Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34118 Publications

Analysis of the Electric-Double-Layer formation by in-situ Rutherford Backscattering Spectrometry

Baghban Khojasteh Mohammadi, N.; Heller, R.; Bergmann, U.; Apelt, S.

A setup for in-situ Rutherford Backscattering Spectrometry (RBS) has been installed at the 2 MV Van-de-Graaff accelerator at the Ion Beam Center (IBC) of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Online analysis of solid-liquid interfaces as well as electro-chemistry experiments are conducted by this technique. A Si3N4 window separates the liquid from the vacuum in the RBS chamber. A He+ beam (E = 1.7 MeV) is utilized for the RBS measurements. RBS as well as Particle Induced X-Ray Emission Spectroscopy (PIXE) spectra are recorded simultaneously to increase the sensitivity for trace elements. The technique was employed for direct measurements of the Electric-Double-Layer (EDL) formation on Si3N4. Investigations of the EDL formation at solid-liquid interfaces are of great significance due to the various valuable applications such as super-capacitors that can be utilized to provide a backup power supply or applied in various other fields [1-3]. In our preliminary experiments, the specific adsorption of Barium ions from a 1mM BaCl2 solution with various pH values was observed in a direct and quantitative manner. Sensitivity of the technique reaches the ppm range and areal densities can be measured down to 0.1 atomic monolayer.
[1]Kötz et al., (2002). The 12th International Seminar on Double Layer Capacitors and Similar Energy Storage Devices, Dec, USA.
[2]Faggioli et al., (1999). J. Power Sources, 84(2): 261.
[3]Simon et al., (2008). Nature materials, 7(11): 845.

Keywords: in-situ RBS; Electric-Double-Layer

  • Lecture (Conference)
    Workshop on Ion and Particle Beams (Ionenstrahl Workshop), 24.-25.04.2018, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-27172
Publ.-Id: 27172


An experimental approach to reactive transport in geomaterials: GeoPET

Kulenkampff, J.; Franke, K.; Gründig, M.; Hildebrand, H.; Karimzadeh, L.; Schymura, S.; Fischer, C.

Detailed understanding of reactive transport in geomaterials of chemical species, including radionuclides, is required for the utilization of the subsoil, e.g. for designing ore production by in-situ leaching, or for radioactive waste disposal. To complement the well-established conventional approach, i.e. computer model simulations based upon bulk material parameters and geochemical data bases, we apply process tomography with positron emission tomography (GeoPET) for direct observation and parameterization of the reactive transport processes. This enables to consider heterogeneity as pervasive feature of processes in complex media. One example is localized flow meandering along fractures, where preferential flow may jeopardize leaching efficiency. On the other hand, fissure networks through otherwise tight material could provide fast transport pathways through geological barriers.
Our workflow consist of 1) production of appropriate PET-nuclides and labelling, 2) transport experiment on samples of drill core size with the labelled species, 3) recording of PET-data (list-mode-files) during the course of tracer propagation, 4) computation of PET-frames with appropriate frame rate and correction for material effects, 5) parameterization of the spatiotemporal data set with the target parameters effective volume distribution and velocity distribution.
The choice of PET-nuclides is broader than in common biomedical PET applications, because longevity and toxicity of the tracers are inconsiderable, but spatial resolution and efficient corrections for attenuation and scatter require attention. The development of the GeoPET method during the past decade is described in Kulenkampff et al. (2016).
As illustration, we present an example from ore leaching, where the leaching solution is flown through an artificial fracture. During leaching we experimentally determined the macroscopic flow field with GeoPET. With these hydrodynamic data we are able to establish a realistic and light-weight reactive transport model which can directly serve for efficient design of leaching.
The procedure is one good example for the benefit of radiotracers for unravelling complex processes by non-destructive molecular imaging. We strongly suggest utilizing this distinguished tool, in particular for .parameterization and upscaling of heterogeneous reactive transport models.

Kulenkampff, J., Gründig, M., Zakhnini, A., Lippmann-Pipke, J. 2016. Geoscientific process monitoring with positron emission tomography (GeoPET), Solid Earth, 7, 1217-1231, 10.5194/se-7-1217-2016.

  • Lecture (Conference)
    RadChem 2018, 13.-18.05.2018, Mariánské Lázně, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-27171
Publ.-Id: 27171


Comparison of different treatment planning approaches for intensity-modulated proton therapy with simultaneous integrated boost for pancreatic cancer

Stefanowicz, S.; Stützer, K.; Zschaeck, S.; Jakobi, A.; Troost, E. G. C.

Background
Neoadjuvant radio(chemo)therapy of non-metastasized, borderline resectable or unresectable locally advanced pancreatic cancer is complex and prone to cause side-effects, e.g., in gastrointestinal organs. Intensity-modulated proton therapy (IMPT) enables a high conformity to the targets while simultaneously sparing the normal tissue such that dose-escalation strategies come within reach. In this in silico study, we compared four IMPT planning strategies including robust multi-field optimization (rMFO) and a simultaneous integrated boost (SIB) for dose-escalation in pancreatic cancer patients.

Methods
For six pancreatic cancer patients referred for adjuvant or primary radiochemotherapy four rMFO-IMPT-SIB treatment strategies of two or three (non-)coplanar beam arrangements were calculated. Dose values for both targets, the elective clinical target volume (CTV) and the SIB, and the organs at risk as well as target conformity and homogeneity indexes, derived from the dose volume histograms, were statistically compared.

Results
All treatment plans of each strategy fulfilled the prescribed doses to the targets (D95%≥95%, D2%≤107%). No significant differences for the conformity index were found (p>0.05), however, treatment plans with a three non-coplanar beam approach were most homogenous to both targets (p<0.045). Dose constraints for large and small bowel as well as for the liver and the spinal cord were met with all beam arrangements. Irrespective of the planning strategies, the dose constraint for the duodenum and stomach were not met. Using the three-beam arrangements, the dose to the left kidney could be significant decreased when compared to a two-beam strategy (p<0.045).

Conclusion
Based on our findings we recommend a three-beam configuration with at least one non-coplanar beam for rMFO-IMPT-SIB in advanced pancreatic cancer patients achieving a homogeneous dose distribution in the target while simultaneously minimizing the dose to the organs at risk.

Keywords: pancreatic cancer; intensity modulated proton therapy; simultaneous integrated boost; dose escalation

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Permalink: https://www.hzdr.de/publications/Publ-27170
Publ.-Id: 27170


High-Yield Optical Undulators Scalable to Optical Free-Electron Laser Operation by Traveling-Wave Thomson-Scattering

Steiniger, K.

All across physics research, incoherent and coherent light sources are extensively utilized.
Especially highly brilliant X-ray sources such as third generation synchrotrons or free-electron lasers have become an invaluable tool enabling experimental techniques that are unique to these kinds of light sources.
But these sources have developed to large scale facilities and a demand in compact laboratory scale sources providing radiation of similar quality arises nowadays.

This thesis focuses on Traveling-Wave Thomson-Scattering (TWTS) which allows for the realization of ultra-compact, inherently synchronized and highly brilliant light sources.
The TWTS geometry provides optical undulators, through which electrons pass and thereby emit radiation, with hundreds to thousands of undulator periods by utilizing pulse-front tilted lasers pulses from high peak-power laser systems.

TWTS can realize incoherent radiation sources with orders of magnitude higher photon yield than established head-on Thomson sources.
Moreover, optical free-electron lasers (OFELs) can be realized with TWTS if state-of-the-art technology in electron accelerators and laser systems is utilized.

Tilting the laser pulse front with respect to the wavefront by half of this interaction angle optimizes electron and laser pulse overlap by compensating the spatial offset between electrons and the laser pulse-front at the beginning of the interaction when the electrons are far from the laser pulse axis. The laser pulse-front tilt ensures continuous overlap between electrons and laser pulse while the electrons cross the laser pulse cross-sectional area. Thus the interaction distance can be controlled in TWTS by the laser pulse width rather than laser pulse duration. Utilizing wide, petawatt class laser pulses allows realizing thousands of optical undulator periods.

This thesis will show that TWTS OFELs emitting ultraviolet radiation are realizable today with existing technology for electron accelerators and laser systems.
The requirements on electron bunch and laser pulse quality of these ultraviolet TWTS OFELs are discussed in detail as well as the corresponding requirements of TWTS OFELs emitting in the soft and hard X-ray range.
These requirements are derived from scaling laws which stem from a self-consistent analytic description of the electron bunch and radiation field dynamics in TWTS OFELs presented within this thesis.
It is shown that these dynamics in TWTS OFELs are qualitatively equivalent to the electron bunch and radiation field dynamics of standard free-electron lasers which analytically proves the applicability of TWTS for the realization of an optical free-electron laser.

Furthermore, experimental setup strategies to generate the pulse-front tilted TWTS laser pulses are presented and designs of experimental setups for the above examples are discussed.
The presented setup strategies provide dispersion compensation, required due to angular dispersion of the laser pulse, which is especially relevant when building compact, high-yield hard X-ray TWTS sources in large interaction angle setups.
An example of such an enhanced Thomson source by TWTS, which provides orders of magnitude higher spectral photon density than a comparable head-on interaction geometry, is presented, too.

Keywords: Traveling-Wave; Thomson scattering; X-ray; free-electron laser; pulse-front tilt

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-089 2018
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-27169
Publ.-Id: 27169


Thick Permalloy films for the imaging of spin texture dynamics in perpendicularly magnetized systems

Finizio, S.; Wintz, S.; Bracher, D.; Kirk, E.; Semisalova, A. S.; Förster, J.; Zeissler, K.; Weßels, T.; Weigand, M.; Lenz, K.; Kleibert, A.; Raabe, J.

Performance combined with simplicity: we demonstrate that thick Permalloy films exhibiting a weak growth-induced perpendicular magnetic anisotropy can be employed as an ideal test system for the study of magnetodynamical processes in perpendicularly magnetized systems exhibiting magnetic textures ranging from isolated magnetic bubbles to more complex n"pi" states.

Keywords: Skyrmion; STXM; PMA

Permalink: https://www.hzdr.de/publications/Publ-27168
Publ.-Id: 27168


Magnetic small-angle neutron scattering

Mühlbauer, S.; Honecker, D.; Perigo, E. A.; Bergner, F.; Disch, S.; Heinemann, A.; Erokhin, S.; Berkov, D.; Leighton, C.; Eskildsen, M. R.; Michels, A.

Small-angle neutron scattering (SANS) is one of the most important techniques for microstructure determination, being utilized in a wide range of scientific disciplines, such as materials science, physics, chemistry, and biology. The reason for its great significance is that conventional SANS is probably the only method capable of probing structural inhomogeneities in the bulk of materials on a mesoscopic real-space length scale, from roughly 1 − 300 nm. Moreover, the exploitation of the spin degree of freedom of the neutron provides SANS with a unique sensitivity to study magnetism and magnetic materials at the nanoscale. As such, magnetic SANS ideally complements more real-space and surface-sensitive magnetic imaging techniques, e.g., Lorentz transmission electron microscopy, electron holography, magnetic force microscopy, Kerr microscopy, or spin-polarized scanning tunneling microscopy. In this review article we summarize the recent applications of the SANS method to study magnetism and magnetic materials. This includes a wide range of materials classes, from nanomagnetic systems such as soft magnetic Fe-based nanocomposites, hard magnetic Nd−Fe−B-based permanent magnets, magnetic steels, ferrofluids, nanoparticles, and magnetic oxides, to more fundamental open issues in contemporary condensed matter physics such as skyrmion crystals, noncollinar magnetic structures in noncentrosymmetric compounds, magnetic/electronic phase separation, and vortex lattices in type-II superconductors. Special attention is paid not only to the vast variety of magnetic materials and problems where SANS has provided direct insight, but also to the enormous progress made regarding the micromagnetic simulation of magnetic neutron scattering.

Permalink: https://www.hzdr.de/publications/Publ-27167
Publ.-Id: 27167


Detecting Beryllium-10 from exotic decays by Accelerator Mass Spectrometry (AMS)

Forstner, O.; Merchel, S.; Lachner, J.; Rugel, G.; Is541 Kollaboration

The one-neutron halo-nucleus 11Be decays via beta-minus to the stable nucleus 11B (t1/2=13.76 s). In rare cases a subsequent emission of a proton leads to the unstable nucleus 10Be. Theoretical calculations predict a branching ratio of this rare decay channel of below 10-7. With the capability of AMS in measuring ultra-low isotopic ratios (10Be/9Be < 10-15) the branching ratio of beta-delayed proton decay to 10Be could be measured for the first time.
A beam of 11Be ions was produced at the radioactive ion beam facility ISOLDE at CERN. After mass separation the ions were implanted in Cu targets. These targets containing the produced 10Be were spiked with low-level 9Be and in the form of BeO chemically prepared as AMS targets at HZDR. The resulting 10Be/9Be ratios were determined via AMS at the VERA laboratory of the University of Vienna. With the known quantity of added 9Be the amount of implanted 10Be was calculated. Due to the low expected branching ratio and the resulting low number of implanted 10Be atoms a high efficiency paired with a low background of the 9Be carrier material was necessary.
To further widen the spectrum of radionuclides measureable by AMS and lowering the detection limits for similar nuclear physics research, we are planning to implement an optical filtering method for selective suppression of isobars by laser photodetachment (LISEL) at the 6 MV tandem accelerator at HZDR.

Keywords: AMS

  • Lecture (Conference)
    Workshop on Ion and Particle Beams (Ionenstrahl Workshop), 24.-25.03.2018, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27166
Publ.-Id: 27166


Plasmonic nanoparticles embedded in single crystals synthesized by gold ion implantation for enhanced optical nonlinearity and efficient Q-switched lasing

Nie, W. J.; Zhang, Y. X.; Yu, H. H.; Li, R.; He, R. Y.; Dong, N. N.; Wang, J.; Hübner, R.; Böttger, R.; Zhou, S. Q.; Amekura, H.; Chen, F.

We report on the synthesis of embedded gold (Au) nanoparticles (NPs) in Nd:YAG single crystals using ion implantation and subsequent thermal annealing. Both linear and nonlinear absorption of the Nd:YAG crystals have been enhanced significantly due to the embedded Au NPs, which is induced by the surface plasmon resonance (SPR) effect in the visible light wavelength band. Particularly, through a typical Z-scan system excited by a femtosecond laser at 515 nm within the SPR band, the nonlinear absorption coefficients of crystals with Au NPs have been observed to be nearly 5 orders of magnitude larger than that without Au NPs. This giant enhancement of nonlinear absorption properties is correlated with the saturable absorption (SA) effect, which is the basis of passive Q-switching or mode-locking for pulsed laser generation. In addition, the linear and nonlinear absorption enhancement could be tailored by varying the fluence of implanted Au+ ions, corresponding to the NP size and concentration modulation. Finally, the Nd:YAG wafer with embedded Au NPs has been applied as a saturable absorber in a Pr:LuLiF4 crystal laser cavity, and efficient pulsed laser generation at 639 nm has been realized, which presents superior performance to the MoS2 saturable absorber based system. This work opens an avenue to enhance and modulate the nonlinearities of dielectrics by embedding plasmonic Au NPs for efficient pulsed laser operation.

Permalink: https://www.hzdr.de/publications/Publ-27165
Publ.-Id: 27165


OpenFOAM – a contributer‘s point of view

Schlegel, F.; Liao, Y.; Oertel, R.; Meller, R.

Der Vortrag behinhaltet einen Überblick über die Arbeiten im Bereich Mehrphasen-Simulation der Abteilung FWDC mit Hilfe der C++-Bibliothek OpenFOAM.

  • Lecture (Conference)
    German CFD Meeting, 06.03.2018, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27164
Publ.-Id: 27164


Magnetic Properties of Coupled Co/Mo/Co Structures Tailored by Ion Irradiation

Wawro, A.; Kurant, Z.; Jakubowski, M.; Tekielak, M.; Pietruczik, A.; Böttger, R.; Maziewski, A.

Modifications of the magnetic properties of Co=Mo=Co films activated by irradiation with 30-keV Ar and 17-keV Ne ion beams are investigated and compared with the influence of 35-keV Ga ions. This system is magnetized in the sample plane and exhibits a twofold anisotropy. The interlayer coupling of magnetization in as-deposited structures is parallel except for the Mo spacer thickness range between 0.5 and 1.0 nm, where the magnetization of the Co layers is antiparallel oriented. The coupling changes and gradually reduced strength of the ferromagnetic properties are compared for all ion types and discussed as a function of the Mo spacer thickness and the ion fluence. The structural evolution of the studied films with increasing fluence determined from TRIDYN simulations is discussed in relation to the observed magnetic changes.We also propose various types of magnonic crystals that can be fabricated by exploiting the results presented in this work.

Keywords: Ion Irradiation; layered magnetic structures; interlayer coupling; magnetism

Permalink: https://www.hzdr.de/publications/Publ-27163
Publ.-Id: 27163


Localized ion beam mixing using a focused Neon beam for future SET applicatons

Xu, X.; Hlawacek, G.; Wolf, D.; Engelmann, H.-J.; Prüfer, T.; Hübner, R.; Bischof, L.; von Borany, J.; Facsko, S.; Heinig, K.-H.

The increased use of personal computing devices and the Internet of Things (IoT) is accompanied by a demand for a computation unit with extra low energy dissipation. The Single Electron Transistor (SET), which uses a Coulomb island to manipulate the movement of single electrons, is a candidate device for future low-power electronics. However, so far its development is hindered by low-temperature requirements and the absence of CMOS compatibility. By combining advanced top-down lithography with botom-up self-assembly of Si nano dots (NDs) we will overcome this barrier.
In this work, Si NDs—suitable as RT Coulomb islands—are formed via ion beam mixing followed by thermally stimulated phase separation. Spatial control over the ND formation is achieved by using the highly focused Neon beam with a diameter of only 2 nm available in the helium ion microscope (HIM).
The impinging energetic ions will locally mix excess Si from a top Si-layer and into a buried SiO 2 layer which is grown on a Si wafer. This results in a mixing volume small enough for restricted Ostwald ripening and successful single ND formation. The formation of spatially controlled single NDs with a diameter of only 2.2 nm is confrmed by comparing the energy fltered transmission electron microscopy (EFTEM) Si plasmon-loss intensity with simulated plasmon loss images. The conditions for ND formation, namely the dependence on primary energy, irradiation fuence, layer thickness and thermal budget during rapid thermal annealing (RTA), are optimized based on an extensive survey of this multidimensional parameter space. The investigation is guided by TRIDYN simulations of the Si excess in an SiO 2 layer due to ion beam mixing and 3D Kinetic Monte-Carlo (3DkMC) simulation for the phase separation during the thermal treatment. To achieve a CMOS compatible mass fabrication of individual NDs the results are than transferred to Si + broad beam irradiation and cross checked by EFTEM. In this case localization will be achieved by pre-structuring the sample into narrow pillars using lithography.
This work has been funded by the European Union’s Horizon 2020 Research and Innovation Program under grant agreement No. 688072 “IONS SET”.

Keywords: HIM

  • Lecture (Conference)
    picoFIB, 31.01.2018, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-27162
Publ.-Id: 27162


External validation of an NTCP model for acute esophageal toxicity in locally advanced NSCLC patients treated with intensity-modulated 5 (chemo-)radiotherapy

Dankers, F.; Wijsman, R.; Troost, E.; Tissing-Tan, C.; Kwint, M.; Belderbos, J.; de Ruysscher, D.; Hendriks, L.; de S.-Oei, L.-F.; Rodwell, L.; Dekker, A.; Monshouwer, R.; Hoffmann, A.; Bussink, J.

