefore the performance of SixC1-x as an absorber layer in solar cells. A significant reduction in the annealing time may suppress the crystallization of the SiC matrix while maintaining the formation of Si NC. In this study, we investigated the crystallization of stoichiometric SiC and Si-rich SiC using conventional rapid thermal annealing (RTA) and nonequilibrium millisecond range flash lamp annealing (FLA). The investigated SixC1-x films were prepared by plasma-enhanced chemical vapor deposition and annealed at temperatures from 700 C to 1100C for RTA and at flash energies between 34 J/cm2 and 62 J/cm2 for FLA. Grazing incidence X-ray diffraction and Fourier transformed infrared spectroscopy were conducted to investigate hydrogen effusion, Si and SiC NC growth, and SiC crystallinity. Both the Si content and the choice of the annealing process affect the crystallization behavior. It is shown that under certain conditions, FLA can be successfully utilized for the formation of Si NC in a SiC matrix, which closely resembles Si NC in a SiC matrix achieved by RTA. The samples must have excess Si, and the flash energy should not exceed 40 J/cm2 and 47 J/cm2 for Si0.63C0.37 and Si0.77C0.23 samples, respectively. Under these conditions, FLA succeeds in producing Si NC of a given size in less crystalline SiC than RTA does. This result is discussed in terms of nucleation and crystal growth using classical crystallization theory. For FLA and RTA samples, an opposite relationship between NC size and Si content was observed and attributed either to the dependence of H effusion on Si content or to the optical absorption properties of the materials, which also depend on the Si content.
Keywords: solar cells, flash lamp annealing, Si, SiC

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Publ.-Id: 24099 - Permalink


Hydrodynamics of Gas-Liquid Cocurrent Upflow in Oscillating Packed Beds for Offshore Marine Applications
Dashliborun, A. M.; Larachi, F.; Schubert, M.;
In this study, the hydrodynamic behavior of inclined stationary and oscillating packed beds with gas-liquid cocurrent upflow mode of operation was investigated. Comprehensive hydrodynamic experiments were carried out using embedded low-intrusive Wire-Mesh Sensors (WMSs) and a hexapod ship motion simulator in order to properly understand the effect of column inclination and movements on gas-liquid flow distribution in the bed cross-section, overall pressure drop, liquid saturation, and pulsing flow inception. Furthermore, liquid residence time and Péclet number estimated by a stimulus-response technique and a macromixing model were presented and discussed with respect to the prevailing flow regimes. The results revealed that the column deviation from the vertical posture and tilting motions significantly alter the hydrodynamics prevailing in the packed bed operating in a concurrent upflow mode. Development of gas-liquid disengagement zones, oscillations in the pressure drop and uniformity factor time series, departure from liquid plug flow character, and delay in the inception of pulsing flow regime were observed as a result of bed inclination and oscillations.
Keywords: Cocurrent upflow packed bed; oscillation; wire mesh sensor; hexapod motion simulator; maldistribution; hydrodynamics

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Publ.-Id: 24098 - Permalink


Untersuchungen zu magnetohydrodynamischen Instabilitäten in Flüssigmetallen
Seilmayer, M.;
This dissertation, “Studies on magnetohydrodynamic instabilities in liquid metal flows”, focuses on two different experiments in a cylindrical Taylor-Couette (TC) geometry. This fundamental set-up consists of an inner and an outer cylinder, which are mounted concentrically. The different radii are defined by the parameters and . The rotation of both cylinders can be set independently by their angular frequencies and . The gap between them is filled with the fluid whose flow is to be investigated. For an ideal non-viscous fluid, Rayleigh’s criterion states that the flow between two concentric cylinders with infinite length is stable against small perturbations as long as the angular momentum increases outward, [1]. Rayleigh’s criterion can be interpreted in a way that an ideal TC-flow remains laminar if the pressure and centrifugal forces are in a stable equilibrium state.
A more general setting is now introduced with an azimuthal magnetic field being applied to the electrical conducting fluid. For this different situation Michael [2] and Chandrasekhar [3] derived an extended stability criterion only for axisymmetric perturbations which is valid for an ideally conducting and non-viscous fluid. The first experiment described in the present dissertation consists of a TC-setup using the eutectic alloy Ga67In20,5Sn12,5 as working fluid. In addition to the common installation an insulated current on the rotation axis with up to 20 kA generates the necessary magnetic field . Michael’s criterion indicates in that case that the flow is stable with respect to axisymmetric perturbations. However, this does not apply for non-axisymmetric perturbations. It was shown theoretically by Rüdiger et al. [4, 5] that the interaction of an azimuthal magnetic field with a laminar rotational flow may become unstable against non-axisymmetric disturbances. This phenomenon is called Azimuthal Magnetorotational Instability (AMRI). The present work gives the first experimental evidence for AMRI in a liquid metal TC-experiment. It is shown that a hydrodynamically stable flow can be disturbed by an applied current free azimuthal magnetic field . The instability itself is then identified as a travelling wave co-rotating with the cylinders.
The second configuration investigated in this work is characterized by a magnetic field profile proportional to the radius. The basis for such an experiment is the remarkable stability criterion from Tayler [6, 7]. It tells that even an ideal fluid at rest can become unstable against non-axisymmetric disturbances. The Tayler instability (TI) in liquid metals can be considered as the incompressible version of the kink instability that is widely known in plasma physics. The TI-experiment confirms the numerical results given by Rüdiger et al. [8, 9] who calculated the onset for the instability in an incompressible liquid metal column with finite conductivity at round about 3 kA.
Both observed phenomena are strongly related to astrophysical processes in which angular momentum transport plays an essential role. What was missing so far was a clear experimental evidence for the described interaction mechanisms between a rotational flow and a magnetic field. The submitted dissertation reports the analysis and results of the first experiments on the two fundamental instabilities AMRI and TI.