Purpose: We externally validated a previously established multivariable normal-tissue complication probability (NTCP) model for Grade ≥2 acute esophageal toxicity (AET) after intensity-modulated (chemo-)radiotherapy or volumetric-modulated arc therapy for locally advanced non-small cell lung cancer.
Experimental design: A total of 603 patients from five cohorts within four different Dutch institutes were included. Using the NTCP model, containing predictors concurrent chemoradiotherapy, mean esophageal dose, gender and clinical tumor stage, the risk of Grade ≥2 AET was estimated per patient and model discrimination and (re)calibration performance was evaluated for all cohorts.
Results: Five validation cohorts experienced higher incidence of Grade ≥2 AET compared to the training cohort (49.3%-70.2% vs 35.6%; borderline significant for one cohort, highly significant for four cohorts). For three cohorts, discriminative performance was similar to the training cohort (area under the curve (AUC) 0.81-0.89 vs 0.84). In the two remaining cohorts the model showed poor discriminative power (AUC 0.64 and 0.63). Reasonable calibration performance was observed in two cohorts, and recalibration further improved performance in all three cohorts with good discrimination. Recalibration for the two poorly discriminating cohorts did not improve performance.
Conclusions: The NTCP model for AET prediction was successfully validated in three out of five patient cohorts. The model did not perform well in two cohorts, which included patients receiving substantially 105 different treatment.
Before applying the model in clinical practice validation of discrimination and calibration performance on a local cohort is recommended. Recalibration of the model is advised to match predicted probabilities to locally observed frequencies of AET.

Permalink: https://www.hzdr.de/publications/Publ-27161
Publ.-Id: 27161


Charge exchange and energy loss of slow highly charged ions transmitted through 2D materials

Wilhelm, R. A.; Creutzburg, S.; Schwestka, J.; Gruber, E.; Kozubek, R.; Lehnert, T.; Leiter, R.; Heller, R.; Krasheninnikov, A.; Facsko, S.; Kaiser, U.; Kotakoski, J.; Schleberger, M.; Aumayr, F.

Slow highly charged ions carry a large amount (several 10 keV) of potential energy, which gets released by target excitation and secondary particle emission upon impact on a solid surface. The energy release can trigger permanent material modifications on semi-conducting and insulating materials [1]. To understand the energy release mechanism and get information on it’s time scale, we use freestanding 2D materials, limiting the interaction time of the ions upon transmission to a few femtoseconds. We detect the ions after the interaction by means of charge state, energy, and angle resolved detection techniques. Further, we detect emitted secondary electrons in coincidence with a particular charge exchange.
Using freestanding single layer graphene, our experimental findings revealed an ultrafast charge exchange and projectile de-excitation mechanism [2,3]. We also determined the in-plane current density in the material, which is transiently active to supply electrons to the ion, to be in the order of 1012A/cm2. Still, graphene is able to sustain these large current densities for a fs-time-scale without rupture. Here we go one step further and present results of ion transmission spectroscopy of single layer hBN and MoS2, which are insulating and semi-conducting, respectively.

  • Invited lecture (Conferences)
    IBMM 2018 - International Conference on Ion Beam Modification of Materials, 24.-29.06.2018, San Antonio, TX, USA

Permalink: https://www.hzdr.de/publications/Publ-27160
Publ.-Id: 27160


From the creation of carbon nanomembranes in a low energy electron microscope to perforation with highly charged ions

Wilhelm, R. A.; Neumann, C.; Küllmer, M.; Winter, A.; Turchanin, A.

Carbon nanomembranes are materials with only nm thickness, which can be used as freestanding membranes in filtration applications. They exhibit interesting properties as they can be e.g. transformed into (semi-)metallic graphene, but are insulating in their pristine phase. Using a Low Energy Electron Microscope allowed us to follow the formation of a carbon nanomembrane by electron-induced cross-linking of a self-assembled monolayer in-situ and in real-time. Releasing the membrane from the substrate and irradiating it with highly chared ions leads finally to regularely sized nanopores.

  • Lecture (others)
    Seminar AG Turchanin, 11.01.2018, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27159
Publ.-Id: 27159


Synemin is a novel co-regulator of non-homologous end joining in head and neck cancer cells

Deville, S. S.; Förster, S.; Cordes, N.

Introduction:
Cancer therapy resistance is one of the major obstacles for higher cure rates. Novel key players of the resistome are focal adhesion proteins (FAPs). As FAPs are critically involved in DNA repair, we here characterize the yet unknown function of the FAP and intermediate filament protein Synemin (SYN) as a novel DNA repair regulator and potential cancer drug target in head and neck squamous cell carcinoma (HNSCC).

Methods and materials:
Our novel 3D High Throughput esiRNA Screen (3DHTesiRNAs) using laminin-rich extracellular matrix (lrECM) was conducted to measure radiation-induced residual DNA double strand breaks (DSBs; foci assay) and clonogenic radiation survival in UTSCC15-pEGFP-53BP1 cells. Validations were performed in 10 additional HNSCC cell lines in 3D lrECM. Upon SYN depletion, DSB repair reporter assays for non-homologous end joining (NHEJ) and homologous recombination (HR) as well as Western Blotting for protein expression and phosphorylation were carried out. SYN depleted cells with and without irradiation were analyzed for kinase activity profiling (PamGene) and protein interactome determination using a sequential immunoprecipitation/mass spectrometry approach.

Results and Discussion:
Among the targets found in the 3DHTesiRNAs, SYN turned out as one of the top FAP candidate determinants of HNSCC cell survival. SYN silencing radiosensitized HNSCC cells, while its exogenous overexpression induced radioprotection. We found an increased SYN/chromatin interaction and a marked perinuclear SYN accumulation post irradiation. Intriguingly, SYN depletion elicited a 40% reduction in NHEJ activity without affecting HR or alt-EJ. In line, ATM, DNA-PKcs and c-Abl phosphorylation as well as Ku70 expression strongly declined in SYN depleted and irradiated cells relative to controls and, in contrast, to the rescue of these protein modifications by SYN overexpression. Single, double and triple depletion of SYN, DNA-PKcs and c-Abl resulted in similar radiosensitization and DSB levels as observed for SYN only, suggesting its upstream role. In the kinome analysis we observed variable changes in the serine/threonine kinases, in contrast to the tyrosine kinases with a pronounce reduced kinase activity after SYN silencing.

Conclusion:
Our data suggest the intermediate filament SYN as a new important determinant of DNA repair, tyrosine kinome and radioresistance of HNSCC cells. These observations further support the notion that DNA repair is controlled by cooperative interactions between nuclear and cytoplasmic proteins.

Keywords: synemin; radiobiology

  • Poster
    EACR 2018 - 25th Biennial Congress of the European Association for Cancer Research, 30.06.-03.07.2018, Amsterdam, Niederlande

Permalink: https://www.hzdr.de/publications/Publ-27158
Publ.-Id: 27158


beta8 integrin critically contributes to pancreatic cancer cell radiochemoresistance and intracellular vesicle trafficking under stress conditions

Lee, W.-C.; Jin, S.; Cordes, N.

Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the five most lethal malignancies in the world and has a 5-year relative overall survival rate of less than 5%. Thus, there is a great need for functional targeting d strategies. As cell-matrix adhesion is essential for the survival, invasion and therapy resistance, we sought to identify the function of 117 focal adhesion proteins (FAP) in PDAC cell radiochemoresistance. Intriguingly, 8 integrin turned out to be one of the most potential novel targets in PDAC.
Material and methods: We performed a 3D endoribonuclease-prepared siRNA (esiRNA)-based high throughput screening (3DHTesiS) in PDAC cell cultures (established and patient-derived (PDC)) grown in laminin-rich extracellular matrix (IrECM). In addition to characterizing 8 integrin expression, distribution and co-localization with other cellular organelles such as golgi apparatus, clonogenic survival assays were performed upon esiRNA-mediated knockdown, X-ray irradiation (6 Gy single dose) and gemcitabine. Fiji software was used to determine Peason’s correlation coefficient, vesicle distribution and expression patterns upon irradiation or gemcitabine. An inhibitor screen was conducted to identify pathway involved in changes of 8 integrin localization upon treatment.
Results: We identified a series of novel targets including 8 integrin. Without cytotoxicity, 8 integrin depletion elicited radiochemosensitization in PDAC, PDCs cell lines and reduced sphere formation and 3D invasion into collagen-I. Intriguingly, we found 8 integrin located in perinuclear area where it colocalized with the cis-Golgi matrix protein GM130. Upon irradiation and gemcitabine, 8 integrin dissociated from the perinuclear region and spread throughput the cytosol without enhanced localization to exosomes; a process abrogated by antimycin A or oligomycin pre-treatment.
Summary: Our findings, generated in 3D lrECM PDAC cell ccultures, suggest 8 integrin as a novel determinant of PDAC radiochemoresistance. Moreover, 8 integrin may, although not found in the cell membrane to facilitate cell adhesion, a critical role in intracellular vesicle trafficking under stress conditions. Ongoing work will unravel the underlying mechanisms how 8 integrin is controlling cytoplasmic and nuclear survival pathways.

Keywords: beta8 integrin; radiotherapy

  • Poster
    EACR 2018 - European Association for Cancer Research, 30.06.-03.07.2018, Amsterdam, Niederlande

Permalink: https://www.hzdr.de/publications/Publ-27157
Publ.-Id: 27157


Switching the uniaxial magnetic anisotropy by ion irradiation induced compensation

Yuan, Y.; Amarouche, T.; Xu, C.; Rushforth, A.; Boettger, R.; Edmonds, K.; Campion, R.; Gallagher, B.; Helm, M.; von Bardeleben, H.; Zhou, S. Q.

In the present work, the uniaxial magnetic anisotropy of GaMnAsP is modified by helium ion irradiation. According to the micro-magnetic parameters, e.g. resonance fields and anisotropy constants deduced from ferromagnetic resonance measurements, a rotation of the magnetic easy axis from out-of-plane [001] to in-plane [100] direction is achieved. From the application point of view, our work presents a novel avenue in modifying the uniaxial magnetic anisotropy in GaMnAsP with the possibility of lateral patterning by using lithography or focused ion beam.

Permalink: https://www.hzdr.de/publications/Publ-27156
Publ.-Id: 27156


Electronic phase separation in insulating (Ga, Mn) As with low compensation: super-paramagnetism and hopping conduction

Yuan, Y.; Wang, M.; Xu, C.; Hübner, R.; Böttger, R.; Jakiela, R.; Helm, M.; Sawicki, M.; Zhou, S.

In the present work, low compensated insulating (Ga,Mn)As with 0.7% Mn is obtained by ion implantation combined with pulsed laser melting. The sample shows variable-range hopping transport behavior with a Coulomb gap in the vicinity of the Fermi energy, and the activation energy is reduced by an external magnetic field. A blocking super-paramagnetism is observed rather than ferromagnetism. Below the blocking temperature, the sample exhibits a colossal negative magnetoresistance. Our studies confirm that the disorder-induced electronic phase separation occurs in (Ga,Mn)As samples with a Mn concentration in the insulator–metal transition regime, and it can account for the observed superparamagnetism and the colossal magnetoresistance.

Permalink: https://www.hzdr.de/publications/Publ-27155
Publ.-Id: 27155


Investigation of a possible electronic phase separation in the magnetic semiconductors Ga1−xMnxAs and Ga1−xMnxP by means of fluctuation spectroscopy

Lonsky, M.; Teschabai-Oglu, J.; Pierz, K.; Sievers, S.; Schumacher, H. W.; Yuan, Y.; Böttger, B.; Zhou, S.; Müller, J.

We present systematic temperature-dependent resistance noise measurements on a series of ferromagnetic Ga1−xMnxAs epitaxial thin films covering a large parameter space in terms of the Mn content x and other variations regarding sample fabrication. We infer that the electronic noise is dominated by switching processes related to impurities in the entire temperature range. While metallic compounds with x>2% do not exhibit any significant change in the low-frequency resistance noise around the Curie temperature TC, we find indications for an electronic phase separation in films with x<2% in the vicinity of TC, manifesting itself in a maximum in the noise power spectral density. These results are compared with noise measurements on an insulating Ga1−xMnxP reference sample, for which the evidence for an electronic phase separation is even stronger and a possible percolation of bound magnetic polarons is discussed. Another aspect addressed in this work is the effect of ion-irradiation-induced disorder on the electronic properties of Ga1−xMnxAs films and, in particular, whether any electronic inhomogeneities can be observed in this case. Finally, we put our findings into the context of the ongoing debate on the electronic structure and the development of spontaneous magnetization in these materials.

Permalink: https://www.hzdr.de/publications/Publ-27154
Publ.-Id: 27154


Time of Flight Backscatter and Secondary Ion Spectrometry in a Helium Ion Microscope

Klingner, N.; Hlawacek, G.; Heller, R.; von Borany, J.; Facsko, S.

Helium Ion Microscopy (HIM) utilizes a Gas Field Ion Source (GFIS) to create a Helium or Neon ion beam with a diameter better than 0.5 nm and 1.8 nm, respectively. The method is well known for its high resolution imaging and nano-fabrication capabilities which it is able to provide not only for conducting but also insulating samples without the need for a conductive coating. The latter specimens are typically found in the fields of biosciences, MEMS/NEMS technology, catalyst research and many others. The availability of He and Ne ions with either low or moderate sputter yields, allow direct write nano-structuring with a precision below 10 nm in the HIM [1, 2].
However, the existing GFIS based focused ion beam (FIB) tools suffer from the lack of a well integrated analytic method that can enrich the highly detailed morphological images with materials contrast. While HIM technology is relatively young several efforts have been made to add such an analytic capability to the technique. So far, ionoluminescence [1, 3], backscattering spectrometry (BS) [1, 4, 5], and secondary ion mass spectrometry (SIMS) using a magnetic sector [6] or time of flight (TOF) setup have been demonstrated [4].
After a brief introduction to HIM itself and a summary of the existing approaches I will focus on our own time of flight based analytic approaches. TOF-HIM is enabled by using a fast blanking electronics to chop the primary beam into pulses with a minimal length of only 20 ns. In combination with an multichannel-plate based stop detector this enables TOF backscatter spectrometry (TOF-BS) using He ions at an energy of only 30 keV. The achieved lateral resolution is 54 nm and represents a world record for spatially resolved backscattering spectrometry. The energy resolution has been measured to be 1.5 keV (5%). This is sufficient to separate most of the elements (see fig. 1) and allows the detection of thin surface layers formed from heavy elements. The results will be compared to the theoretical reachable lateral and energy resolution and the limiting experimental and physical constraints of this approach will be reviewed.
Finally first TOF-SIMS results obtained with a very simple experimental configuration will be presented. Based on the findings obtained with this poor man’s version of TOF-SIMS setup a dedicated extraction optics for secondary ions has been designed and tested. This revised setup can be operated in point and shoot mode to obtain high resolution SIMS data or in imaging mode to obtain element maps of the specimen surface. First experiments revealed a very high relative transmission of up to 76% which is crucial to collect enough signal from nanoparticles prior to their complete removal by ion sputtering. For m/q ≤ 80 u a Dm ≤ 0.3 u has been achieved. This is sufficient for many life science applications that rely on the isotope identification of light elements (e.g.: C, N). The lateral resolution of 8 nm has been evaluated using the knife edge method and a 75%/25% criterion which represents a world record for spatially resolved secondary ion mass spectrometry.

Keywords: HIM

  • Invited lecture (Conferences)
    Microscopy and Microanalysis, 05.-09.08.2018, Baltimore, USA
    DOI: 10.1017/S1431927618004506
  • Lecture (Conference)
    CAARI - 25th Conference on Application of Accelerators in Research and Industry, 13.-17.08.2018, Fort Worth, USA
  • Lecture (Conference)
    AVS International Symposium & Exhibition, 21.-26.10.2018, Long Beach, USA

Permalink: https://www.hzdr.de/publications/Publ-27153
Publ.-Id: 27153


Harnessing the Coordination Chemistry of 1,4,7-Triazacyclononane for Biomimicry and Radiopharmaceutical Applications

Joshi, T.; Kubeil, M.; Nsubuga, A.; Singh, G.; Gasser, G.; Stephan, H.

TACN-based mono- and poly-nuclear metal complexes have found extensive use as biological mimics for understanding the structural and operational aspects of complex natural systems. Their coordination flexibility has also provided researchers access to a vast library of radiometal binding motifs that display excellent thermodynamic stability and kinetic inertness upon metal complexation. Synthetic modification on the TACN backbone has yielded ligands that can form metal complexes with coordination geometries well-suited for these applications. In particular, Leone Spiccia’s research has played a significant role in accelerating the progress in these two fields. With a focus on providing an overview of his contributions to the biomimicry and radiopharmaceutical disciplines, this minireview uses relevant examples to put in perspective the utility of macrocyclic coordination chemistry for biological inorganic chemistry applications.

Keywords: 1; 4; 7-Triazacyclononane; Coordination Chemistry; Metal complexes; Metallobiosites; Radiopharmaceuticals

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Permalink: https://www.hzdr.de/publications/Publ-27152
Publ.-Id: 27152


RODARE Logos

Frust, T.

RODARE (Rossendorf Data Repository) is the institutional data repository at Helmholtz-Zentrum Dresden-Rossendorf. The initial logos of the platform are collected in this upload and are available as Open Access.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-02-28
    DOI: 10.14278/rodare.1
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-27151
Publ.-Id: 27151


Exploration targeting by multivariate compositional extrema

van den Boogaart, K. G.; Tolosana Delgado, R.; Mckinley, J.

Many different exploration targeting methods exist, like weights of evidence; inferring the probability of a deposit based on a local geology; genetic models identifying favourable conditions; and fractal based methods trying to identify regions of high value of certain fractal measures. This contribution proposes an approach potentially useful for deposits under cover: to find locations which are locally extrema on a certain spatial scale.

While surface features typically dominate the absolute values of measurements, covered objects can still produce large halos of much smaller absolute value. Our method thus looks for halos at a certain spatial scale. It does so by estimating a band filtered negative of the second derivative of the random field from spatial data, either from regular data or from a geostatistical analysis. In a certain sense this is looking for local peakiness, but filters the high frequency noise from surface effects by means of signal processing methods. The local maxima and their surrounding are then taken as the potential targets.

In a multivariate surface dataset, as provided by a geochemical exploration campaign, such a filter can be applied to the complete vector (i.e. the clr or ilr transformed compositions). This results is a nought mean compositional random field. Furthermore the bandwidth of the filter can be varied and considered as a third dimension. In this 3D map, we can again find various types of extremal points. The location on the 2D geographic space of the extreme value of the signal depends on the location of the deposit. Furthermore, the location on the third dimension relates to the deposit size or depth, and its compositional value describes its geochemical properties.

We demonstrate the effects of the method with a regional geochemical exploration dataset.