[1] Rayleigh, Proc. R. Soc. London, Ser. A, 93(648), 148‑154, 1917.
[2] D. H. Michael, Mathematika, 1, 45‑50, 1954.
[3] S. Chandrasekhar, Proc.Roy.Soc.-A, 216(1126), 293‑309, 1953.
[4] G. Rüdiger et al. MNRAS, 377(4), 1481‑1487, 2007.
[5] G. Rüdiger et al. Astron. Nachr., 328, 1158‑1161, 2007.
[6] R. J. Tayler, Proc. R. Soc. London, Ser. B, 70(1), 31‑48, 1957.
[7] R. J. Tayler, MNRAS, 161(4), 365‑380, 1973.
[8] G. Rüdiger et al., Astron. Nachr., 332(1), 17‑23, 2011.
[9] G. Rüdiger et al., Astrophys. J., 755(2), 181, 2012.
Keywords: MRI, magnetohydrodynamic instabilities, Azimuthal Magnetorotational Instability,Tayler instability
  • Book (Authorship)
    Dresden: TUDpress, 2016
    261 Seiten

Publ.-Id: 24097 - Permalink


Cm3+ incorporation in La1-xGdxPO4 monazites: a TRLFS and XAFS study
Huittinen, N.; Scheinost, A. C.; Wilden, A.; Arinicheva, Y.;
Crystalline ceramic materials show promise as potential waste forms for immobilization of high-level radioactive wastes. Especially for the immobilization of trivalent minor actinides (MA) and plutonium, some ceramic materials such as the lanthanide phosphates (LnPO4) crystallizing in the monazite structure have been envisioned as host materials due to their thermal stability, high radiation tolerance, and chemical durability [1]. Thus, for a reliable long-term safety assessment of nuclear waste repositories for conditioned radioactive waste, a fundamental understanding of the MA incorporation process in these envisioned ceramic matrices is required.
In the present study, the incorporation of the minor actinide Cm3+ in a series of La1-xGdxPO4 (x = 0, 0.2, 0.5, 0.8, 1) monazite solid solutions has been investigated using time-resolved laser fluorescence- (TRLFS) and Cm L3-edge x-ray absorption fine-structure spectroscopy (XAFS).
The Cm3+ excitation spectra obtained with the TRLFS method of the pure LaPO4 and GdPO4 end-members (Figure 1) show four well-resolved peaks corresponding to the 4-fold splitting of the Cm3+ ground state. The highly resolved ground-state splitting indicates the presence of only one, very well-defined, crystalline environment for the incorporated Cm3+ cation in the La and Gd monazite end-members. The situation changes when examining the solid solution compositions (La0.8Gd0.2PO4, La0.5Gd0.5PO4, and La0.2Gd0.8PO4) where the complete loss of the splitting fine-structure and the broadening of the excitation peaks indicate a decrease of the short-range order in these solid solutions.
The fitting of the first coordination shell of our Cm L3 XAFS data (Figure 2) for LaPO4, La0.5Gd0.5PO4, and GdPO4, indicate a contraction of the Cm-O distance when going from the larger LaPO4 monazite toward GdPO4 (see Table 1). In addition the Debye-Waller (DW, σ2) factor (which is an indicator for thermal and structural disorder) decreases substantially from 0.0079 Å2 in LaPO4 to 0.004 Å2 in GdPO4, while an increase is observed for the solid-solution composition (0.0112 Å2). The shortening of the Cm···O bond distance can be understood by the decreasing size of the monazite unit cell when going from the larger La3+-bearing host toward the smaller GdPO4. The differences in the DW factors between the monazite end-members can be explained when examining our previously obtained results for Eu3+ incorporation in LnPO4 monazites [2]. Here we could show that a larger mismatch between host and dopant radii causes a larger distortion of the monazite crystal lattice around the trivalent dopant. The cation radii of nine-fold coordinated La3+, Cm3+, and Gd3+ are 121.6 Å [3], 114.6 Å [4], and 110.7 Å [3], respectively. Thus, the larger mismatch of host and dopant radii in Cm3+-doped LaPO4 could explain the larger DW factor than obtained for Cm3+ incorporation in GdPO4. The large DW factor obtained for La0.5Gd0.5PO4 in comparison to the monazite end-members is in concordance with the excitation line broadening observed for the monazite solid solutions in our Cm3+ excitation spectra (Figure 1), implying an increasing disordering of the monazite crystal structure. In our previous work investigating the incorporation of Eu3+ in La1-xGdxPO4 monazites [5], the systematic excitation line broadening could be attributed to and increasing broadening of the Eu∙∙∙O bond distance distribution in the synthetic solid solution series when going from the pure end-members with very well-defined Eu∙∙∙O distances toward the La0.5Gd0.5PO4 composition.