Keywords: Potential Mapping; Geostatistics; Signal Analysis

  • Lecture (Conference)
    IAMG 2018 - 19th Annual Conference of the International Association for Mathematical Geosciences, 02.-09.09.2018, Olomouc, Česká republika
  • Contribution to proceedings
    IAMG 2018 - 19th Annual Conference of the International Association for Mathematical Geosciences, 02.-09.09.2018, Oulomoc, Česká republika
    Short Abstracts of IAMG2018 – The 19th Annual Conference of the International Association for Mathematical Geosciences, Olomouc, Czech Republic: IAMG, 978-80-270-4612-6

Permalink: https://www.hzdr.de/publications/Publ-27150
Publ.-Id: 27150


Analyse der Bildrekonstruktion auf Basis von irregulären Gittern für die Untersuchung von Mehrphasenströmungen mittels ultraschneller Röntgen-Computertomographie

Pfahl, A.

Hauptbestandteil dieser Arbeit ist die ausführliche Evaluation der computertomographischen Bildgebung auf diversen irregulären Gitterstrukturen. Obwohl das derzeitige Standardverfahren der Bildrekonstruktion, die gefilterte Rückprojektion auf regulären Pixelgittern, sich im Besonderen für einen schnellen Bildgebungsprozess und die Verarbeitung großer Datenmengen eignet, so verfügen die resultierenden Bilder aufgrund der dabei notwendigen Interpolationsschritte über eine Bildqualität, die den Anforderungen in einigen Anwendungsgebieten nicht genügt. Aus diesem Grund rückt zur Vermeidung bzw. Reduzierung der Interpolationsfehler ein alternativer Lösungsansatz, basierend auf algebraischen Rekonstruktionstechniken, unter Einbezug der realen Geometrie des bildgebenden Systems, der dadurch bedingten maximal erreichbaren
Ortsauflösung sowie Vorwissen über das Untersuchungsobjekt mithilfe irregulärer Rekonstruktionsgitter in den Fokus.
Da die Erzeugung irregulärer Gitterstrukturen zumeist mit einem hohen Rechen- und Speicheraufwand verbunden ist, müssen effiziente Algorithmen erarbeitet und implementiert werden. Auch die aus den Gittern resultierenden stark unterbestimmten Gleichungssysteme, für die die üblicherweise zum Einsatz kommenden algebraischen Verfahren keine respektablen Lösungen hervorbringen, stellen eine Herausforderung dar. Daher müssen alternative Algorithmen betrachtet werden. Die Beurteilung der irregulären Gitter und somit des vom Standard abweichenden Konzeptes erfolgt schließlich anhand globaler und lokaler Bildgütekriterien und stets im Vergleich zur Rekonstruktion auf regulären Pixelgittern in der Hoffnung, eine signifikante Qualitätssteigerung in den rekonstruierten Bildern verzeichnen zu können.

Keywords: ultraschnell; Röntgen; Computertomographie; Bildrekonstruktion

  • Master thesis
    Universität zu Lübeck, 2018
    Mentor: Martina Bieberle, Thorsten M. Buzug
    73 Seiten

Permalink: https://www.hzdr.de/publications/Publ-27149
Publ.-Id: 27149


Virtual mineral processing simulation in software MLALookUP

Krupko, N.; Kern, M.; van den Boogaart, K. G.

Designing a more effective and productive mineral processing plant is a major objective for engineers and researchers. An optimized flowsheet produces one or more concentrates with high recovery and grade of the target mineral(s) and low impurities of minerals that reduce the value of the concentrate. In the initial stages of flowsheet development, lab-scale experiments are prepared and meticulously reviewed. This process is very time-consuming and cost-intensive. Furthermore, the results of these experiments can be inconclusive.
To overcome these problems, a virtual mineral processing simulation software called MLALookUP was developed. The simulation model helps to predict the performance of a processing plant and to find the optimal order of processing techniques to reach the targeted concentrate composition. MLALookUP uses data from mineral liberation analysis (MLA), a tool that generates and analyses high-resolution images with compositional particle information by combining scanning electron microscopy and energy-dispersive X-ray spectroscopy.
The software uses geometallurgical properties of the material that was analyzed with MLA. Depending on these properties, MLALookUP runs virtual separation machines, which are prepared and analyzed by the user on the basis of threshold parameters. Starting with the feed material, a sequence of virtual separation machines simulates all processing steps until the final concentrate. In this way, the values of grade, recovery and mass proportion are predicted in each stream. The software gives the possibility to vary processing threshold parameters and to define the optimal order of processing experiments in a flowsheet.

  • Contribution to proceedings
    IAMG2018 - 19th Annual Conference of the International Association for Mathematical Geosciences, 02.-08.09.2018, Olomouc, Česká republika
    Short Abstracts of IAMG2018 – The 19th Annual Conference of the International Association for Mathematical Geosciences, Olomouc, Czech Republic: IAMG, 978-80-270-4612-6

Permalink: https://www.hzdr.de/publications/Publ-27147
Publ.-Id: 27147


The metrics of calorimetry in radionuclide-dependent plant metabolism

Fahmy, K.; Sachs, S.; Bok, F.; Geipel, G.; Oertel, J.

Radioecological studies depend on the quantitative toxicity assessment of environmental radionuclides. At low dose exposure, the life span of affected organisms is barely shortened enabling the transfer of radionuclides through an almost intact food chain. Lethality-based toxicity estimates are not adequate in this regime because they require higher concentrations. However, increased radionuclide concentration alters its speciation, rendering the extrapolation to the low dose exposure chemically inconsistent. Here, we demonstrate that microcalorimetry provides a sensitive real-time monitor of toxicity of uranium (in the U(VI) oxidation state) in a plant cell model of Brassica napus. We introduce the calorimetric descriptor “metabolic capacity” and show that it correlates with enzymatically determined cell viability. It is independent of physiological models and robust against the naturally occurring fluctuations in the metabolic response to U(VI) of plant cell cultures. In combination with time-resolved laser-induced fluorescence spectroscopy and thermodynamic modeling, we show that the plant cell metabolism is affected predominantly by hydroxo-species of U(VI) with an IC50 threshold of ~90 µM. The data emphasize the yet little exploited potential of microcalorimetry for the speciation-sensitive ecotoxicology of radionuclides.

Keywords: microcalorimetry; time-resolved laser fluorescence; metabolism; uranium; ecology

  • Lecture (Conference)
    XX Conference of International Society for Biological Calorimetry (ISBC 2018), 13.-15.06.2018, Krakow, Polen

Permalink: https://www.hzdr.de/publications/Publ-27146
Publ.-Id: 27146


Probing charged lepton flavor violation with the Mu2e experiment

Mueller, S. E.

The Mu2e experiment, currently under construction at the Fermi National Accelerator Laboratory near Chicago, will search for the neutrinoless conversion of muons to electrons in the field of an aluminum nucleus. This charged lepton flavor-changing process is highly suppressed in the Standard Model and therefore undetectable. There exist however scenarios for physics beyond the Standard Model that predict small but observable rates.The Mu2e experiment aims at a sensitivity four orders of magnitude better than existing experiments. This is achieved by a rigorous control of all backgrounds that could mimic the monoenergetic signal electron.

The design and status of the Mu2e experiment will be presented. In addition, I will highlight the results from several test runs carried out at HZDR's ELBE facility to study the radiation hardness and performance of components for the Mu2e calorimeter and for the detector that monitors the rate of stopped muons in the aluminum target.

Keywords: charged lepton flavor violation; muon to electron conversion; MU2E; ELBE

  • Lecture (Conference)
    DPG Spring Meeting 2018, 26.02.-02.03.2018, Bochum, Germany

Permalink: https://www.hzdr.de/publications/Publ-27145
Publ.-Id: 27145


Cost-competitiveness of siderophores in recovering of critical metals from waste streams

Jain, R.; Pollmann, K.

Siderophores are known for their specificity and sensitivity towards the critical metals whose supply is at risk in future. Thus, the use of these siderophores for the recovery of these critical metals from their low concentrated wastewater is very attractive options. However, there is no detailed cost estimation for their application in wastewater. This study detailed the economic feasibility of application of desferrioxamines for the recovery of gallium from industrial wastewater. The study looked into the factors such as regeneration recycles, downstream processing, cost of gallium, operational cost of the technology and cost & grade of desferrioxamine production. The calculations showed that minimum 10 regeneration cycles are required for the cost-effectiveness of the technology. Further, siderophores, at the present level of technology, are easily economically feasible for metals costing 300 € per Kg (indium and dysprosium).

  • Lecture (Conference)
    Sustainable mineral 2018, 14.-15.06.2018, Windhoek, Namibia

Permalink: https://www.hzdr.de/publications/Publ-27144
Publ.-Id: 27144


Formation and Aggregation of ZrO2 Nanoparticles on Muscovite (001)

Qiu, C.; Eng, P. J.; Hennig, C.; Schmidt, M.

The aggregation of nanoparticles is a key step in the formation of solid phases and a controlling factor for the behavior of suspended nanoparticles in solution. Using a charged mineral surface [muscovite (001)] we apply the surface X-ray diffraction techniques Crystal Truncation Rod (CTR) measurements and Resonant Anomalous X-ray reflectivity (RAXR) to investigate the aggregation process of Zr nanoparticles at the sub-nm scale. The aggregation process was studied as a function of ionic strength (0, 1, 10, and 100 mM NaCl), and the interfacial particles were characterized by CTR/RAXR and AFM. The observations are consistent with an aggregation process that follows a multi-step mechanism, which starts with the 3D aggregation of primary building units to form nanosheets. These sheets continue to grow through addition of building units to their reactive edges at higher ionic strength. Once the size and concentration of aggregates is sufficient, “face-to-face” stacking of nanosheets becomes the preferred aggregation mechanism as this minimizes the electrostatic repulsion of the charge that accumulates along nanosheet edges.

Keywords: Zr; muscovite; X-ray surface diffraction

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-27143
Publ.-Id: 27143


Experimental Investigation on the Heat Transfer of Innovative Finned Tubes for Passive Cooling of Nuclear Spent Fuel Pools

Unger, S.; Beyer, M.; Arlit, M.; Hampel, U.

In beyond-design-basis accidents active spent fuel pool cooling by pumps may not be possible. Promising concepts to enhance the reliability of nuclear power plants are passive heat removal systems using air as an unlimited heat sink. However the major drawbacks of such systems are small heat transfer coefficients, particularly on air side. Thus finned tube bundle heat exchangers are used to extend the heat transfer surface. However, conventional heat exchangers are limited in heat transfer capacity. For this purpose an innovative fin design was developed and experimentally investigated. A significant heat transfer enhancement was found for a moderate flow disturbance.

  • Contribution to proceedings
    49th Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Deutschland
    Proceedings of the 49th Annual Meeting on Nuclear Technology
  • Lecture (Conference)
    49th Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27142
Publ.-Id: 27142


High-field magnetoelasticity of Tm2Co17 and comparison with Er2Co17

Andreev, A. V.; Zvyagin, A. A.; Skourski, Y.; Yasin, S.; Zherlitsyn, S.

Acoustic properties (ultrasound velocity and attenuation) and magnetostriction were measured in pulsed fields up to 60 T applied along the c axis of Tm2Co17 single crystal. Similar to Er2Co17, the transition in Tm2Co17 is accompanied by clear anomalies in the sound velocity. The observed 0.3% jump of the sound velocity at the transition is negative in Tm2Co17, whereas it is positive in Er2Co17. The magnetostriction at the transition also differs very much from that in Er2Co17. In Tm2Co17, the transition is accompanied by a smooth minimum of 0.15×10-4 in longitudinal magnetostriction whereas in Er2Co17 by a very sharp expansion of much larger magnitude (1.2×10-4). In the transverse mode, the effect in Tm2Co17 looks as very broad minimum of low amplitude (<0.1×10-4) whereas in Er2Co17 as very sharp and large shrinkage (2.6×10-4). Thus, both the magnetoacoustics and magnetostriction are rather different in Tm2Co17 and Er2Co17. This supports different nature of the field-induced transitions in these compounds.

Permalink: https://www.hzdr.de/publications/Publ-27141
Publ.-Id: 27141


Unconventional field induced phases in a quantum magnet formed by free radical tetramers

Saúl, A.; Gauthier, N.; Askari, R. M.; Coté, M.; Maris, T.; Reber, C.; Lannes, A.; Luneau, D.; Nicklas, M.; Law, J. M.; Green, E. L.; Wosnitza, J.; Bianchi, A. D.; Feiguin, A.

We report experimental and theoretical studies on themagnetic and thermodynamic properties ofNIT-2Py, a free radical based organic magnet. From magnetization and specific-heat measurements we establish the temperature versus magnetic field phase diagram which includes two Bose-Einstein condensates (BEC) and an infrequent half-magnetization plateau. Calculations based on density functional theory demonstrate that magnetically this system can be mapped to a quasi-two-dimensional structure of weakly coupled tetramers. Density matrix renormalization group calculations show the unusual characteristics of the BECs where the spins forming the low-field condensate are different than those participating in the high-field one.

Permalink: https://www.hzdr.de/publications/Publ-27140
Publ.-Id: 27140


Multiplet of skyrmion states on a curvilinear defect: Reconfigurable skyrmion lattices

Kravchuk, V. P.; Sheka, D. D.; Kákay, A.; Volkov, O. M.; Rößler, U. K.; van den Brink, J.; Makarov, D.; Gaididei, Y.

Typically, the chiral magnetic Skyrmion is a single-state excitation. Here we propose a system, where multiplet of Skyrmion states appears and one of these states can be the ground one. We show that the presence of a localized curvilinear defect drastically changes the magnetic properties of a thin perpendicularly magnetized ferromagnetic film. For a large enough defect amplitude a discrete set of equilibrium magnetization states appears forming a ladder of energy levels. Each equilibrium state has either a zero or a unit topological charge; i.e., topologically trivial and Skyrmion multiplets generally appear. Transitions between the levels with the same topological charge are allowed and can be utilized to encode and switch a bit of information. There is a wide range of geometrical and material parameters, where the Skyrmion level has the lowest energy. Thus, periodically arranged curvilinear defects can result in a Skyrmion lattice as the ground state.

Keywords: Skyrmions; curvilinear defects

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Permalink: https://www.hzdr.de/publications/Publ-27139
Publ.-Id: 27139


Clinical translation and regulatory aspects of CAR/TCR-based adoptive cell therapies-the German Cancer Consortium approach.

Krackhardt, A. M.; Anliker, B.; Hildebrandt, M.; Bachmann, M.; Eichmüller, S. B.; Nettelbeck, D. M.; Renner, M.; Uharek, L.; Willimsky, G.; Schmitt, M.; Wels, W. S.; Schüssler-Lenz, M.

Adoptive transfer of T cells genetically modified by TCRs or CARs represents a highly attractive novel therapeutic strategy to treat malignant diseases. Various approaches for the development of such gene therapy medicinal products (GTMPs) have been initiated by scientists in recent years. To date, however, the number of clinical trials commenced in Germany and Europe is still low. Several hurdles may contribute to the delay in clinical translation of these therapeutic innovations including the significant complexity of manufacture and non-clinical testing of these novel medicinal products, the limited knowledge about the intricate regulatory requirements of the academic developers as well as limitations of funds for clinical testing. A suitable good manufacturing practice (GMP) environment is a key prerequisite and platform for the development, validation, and manufacture of such cell-based therapies, but may also represent a bottleneck for clinical translation. The German Cancer Consortium (DKTK) and the Paul-Ehrlich-Institut (PEI) have initiated joint efforts of researchers and regulators to facilitate and advance early phase, academia-driven clinical trials. Starting with a workshop held in 2016, stakeholders from academia and regulatory authorities in Germany have entered into continuing discussions on a diversity of scientific, manufacturing, and regulatory aspects, as well as the benefits and risks of clinical application of CAR/TCR-based cell therapies. This review summarizes the current state of discussions of this cooperative approach providing a basis for further policy-making and suitable modification of processes.

Keywords: CAR/TCR-transgenic T cells; Cellular therapy; Clinical translation; Regulatory aspects

Permalink: https://www.hzdr.de/publications/Publ-27138
Publ.-Id: 27138


On the insulator-to-metal transition in titanium-implanted silicon

Liu, F.; Wang, M.; Berencén, Y.; Prucnal, S.; Engler, M.; Hübner, R.; Yuan, Y.; Heller, R.; Böttger, R.; Rebohle, L.; Skorupa, W.; Helm, M.; Zhou, S.

Hyperdoped silicon with deep level impurities has attracted much research interest due to its promising optical and electrical properties. In this work, single crystalline silicon supersaturated with titanium is fabricated by ion implantation followed by both pulsed laser melting and flash lamp annealing. The decrease of sheet resistance with increasing Ti concentration is attributed to a surface morphology effect due to the formation of cellular breakdown at the surface and the percolation conduction at high Ti concentration is responsible for the metallic-like conductivity. The insulator-to-metal transition does not happen. However, the doping effect of Ti incorporation at low concentration is not excluded, which might be responsible for the sub-bandgap optical absorption reported in literature.

Keywords: Hyperdoped silicon; deep level impurities; flash lamp annealing; insulator-to-metal transition

Permalink: https://www.hzdr.de/publications/Publ-27136
Publ.-Id: 27136


Intensity-modulated proton therapy decreases dose to organs at risk in low-grade glioma patients: results of a multicentric in silico ROCOCO trial

Eekers, D.; Roelofs, E.; Cubillos-Mesias, M.; Niel, C.; Smeenk, R.; Minken, A.; Granzier, M.; Janssens, G.; Kaanders, J.; Lambin, P.; Troost, E. G. C.

Background and Purpose
Patients with low-grade glioma (LGG) have a prolonged survival expectancy due to better discriminative tumor classification and multimodal treatment. Consequently, longterm treatment toxicity, e.g., neurocognitive function, gains importance. Contemporary radiotherapy techniques such as intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), Tomotherapy (TOMO) and intensity-modulated proton therapy (IMPT) enable high-dose irradiation of the target but they differ regarding delivered dose to organs at risk (OARs). The aim of this comparative in silico study was to determine the dosimetric differences in delivered doses to the OARs.
Material and Methods
Imaging datasets of twenty-five LGG patients having undergone postoperative radiotherapy were included. For each of these patients, in silico treatment plans to a total dose of 50.4Gy to the target volume were generated for the four treatment modalities investigated (i.e., IMRT, VMAT, TOMO, IMPT). Resulting treatment plans were analyzed regarding dose to target and surrounding OARs comparing IMRT, TOMO and IMPT to VMAT (reference technique).
Results
In total, 100 treatment plans for the twenty-five patients were analyzed. Compared to VMAT the IMPT mean dose (Dmean) for 9 out of 10 (90%) OARs was statistically significantly (p<0.02) reduced, for TOMO 3/10 (30%) and 1/10 (10%) for IMRT. IMPT was the prime modality reducing dose to the OARs followed by TOMO. The pituitary gland was best spared by TOMO (Table 2).
Conclusions
The low dose volume to the majority of OARs was significantly reduced when using IMPT compared to VMAT. Whether this will lead to a significant reduction in neurocognitive decline is to be determined in carefully designed future clinical trials.

Keywords: In silico planning study; Low Grade Glioma; Photon and proton irradiation; IMPT; VMAT; IMRT; TOMO

Permalink: https://www.hzdr.de/publications/Publ-27134
Publ.-Id: 27134


Probe of plutonium oxide nanoparticles at the large-scale facility

Gerber, E.; Romanchuk, A.; Pidchenko, I.; Hennig, C.; Trigub, A.; Weiss, S.; Scheinost, A.; Kalmykov, S.; Kvashnina, K.

Plutonium is a chemical element of a most significant concern at the nuclear legacy sites. The problem of the plutonium migration plays an important role in the environmental radioactivity because of its high radiological toxicity. It was shown previously that plutonium migrates in the subsurface environment on the kilometer scale at some previously contaminated sites [1-2]. During the last few years due to the evolution of spectroscopic and microscopic techniques it was found that so called “colloidal Pu(IV) polymers” actually represents as aggregates of PuO2 nanoparticles with size ~ 2 nm. [3-4]. Investigation of plutonium oxides nanoparticles is complicated, as plutonium can exist in four partially unstable oxidation states in aqueous solution: III, IV, V, VI under environmental conditions. At the same time, presence of Pu in different oxidation states in PuO2 structure is still an open question.

This contribution will show first results of plutonium oxide nanoparticles studies at the large-scale facility – The European Synchrotron (ESRF) by X-ray spectroscopy and X-ray diffraction methods. Plutonium nanoparticles were prepared by rapid chemical precipitation using precursors in the different oxidation states. These precursors were obtained by chemical reduction or oxidation of Pu stock solution. The obtained nanoparticles were characterized by high energy resolution fluorescence detection (HERFD) [5] X-ray absorption spectroscopy, extended X-ray absorption fine structure (EXAFS) and X-ray diffraction (XRD) techniques. The experiments were performed at the Rossendorf Beamline (ROBL) at the ESRF, dedicated to actinide science, where we recently installed a novel X-ray emission spectrometer with ground-breaking detection limits. The recently upgraded ROBL beamline at the ESRF provides now a unique opportunity to study actinide materials by several experimental techniques - HERFD, XES, RIXS [6], EXAFS and XRD simultaneously. We will show how the detailed information about local and electronic structure and plutonium oxidation state in different nanoparticles can be obtained using the variety of methods at large scale facilities.


References
[1] A.B. Kersting et al., Nature 397, 56, (1999).
[2] A.P. Novikov et al., Science 314, 638 (2006).
[3] B.A. Powell et al., Environ. Sci. Technol. 45, 2698 (2011).
[4] A.R. Romanchuk et al., Geochim. Cosmochim. Acta. 121, 29 (2013).
[5] K.O. Kvashnina et al., Phys. Rev. Lett. 111, 253002 (2013).
[6] K.O. Kvashnina et al., J. Electron. Spectrosc. Relat. Phenom. 194, 27 (2013).

Keywords: nanoparticles; plutonium; HERFD; EXAFS; XRD

  • Lecture (Conference)
    48èmes Journées des Actinides (JdA2018), 21.-24.03.2018, Praia de Porto Novo, Portugal

Permalink: https://www.hzdr.de/publications/Publ-27133
Publ.-Id: 27133


Metabolism Studies - experiences, pitfalls and results

Ludwig, F.-A.

Experiences, pifalls and results of latest metabolism studies are presented and demonstrated by examples from own research.

Keywords: metabolism; PET; fluorine-18; [18F]flubatine; [18F]fluspidine; liver microsomes; clinical studie; LC-MS

  • Lecture (others)
    Doctoral Colloquium, 22.02.2018, Dresden-Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27131
Publ.-Id: 27131


Investigation of decommissioned reactor pressure vessels of the nuclear power plant Greifswald

Viehrig, H.-W.; Altstadt, E.; Houska, M.; Müller, G.; Ulbricht, A.; Konheiser, J.; Valo, M.

The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald nuclear power plant representing the first generation of Russian-type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The Greifswald RPVs of 4 units represent different material conditions as follows:
• Irradiated (Unit 4),
• irradiated and recovery annealed (Units 2 and 3), and
• irradiated, recovery annealed and re-irradiated (Unit1).
The recovery annealing of the RPV was performed at a temperature of 475° for about 152 hours and included a region covering ±0.70 m above and below the core beltline welding seam.
Material samples of a diameter of 119 mm called trepans were extracted from the RPV walls. The research program is focused on the characterisation of the RPV steels (base and weld metal) across the thickness of the RPV wall. This report presents test results measured on the trepans from the beltline welding seam No. SN0.1.4. and forged base metal ring No. 0.3.1. of the Units 1 2 and 4 RPVs. The key part of the testing is focussed on the determination of the reference temperature T0 of the Master Curve (MC) approach following the ASTM standard E1921 to determine the facture toughness, and how it degrades under neutron irradiation and is recovered by thermal annealing. Other than that the mentioned test results include Charpy-V and tensile test results. Following results have been determined:
• The mitigation of the neutron embrittlement of the weld and base metal by recovery annealing could be confirmed.
• KJc values of the weld metals generally followed the course of the MC though with a large scatter.
• There was a large variation in the T0 values evaluated across the thickness of the multilayered welding seams.
• The T0 measured on T-S oriented SE(B) specimens from different thickness locations of the welding seams strongly depended on the intrinsic structure along the crack front.
• The reference temperature RT0 determined according to the “Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs - VERLIFE” and the fracture toughness lower bound curve based thereon are applicable on the investigated weld metals.
• A strong scatter of the fracture toughness KJc values of the recovery annealed and re-irradiated and the irradiated base metal of Unit 1 and 4, respectively is observed with clearly more than 2% of the values below the MC for 2% fracture probability. The application of the multimodal MC-based approach was more suitable and described the temperature dependence of the KJc values in a satisfactory manner.
• It was demonstrated that T0 evaluated according to the SINTAP MC extension represented the brittle fraction of the data sets and is therefore suitable for the nonhomogeneous base metal.
• The efficiency of the large-scale thermal annealing of the Greifswald WWER 440/V230 Unit 1 and 2 RPVs could be confirmed.

Keywords: reactor pressure vessel; decommissione; base metal; welding seam; cladding; fracture toughness; integrity assessment

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-088 2018
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-27130
Publ.-Id: 27130


Investigation of Heat Transfer from Dried Rod Surfaces in a Spent Fuel Mock-up with a Thermal Anemometry Grid Sensor

Arlit, M.; Schleicher, E.; Hampel, U.

Within the paper we will give a brief description of the TAGS and the test facility ALADIN. Furthermore, we will discuss the role of convective cooling by steam of heated rods during boil-off experiments by parameters measured with the TAGS.

  • Contribution to proceedings
    49th Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Deutschland
    Proceedings of the 48th Annual Meeting on Nuclear Technology, 978-3-926956-95-8

Permalink: https://www.hzdr.de/publications/Publ-27129
Publ.-Id: 27129


Gyro Nozzle – An innovative Submerged Entry Nozzle Design for Billet and Bloom casting

Hackl, G.; Tang, Y.; Nitzl, G.; Schurmann, D.; Willers, B.; Eckert, S.

Mathematical simulations by means of CFD and physical models operated with liquid metal were utilized to investigate the flow characteristics obtained by the use of RHI-Magnesita’s Gyro nozzle in the mould region with a round cross section. The focus of this work was to characterize the interaction with a mold electro-magnetic stirrer (M-EMS) and compare the results with a conventional straight through SEN design. Even without the use of an electromagnetic stirrer the Gyro nozzle establishes a rotational flow in the mold. When a rotational magnetic field is applied the velocity profile at the meniscus is not severely affected. Strong fluctuations and the formation of vortices, as detected with a standard SEN, were not observed. In contrast, with increasing distance to the meniscus the rotational flow is stronger established when compared to the standard SEN, which should be beneficial in terms of the crystallization pattern of the solidified steel. The flow in general is more stable, independent of the operating conditions. Both modeling approaches show the same trend. Based on the obtained results it can be stated, that the Gyro nozzle shows a superior behavior over conventional straight through SEN designs for both the stirred and non-stirred case.

Keywords: CFD; liquid metal modeling; M-EMS; SEN; isostatically pressed products

Related publications

  • Contribution to proceedings
    AISTech 2018, 07.-10.05.2018, Philadelphia, USA
    AISTech 2018 Proceedings, Warrendale, PA, USA: Association for Iron & Steel Technology (AIST), 978-1-935117-72-8, 1655-1662
  • Iron & Steel Technology 16(2019)7, 84-90
  • Bulletin - The Journal of Refractory Innovations (2019), 52-57

Permalink: https://www.hzdr.de/publications/Publ-27128
Publ.-Id: 27128


Nε-Acryloyllysine piperazides as irreversible inhibitors of transglutaminase 2 – synthesis, structure-activity relationships and pharmacokinetic profiling

Wodtke, R.; Hauser, C.; Ruiz-Gómez, G.; Jäckel, E.; Bauer, D.; Lohse, M.; Wong, A.; Pufe, J.; Ludwig, F.-A.; Fischer, S.; Hauser, S.; Greif, D.; Pisabarro, M. T.; Pietzsch, J.; Pietsch, M.; Löser, R.

Transglutaminase 2 (TGase 2)-catalysed transamidation represents an important posttranslational mechanism for protein modification with implications in physiological and pathophysiological conditions including fibrotic and neoplastic processes. Consequently, this enzyme is considered a promising target for the diagnosis and therapy of these diseases. In this study, we report on the synthesis and kinetic characterisation of Nε-acryloyllysine piperazides as irreversible inhibitors of TGase 2. Systematic structural modifications on 54 new compounds were performed with a major focus on fluorine-bearing substituents due to the potential of such compounds to serve as radiotracer candidates for positron emission tomography. The determined inhibitory activities ranged from 100-10000 M-1s-1, which resulted in comprehensive structure-activity relationships. Structure-activity correlations using various substituent parameters accompanied by covalent docking studies provide an advanced understanding of the molecular recognition for this inhibitor class within the active site of TGase 2. Selectivity profiling of selected compounds for other transglutaminases demonstrated an excellent selectivity towards transglutaminase 2. Furthermore, an initial pharmacokinetic profiling of selected inhibitors was performed including the assessment of potential membrane permeability and liver microsomal stability.

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Permalink: https://www.hzdr.de/publications/Publ-27127
Publ.-Id: 27127


Introduction into CMFD: Basic equations of multiphase flows and the Euler-Euler approach

Hoehne, T.

Computational fluid dynamics (CFD) is one of the branches of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems that involve fluid flows.
Computers are used to perform the millions of calculations required to simulate the interaction of liquids and gases with surfaces defined by boundary conditions.
Even with high-speed supercomputers only approximate solutions can be achieved in many cases.
Ongoing research, however, may yield software that improves the accuracy and speed of complex simulation scenarios such as transonic or turbulent flows.
Validation and verification of such software is necessary using high resolution experiments.

Keywords: multiphase flow; CFD; super computing; Euler-Euler

  • Invited lecture (Conferences)
    Multiphase flow CFD workshop, 05.-07.06.2018, Changsha, China
  • Contribution to proceedings
    Multiphase flow CFD workshop, 05.-07.06.2018, Changsha, China

Permalink: https://www.hzdr.de/publications/Publ-27126
Publ.-Id: 27126


Stratified & Segregated Flow Modelling - AIAD

Hoehne, T.

Today: Limits in simulating stratified & segregated two phase flow
Algebraic Interfacial Area Density Model (AIAD)
Free Surface Drag
Turbulence Damping
Sub-grid wave turbulence (SWT)
Verification and Validation is going on – more experimental data are required for the validation

Keywords: AIAD; CFD; SWT; Drag

  • Invited lecture (Conferences)
    Multiphase Flow Workshop, 05.-07.06.2018, Changsha, China
  • Contribution to proceedings
    Multiphase flow CFD Workshop, 05.-07.06.2018, Changsha, China

Permalink: https://www.hzdr.de/publications/Publ-27125
Publ.-Id: 27125


Numerical simulation of the IAEA benchmark regarding ROCOM PTS test cases

Hoehne, T.; Kliem, S.

The development, verification and validation of CFD codes in respect to Nuclear Power Plant (NPP) safety and design necessitates further work on the complex physical modelling processes involved, and on the development of efficient numerical schemes needed to solve the basic equations. Therefore, a set of ROCOM CFD-grade test data were made available to set up an International Atomic Energy Agency (IAEA) benchmark, relating to PTS scenarios. The benchmark deals with the injection of the relatively cold Emergency Core Cooling (ECC) water which can induce buoyancy-driven stratification. Data obtained from the PTS experiment were compared in the study presented here with predictions obtained from CFD software. In addition a test case without buoyancy forces was selected to show the influence of density differences. Compared to the earlier study, significant progress was made in the development of CFD codes concerning both numerical aspects and physical modelling; here especially the treatment of turbulence. The CFX code (and turbulence modelling approaches) shows a respectable qualitative agreement with the experimental data. The dominant mixing phenomena have been treated correctly. Further, experimental and numerical analysis together seems necessary to better understand the flow behaviour under momentum driven flow conditions at low velocities.

Keywords: ROCOM; PTS; CFX; ECC

  • Contribution to proceedings
    CFD4NRS-7 OECD-NEA & IAEA Workshop "Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation", 04.-06.09.2018, Shanghai, China
  • Lecture (Conference)
    CFD4NRS-7 OECD-NEA & IAEA Workshop "Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation", 04.-06.09.2018, Shanghai, China

Permalink: https://www.hzdr.de/publications/Publ-27124
Publ.-Id: 27124


A novel CFD multi-field concept of boiling including flow pattern transitions in a vertical pipe

Hoehne, T.; Krepper, E.; Lucas, D.

The paper presents the extension of the GENTOP model for phase transfer and discusses the sub-models used. Boiling flow inside a wall heated vertical pipe is simulated by a multi-field CFD approach. Sub-cooled water enters the pipe from the lower end and heats up first in the near wall region leading to the generation of small bubbles. Further along the pipe larger and larger bubbles are generated by coalescence and evaporation. This leads to transitions of the two-phase flow patterns from bubbly to churn-turbulent and annular flow. The CFD simulation bases on the recently developed GEneralized TwO Phase flow (GENTOP) concept. It is a multi-field model using the Euler-Euler approach. It allows the consideration of different local flow morphologies including transitions between them. Small steam bubbles are handled as dispersed phases while the interface of large gas structures is statistically resolved. The GENTOP sub-models and the Wall Boiling Model need a constant improvement and separate, intensive validation effort using CFD grade experiments.

Keywords: multi-phase; boiling; GENTOP; multi-scale; CFD

  • Contribution to proceedings
    XI International Conference on Computational Heat and Mass Transfer - ICCHMT 2018, 21.-24.05.2018, Krakau, Polen
  • Lecture (Conference)
    XI International Conference on Computational Heat and Mass Transfer - ICCHMT 2018, 21.-24.05.2018, Krakau, Polen

Permalink: https://www.hzdr.de/publications/Publ-27123
Publ.-Id: 27123


Current status of CFD codes - possibilities, limitations, current developments and future trends

Hoehne, T.

Single and multiphase flows occur in many industrial processes. Reliable predictions on flow characteristics are necessary for the design, process optimization and safety analysis of related apparatuses and processes. Experimental investigations are expensive and in most cases not transferable to modified geometries or different scales and flow conditions. For this reason there is a strong requirement for numerical tools. With the use of modern multiprocessor machines, application areas are expected to broaden, and progress to accelerate. Accompanying this drive forwards is a need to establish quality and trust in the predictive capabilities of the codes, and, as a consequence of open public awareness.

Due to the 3D nature of flows and the importance of turbulence in most cases this means a strong need for reliable 3D CFD-tools rather than 1D system codes or simplified correlations. The general aim is to provide simulation tools for the design, optimization and safety analyses of medium and large scale applications in which single/multiphase flows are involved. Such tools can contribute to improve the efficient use of energy and resources (e.g. in chemical engineering and oil industries) and to guarantee the safe operation (especially nuclear safety) – provided that they are predictive.

Presently the predictive capabilities for basic hydrodynamics are restricted due to limitations of the closure models. For this reason one focus of our fluid dynamics research is the improvement of the closures first for adiabatic flow modelling but also phase transfer, chemical reactions etc. have to be considered.

The current status of commercial (like ANSYS CFX, Fluent) and open source (like OpenFoam) CFD tools and available models will be discussed. Code comparisons of similar problems will show the possibilities and limitations of each CFD code system.

These activities will help to improve the CFD codes capabilities in energy related industrial applications.

Keywords: CFD

  • Invited lecture (Conferences)
    REMOO-2018 Conference, 29.-31.05.2018, Venedig, Italien
  • Contribution to proceedings
    REMOO-2018 Conference, 29.-31.05.2018, Venedig, Italien

Permalink: https://www.hzdr.de/publications/Publ-27122
Publ.-Id: 27122


Numerical simulation of a counter-current flow experiment at the WENKA channel using a droplet entrainment model

Hoehne, T.; Gabriel, S.

One drawback today in simulating horizontal wavy two-phase flows is that there is no treatment of droplet formation mechanisms at the liquid surface. For self-generating waves and slugs, the interfacial momentum exchange and the turbulence parameters have to be modelled correctly. Furthermore, understanding and considering the mechanism of droplet entrainment for heat and mass transfer processes is of great importance in the nuclear industry.
Therefore a step of improvement of modelling liquid/gas interfaces is the consideration of droplet entrainment mechanisms. The proposed entrainment model assumes that due to liquid turbulence the interface gets rough and wavy leading to the formation of droplets. The new approach is validated against existing horizontal two-phase flow data from the WENKA (Water ENtraninment Channel KArlsruhe) channel.
Tests were carried out for water and air at ambient pressure and temperature. High speed videometry was applied to obtain velocities from flow pattern maps of the rising and falling fluid. In the horizontal part of the channel with partially reversed flow the fluid velocities were measured by planar particle image velocimetry. The test MP 28 with droplet generation at the reversed flow conditions was utilized to compare it with the simulation data. The agreement of the experimental findings and CFD results is acceptable. Also the droplet mass flow was compared and showed the applicability of the droplet entrainment model. Further work is necessary to validate the model for different flow conditions.

Keywords: CFD; Two-phase flow; WENKA; AIAD

  • Lecture (others)
    CFD-Verbundtreffen, 06.03.2018, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27121
Publ.-Id: 27121


A multiscale approach simulating boiling in a heated pipe including flow pattern transition

Hoehne, T.; Krepper, E.; Lucas, D.; Montoya, G.

The paper presents the extension of the GENTOP model for phase transfer and discusses the sub-models used. Boiling flow inside a wall heated vertical pipe is simulated by a multi-field CFD approach. Sub-cooled water enters the pipe from the lower end and heats up first in the near wall region leading to the generation of small bubbles. Further along the pipe larger and larger bubbles are generated by coalescence and evaporation. This leads to transitions of the two-phase flow patterns from bubbly to churn-turbulent and annular flow. The CFD simulation bases on the recently developed GEneralized TwO Phase flow (GENTOP) concept. It is a multi-field model using the Euler-Euler approach. It allows the consideration of different local flow morphologies including transitions between them. Small steam bubbles are handled as dispersed phases while the interface of large gas structures is statistically resolved. The GENTOP sub-models and the Wall Boiling Model need a constant improvement and separate, intensive validation effort using CFD grade experiments.

Keywords: multi-phase; boiling; GENTOP; multi-scale; CFD

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Permalink: https://www.hzdr.de/publications/Publ-27120
Publ.-Id: 27120


EASY – Evidence of design basis accidents mitigation solely with passive safety systems

Buchholz, S.; Schaffrath, A.; Bonfigli, G.; Kaczmarkiewicz, N.; Sporn, M.; Schäfer, F.; Wagner, T.