Our spectroscopic results obtained in the present study show that Cm3+ is substituted for the host cation sites in all investigated monazites. Although the spectroscopic data suggest a disordering of the monazite solid solution series due to less explicit Ln∙∙∙O bond distances in the mixed solids, the spectroscopic investigations also imply that no preferential incorporation of dopants on host cation sites with similarly sized cation radii occurs, which is of great importance when considering the performance of monazite materials as immobilization matrices for highly radioactive actinide compounds.

[1] G. R. Lumpkin (2006) “Ceramic waste forms for actinides.” Elements 2: 365-372.
[2] N. Huittinen et al. (submitted) Using Eu3+ as an atomic probe to investigate the local environment in LaPO4 GdPO4 monazite end-members.
[3] R. D. Shannon (1976) Revised effective ionic radii and systematic studies of interatomic distances
in halides and chalcogenides. Acta Cryst. A32, 751–767.
[4] F. H. David and V. Vokhmin (2003) Thermodynamic properties of some tri- and tetravalent actinide aquo ions. New J. Chem., 27, 1627–1632.
[5] N. Huittinen et al. (submitted) Structural incorporation of Eu3+ in La1-xGdxPO4 monazite solid solutions: A combined spectroscopic and computational study.
  • Poster
    9th international conference on nuclear and radiochemistry (NRC9), 29.08.-02.09.2016, Helsinki, Finland

Publ.-Id: 24096 - Permalink


Hydrous 18F-fluoroethylation – leaving off the azeotropic drying
Kniess, T.; Laube, M.; Steinbach, J.;
The study describes the development of a simple and effective method for [18F]fluoroethylation, called as smart [18F]fluoroethylation without azeotropic drying, by elution of a [18F]fluoride loaded QMA column with a K2CO3/K222/acetonitrile solution containing 2% (v/v) water directly to the 1,2-ethylene glycol-bis-tosylate precursor. The method was exemplified on the radiosynthesis of three COX-2 inhibitors with different core structures. In comparison to conventional [18F]fluoroethylation, the reaction time was generally shortened and the radiochemical yield was improved in each case by factor 4-5 by this approach.

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Publ.-Id: 24095 - Permalink


Probing structural homogeneity of La1-xGdxPO4 monazite-type solid solutions by combined spectroscopic and computational studies
Huittinen, N.; Arinicheva, Y.; Kowalski, P. M.; Vinograd, V. L.; Neumeier, S.; Bosbach, D.;
Here we study the homogeneity of Eu3+-doped La1-xGdxPO4 (x = 0, 0.11, 0.33, 0.55, 0.75, 0.92, 1) monazite-type solid solutions by a combination of Raman and time-resolved laser fluorescence spectroscopies (TRLFS) with complementary quasi-random structure-based atomistic modeling studies. For the intermediate La0.45Gd0.55PO4 composition we detected a significant broadening of the Raman bands corresponding to the lattice vibrations of the LnO9 polyhedron, indicating much stronger distortion of the lanthanide cation site than the PO4 tetrahedron. A distortion of the crystal lattice around the dopant site was also confirmed in our TRLFS measurements of Eu3+ doped samples, where both the half width (FWHM) of the excitation peaks and the 7F2/7F1 ratio derived from the emission spectra increase for intermediate solid-solution compositions. The observed variation in FWHM correlates well with the simulated distribution of Eu∙∙∙O bond distances within the investigated monazites. The combined results imply that homogenous Eu3+-doped La1-xGdxPO4 monazite-type solid solutions are formed over the entire composition range, which is of importance in the context of using these ceramics for immobilization of radionuclides.
Keywords: monazite, solid solution, Eu3+ incorporation, Raman, TRLFS, ab initio, force field simulations