Current advanced reactor designs of generation III and III+ as well as SMR are extensively providing passive safety systems in order to control design basis accidents. Assessment of these systems is needed to verify their functionality. This can be done by experiments and computer calculations. For the latter, well validated computer codes are needed, which are able to simulate the behaviour of these systems reliably. On the basis of the KERENA reactor concept (AREVA) the currently running EASY project is performed to validate and enhance the code system AC2 for such applications. Experimental data of the large scaled INKA test facility in Karlstein (Main) is used for the validation process. During EASY, model improvement of AC2 as well as validation calculations are performed. Beside the enhancement of the coupling between the two codes ATHLET and COCOSYS, a model for the simulation of the behaviour of the passive flooding valve has been created. Additionally the 3D model of ATHLET has been enhanced in order to simulate a water surface within the 3D domain of a large water pool (e.g. for the core flooding pool in KERENA). Validation of AC2 is performed in two steps: At first single component tests with fixed boundary conditions performed at INKA in the past are used. The second step is the validation of AC2 against in EASY performed new experiments regarding design basis accidents of KERENA (SB-LOCA, LB-LOCA and SBO).

Keywords: ATHLET; KERENA; INKA; EASY

  • Contribution to proceedings
    Jahrestagung Kerntechnik, Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Deutschland
    EASY – Evidence of design basis accidents mitigation solely with passive safety systems
  • Lecture (Conference)
    Jahrestagung Kerntechnik, Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27119
Publ.-Id: 27119


Post-test analysis of the RPV lower head leak experiment at the INKA test facility using ATHLET

Sporn, M.; Schuster, C.; Hurtado, A.; Hampel, U.; Schäfer, F.

The KERENA reactor with 1,250 MW electrical power is an evolutionary boiling-water reactor (BWR) concept jointly developed by AREVA GmbH and PreussenElektra GmbH. It is a Generation III+ reactor with innovative passive safety systems such as emergency and containment cooling condenser, core flooding system and pressure pulse transmitter (PPPT) to complement the safety concept of a BWR. One design goal of the KERENA reactor concept is, that in case of an accident the core can be cooled for at least 72 hours by passive safety systems only. The INKA test facility at AREVA in Karlstein was built to investigate the heat removal capabilities and the interaction of the passive safety systems and components of the KERENA concept during different accidental scenarios. This test facility represents the KERENA main components like RPV, flooding and pressure suppression pool, drywell and shielding/storage pool, emergency condenser and containment cooling condenser at a sophisticated geometrical and power scaling. In summer 2017 at the INKA test facility a feed water line break, a leak at the lower head of the RPV and a station blackout were experimentally simulated to investigate the integral plant behaviour and the designated safety functions of each single passive component. An existing ATHLET input deck of the INKA test facility, which was already validated against the INKA experiment of a main steam line break, was extended by a PPPT model and the break lines for the loss of coolant experiments. Pre- and post-test calculations for the “leak at the lower head of the RPV” experiment were conducted to assess and validate the input deck. The experiment has shown that the passive safety systems are capable to remove the decay heat and the core flooding system was also triggered in this accident sequence. Comparing the ATHLET simulations with the experimental data, some deviations were found, which are currently being investigated and treated by ATHLET input data adjustments.

Keywords: ATHLET; KERENA; INKA; EASY

  • Contribution to proceedings
    Jahrestagung Kerntechnik, Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Deutschland
    Proceedings of the Annual Meeting on Nuclear Technology
  • Lecture (Conference)
    Jahrestagung Kerntechnik, Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27118
Publ.-Id: 27118


Overview of research and therapy facilities for radiobiological experimental work in particle therapy. Report from the European Particle Therapy Network radiobiology group

Dosanjh, M.; Jones, B.; Pawelke, J.; Pruschy, M.; Singers Sørensen, B.

Particle therapy (PT) as cancer treatment, using protons or heavier ions, can provide a more favourable dose distribution compared to x-rays. While the physical characteristics of particle radiation have been the aim of intense research, less focus has been placed on the actual biological responses arising from particle irradiation.
One of the biggest challenges for proton radiobiology is the RBE, with an increasing concern that the clinically-applied generic RBE-value of 1.1 is an approximation, as RBE is a complex quantity, depending on both biological and physical parameters, such as dose, LET, cellular and tissue radiobiological characteristics, as well as the endpoints being studied. Most of the available RBE data derive from in vitro experiments, with very limited in vivo data available, especially in late-reacting tissues, which provide the main constraints and influence the quality of life endpoints in radiotherapy. There is a need for systematic, large-scale studies to thoroughly establish the biology of particle radiation in a number of different experimental models in order to refine biophysical mathematical models that can potentially be used to guide PT.
The overall objective of the European Particle Therapy Network (EPTN) WP6 is to form a network of research and therapy facilities in order to coordinate and standardise the radiobiological experiments, to obtain more accurate predictive parameters than in the past. Coordinated research is required in order to obtain the most appropriate experimental data. The aim in this paper is to describe the available radiobiology infrastructure of the centers involved in EPTN WP6.

Keywords: particle therapy; radiobiology; RBE; EPTN

Permalink: https://www.hzdr.de/publications/Publ-27117
Publ.-Id: 27117


Study on optimal scintillation detectors for ultrafast electron beam X-ray CT scanners

Iskander, K. N. A.

Currently, ROFEX systems rely on CZT detectors to convert X-rays directly into electric signals. Despite simplicity and high X-ray detection efficiency, the performance of the CZT detectors is limited as a consequence of polarization effects that saturate the detector output, and hence degrades the quality of the reconstructed image. Furthermore, CZT detectors require high bias voltage (1-2 KV) to operate besides manufacturing challenges due to the limited crystal growth of the CZT material. With the intention to overcome the above-stated problems, scintillation-based detectors have been suggested to replace the CZT detectors in ROFEX scanners. For the design of an optimal scintillation-based detector system, suitable scintillators, photodetectors as well as a suitable front-end have to be selected, analyzed and tested.

Keywords: radiation detectors; scintillation detectors; ultrafast electron beam X-ray CT

  • Diploma thesis
    Anhalt University of Applied Science, 2018
    Mentor: Dr. André Bieberle
    66 Seiten
  • Lecture (others)
    Verteidigung der Masterarbeit, 22.02.2018, Köthen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27116
Publ.-Id: 27116


PANAS – Experimental and theoretical investigations of generic thermal hydraulic issues of passive safety systems

Schuster, C.; Lippmann, W.; Hampel, U.; Walther, M.; Leyer, S.

To guarantee the nuclear safety which means keeping the radioactivity inside the fuel rods it is necessary to remove the decay heat in all circumstances of normal and abnormal operation situations. Decay heat removal systems of the present reactor fleet are based on active components like pumps, motor driven valves, electrically I&C etc. They depend on the supply of additional energy which could fail how it was imposingly demonstrated in Fukushima. Virtually all new reactor designs of generation 3+ are characterized by the implementation of various passive safety components.
Passive Residual Heat Removal (PRHR) systems use heat transfer induced density differences to provide sufficient driving forces to establish a system mass flow in natural circulation loops of various configurations. Thus in order to design and model the system performance the determination of the heat transfer resistances is a crucial part since it influences the quality of calculation results on two sides: the heat transferred to the coolant as well as the mass flow of the coolant. Today’s state-ofthe-art PRHR systems use mostly the phase transition between the liquid and the vapor phase of the coolant to maximize the system mass flow and thus the performance. Precondition for the adoption of PRHR systems in nuclear reactors is the verification of the functional capability in all operation modes of the power plant. Therefore a comprehensive experimental work at different mockup scales combined with theoretical investigations (e. g. CFD and system codes) has to be undertaken.

Keywords: Passive safety systems; heat transfer; CFD

  • Lecture (Conference)
    49th Annual Meeting on Nuclear Technology (AMNT 2018), 29.-30.05.2018, Berlin, Deutschland
  • Contribution to proceedings
    49th Annual Meeting on Nuclear Technology (AMNT 2018), 29.-30.05.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27115
Publ.-Id: 27115


Role of sodium carbonate in scheelite flotation – a multi-faceted reagent

Kupka, N.; Rudolph, M.

Even though sodium carbonate is a reagent frequently used in flotation, its role is mostly described as a buffering pH modifier and a pulp dispersant. In the case of scheelite flotation, it has been hinted that sodium carbonate improves both grade and/or recovery but the mechanism itself is ambiguous at best or at least has not been distinctly reported in the literature. Furthermore, the addition of depressants such as sodium silicate or quebracho could be triggering additional mechanisms. Through batch flotation testwork on a skarn scheelite ore with high calcite content, single mineral flotation and contact angle measurements, this article aims at demonstrating that sodium carbonate is a multi-faceted reagent, which serves as a buffering pH modifier, a pulp dispersant precipitating calcium and magnesium ions in suspension, a depressant for calcite and calcium silicates and also a promoter for scheelite. It acts mostly synergistically and partially antagonistically with other depressants, notably sodium silicate and quebracho.

Keywords: sodium carbonate; scheelite flotation; mechanism

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Permalink: https://www.hzdr.de/publications/Publ-27114
Publ.-Id: 27114


Analysis of Flow Patterns in High Gravity Equipment Using Gamma‑ray Computed Tomography

Groß, K.; Bieberle, A.; Gladyszewski, K.; Schubert, M.; Skiborowski, M.; Górak, A.

Fluctuating and fast changing markets create a need for flexible equipment to adjust the production capacity to the actual demand. Application of Rotating Packed Beds (RPBs) in chemical production may meet these needs because of their modularity and flexibility. In this equipment the liquid traffic in the apparatus is caused by the centrifugal force and the mass transfer occurs mainly in a ring shaped rotating packing. Changing rotational speed offers an additional degree of freedom in equipment operation, as compared to standard columns. The advantages are an increasing capacity in a compact machine size, while providing enhanced mass transfer.
One of the reasons why RPBs are seldomly applied in Europe is the yet limited knowledge about the occurring flow mechanisms. Early studies by Burns et al. [1] mostly rely on visual observations and photographs. More recently Yang et al. [2] presented first results derived by the application of x-ray computed tomography. However, the results of their study are limited, because no gas flow was present in the experiments and their radial packing length was restricted to several centimeters.
In the present study we present observations of flow patterns within RPB, gained by using high energy intensity of the gamma radiation source. We investigated the flow behavior within an RPB with packing diameters of up to 480 mm. In addition to the classical computed tomography, angular resolved analysis is presented which allows for the observation of flow patterns relative to the motion of the rotor. Therefore they give insight about lateral movement of the liquid and first guidelines for the design of packings specific to RPBs can be made.

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrentechnik, Membrantechnik und Mischvorgänge, 27.-28.02.2018, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27113
Publ.-Id: 27113


Biodistribution studies of ultrasmall silicon nanoparticles and carbon dots in experimental rats and tumor mice

Licciardello, N.; Hunoldt, S.; Bergmann, R.; Singh, G.; Mamat, C.; Faramus, A.; Ddungu, J. L. Z.; Silvestrini, S.; Maggini, M.; de Cola, L.; Stephan, H.

Ultrasmall clearable nanoparticles possess enormous potential as cancer imaging agents. In particular, biocompatible silicon nanoparticles (Si NPs) and carbon quantum dots (CQDs) hold great potential in this regard. Their facile surface functionalization easily allows the introduction of different labels for in vivo imaging. However, to date, a thorough biodistribution study by in vivo positron emission tomography (PET) as well as a comparative study of Si vs C particles of similar size are missing. In this contribution, ultrasmall (size < 5 nm) Si NPs and CQDs were synthesized and characterized by high-resolution transmission electron microscopy (HR-TEM), Fourier-transform infrared (FTIR), absorption and steady-state emission spectroscopy. Subsequent functionalization of NPs with a near-infrared dye (Kodak-XS-670) or a radiolabel (64Cu) enabled a detailed in vitro and in vivo study of the particles. For radiolabeling experiments, the bifunctional chelating agent S-2-(4-Isothiocyanatobenzyl)-1,4,7-triaazacyclononane-1,4,7-triacetic acid (p-SCN-Bn-NOTA) was conjugated to the amino surface groups of the respective NPs. Efficient radiolabeling of NOTA-functionalized NPs with the positron emitter 64Cu was found. The biodistribution and PET studies showed a rapid renal clearance from the in vivo systems for both variants of the nanoparticles. Interestingly, the different derivatives investigated exhibited significant differences in the biodistribution and pharmacokinetic properties. This can mostly be attributed to different surface charge and hydrophilicity of the NPs, arising from the synthetic strategy used to prepare the particles.

Keywords: silicon nanoparticles; carbon quantum dots; copper-64; biodistribution; small animal positron emission tomography

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Permalink: https://www.hzdr.de/publications/Publ-27112
Publ.-Id: 27112


Thermal Conductivity Survey of Different Manufactured Insulation Systems of Rectangular Copper Wires

Seilmayer, M.; Katepally, V. K.

Especially in high power applications, thermal design of magnetic field coils is a critical part of efficient electromagnetic system design. Since thermal expansion of the coil effects magnetic field geometry, temperature drop across the windings should be kept as low as possible. Here the insulation system between wires guides ohmic heat to the surface of the coil and influences the total thermal performance. Because of very less information about the general thermal performance and quality of manufactured multilayer insulation systems, the present survey investigates several variants made of enameled wires and Polyimide film wrapped wires. Hereby, different joining technologies like bonding or backfilling determine the thermal conductivity, which obviously differs from values of individual raw materials. Best performance could be gained with a Kapton– CR film wrapped wire, backfilled with high thermal conductivity resin. Finally, the survey concludes that manufactured insulation systems drop approximately ten to twenty percent of the thermal conductivity, which could be theoretically achieved by an optimal layer composition of individual raw materials.

Keywords: Power cable thermal factors; Insulation thermal factors; Coil design; DRESDYN; High Power

Permalink: https://www.hzdr.de/publications/Publ-27111
Publ.-Id: 27111


Hydrogen burning: Study of the 22Ne(p,gamma)23Na, 3He(alpha,gamma)7Be and 7Be(p, gamma)8B reactions at ultra-low energies

Takács, M. P.

The neon-sodium cycle (NeNa cycle) of hydrogen burning is active in stars of the Asymptotic Giant Branch, in classical novae, and in supernovae of type Ia. The thermonuclear reaction rate of the 22Ne(p,γ)23Na reaction is determined by a large number of resonances, and it represents the most uncertain rate in the NeNa cycle. This PhD thesis reports on an experiment to study tentative 22Ne(p,γ)23Na resonances at Elab = 71 and 105 keV, as well as the direct capture component of the reaction rate for Elab ≤ 400 keV. The measurements were performed deep underground at the Laboratory for Un- derground Nuclear Astrophysics - LUNA (Gran Sasso, Italy), taking advantage of the strong reduction in the cosmic ray induced background. The LUNA-400-kV electrostatic accelerator and a differentially pumped, windowless gas target of iso- topically enriched 22Ne gas were used. The γ-rays from the reaction were detected with a 4π bismuth germanate scintillator. The data show upper limits on the strengths of the resonances at Elab = 71 and 105 keV of 5.8 × 10−11 and 7.0 × 10−11 eV respectively. The resonances at Elab = 156.2, 189.5 and 259.7 keV have been re-studied and show 20% higher strength than the literature. The present experiment did not show any evidence for the direct capture process at the low energies studied. In addition to the experimental work at LUNA, the 3He(α, γ)7Be and 7Be(p, γ)8B reactions were studied using the most recent solar neutrino data available. Based on the standard solar model and the experimentally measured fluxes of solar 7Be and 8B neutrinos, the astrophysical S-factors of both reactions were evaluated directly in the solar Gamow peak.

Keywords: Nuclear Astrophysics; Solar Neutrinos; LUNA; Neon-sodium cycle

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-087 2018
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-27110
Publ.-Id: 27110


Sorption of iodine in soils: insight from selective sequential extractions and X-ray absorption spectroscopy

Köhler, F.; Riebe, B.; Scheinost, A. C.; König, C.; Hölzer, A.; Walther, C.

The environmental fate of iodine is of general geochemical interest as well as of substantial concern in the context of nuclear waste repositories and reprocessing plants. Soils, and in particular soil organic matter (SOM), are known to play a major role in retaining and storing iodine. Therefore, we investigated iodide and iodate sorption by four different reference soils for contact times up to 30 days. Selective sequential extractions and X-ray absorption spectroscopy (XAS) were used to characterize binding behavior to different soil components, and the oxidation state and local structure of iodine. For iodide, sorption was fast with 73 to 96% being sorbed within the first 24 h, whereas iodate sorption increased from 11–41% to 62–85% after 30 days. The organic fraction contained most of the adsorbed iodide and iodate. XAS revealed a rapid change of iodide into organically bound iodine when exposed to soil, while iodate did not change its speciation. Migration behavior of both iodine species has to be considered as iodide appears to be the less mobile species due to fast binding to SOM, but with the potential risk of mobilization when oxidized to iodate.

Keywords: iodine; iodate; iodite; soils; XAFS; sequential extraction; sorption

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Permalink: https://www.hzdr.de/publications/Publ-27109
Publ.-Id: 27109


Overexpression of receptor tyrosine kinase EphB4 triggers tumor growth and hypoxia in A375 melanoma xenografts: insights from multitracer small animal imaging experiments

Neuber, C.; Belter, B.; Meister, S.; Hofheinz, F.; Bergmann, R.; Pietzsch, H.-J.; Pietzsch, J.

Experimental evidence has associated receptor tyrosine kinase EphB4 with tumor angiogenesis also in malignant melanoma. Considering the limited in vivo data available, we have conducted a systematic multitracer and multimodal imaging investigation in EphB4-overexpressing and mock-transfected A375 melanoma xenografts. Tumor growth, perfusion, and hypoxia were investigated by positron emission tomography. Vascularization was investigated by fluorescence imaging in vivo and ex vivo. The approach was completed by magnetic resonance imaging, radioluminography ex vivo, and immunohistochemical staining for blood and lymph vessel markers. Results revealed EphB4 to be a positive regulator of A375 melanoma growth, but a negative regulator of tumor vascularization. Resulting in increased hypoxia, this physiological characteristic is considered as highly unfavorable for melanoma prognosis and therapy outcome. Lymphangiogenesis, by contrast, was not influenced by EphB4 overexpression. In order to distinguish between EphB4 forward and EphrinB2, the natural EphB4 ligand, reverse signaling a specific EphB4 kinase inhibitor was applied. Blocking experiments show EphrinB2 reverse signaling rather than EphB4 forward signaling to be responsible for the observed effects. In conclusion, functional expression of EphB4 is considered a promising differentiating characteristic, preferentially determined by non-invasive in vivo imaging, which may improve personalized theranostics of malignant melanoma.

Keywords: Eph receptor tyrosine kinase family; Ephrin ligands; tumor microenvironment; malignant melanoma; small animal positron emission tomography; tumor angiogenesis; tumor hypoxia

Permalink: https://www.hzdr.de/publications/Publ-27108
Publ.-Id: 27108


Experimentelle Untersuchung der Wärmeübertragung, des Druckverlustes und des Strömungsfeldes an ovalen Rippenrohren unter Variation des Anströmwinkels

Unger, S.; Beyer, M.; Arlit, M.; Hampel, U.

Einleitung
Rippenrohrwärmeübertrager finden in vielen Bereichen der Industrie Anwendung, wie beispielsweise in der Klimatechnik, Kältetechnik, Kraftwerkstechnik und in chemischen Anlagen. Da ca. 90% des gesamten thermischen Widerstandes gasseitig auftreten, werden hier Oberflächenerweiterungen in Form von Rippen genutzt. Bei vielen Anwendungsfällen werden die Rippenrohrwärmeübertrager geneigt installiert, um den benötigten Bauraum zu reduzieren oder um ein Abfließen von Kondensat auf der Rohrinnenseite zu gewährleisten. Daher soll der Einfluss des Anströmwinkels auf die Wärmeübertragungsleistung und Strömungscharakteristik untersucht und beschrieben werden.

Messtechnik, experimenteller Aufbau und Durchführung
Die stationären Messungen wurden in einem ca. 6.5 m langen, senkrechten und transparenten Strömungskanal mit rechteckigem Querschnitt durchgeführt. Im Einströmbereich des Kanals befinden sich drei Sieb- sowie ein Wabengleichrichter zur Strömungsformierung an die sich eine Testsektion mit den zu untersuchenden Rippenrohren anschließt. Es wurden 3 Rippenrohre mit Rippenabständen von 6 mm,11 mm und 16 mm jeweils unter vier Anströmwinkeln (0°,20°,30° und 40°) untersucht. Die Strömung wurde durch einen Kompressor aufgeprägt und die mittlere Strömungsgeschwindigkeit zwischen 0,5 m/s und 3 m/s variiert. Die ovalen Rippenrohre wurden additiv aus 316L Edelstahl (Wärmeleitfähigkeit: 16.2 W/mK) gefertigt und sind durch Haltebuchsen an den Kanalwänden fixiert. Der Austausch von Haltebuchsen und dazugehörigen Kanalwänden ermöglichte die Positionierung der Rippenrohre mit den erforderlichen Winkeln. Im Inneren der Rippenrohre befinden sich drei elektrisch beheizte Heizpatronen. Um eine gute Wärmeleitung zum Rippenrohr zu gewährleisten, sind die Zwischenräume mit Kupferpulver ausgefüllt. Aus jeweils drei stromaufwärts und –abwärts angeordneten Thermoelementen wurde die mittlere Lufttemperatur bestimmt. Das radiale Temperaturprofil der Rippen wurde mithilfe von 12 Thermoelementen entlang der Rippenoberfläche vermessen, um den Rippenwirkungsgrad zu bestimmen. An senkrechten Bohrungen der Kanalwand unter- und oberhalb der Testsektion befinden sich die Anschlüsse der Differenzdruckmessung.
Zur Einstellung der stationären Versuchsrandbedingungen wurde die mittlere Oberflächentemperatur des Rippenrohres, durch Anpassung der elektrischen Leistung in Abhängigkeit von der Anströmgeschwindigkeit konstant bei 60° C gehalten. Die Aufzeichnung der Messdaten erfolgte mit einer zeitlichen Auflösung von 1Hz. Ein Temperaturgittersensor wurde verwendet um in 16 Messstellen stromabwärts der Versuchsstrecke das Temperatur- und Geschwindigkeitsfeld mithilfe von Widerstandstemperaturmessung und thermischer Anemometrie zu bestimmen.

Ergebnisse
Die Messergebnisse zeigen einen deutlichen Anstieg des Wärmeübergangskoeffizienten mit größerem Rippenabstand. Hintergrund sind die Strömungsgrenzschichten, welche bei niedrigerem Abstand der Rippen schon früher stromabwärts zusammenwachsen und den Wärmeübergangskoeffizient reduzieren. Des Weiteren wurde festgestellt, dass bei einem Rippenabstand von 6 mm der Rippenwirkungsgrad am höchsten und bei 16 mm am kleinsten ist. Generell wurden höhere Temperaturen der Rippe im thermischen Nachlaufgebiet hinter dem Rohr sowie niedrigere Rippentemperaturen im Anströmbereich des Rippenrohres gemessen. Aufgrund der erhöhten Oberfläche ist bei 6 mm Rippenabstand der Druckverlust am höchsten, gefolgt von den Abständen 11 mm und 16 mm.
Durch einen erhöhten Anströmwinkel von 40° nimmt die Turbulenz entlang der Rippenoberfläche zu und der Wärmeübergangskoeffizient erhöht sich um 38 % bei 6 mm Rippenabstand gegenüber der senkrechten Anströmung. Der Druckverlust nimmt mit dem Anströmwinkel stark zu. Somit ist der Druckverlust in der 40° Position gegenüber der senkrechten Anströmung für 6 mm um den Faktor 3.23 größer.

  • Lecture (Conference)
    Jahrestreffen der ProcessNet Fachgruppen Mehrphasenströmungen (MPH), Wärme- und Stoffübertragung (WSUE) und Computional Fluid Dynamics (CFD), 06.-07.03.2018, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27107
Publ.-Id: 27107


Projektidee KESS Kreislaufwirtschaftliches EntscheidungsSimulationsSystem

van den Boogaart, K. G.

Das Projekt KESS - Kreislaufwirtschaftliches EntscheidungsSimulationsSystem beschäftigt sich mit der Vorhersage von Entscheidungen, Wert- und Stoffströmen einer zukünfigen Kreislaufwirtschaft. Gesucht werden Kooperationspartner aus den Bereichen Psychologie, Wirtschaftsrecht, Wirtschaft, Reuse, Repair, und Recyclingmodellierung, sowie Mathematik und Informatik. Besonders Willkommen sind Wirtschaftsunternehmen mit Fragestellungen zu zukünftigen Geschäftsmodellen im Rahmen der Kreislaufwirtschaft.

Keywords: Kreislaufwirtschaft; Spieltheorie; Entscheidungstheorie; Stoffstrommodellierung

  • Lecture (others)
    Vernetzungs- und Informationsveranstaltung, 22.02.2018, Berlin, Deutschlad

Permalink: https://www.hzdr.de/publications/Publ-27106
Publ.-Id: 27106


Effect of background electrolyte composition on the sorption behavior of Th(IV) and Zr(IV) on the muscovite (001) basal plane

Schmidt, M.; Qiu, C.; Hellebrandt, S.; Hennig, C.; Eng, P. J.; Skanthakumar, S.; Soderholm, L.

Reliable long-term predictions about the safety of a potential nuclear waste repository must be based on a sound, molecular-level comprehension of the geochemical behavior of the radionuclides. Especially, their reactivity at the water/mineral interface will control their mobility and thus hazard potential.[1] A recent study has found a surprising dependency of the uptake of Th(IV) on the muscovite (001) basal plane on the composition of the background electrolyte.[2]
Two effects were observed a sorption reducing effect of ClO4- relative to Cl- and a sorption increasing effect of Li+ relative to Na+. Thus, a simple change from NaClO4 medium to LiClO4 led to an increase in surface occupancy by more than two orders of magnitude, which subsequently leads to the formation of Th(IV)-(hydr)oxo-nanoparticles. A mechanistic interpretation is hitherto not available, so it remains unknown whether cation and anion effects occur independently and whether the background electrolyte’s cation affects the formation of nanoparticles in solution or increases sorption at the water/mineral interface.
To probe whether anion and cation effects occur independently, Th(IV) sorption was studied in the presence of LiCl and KCl ([Th] = 0.1 mM, pH = 3.3, I = 0.1 M) using the surface X-ray diffraction techniques crystal truncation rod (CTR) diffraction and resonant anomalous X-ray reflectivity (RAXR). The finding show strong uptake at the muscovite basal plane in both cases, exceeding the surface occupancy previously described in NaCl media,[3] thus confirming that the cation effect is indeed independent of the background electrolyte’s anion.
To elucidate whether the observed differences occur, when oligomers are present before introduction of the mineral surface, we studied the uptake behavior of Zr(IV). Zr(IV) has a much more pronounced hydrolysis, and similar subsequent formation of oligomers and nanoparticles compared to Th(IV). The interfacial structure of muscovite was characterized in contact with Zr(IV) in solutions of various background electrolytes MCl (M = Li – Cs, [Zr] = 0.1 mM; pH 2.5, I = 0.1 M). In parallel, we performed AFM to characterize the morphology of any particles found on the mineral surface. The results clearly show that only small differences are induced by the electrolyte composition, which are generally well explained by the alkali cations sorption affinity and speciation at the muscovite (001) basal plane. Apparently, the background electrolyte effect is suppressed (or not effective at all) when the initial speciation of the metal is as small oligomers, indicating that the effects observed for Th(IV) occur at the water/mineral interface, and not in solution.

(1) Geckeis, H.; Lützenkirchen, J.; Polly, R.; Rabung, T.; Schmidt, M., Chem. Rev. 2013, 113, 1016-1062.
(2) Schmidt, M.; Hellebrandt, S.; Knope, K. E.; Lee, S. S.; Stubbs, J. E.; Eng, P. J.; Soderholm, L.; Fenter, P., Geochim. Cosmochim. Acta 2015, 165, 280-293.
(3) Schmidt, M.; Lee, S. S.; Wilson, R. E.; Soderholm, L.; Fenter, P., Geochim. Cosmochim. Acta 2012, 88, 66-76.

Keywords: Actinides; thorium; zirconium; CTR; RAXR; surface diffraction; sorption; interfacial processes; background electrolyte

  • Lecture (Conference)
    RadChem 2018, 13.-18.05.2018, Marianske Lazne, Tschechische Republik

Permalink: https://www.hzdr.de/publications/Publ-27105
Publ.-Id: 27105


Near-field optical examination of potassium n-butyl 2 xanthate / chalcopyrite flotation products

Firkala, T.; Kuschewski, F.; Nörenberg, T.; Klopf, J. M.; Pashkin, A.; Foerstendorf, H.; Rudolph, M.; Kehr, S. C.; Eng, L. M.

The present study introduces scattering-type scanning near-field infrared optical nanospectroscopy (s-SNIM) as a valuable and well-suited tool for spectrally fingerprinting n-butyl xanthate (KBX) molecules adsorbed to chalcopyrite (CCP) sample surfaces. The collector KBX is well known to float CCP and is used in beneficiation. We thus identify KBX molecules both by IR optical far and near field techniques, applying attenuated total internal reflection Fourier-transform infrared spectroscopy (ATR FT-IR) in comparison to s-SNIM, respectively. The major KBX band around 880 cm−1 is probed in s-SNIM using both the tunable free-electron laser FELBE at the Helmholtz-Zentrum Dresden-Rossendorf, Germany and CO2 table-top laser illumination. We then are able to monitor the KBX agglomeration in patches of < 500 nm in diameter at the CCP surface, but equally to nanospectroscopically identify the presence of KBX molecules down to the 10−4 M concentration.

Keywords: potassium n-butyl xanthate; chalcopyrite; flotation; near-field nanoscopy; IR spectroscopy; scanning probe microscopy; fingerprint region; ultra-low concentration

Permalink: https://www.hzdr.de/publications/Publ-27104
Publ.-Id: 27104


Magnetic stirring and sonication of metal melts

Gerbeth, G.

  • Invited lecture (Conferences)
    XVIII International UIE-Congress, 06.-09.06.2017, Hannover, Germany

Permalink: https://www.hzdr.de/publications/Publ-27103
Publ.-Id: 27103


Experimental Modelling of Metallurgical Processes

Eckert, G.; Gerbeth, S.

  • Invited lecture (Conferences)
    12th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries - SINTEF, 30.05.-01.06.2017, Trondheim, Norway

Permalink: https://www.hzdr.de/publications/Publ-27102
Publ.-Id: 27102


High energy resolution X-ray spectroscopy and diffraction studies of plutonium oxide nanoparticles

Gerber, E.; Romanchuk, A.; Pidchenko, I.; Hennig, C.; Trigub, A.; Weiss, S.; Scheinost, A.; Kalmykov, S.; Kvashnina, K.

The release of radioactive plutonium (Pu) into the environment is of general concern due to the high radiotoxicity and long half-life of its main isotopes. Previous research has shown that plutonium migrates in the subsurface environment on the kilometer scale at some previously contaminated sites [1-4]. Additionally, previous research demonstrated the spontaneous formation of Pu oxide nanoparticles under certain environmental conditions [5]. However, fundamental properties of such Pu oxide nanoparticles, including their local, crystal and electronic structure, remain largely unexplored, hence it is difficult to understand their formation or to predict their transport in the environment.

Plutonium may exist in four oxidation states, III, IV, V, VI, in aqueous solution under environmental conditions, which can change relatively easily. While Pu(IV) is the dominant oxidation state in such PuO2-like nanoparticles, their exact composition in terms of oxidation states and local structure remains an open question. Therefore, it is necessary to advance the fundamental understanding of the Pu oxide nanoparticles and to review the processes, through which the formation of Pu oxide nanoparticles takes place.

This contribution will give an overview on the results of Pu oxide nanoparticle research conducted at the Rossendorf Beamline at The European Synchrotron (ESRF) [6]. Pu oxide nanoparticles were prepared by rapid chemical precipitation using precursors in the different oxidation states (Pu(III), Pu(IV), Pu(V) and Pu(VI)). These precursors were obtained by chemical reduction or oxidation of Pu stock solution.

The recently upgraded ROBL beamline at the ESRF, dedicated to actinide science, provides now a unique opportunity to characterize actinide materials by several experimental techniques simultaneously. We will show how the detailed information about local and electronic structure and Pu oxidation state in different nanoparticles can be obtained using the variety of methods: Extended X-ray absorption fine structure (EXAFS [7]), X-ray absorption near edge structure (XANES), high-energy resolution fluorescence detection (HERFD) X-ray absorption spectroscopy [8-10], resonant inelastic X-ray scattering (RIXS [11]), and X-ray diffraction techniques.

  • Lecture (Conference)
    17th International Conference on X-ray Absorption Fine Structure, 22.-27.07.2018, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-27101
Publ.-Id: 27101


Interaction of Stem Cell Properties and DNA Repair determine the Radiosensitizing Effect after Inhibition of CHK1, RAD51 and PARP1 in TNBCs

Meyer, F.; Becker, S.; Niecke, A.; Werner, S.; Peitzsch, C.; Hein, L.; Dubrovska, A.; Goy, Y.; Parplys, A.; Petersen, C.; Riepen, B.; Zielinski, A.; Rothkamm, K.; Borgmann, K.

Permalink: https://www.hzdr.de/publications/Publ-27100
Publ.-Id: 27100


Discrimination of ceramic surface finishing by vertical scanning interferometry

Ionescu, C.; Fischer, C.; Hoeck, V.; Luttge, A.

Finishing techniques are significant markers of the technological “knowhow” involved in the production of the clay-based traditional ceramic ware.
In order to provide a reliable tool to discriminate among two main surface processing techniques, i.e. smoothing and burnishing, vertical scanning interferometry (VSI) – a recently developed non-destructive technique for analyzing the surface roughness and topography, is applied. The smoothed areas have an obvious roughness expressed by linear structures. The latter are made of parallel ridges and trenches with an average depth of 15–20 μm. Burnishing leads to a lower topography and a lower roughness compared to the smoothed surface section. The VSI quantifies the spatial distribution of the surface building blocks, which consist of phyllosilicate aggregates of variable size. The statistical treatment of the roughness data obtained by VSI shows that the surface topography provides significant information on the pottery processing and a clear qualitative and quantitative discrimination between different surfaces. VSI supports the reconstitution of the chaȋne opératoire for traditional ceramic pottery and the recognition of the surface finishing techniques.

Permalink: https://www.hzdr.de/publications/Publ-27098
Publ.-Id: 27098


Recent update on the KLOE ISR-measurements

Keshavarzi, A.; Müller, S. E.; Teubner, T.; Venanzoni, G.

Recent updates on KLOE ISR measurements

  • Invited lecture (Conferences)
    Workshop on hadronic vacuum polarization contributions to muon g-2, 12.-14.02.2018, KEK Tsukuba, Japan

Permalink: https://www.hzdr.de/publications/Publ-27097
Publ.-Id: 27097


Intratumoral heterogeneity and TERT promoter mutations in progressive/higher-grade meningiomas

Juratli, T. A.; Thiede, C.; Koerner, M. V. A.; Tummala, S. S.; Daubner, D.; Shankar, G. M.; Williams, E. A.; Martinez-Lage, M.; Soucek, S.; Robel, K.; Penson, T.; Krause, M.; Appold, S.; Meinhardt, M.; Pinzer, T.; Miller, J. J.; Krex, D.; Ely, H. A.; Silverman, I. M.; Christiansen, J.; Schackert, G.; Wakimoto, H.; Kirsch, M.; Brastianos, P. K.; Cahill, D. P.

Background: Recent studies have reported mutations in the telomerase reverse transcriptase promoter (TERTp) in meningiomas. We sought to determine the frequency, clonality and clinical significance of telomere gene alterations in a cohort of patients with progressive/higher-grade meningiomas.

Methods: We characterized 64 temporally- and regionally-distinct specimens from 26 WHO grade III meningioma patients. On initial diagnoses, the meningiomas spanned all WHO grades (3 grade I, 13 grade II and 10 grade III). The tumor samples were screened for TERTp and ATRX/DAXX mutations, and TERT rearrangements. Additionally, TERTp was sequenced in a separate cohort of 19 patients with radiation-associated meningiomas. We examined the impact of mutational status on patients’ progression and overall survival.

Results: Somatic TERTp mutations were detected in six patients (6/26 = 23%). Regional intratumoral heterogeneity in TERTp mutation status was noted. In 4 patients, TERTp mutations were detected in recurrent specimens but not in the available specimens of the first surgery. Additionally, a TERT gene fusion (LPCAT1-TERT) was found in one sample. In contrary, none of the investigated samples harbored an ATRX or DAXX mutation. In the cohort of radiation-induced meningiomas, TERTp mutation was detected in two patients (10.5%). Importantly, we found that patients with emergence of TERTp mutations had a substantially shorter OS than their TERTp wild-type counterparts (2.7 years, 95% CI 0.9 – 4.5 years versus 10.8 years, 95% CI 7.8 -12.8 years, p=0.003).

Conclusions: In progressive/higher-grade meningiomas,TERTp mutations are associated with poor survival, supporting a model in which selection of this alteration is a harbinger of aggressive tumor development. In addition, we observe spatial intratumoral heterogeneity of TERTp mutation status, consistent with this model of late emergence in tumor evolution. Thus, early detection of TERTp mutations may define patients with more aggressive meningiomas. Stratification for TERT alterations should be adopted in future clinical trials of progressive/higher-grade meningiomas.

Permalink: https://www.hzdr.de/publications/Publ-27096
Publ.-Id: 27096


An Image Reconstruction Framework and Camera Prototype Aimed for Compton Imaging for In-vivo Dosimetry of Therapeutic Ion Beams

Schoene, S.; Enghardt, W.; Fiedler, F.; Golnik, C.; Pausch, G.; Rohling, H.; Kormoll, T.

Prompt γ-ray imaging in hadron therapy is a novel approach for range verification. Due to the high energy of prompt γ-rays emitted during therapeutic irradiation in the order of MeV, Compton imaging is a feasible method. In this work, an imaging prototype together with the corresponding data handling and an image reconstruction framework are presented. Data and reconstructed images from laboratory measurements are shown and evaluated. A spatial resolution of 7 mm full width at half maximum in a distance of 7 cm has been achieved. More importantly, current limitations were identified for further work. It has been shown that an assumption on the unknown initial photon energy can considerably improve the imaging result.