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Publ.-Id: 24094 - Permalink


Using Eu3+ as an atomic probe to investigate the local environment in LaPO4–GdPO4 monazite end-members
Huittinen, N.; Arinicheva, Y.; Schmidt, M.; Neumeier, S.; Stumpf, T.;
In the present study, we have investigated the luminescent properties of Eu3+ as a dopant in a series of synthetic lanthanide phosphates from the monazite group. Systematic trends in the spectroscopic properties of Eu3+ depending on the size of the host cation and the dopant to ligand distance have been observed. Our results show that the increasing match between host and dopant radii when going from Eu3+-doped LaPO4 toward the smaller GdPO4 monazite decreases both the full width at half maximum of the Eu3+ excitation peak, as well as the 7F2/7F1 emission band intensity ratio. The decreasing Ln-O bond distance within the LnPO4 series causes a systematic bathochromic shift of the Eu3+ excitation peak, showing a linear dependence of both the host cation size and the Ln-O distance. The linear relationship can be used to predict the energy band gap for Eu3+-doped monazites for which no Eu3+ luminescent data is available. Finally, mechanisms for metal-metal energy transfer between host and dopant lanthanides have been explored based on recorded luminescence lifetime data. Luminescence lifetime data for Eu3+ incorporated in the various monazite hosts clearly indicated that the energy band gap between the guest ion emission transition and the host ion absorption transition can be correlated to the degree of quenching observed in these materials with otherwise identical geometries and chemistries.
Keywords: Eu3+, Monazite, Incorporation, TRLFS, Luminescence, Quenching

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Publ.-Id: 24093 - Permalink


Rotational friction of dipolar colloids measured by driven torsional oscillations
Steinbach, G.; Gemming, S.; Erbe, A.;
Despite its prominent role in the dynamics of soft materials, rotational friction remains a quantity that is difficult to determine for many micron-sized objects. Here, we demonstrate how the Stokes coefficient of rotational friction can be obtained from the driven torsional oscillations of single particles in a highly viscous environment. The idea is that the oscillation amplitude of a dipolar particle under combined static and oscillating fields provides a measure for the Stokes friction. From numerical studies we derive a semi-empirical analytic expression for the amplitude of the oscillation, which cannot be calculated analytically from the equation of motion. We additionally demonstrate that this expression can be used to experimentally determine the rotational friction coefficient of single particles. Here, we record the amplitudes of a field-driven dipolar Janus microsphere with optical microscopy. The presented method distinguishes itself in its experimental and conceptual simplicity. The magnetic torque leaves the local environment unchanged, which contrasts with other approaches where, for example, additional mechanical (frictional) or thermal contributions have to be regarded.

Publ.-Id: 24091 - Permalink


MIR and THz spectroscopy of condensed matter
Helm, M.;
MIR and THz spectroscopy of condensed matter
Keywords: infrared, THz, condensed matter
  • Invited lecture (Conferences)
    Summer School NanoTech Tera-Mir, 29.08.-01.09.2016, Porquerolles, Hyeres, France

Publ.-Id: 24090 - Permalink


Adhesion- and stress-related adaptation of glioma radiochemoresistance is circumvented by β1 integrin/JNK co-targeting
Vehlow, A.; Klapproth, E.; Storch, K.; Dickreuter, E.; Seifert, M.; Dietrich, A.; Bütof, R.; Temme, A.; Cordes, N.;
Resistance of cancer stem-like and cancer tumor bulk cells to radiochemotherapy and destructive infiltration of the brain fundamentally influence the treatment efficiency to cure of patients suffering from Glioblastoma (GBM). The interplay of adhesion and stress-related signaling and activation of bypass cascades that counteract therapeutic approaches remain to be identified in GBM cells. We here show that combined inhibition of the adhesion receptor β1 integrin and the stress-mediator c-Jun N-terminal kinase (JNK) induces radiosensitization and blocks invasion in stem-like and patient-derived GBM cultures as well as in GBM cell lines. In vivo, this treatment approach not only significantly delays tumor growth but also increases median survival of orthotopic, radiochemotherapy-treated GBM mice. Both, in vitro and in vivo, effects seen with β1 integrin/JNK co-inhibition are superior to the monotherapy. Mechanistically, the in vitro radiosensitization provoked by β1 integrin/JNK targeting is caused by defective DNA repair associated with chromatin changes, enhanced ATM phosphorylation and prolonged G2/M cell cycle arrest. Our findings identify a β1 integrin/JNK co-dependent bypass signaling for GBM therapy resistance, which might be therapeutically exploitable.
Keywords: β1 integrin, JNK, radiochemoresistance, GBM stem-like cells, orthotopic GBM mouse model

Publ.-Id: 24089 - Permalink


Head and neck cancer cell radiosensitization upon dual targeting of c-Abl and beta1-integrin
Koppenhagen, P.; Dickreuter, E.; Cordes, N.;
Integrin-mediated cell adhesion to extracellular matrix (ECM) critically contributes to cancer cell therapy resistance and DNA double strand break (DSB) repair. c-Abl tyrosine kinase has been linked to both of these processes. Based on our previous findings indicating c-Abl hyperphosphorylation on tyrosine (Y) 412 and threonine (T) 735 upon beta1-integrin knockdown, we hypothesized c-Abl tyrosine kinase as an important mediator of beta1-integrin signaling for radioresistance. In a panel of 8 cell lines from different solid cancer types grown in 3D laminin-rich ECM cultures, we targeted beta1 integrin with AIIB2 (mAb) and c-Abl with Imatinib with and without X-ray irradiation and subsequently examined clonogenic survival, residual DSBs, protein expression and -phosphorylation. Single or combined treatment with AIIB2 and Imatinib resulted in cell line-dependent cytotoxicity. Intriguingly, a subgroup in this cell line panel responding to AIIB2/Imatinib treatment with higher radiosensitization relative to both single treatments was identified. Likewise, AIIB2/Imatinib co-treatment elicited a significantly higher number of residual DSBs than controls, which was accompanied by decreased Ku70 expression and enhanced ATM S1981 phosphorylation. Mechanistically, c-Abl was located in the beta1-integrin/JNK signaling axis and abrogated AIIB2/Imatinib-related radiosensitization when exogenously overexpressed in either wildtype or constitutively activated form. Our data generated in more physiological 3D cancer cell culture models indicate c-Abl as important determinant of radioresistance and DNA repair downstream of beta1-integrin. For solid cancers, c-Abl phosphorylation status might be an indicator for reasonable Imatinib application as adjuvant for conventional radio(chemo)therapy.
Keywords: beta1-integrin, c-Abl, Imatinib, ionizing radiation, DNA-repair

Publ.-Id: 24088 - Permalink


Theranostic mercury part 2: Production of 197(m)Hg via the 197Au(d,2n) reaction
Lebeda, O.; Walther, M.; Preusche, S.; Pietzsch, H.-J.; Steinbach, J.;
The access to no-carrier-added 197(m)Hg using proton irradiation of gold targets and subsequent product separation was recently reported. One of the limiting factors of the large-scale production of this theranostic radionuclide is rather low yield of the 197Au(p,n)197(m)Hg reaction. In contrast, significantly larger cross-sections have been reported for 197Au(d,2n) reaction. In spite of somewhat larger linear energy transfer of deuterons in gold, the latter reaction seems to result in larger achievable activity of 197(m)Hg. We have, therefore, explored its potential for the 197(m)Hg production in a pilot experiment.
Keywords: no-carrier-added 197(m)Hg, theranostic, cross-section, deuteron
  • Lecture (Conference)
    16th International Workshop on Targetry and Target Chemistry (WTTC16), 29.08.-01.09.2016, Santa Fe, USA

Publ.-Id: 24087 - Permalink


Theranostic mercury part 1: A new Hg/Au separation by a resin based method
Walther, M.; Lebeda, O.; Preusche, S.; Pietzsch, H.-J.; Steinbach, J.;
The production and separation of no-carrier-added 197(m)Hg for imaging and therapy research based on the 197Au(p,n)197(m)Hg reaction was recently reported. However, large-scale production requires the development of a rapid, reliable method for Hg/Au separation. Ideally, a solid phase sorbent is used to bind at least one of the two metal ions reversibly, allowing for the product elution into a small volume. Di(2-ethylhexyl)orthophosphoric acid (HDEHP) im-pregnated onto an inert support as the so called LN resin (LaNthanides) was examined for this application.
Keywords: no-carrier-added 197(m)Hg, therapy, Hg/Au separation
  • Lecture (Conference)
    16th International Workshop on Targetry and Target Chemistry (WTTC16), 29.08.-01.09.2016, Santa Fe, USA
  • Contribution to proceedings
    16th International Workshop on Targetry and Target Chemistry, WTTC 2016, 29.08.-01.09.2016, Santa Fe, United States, 978-073541517-1
    DOI: 10.1063/1.4983554

Publ.-Id: 24086 - Permalink


Development of a F-18-labeled Diaryl-Substituted Dihydropyrrolo[3,2,1-hi]indole as Potential Probe for Functional Imaging of Cyclooxygenase-2 with PET
Gassner, C.; Neuber, C.; Laube, M.; Bergmann, R.; Kniess, T.; Pietzsch, J.ORC
High COX-2 expression is associated with tumor progression and poor treatment response. Imaging of functional COX-2 expression by PET would provide beneficial information for theranostics. Here we describe precursor synthesis and radiolabeling attempts of (dihydro)pyrrolo[3,2,1-hi]indoles [18F]DHPI and [18F]PI, two novel tricyclic COX-2 inhibitors. Contrary to [18F]PI, [18F]DHPI was accessible by [18F]fluorination under mild basic conditions and McMurry cyclization. Radiopharmacological evaluation was performed in vitro by investigating cellular uptake in human COX-2-positive cells, and in vivo in rats and A2058-melanoma xenograft mice, by focusing on metabolic stability and tumor uptake. To assess COX-2 specificity, blocking experiments with celecoxib were performed. Despite of high COX-2 selectivity and metabolic stability, [18F]DHPI did not show COX-2-dependent cell and tissue uptake, in part explained by high unspecific binding. Since appropriate lipophilicity is a prerequisite for targeting intracellularly localized COX-2, future efforts should focus on use of longer-lived radionuclides and/or targeted delivery systems.
Keywords: Cancer; Malignant melanoma; Molecular imaging; Radiochemistry; Selective cyclooxygenase-2 inhibitors; Tumor xenograft models