Permalink: https://www.hzdr.de/publications/Publ-27095
Publ.-Id: 27095


Robustness evaluation of single-and multifield optimized proton plans for unilateral head and neck

Cubillos-Mesías, M.; Baumann, M.; Troost, E. G. C.; Appold, S.; Krause, M.; Richter, C.; Stützer, K.

Permalink: https://www.hzdr.de/publications/Publ-27094
Publ.-Id: 27094


Adhesion- and stress-related adaptation mechanisms eliciting glioblastoma radiochemoresistance can be effectively circumvented by beta1 integrin/JNK co-targeting

Vehlow, A.; Klapproth, E.; Storch, K.; Dickreuter, E.; Seifert, M.; Dietrich, A.; Bütof, R.; Temme, A.; Cordes, N.

Glioblastoma multiforme (GBM) is the most common brain tumor in adults and characterized by poor clinical outcome due to genetic and epigenetic alterations in resistance-mediating genes and destructive infiltration into the normal brain. Upon therapy, malignant tumors show adaptation to maintain their homeostasis. Two critical determinants of this adaptation process are cell adhesion by beta1 integrins and stress signaling via c-Jun N-terminal kinases (JNK). Here, we evaluated the potential of simultaneous beta1 integrin/JNK targeting to overcome GBM adaptation controlling radiochemoresistance and invasion.

Comparative Oncomine data base analysis was performed on the expression of JNK1/2/3 isoforms, beta1 integrin and its ligands in GBM with normal brain. Different human GBM cell populations (patient-derived, stem-like, established) were analyzed for sphere formation, clonogenicity, 3D collagen type-1 invasion, cell cycling, chromatin organization, DNA double strand break (DSB) repair (γH2AX foci assay), broad-spectrum phosphoproteome analysis, FACS analysis and protein expression/phosphorylation upon irradiation (0-6 Gy X-rays) and chemotherapy (Temozolomide) with and without single and simultaneous inhibition of beta1 integrin (AIIB2) and JNK (SP600125, JNKi). The radiochemosensitizing potential of AIIB2/JNKi was also investigated in an orthotopic GBM mouse model using stem-like cells.

In contrast to JNK isoforms, beta1 integrin and col1 showed significant overexpression in GBM compared with normal brain. While single inhibition of beta1 integrin and JNK mediated cytotoxicity, only combined targeting resulted in radiochemosensitization. Intriguingly, double AIIB2/JNKi treatment abrogated GBM cell invasion. Importantly, dual beta1 integrin/JNK inhibition elicited a significant reduction in tumor growth and longer survival of mice concomitantly treated with radiotherapy/Temozolomide. Mechanistically, JNK blocking induced beta1 integrin expression for stimulating diverse signaling pathways controlling cell cycling, invasion and radiochemosensitivity. Radiosensitization by AIIB2/JNKi is caused by enhanced ATM phosphorylation and prolonged G2/M cell cycle arrest as well as impaired DNA double strand break repair in the context of elevated levels of euchromatin.

In summary, our data reveal that dual beta1 integrin/JNK targeting efficiently impairs adhesion and stress-related adaptation mechanisms involved in radiochemoresistance and invasion. More in-depth evaluation is warranted to clarify the potential of this kind of beta1 integrin/JNK multi-targeting strategy administrated concomitantly to standard radiochemotherapy in patients suffering from GBM.

Permalink: https://www.hzdr.de/publications/Publ-27093
Publ.-Id: 27093


Annual Report 2017 - Institute of Resource Ecology

Stumpf, T.; Foerstendorf, H.; Bok, F.; Richter, A.

THE INSTITUTE OF RESOURCE ECOLOGY (IRE) IS ONE of the eight institutes of the Helmholtz-Zentrum Dresden – Rossendorf (HZDR). The research activities are mainly integrated into the program “Nuclear Waste Management, Safety and Radiation Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-085 2018
    ISSN: 2191-8708, eISSN: 2191-8716

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27092
Publ.-Id: 27092


Extension of the reactor dynamics code DYN3D to SFR applications – Part III: validation against the initial phase of the Phenix EOL natural convection test

Nikitin, E.; Fridman, E.

The reactor dynamics code DYN3D, initially developed for LWR applications, is being extended for steady state and transient analyses of Sodium cooled Fast Reactor (SFR) cores. The extension includes the development of the few-group cross section generation methodology, updating of the thermal-hydraulic database with thermal-physical properties of sodium, and development of the thermal-mechanical model to account for thermal expansion effects of the core components.
Part I of the paper provided a detailed description of the recently implemented thermal expansion models able to treat axial expansion of fuel rod and radial expansion of diagrid. The results of the initial verification test were also presented in Part I of the paper.
The capability of the extended version of DYN3D to perform steady state and transient analyses of SFR cores was validated using selected tests from the end-of-life experiments conducted at the Phenix reactor. Steady state analysis of the control rod withdrawal tests is covered in Part II of the paper.
Part III of the paper reports on the results of the transient analysis of the initial stage of the natural circulation test from the Phenix end-of-life experiments.

Keywords: SFR; Phenix EOL tests; thermal expansion; nodal diffusion; transient analysis; DYN3D; Serpent

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Permalink: https://www.hzdr.de/publications/Publ-27091
Publ.-Id: 27091


Ein möglicher prognostischer Biomarker für das Therapieansprechen und therapeutisches Zielmolekül zur Strahlensensitivierung in Kopf-Hals-Plattenepithelkarzinomen

Digomann, D.; Kurth, I.; Linge, A.; Hein, L.; Baumann, M.; Dubrovska, A.

  • Abstract in refereed journal
    Strahlentherapie und Onkologie 193(2017), S25-S26

Permalink: https://www.hzdr.de/publications/Publ-27090
Publ.-Id: 27090


Extension of the reactor dynamics code DYN3D to SFR applications – Part II: validation against the Phenix EOL control rod withdrawal tests

Nikitin, E.; Fridman, E.

The reactor dynamics code DYN3D, initially developed for LWR applications, is being extended for steady state and transient analyses of Sodium cooled Fast Reactor (SFR) cores. The extension includes the development of the few-group cross section generation methodology, updating of the thermal-hydraulic database with thermal-physical properties of sodium, and development of the thermal-mechanical model to account for thermal expansion effects of the core components.
Part I of the paper provided a detailed description of the recently implemented thermal expansion models able to treat axial expansion of fuel rod and radial expansion of diagrid. The results of the initial verification test were also presented in Part I of the paper.
The capability of the extended version of DYN3D to perform steady state and transient analyses of SFR cores was validated using selected tests from the end-of-life experiments conducted at the Phenix reactor. Part II of the paper reports on the results of the steady state analysis of the control rod withdrawal tests from the Phenix end-of-life experiments. The transient analysis of the initial stage of the natural circulation test is covered in Part III of the paper.

Keywords: SFR; Phenix EOL tests; thermal expansion; nodal diffusion; transient analysis; DYN3D; Serpent

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Permalink: https://www.hzdr.de/publications/Publ-27089
Publ.-Id: 27089


Extension of the reactor dynamics code DYN3D to SFR applications – Part I: thermal expansion models

Nikitin, E.; Fridman, E.

The reactor dynamics code DYN3D, initially developed for LWR applications, is being extended for steady-state and transient analyses of Sodium cooled Fast Reactor (SFR) cores. In contrast to LWRs, thermal expansions of SFR core and reactor components such as fuel, cladding, diagrid, control rod (CR) drivelines, vessel, etc. provide essential reactivity feedbacks under normal and transient conditions.
Since DYN3D was originally oriented to the LWRs analyses, the modeling of thermal expansion mechanisms was not considered in the code. Therefore, the development of a new thermal-mechanical module accounting for thermal expansions has been initiated as a part of the SFR related activities. At first step, the DYN3D code was extended with the capability of treating two important thermal expansion effects occurring within the core, namely axial expansion of fuel rod and radial expansion of diagrid.
Part I of the paper provides a detailed description of the newly implemented models and presents the results of the initial verification study performed on a full core level using a large oxide SFR core from the OECD/NEA benchmark and a Phenix end-of-life core from the static neutronic IAEA benchmark.
Two IAEA benchmarks on the Phenix end-of-life experiments were used for a more detailed validation of the extended version of DYN3D. While the Part II presents the validation study performed against the static neutronic benchmark of the control rod withdrawal tests, the results of the initial stage of the natural circulation test are covered in Part III of the paper.

Keywords: SFR; thermal expansion; nodal diffusion; Monte Carlo; Serpent; DYN3D

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Permalink: https://www.hzdr.de/publications/Publ-27088
Publ.-Id: 27088


Preparation of small animal irradiation experiments with laser-accelerated protons

Kroll, F.; Beyreuther, E.; Brack, F. E.; Gaus, L.; Karsch, L.; Kraft, S.; Metzkes, J.; Pawelke, J.; Schlenvoigt, H. P.; Schürer, M.; Zeil, K.; Schramm, U.

  • Open Access Logo Abstract in refereed journal
    Biomedical Engineering / Biomedizinische Technik 62(2017)Suppl. 1, S239
    DOI: 10.1515/bmt-2017-5044

Permalink: https://www.hzdr.de/publications/Publ-27087
Publ.-Id: 27087


The oxidation of borohydrides by photoexcited [UO2(CO3)3]4−

Takao, K.; Tsushima, S.

The carbonate ion is an effective quencher of uranyl(VI) luminescence and makes uranyl(VI) tricarbonate barely luminecent and photochemically inactive. We demonstrate here that photoexcited uranyl(VI) tricarbonate, *[UVIO2(CO3)3]4− can however oxidize borohydrides (BH3X, X = H, CN) to give boric acid and H2 gas, reducing itself to [UVO2(CO3)3]5−. This hypothesis was supported by UV-Vis and NMR spectroscopies as well as quantum chemical calculations. The charge transfer states associated with photoreduction processes were modelled by density functional theory calculations. These results suggest that the mechanism of photoreduction of [UVIO2(CO3)3]4− is similar to that in [[UVIO2(H2O)5]2+ and that it occurs through one–photon reduction process.

Permalink: https://www.hzdr.de/publications/Publ-27086
Publ.-Id: 27086


Crystal dissolution kinetics studied by a combination of Monte Carlo and Voronoi methods

Rohlfs, R. D.; Fischer, C.; Kurganskaya, I.; Luttge, A.

Kinetic Monte Carlo (kMC) methods have been used extensively for the study of crystal dissolution kinetics and surface reactivity. A current restriction of kMC simulation calculations is their limitation in spatial system size. Here we explore a new and very fast method for the calculation of the reaction kinetics of a dissolving crystal, capable of being used for much larger systems. This method includes a geometrical approach, the Voronoi distance map, to generate the surface morphology including etch pit evolution and to calculate reaction rate maps and rate spectra in an efficient way. We calculate Voronoi distance maps that are based on a distance metric corresponding to the crystal lattice, weighted additively in relation to stochastic etch pit depths.
We show the opportunity to parameterize Voronoi distance maps by kMC simulation results. As a result, the resulting temporal sequences of Voronoi maps provide kinetic information.
By comparing temporal sequences of kMC simulation and Voronoi distance maps of identical etch pit distributions, we demonstrate the opportunity of making specific predictions about the dissolution reaction kinetics, based on rate maps and rate spectra. The dissolution of an initially flat Kossel crystal surface served as an example to show that a sequence of Voronoi calculations can predict dissolution kinetics based on the information about the distribution of screw defects.
The results prove the geometrical relationship between material flux from the surface at a certain point and the distance (or, when considering anisotropy, a function of distance) to the nearest defect. In this study, for the sake of comparability, the calculations are made using input parameters directly derived from the KMC models operating at the atomic scale. We show that, using values of v(rpit) and weighting factors obtained by kMC, the resulting surface morphologies and material flux are almost identical. This implies that discrete Voronoi calculations of starting and end points of the dissolution are sufficient to calculate material flux maps, without having to simulate all-atomic time-consuming calculations in between. This opens a new promising venue to efficiently upscale full-atomic KMC models to the continuum macroscopic level where reactive transport and Lattice Boltzmann calculations can be applied.

Keywords: fluid-solid reaction kinetics; kinetic Monte Carlo simulation; Voronoi distance; rate map; rate spectra

Permalink: https://www.hzdr.de/publications/Publ-27085
Publ.-Id: 27085


Experimental observation of Bethe strings

Wang, Z.; Wu, J.; Yang, W.; Bera, A. K.; Kamenskyi, D.; Islam, A. T. M. N.; Xu, S.; Law, J. M.; Lake, B.; Wu, C.; Loidl, A.

Almost a century ago, string states—complex bound states of magnetic excitations—were predicted to exist in one-dimensional quantum magnets. However, despite many theoretical studies, the experimental realization and identification of string states in a condensed-matter system have yet to be achieved. Here we use high-resolution terahertz spectroscopy to resolve string states in the antiferromagnetic Heisenberg–Ising chain SrCo2V2O8 in strong longitudinal magnetic fields. In the field-induced quantum-critical regime, we identify strings and fractional magnetic excitations that are accurately described by the Bethe ansatz. Close to quantum criticality, the string excitations govern the quantum spin dynamics, whereas the fractional excitations, which are dominant at low energies, reflect the antiferromagnetic quantum fluctuations. Today, Bethe’s result1 is important not only in the field of quantum magnetism but also more broadly, including in the study of cold atoms and in string theory; hence, we anticipate that our work will shed light on the study of complex many-body systems in general.

Keywords: Bethe ansatz; string excitations; Heisenberg-Ising chain; THz/infrared spectroscopy; high magnetic field

Permalink: https://www.hzdr.de/publications/Publ-27084
Publ.-Id: 27084


Origin of field-induced discontinuous phase transitions in Nd2Fe17

Diop, L. V. B.; Kuz'Min, M. D.; Skokov, K. P.; Skourski, Y.; Gutfleisch, O.

Magnetic properties of a trigonal ferromagnet Nd2Fe17 have been studied on single crystals in steady (14 T) and pulsed (32 T) magnetic fields. The easy-magnetization direction lies close to the [120] axis, deviating from the basal plane by 2.9° (at T = 5 K). Of particular interest is the low-temperature magnetization process along the high-symmetry axis [001], which is the hard direction. This process is discontinuous and involves two first-order phase transitions (FOMPs). One of them (at 20 T) is a symmetry FOMP similar to that observed in Sm2Fe17. The second transition (at 10.4 T) is unusual: as the magnetization turns abruptly toward the applied field, it also changes its azimuthal orientation (the angle ϕ) by 60°. Both transitions can be reasonably accounted for by the presence of a significant sixth-order trigonal anisotropy term.

Permalink: https://www.hzdr.de/publications/Publ-27083
Publ.-Id: 27083


Spectroscopic and batch studies of technetium uptake by siderite

Schmeide, K.; Rossberg, A.; Weiss, S.; Scheinost, A. C.

99Tc is a long-lived (t1/2 = 2.1 x 105 years) β-emitter formed during the fission of U and is of major concern for radioactive waste disposal. Its environmental mobility is primarily governed by the oxidation states VII and IV, with TcVII forming the highly mobile TcO4 aquo anion, whereas TcIV is rather immobile due to the low solubility of its hydrolysis products. Redox processes, which are able to convert TcVII into TcIV, are hence of paramount importance for the safety of radioactive waste repositories. FeII-bearing minerals, ubiquitous in nature but also forming as corrosion products of the steel canisters foreseen as a possible first enclosure of radioactive waste, play a vital role in these redox reactions due to their high redox reactivity and high sorption capacity, as has been shown not only for Tc, but also for Se, U, Np and Pu.
We studied the TcVII uptake by siderite (FeCO3), a typical FeII mineral in carbonate-rich environments, in the relevant pH range 7 – 12.6 under anoxic conditions by means of batch sorption experiments and by X-ray absorption spectroscopy. Sorption experiments showed that Tc retention by siderite is fast and efficient (log Rd ~5) across the investigated pH range and independent of ionic strength (0.1 – 1 M NaCl). Tc K-edge X-ray absorption near-edge structure (XANES) data confirmed that the Tc immobilization is due to the surface-mediated reduction of TcVII to TcIV. The local structure of TcIV in Tc siderite sorption samples and Tc siderite coprecipitates probed by extended X-ray absorption fine-structure (EXAFS) spectroscopy revealed three different species: In the pH range 7.8 to 11.8, TcO2-dimers form inner-sphere sorption complexes at the surface of the initial siderite phase as well as on secondary magnetite or green rust formed during the redox reaction. Between pH 11.9 and 12.6, a mixed Fe/Tc hydroxocarbonate precipitate (chukanovite-like) is formed.
The results showed that siderite contributes effectively to the retention of Tc under repository conditions through formation of strong sorption complexes and precipitation of hydroxocarbonate phases with low solubility.

Keywords: Technetium; siderite; reduction; adsorption; incorporation; technetium carbonate; X-ray absorption spectroscopy

  • Contribution to proceedings
    RadChem 2018-18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázně, Czech Republic
    Czech Chemical Society Symposium Series, 18th Radiochemical Conference, Mariánské Lázně, Czech Republic, 13-18 May 2018, Booklet of Abstracts, 59
  • Lecture (Conference)
    RadChem 2018-18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázně, Czech Republic
  • Lecture (Conference)
    10th International Symposium on Technetium and Rhenium – Science and Utilization, 03.-06.10.2018, Moscow, Russia

Permalink: https://www.hzdr.de/publications/Publ-27082
Publ.-Id: 27082


Multi-Point Statistics for Tailings Deposits

Selia, S. R. R.; Tolosana-Delgado, R.; van den Boogaart, K. G.; Schaeben, H.

Technical and economic evolution of the mineral industry resulted in a new view of mining tailings. Formerly tailings are considered not valuable but now they become new resources that have promising economic values. The spatial estimation of mineral distribution is essential for optimally exploiting tailings, but this faces several issues such as non-stationarities, complex and artificial structures, and limited historic information on the feed streams and spilling points. Multi-Point Statistics methods are capable of reproducing complicated structures more appropriately as compared to two-point statistics methods. This paper proposes a new framework for performing Multi-Point Statistics on tailings deposits. Instead of using one big training image, we used several training images. In this way we can use different joint distributions at different locations to cope with the nonstationarity of tailings deposits. By providing and eventually weighting training images generated with different forward modelling parameters we can handle the uncertainty about the history of the deposit, while still exploiting available historic information. The framework is illustrated through a test on a synthetic tailings model. The synthetic truth and the training images are generated using Delft3D-Flow, an open source process-based modelling program that can also perform stratigraphic forward modeling in deltaic depositional environments. The MPS analysis is based on a new implementation with advanced capabilities.