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  • Secondary publication expected

Publ.-Id: 24085 - Permalink


A Guide on Spectral Methods Applied to Discrete Data in One Dimension
Seilmayer, M.; Ratajczak, M.;
Spectral analysis in conjunction with discrete data in one and more dimensions can become a challenging task, because the methods are sometimes difficult to understand. This paper intends to provide an overview about the usage of the Fourier transform, its related methods and focuses on the subtleties to which the users must pay attention. Typical questions, which are often addressed to the data, will be discussed. Such a problem can be the issue of frequency or band limitation of the signal. Or the source of artifacts might be of interest, when a Fourier transform is carried out. Another topic is the issue with fragmented data. Here, the Lomb-Scargle method will be explained with an illustrative example to deal with this special type of signal. Furthermore, a challenge encountered very often is the time-dependent spectral analysis, with which one can evaluate the point in time when a certain frequency appears in the signal. The information to solve such problems and to answer this questions is spread over many disciplines ranging from mathematics, electrical engineering, economic science to astrophysics. The goal of the first part of this paper is to collect the important information about the common methods to give the reader a guide on how to use these for application on one-dimensional data. The second part of this paper will then address the two- and more-dimensional data. The introduced methods are supported by the 'spectral' package, which has been published for the statistical environment R prior this article.
Keywords: spectral analysis, Fourier transform Hilbert transform R spectral

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Publ.-Id: 24083 - Permalink


Common methods of spectral data analysis
Seilmayer, M.;
Fourier and Hilbert transforms are utilized to perform several types of spectral analysis on the supplied data. Also gapped and irregularly spaced data can be processed. A user friendly interface helps to interpret the results.
Keywords: spectral analysis Fourier transform Hilbert transform R
  • Software in external data repository
    Publication year 2016
    Programming language: R
    System requirements: Windows, Linux, MacOS, R (>= 2.15.0)
    License: GPL-2 (Link to license text)
    Hosted on CRAN: Link to location

Publ.-Id: 24082 - Permalink


rasterImage
Seilmayer, M.;
This is a wrapper function for image(), which makes reasonable raster plots with nice axis and other useful features.
Keywords: plot function R
  • Software in external data repository
    Publication year 2016
    Programming language: R
    System requirements: Windows, Linux, MacOS, R (>= 2.15.0)
    License: GPL-2 (Link to license text)
    Hosted on CRAN: Link to location

Publ.-Id: 24081 - Permalink


Progress of the Felsenkeller shallow-underground accelerator for nuclear astrophysics
Bemmerer, D.; Cavanna, F.; Cowan, T. E.; Grieger, M.; Hensel, T.; Junghans, A. R.; Ludwig, F.; Müller, S. E.; Rimarzig, B.; Reinicke, S.; Schulz, S.; Schwengner, R.; Stöckel, K.; Szücs, T.; Takács, M. P.; Wagner, A.; Wagner, L.; Zuber, K.;
Low-background experiments with stable ion beams are an important tool in order to put the understanding of stellar hydrogen, helium, and carbon burning on a solid experimental foundation. The pioneering work in this regard has been done by the LUNA collaboration at Gran Sasso, using a 0.4 MV accelerator. In the present contribution, the status of the project for a higher-energy underground accelerator is reviewed. Two tunnels of the Felsenkeller underground site in Dresden, Germany, are currently being refurbished for the installation of a 5 MV high-current Pelletron accelerator. Construction work is on schedule and expected to complete in August 2017. The accelerator will provide intense, 50μA, beams of 1H+, 4He+, and 12C+ ions, enabling research on astrophysically relevant nuclear reactions with unprecedented sensitivity.
Keywords: Felsenkeller underground nuclear astrophysics
  • Open Access LogoContribution to proceedings
    Nuclei in the Cosmos XVI, 20.-24.06.2016, Niigata, Japan
    Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016) JPS Conf. Proc. 14, 021106 (2017), 021106
    DOI: 10.7566/JPSCP.14.021106
  • Contribution to WWW
    arXiv Preprint-Server: http://arxiv.org/pdf/1609.05819v1.pdf

Publ.-Id: 24079 - Permalink


The surface reactions of U(VI) on γ-Al2O3 In situ spectroscopic evaluation of the transition from sorption complexation to surface precipitation
Müller, K.ORC; Foerstendorf, H.; Rossberg, A.
Aluminates, representing an essential component of clay minerals, play a decisive role in regulating the mobility of contaminants in rock and soil formations, in particu-lar due to their tendency to form coatings on mineral surfaces [1].
In this work, U(VI) sorption on γ-Al2O3 is comparatively investigated using in situ vibrational and X-ray absorption spectroscopy. The focus was set to micromolar U(VI) concentrations and a variety of environmentally relevant sorption parameters in order to resolve discrepancies reported earlier [2-4].
Time-resolved (TR) IR spectroscopic sorption experiments at the alumina-water in-terface evidence the formation of three different species as a function of surface loading (c.f. Fig.): a monomeric carbonate complex, an oligomeric surface complex and a surface precipitate. These results are confirmed by IR experiments performed at different flow rates, pH values, ionic strengths, U(VI) concentrations, and in inert gas atmosphere. Results of EXAFS experiments of batch samples are consistent to these findings [5].
  • Poster
    3rd International Workshop on Advanced Techniques in Actinide Spectroscopy, 07.-10.11.2016, Richland, USA

Publ.-Id: 24078 - Permalink


High resolution x-ray Thomson scattering measurements from cryogenic hydrogen jets using the linac coherent light source
Fletcher, L. B.; Zastrau, U. B.; Galtier, E. A.; Gamboa, E. J. A.; Goede, S. A.; Schumaker, W. A.; Ravasio, A. A.; Gauthier, M. A.; Macdonald, M. J. A.; Chen, Z. A.; Granados, E. A.; Lee, H. J. A.; Fry, A. A.; Kim, J. B. A.; Roedel, C. A.; Mishra, R. A.; Pelka, A. F.; Kraus, D.; Barbrel, B. G.; Döppner, T. H.; Glenzer, S. H. A.;
We present the first spectrally resolved measurements of x-rays scattered from cryogenic hydrogenjets in the single photon counting limit. The 120 Hz capabilities of the LCLS, together with a novelhydrogen jet design [J. B. Kimet al., Rev. Sci. Instrum. (these proceedings)], allow for the ability torecord a near background free spectrum. Such high-dynamic-range x-ray scattering measurementsenable a platform to study ultra-fast, laser-driven, heating dynamics of hydrogen plasmas. Thismeasurement has been achieved using two highly annealed pyrolytic graphite crystal spectrometers tospectrally resolve 5.5 keV x-rays elastically and inelastically scattered from cryogenic hydrogen andfocused on Cornell-SLAC pixel array detectors [S. Herrmannet al., Nucl. Instrum. Methods Phys.Res., Sect. A718, 550 (2013)].

Publ.-Id: 24077 - Permalink


Phase Shift and Reflection of Spin Waves at Magnetic Domain Walls in Thin Films
Körber, L.; Wagner, K.; Lindner, J.; Fassbender, J.ORC; Schultheiß, H.
Investigating the transmission of magneto-static surface waves through 180° Néel walls using micromagnetic simulations.
Keywords: spin waves, phase shift, micromagnetic simulation, reflection, domain wall
  • Poster
    Spin, Waves and Interactions, 31.08.-02.09.2016, Greifswald, Deutschland

Publ.-Id: 24076 - Permalink


Magnetic domain walls as reconfigurable spin-wave nano-channels
Wagner, K.; Kakay, A.; Schultheiß, K.; Henschke, A.; Sebastian, T.; Lindner, J.; Fassbender, J.ORC; Schultheiß, H.
Use of magnetic domains as nano channels for spin wave propagation
  • Lecture (Conference)
    Spin, Waves and Interaction, 31.08.-02.09.2016, Greifswald, Deutschland

Publ.-Id: 24075 - Permalink


Modern Measurement Methods of Brillouin Light Scattering
Osten, J.; Schultheiß, H.; Wagner, K.; Körber, L.; Wehrmann, F.; Hula, T.;
Explanation of different measurement methods of BLS: phase, time, wavevector, frequency and spacial resolved
Keywords: BLS
  • Poster
    Spins, Waves and Interactions, 31.08.-02.09.2016, Greifswald, Deutschland

Publ.-Id: 24074 - Permalink


The role of automated mineralogy in geometallurgy: two case studies
Birtel, S.; Kern, M.; Heinig, T.; Gutzmer, J.;
SEM-based automated mineralogy is well established as a key tool in geometallurgical assessments, as it provides quantitative data on mineralogy and microstructure. It is widely used to improve the recovery of those constituents (ore minerals) that contain the major products (metals) of existing or planned mining operations and processing plants. Less common, however, is the use of automated mineralogy to study the presence and distribution of possible by-product or even penalty constituents. In this contribution, we present the results of two case studies that reveal the benefit of application of automated mineralogy to define beneficiation potential for economically significant by-products in large operations. Systematic plant surveys were carried out at one fluorite mine and one porphyry copper deposit. For the fluorite deposit, the plant survey was combined with an assessment of the undisturbed feed material.
Case study 1: For the recovery of REE as a potential by-product in a fluorite mine, blocks were sampled before mining, the material was subsequently followed through the flotation plant, sampling all crucial steps. Samples illustrate that the material from the tailings stream, i.e., the material being considered as waste, is strongly enriched in the two dominant REE-bearing minerals contained in the ore: monazite and xenotime. These REE-bearing minerals are well liberated, thus leading to the conclusion that it may be feasible to produce a REE concentrate as a by-product by only slight modification of the current flow sheet.
Case study 2 focused on the improvement of Mo recovery of a world-class porphyry copper deposit. Samples were taken systematically from the flotation plant also considering residence times. Particular flotation stages accounting for significant Mo losses due to bad molybenite liberation were identified. Lab-scale flotation tests were carried out to improve Mo recovery. Results indicate a clear influence of grain shape, grain size and residence time on the recovery.
Keywords: automated mineralogy, by products, REE, process optimization
  • Contribution to proceedings
    3rd international Seminar on geometallurgy, Editors: Regina Baumgartner, Adam Johnston, 11.-13.12.2016, Lima, Peru
    GEOMET 2016, 3rd International Seminar on Geometallurgy, Santiago, Chile: Gecamin, 978-956-9393-68-6, 58-59
  • Lecture (Conference)
    3rd international Seminar on Geometallurgy, 11.-13.12.2016, Lima, Peru

Publ.-Id: 24073 - Permalink


An Electrochemical and Photoelectron Spectroscopy Study of a Low Temperature Liquid Metal Battery Based on an Ionic Liquid Electrolyte
Lalau, C.-C.; Dimitrova, A.; Himmerlich, M.; Ispas, A.; Weier, T.; Krischok, S.; Bund, A.;
We report the design of a low-temperature liquid metal battery (LMB). Li and Ga as the negative and positive electrode, respectively, are used in combination with a room temperature ionic liquid as an electrolyte. 1 mol/L lithium bis(trifluoromethylsulfonyl)imide (Li[TFSI]) in 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl)imide ([BMP][TFSI]) is chosen as electrolyte. The battery operates at 220 °C which is a relatively low temperature for a LMB and shows good electrochemical performance at low current density. The cells were cycled for more than 600 h and achieved a round-trip Coulombic efficiency close to 100% and an average voltage efficiency of 66% resulting in an overall energy efficiency of 65%. At higher current densities, however, the system showed up to 75% irreversible capacity loss after three cycles. To understand the origin of this strong deterioration, we characterized the surface and the bulk properties of the Ga cathode using X-ray Photoelectron Spectroscopy. Especially at higher current densities a decomposition of the electrolyte was found. The chemical changes that occurred and the elemental distribution at the Ga cathode are analyzed based on XPS measurements at different stages of the battery charge/discharge cycling.
Keywords: liquid metal battery, ionic liquids

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Publ.-Id: 24072 - Permalink


Depth profiled ion implantation doping using an energy filter based on Si membrane
Akhmadaliev, S.; Krippendorf, F.; Bezerra, E. B. D.; von Borany, J.; Csato, C.; Rüb, M.; Zowalla, A.;
An important step during fabrication of modern semiconductor devices is doping of the material by means of ion implantation. For some applications in power or optoelectronics also special non-Gaussian shaped buried implantation profiles are required. The conventional way to create accurate shaped doping profiles by using multiple implantations of mono-energetic ions with subsequent thermal annealing is quite time consuming. An alternative approach is the application of an ion beam exhibiting the desired energy and flux distribution. For applications of less accuracy metallic foils with various thicknesses have been applied as energy filters (EF). A relatively new method is a filter made of micro-mechanically manufactured silicon membranes with modulated thickness which changes the energy of the initially mono-energetic ion beam from an accelerator and converts quasi-Gaussian shaped implantation profile into the specified one [1]. An example of such an EF shown in Fig.1 which can be used for homogeneous buried box-like doping profiles covering a doping depth of several micrometers. The ions with equal energies Eo will have different energies after the filter depending on the local thickness of the material and the resulting ion ranges are in different depth in the substrate.
There are some challenges by using this technique. Besides the reliable and reproducible fabrication of the energy filter, aspects like thermal stability, ion beam sputtering or geometrical constrains have to be considered. Another difficulty of this method is the monitoring of the ion flux after the EF in order to control the implanted dose. A Faraday cup setup cannot be directly applied because of the recharging of the ions by the EF and their undefined charge state after the filter, so the process needs precise calibration for each ion type and energy. A Si EF fabricated at Ernst-Abbe Hochschule was calibrated and taken for the doping of 4” wafers using the wafer-handler with the mechanical scanning system at 3 MV tandem accelerator at HZDR [2]. The experiments deliver promising results and demonstrate the possibility of application this method for doping purposes.
References
[1] M. Rüb, DE Patent App, 2012, DE102011075350 A1
[2] C. Csato et al., Nucl. Instr. Meth. B 365 (2015) 182
Keywords: SiC, energy filter, ion implantation
  • Lecture (Conference)
    ECAART-12, The 12th European Conference on Accelerator in Applied Research and Technology, 03.-08.07.2016, Jyväskylä, Finnland

Publ.-Id: 24071 - Permalink


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