Keywords: Multi-Point Statistics; Mining Tailings; Synthetic Training Images

  • Lecture (Conference)
    IAMG 19th Annual Conference, 02.-08.09.2018, Olomouc, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-27081
Publ.-Id: 27081


Radiative neutron capture on 242Pu in the resonance region at the CERN n_TOF-EAR1 facility

Lerendegui-Marco, J.; Guerrero, C.; Mendoza, E.; Quesada, J. M.; Eberhardt, K.; Junghans, A. R.; Krtička, M.; Aberle, O.; Andrzejewski, J.; Audouin, L.; Bécares, V.; Bacak, M.; Balibrea, J.; Barbagallo, M.; Barros, S.; Bečvář, F.; Beinrucker, C.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brugger, M.; Caamaño, M.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Cardella, R.; Casanovas, A.; Castelluccio, D. M.; Cerutti, F.; Chen, Y. H.; Chiaveri, E.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Cosentino, L.; Damone, L. A.; Diakaki, M.; Dietz, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Finocchiaro, P.; Furman, V.; Göbel, K.; García, A. R.; Gawlik, A.; Glodariu, T.; Gonçalves, I. F.; González-Romero, E.; Goverdovski, A.; Griesmayer, E.; Gunsing, F.; Harada, H.; Heftrich, T.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Katabuchi, T.; Kavrigin, P.; Ketlerov, V.; Khryachkov, V.; Kimura, A.; Kivel, N.; Kokkoris, M.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Lo Meo, S.; Lonsdale, S. J.; Losito, R.; Macina, D.; Marganiec, J.; Martínez, T.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Matteucci, F.; Maugeri, E. A.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Mirea, M.; Montesano, S.; Musumarra, A.; Nolte, R.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Porras, J. I.; Praena, J.; Rajeev, K.; Rauscher, T.; Reifarth, R.; Riego-Perez, A.; Rout, P. C.; Rubbia, C.; Ryan, J. A.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Sedyshev, P.; Smith, A. G.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tassan-Got, L.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vlachoudis, V.; Vlastou33, R.; Wallner, A.; Warren, S.; Weigand, M.; Weiss, C.; Wolf, C.; Woods, P. J.; Wright, T.; Žugec, P.

The spent fuel of current nuclear reactors contains fissile plutonium isotopes that can be combined with uranium to make mixed oxide (MOX) fuel. In this way the Pu from spent fuel is used in a new reactor cycle, contributing to the long-term sustainability of nuclear energy. However, an extensive use of MOX fuels, in particular in fast reactors, requires more accurate capture and fission cross sections for some Pu isotopes. In the case of 242Pu there are sizable discrepancies among the existing capture cross-section measurements included in the evaluations (all from the 1970s) resulting in an uncertainty as high as 35% in the fast energy region. Moreover, postirradiation experiments evaluated with JEFF-3.1 indicate an overestimation of 14% in the capture cross section in the fast neutron energy region. In this context, the Nuclear Energy Agency (NEA) requested an accuracy of 8% in this cross section in the energy region between 500 meV and 500 keV. This paper presents a new time-of-flight capture measurement on 242Pu carried out at n_TOF-EAR1 (CERN), focusing on the analysis and statistical properties of the resonance region, below 4 keV. The 242Pu(n,γ) reaction on a sample containing 95(4) mg enriched to 99.959% was measured with an array of four C6D6 detectors and applying the total energy detection technique. The high neutron energy resolution of n_TOF-EAR1 and the good statistics accumulated have allowed us to extend the resonance analysis up to 4 keV, obtaining new individual and average resonance parameters from a capture cross section featuring a systematic uncertainty of 5%, fulfilling the request of the NEA.

Keywords: Neutron physics; nuclear reactions; radiative capture; reactor fuel and coolants; radioactive waste

Permalink: https://www.hzdr.de/publications/Publ-27080
Publ.-Id: 27080


Retention of Tc(VII) by pyrite nanoparticles

Rodríguez Hernández, D. M.; Mayordomo-Herranz, N.; Müller, K.

One of the major pollutants in nuclear waste is 99Tc, a redox-sensitive fission product from 235U and 239Pu with a long half-life of 2.14 X 105 years. Under environmental oxidizing conditions, 99Tc mainly exists in aqueous solution as pertechnetate, TcO4-, which is a highly water-soluble ion that does not sorb significantly on minerals or sediments 1, so that, it is considered as inert with high risk to migrate through the environment. Under reducing conditions, Tc mobility is hampered by formation of Tc(IV) with significantly lower solubility 2. Pyrite, on one hand, is a good sorbent for Tc(VII) due to the presence of the functional groups FeOH and FeSH, and on the other hand, Tc(VII) is reduced to Tc(IV) by the interaction with structural Fe2+ and possibly with sulfur atoms. Moreover, Bruggeman et al. 3 found considerably increased Tc sorption when adding pyrite to boom clay in the presence of humic substances, which also favor the Tc retention4,5.

In this work synthetized pyrite nanoparticles 6 were used to investigate Tc sorption in classical batch sorption experiments.


References

1. Lieser, K. H. & Bauscher, C. H. Technetium in the hydrosphere and in the geosphere. Radiochimica Acta 42, 205–214 (1987).
2. Meena, A. H. & Arai, Y. Environmental geochemistry of technetium. Environ. Chem. Lett. 15, 241–263 (2017).
3. Bruggeman, C., Maes, A. & Vancluysen, J. The identification of FeS2 as a sorption sink for Tc(IV). Phys. Chem. Earth 32, 573–580 (2007).
4. Maes, A., Geraedts, K., Bruggeman, C., Vancluysen, J., Rossberg, A. & Hennig, C. Evidence for the Interaction of Technetium Colloids with Humic Substances by X-ray Absorption Spectroscopy. Environ. Sci. Technol. 38, 2044–2051 (2004).
5. Geraedts, K. & Maes, A. Determination of the conditional interaction constant between colloidal technetium(IV) and Gorleben humic substances. Appl. Geochemistry 23, 1127–1139 (2008).
6. Bai, Y., Yeom, J., Yang, M., Cha, S., Sun, K. & Kotov, K. Universal synthesis of single-phase pyrite FeS2 nanoparticles, nanowires, and nanosheets. J. Phys. Chem. C 117, 2567–2573 (2013).

Keywords: Pyrite; Technetium

  • Poster
    18th Radiochemical Conference - RadChem 2018, 13.-18.05.2018, Mariánské Lázně, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-27079
Publ.-Id: 27079


Electrical properties of surface and interface layers of the N- and In-polar undoped and Mg-doped InN layers grown by PA MBE

Komissarova, T. A.; Kampert, E.; Law, J.; Jmerik, V. N.; Paturi, P.; Wang, X.; Yoshikawa, A.; Ivanov, S. V.

Electrical properties of N-polar undoped and Mg-doped InN layers and In-polar undoped InN layers grown by plasma-assisted molecular beam epitaxy (PA MBE) were studied. Transport parameters of the surface and interface layers were determined from the measurements of the Hall coefficient and resistivity as well as the Shubnikov-de Haas oscillations at magnetic fields up to 60 T. Contributions of the 2D surface, 3D near-interface, and 2D interface layers to the total conductivity of the InN films were defined and discussed to be dependent on InN surface polarity, Mg doping, and PA MBE growth conditions.

Permalink: https://www.hzdr.de/publications/Publ-27078
Publ.-Id: 27078


U(VI) toxicity onto canola cells: Correlation of microcalorimetric data with cell viability and U(VI) speciation

Sachs, S.; Fahmy, K.; Oertel, J.; Geipel, G.; Bok, F.

The transfer of radionuclides into the food chain is of central concern for the safety assessment of both nuclear waste repositories and radioactive contaminated areas, such as legacies of the former uranium mining. The interaction of radionuclides with plants is mostly described by transfer factors without knowing the underlying processes. However, previous studies showed, for instance, a speciation-dependent influence of radionuclide uptake and translocation in plants [1]. Heavy metal stress induces the synthesis of metal-binding metabolites, storage of metal chelates in vacuoles or the secretion into the rhizosphere [2], which changes the plant cell metabolism.
We studied the interaction of U(VI) with canola cells (Brassica napus) as model system for plants focusing on the concentration-dependent impact of U(VI) on the cell metabolism. The metabolic heat flow of the cells was monitored by isothermal microcalorimetry, a highly sensitive real-time monitor that allows the detection of actinide toxicity in environmentally relevant concentrations. The calorimetric data were compared to the enzymatically determined cell viability. The U(VI) speciation in the cell culture medium was studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS) and thermodynamic modeling to correlate the impact of U(VI) on the cell activity with its speciation [3].
Brassica napus cells showed a temporal decrease in metabolic thermal power and a general reduction of heat production with increasing U(VI) concentration. So far, metabolic calorimetry suffered from the lack of models describing metabolic decline. To overcome this, the model-independent descriptor “metabolic capacity” that allows the evaluation of calorimetric data of declining metabolic phases was introduced in our work. The obtained normalized “metabolic capacities” and the normalized enzymatically determined cell viabilities showed an almost ideal correlation and were, to a very good approximation, linearly related at U(VI) concentrations up to 200 µM U(VI). The combination with TRLFS and thermodynamic modeling indicated that the cell metabolism was affected predominantly by U(VI) hydroxo species [3].
This presentation will demonstrate the potential of life cell microcalorimetry for radioecological studies, including the discrimination between chemotoxic and radiotoxic effects of uranium at the low dose regime.

References
[1] Ebbs, S.D., Brady, J., Kochian, L.V., Role of uranium speciation in the uptake and translocation of uranium in plants. J. Exp. Bot. 49 (1998) 1183-1190.
[2] Weiler, E., Nover, L., Allgemeine und molekulare Botanik. Georg Thieme Verlag, Stuttgart, 2008.
[3] Sachs, S., Geipel, G., Bok, F., Oertel, J., Fahmy, K., Calorimetrically determined U(VI) toxicity in Brassica napus correlates with oxidoreductase activity and U(VI) speciation. Env. Sci. Technol. 51 (2017) 10843-10849.

Keywords: plants; plant cells; actinides; uranium; toxicity; metabolism; speciation; isothermal microcalorimetry; TRLFS; thermodynamic modeling

  • Contribution to proceedings
    18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázne, Czech Republic
    Czech Chemical Society Symposium Series, 18th Radiochemical Conference, Mariánské Lázne, Czech Republic, 13-18 May 2018, Booklet of Abstracts, 188
  • Lecture (Conference)
    18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázne, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-27077
Publ.-Id: 27077


Investigation of the laser-plasma interaction with the method of small- angle x-ray scattering (SAXS) at an XFEL

Rödel, M.; Pelka, A.; Kluge, T.; Laso Garcia, A.; Mcbride, E.; Rödel, C.; Prencipe, I.; Hartley, N.; Kraus, D.; Gutt, C.; Schramm, U.; Cowan, T. E.

The combination of ultra-intense lasers with x-ray free-electron lasers (XFELs) opens up a variety of applications in plasma and shock physics. Many phenomena during the laser-target interaction happen on short time scales in the range from femto- to picoseconds and length scales of tens of nanometers to a few micrometers. Unlike the ultra-short, highly coherent x-ray pulse, optical methods or conventional continuous x-ray sources cannot probe the dynamics of the bulk material with sufficient temporal and spatial resolution. Here we will show the potential of SAXS in combination with short-pulse laser experiments. With this method it is possible to draw conclusions about the electron density distribution in the target by analyzing the XFEL diffraction pattern in the vicinity of the direct beam. A setup to perform such SAXS experiments was developed and optimized during a beamtime at the Matter in Extreme Conditions instrument (MEC) at the Linear Coherent Light Source (LCLS) in Stanford. We will discuss the setup and present a preliminary analysis of the data obtained during this experiment.

  • Lecture (Conference)
    DPG-Frühjahrstagung Dresden 2017, 19.-24.03.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27076
Publ.-Id: 27076


MHD of liquid metal batteries

Weber, N.; Ashour, R.; Herreman, W.; Horstmann, G.; Kelley, D.; Landgraf, S.; Nore, C.; Personnettaz, P.; Stefani, F.; Weier, T.

Liquid metal batteries (LMBs), developed originally during the 1960s in the United States, experienced a renaissance some ten years ago at MIT. Built as stable density stratification of two liquid metals, which are separated by a molten salt, they offer potentially very cheap stationary energy storage. Thus, LMBs may be the key enabler for a large scale deployment of highly fluctuating renewable energy sources. Especially their potentially long life time, the extremely high current densities and the cheap active materials make the cells an ideal candidate for stationary energy storage.
Fluid flows will naturally appear in the fully liquid cells. On the one hand, convection can be beneficial when enhancing mass transfer and improving the cell efficiency. On the other hand, strong flow must be avoided to ensure a safe operation.
The talk will give an introduction to the set-up and working principle of LMBs. The second part will be devoted to fluid dynamic
instabilities in the cells; both numerical and experimental results will be presented. The talk will focus on long wave MHD interface instabilities (as known from aluminium reduction cells), on thermal convection, and electro-vortex flow.

  • Lecture (Conference)
    Third Russian Conference on Magnetohydrodynamics, 18.06.2018, Perm, Russland

Permalink: https://www.hzdr.de/publications/Publ-27075
Publ.-Id: 27075


Tc immobilization on gamma alumina: a study of the reductant presence and absence

Mayordomo, N.; Müller, K.

Technetium isotope 99Tc is a fission product of environmental concern, due to its high mobility and its elevated lifetime (2.13×105 years). Among their possible oxidation states, Tc(VII) and Tc(IV) are the most stable ones. On one hand, Tc(VII) occurs under oxidizing redox conditions, being pertechnetate (TcO4-) the main species, which is considered an inert and mobile anion that hardly interacts with minerals. On the other hand, Tc(IV) is present under reducing conditions and it is mainly found as solid, TcO2, since it has a very low solubility product. Studies dealing with Tc immobilization in groundwater normally consider the use of reductants or mineral containing reductant moieties to favor the transformation of Tc(VII) to Tc(IV) with the aim of decreasing its migration in water fluxes.
Nano particular gamma alumina is a well suited sorbent for anions because of the high values of surface to volume ratio, specific surface area and point of zero charge. Indeed, we have already observed the efficient sorption capacity of gamma alumina against Se(IV) anions [1]. Thus, per se, alumina is a promising candidate to sorb Tc(VII). Nevertheless, for Tc(VII) low sorption is expected. However, previous studies have reported the higher Tc retention when the mineral is in contact with a reductant [2,3]. Thus, we will study the reductiuon of Tc(VII) to Tc(IV) on nano particular gamma alumina in presence of Fe2+.
This work has been developed in the frame of VESPA II project, supported by the German Ministry of Economy and Energy (BMWi).
[1] N. Mayordomo, H. Foerstendorf, J. Lützenkirchen, K. Heim, S. Weiss, Ú. Alonso, T. Missana, K. Schmeide, N. Jordan, Selenium(IV) sorption onto γ-Al2O3: a consistent description of the surface speciation by spectroscopy and thermodynamic modeling, Environ. Sci. Technol. Accepted (2017). doi:10.1021/acs.est.7b04546.
[2] R.M. Asmussen, J.J. Neeway, A.R. Lawter, T.G. Levitskaia, W.W. Lukens, N.P. Qafoku, The function of Sn(II)-apatite as a Tc immobilizing agent, J. Nucl. Mater. 480 (2016) 393–402. doi:10.1016/j.jnucmat.2016.09.002.
[3] T. Peretyazhko, J.M. Zachara, S.M. Heald, B.H. Jeon, R.K. Kukkadapu, C. Liu, D. Moore, C.T. Resch, Heterogeneous reduction of Tc(VII) by Fe(II) at the solid-water interface, Geochim. Cosmochim. Acta. 72 (2008) 1521–1539. doi:10.1016/j.gca.2008.01.004.

Keywords: Technetium; alumina; Fe

  • Lecture (Conference)
    18th Radiochemical conference, 13.-18.05.2018, Mariánské Lázně, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-27074
Publ.-Id: 27074


Detection Systems for Range Monitoring in Proton Therapy: Needs and Challenges

Pausch, G.; Berthold, J.; Enghardt, W.; Römer, K.; Straessner, A.; Wagner, A.; Werner, T.; Kögler, T.

In-vivo range verification has been a hot topic in particle therapy for more than a decade. In spite of vast efforts made by research groups all over the world, clinical means for routinely monitoring the range of therapeutic proton or carbon ion beams in the patient’s body and to ensure their correspondence with the treatment plan are not yet available. The paper reviews recent approaches with focus on prompt-gamma based methods, and points to challenges that have not yet been fully recognized or discussed: First, the macro time structure of treatment beams in common proton therapy facilities requires detection systems with extreme load tolerance, throughput capability, and stability against load variations. Second, the test time available for verifying the range of a single pencil beam spot is of the order of milliseconds, which limits the number of prompt gamma events that can be detected and processed. Tight event selection by passive or active collimation as applied in all imaging setups sharpens the information carried by a valid event but strongly reduces their total number. It might be better to use a multitude of uncollimated detectors acquiring time and energy signatures of every gamma hit with reasonable precision, and to pick up all the pieces of information comprised in timing, energy, and coincidence patterns irrespective of their sharpness. This would maximize the number of valid events on the expense of information sharpness, and could eventually increase the total yield of information exploitable for range verification. Some aspects of such a strategy have already been realized with the Prompt Gamma-Ray Timing (PGT) and the Prompt Gamma Peak Integration (PGPI) techniques proposed recently. Data analysis schemes for a more generalized approach have not yet been developed, but the hardware to be used can already be sketched: Prompt gamma rays should be detected with scintillation detector blocks consisting of single pixels with individual light readouts and independent electronics channels, similar to those developed for applications as PET-MR. Prompt-gamma detection is, however, much more demanding with respect to dynamic range, energy resolution, load acceptance, and stability. The paper will detail and discuss corresponding requirements that represent a challenge for the detector physics community, and report on activities at HZDR and OncoRay to explore the available options.

Keywords: Partikeltherapie; Protonentherapie; Reichweitekontrolle; Prompte Gammastrahlung; Gammakamera; Gammaspektroskopie; Zeitspektroskopie; Lasteffekte; Stabilisierung; Particle therapy; proton therapy; range verification; prompt gamma; gamma detection; gamma imaging; gamma spectroscopy; timing spectroscopy; load effects; stabilization

  • Lecture (Conference)
    2018 Symposium on Radiation Measurements and Applications (SORMA XVII), 11.-14.06.2018, Ann Arbor, MI, USA
  • Open Access Logo Nuclear Instruments and Methods in Physics Research A 954(2020), 161227
    DOI: 10.1016/j.nima.2018.09.062

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Permalink: https://www.hzdr.de/publications/Publ-27073
Publ.-Id: 27073


ChimeraTK OPC UA Adapter for the Integration of a MicroTCA.4 based digital LLRF

Steinbrück, R.; Kuntzsch, M.; Zenker, K.; Hierholzer, M.; Killenberg, M.; Iatrou, C. P.; Rahm, J.

The superconducting linear accelerator ELBE at Helmholtz-Center Dresden-Rossendorf is a versatile light source operated in continuous wave mode. Currently there is a transition from an analogue low level radio frequency control (LLRF) to a digital MicroTCA.4 based solution developed at DESY, Hamburg. Control system integration is realized collaboratively by DESY, Technische Universität Dresden (TUD) and HZDR with ChimeraTK and the incorporated OPC UA adapter. The poster gives an overview of the variable mapping scheme used to represent LLRF data in the OPC UA server address space, the graphical user interface and first integration test results.

Keywords: ELBE MicroTCA.4 LLRF "OPC UA" ChimeraTK

  • Lecture (others)
    6th MicroTCA Workshop for Industry and Research, 04.-07.12.2017, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27072
Publ.-Id: 27072


DNA mold templated assembly of conductive gold nanowires

Bayrak, T.; Helmi, S.; Ye, J.; Kauert, D.; Kelling, J.; Schönherr, T.; Erbe, A.; Seidel, R.

We introduce a new concept for the solution-based fabrication of conductive gold nanowires using DNA templates. To this end we employ DNA nanomolds inside which electroless gold deposition is initiated by site-specifically attached seeds. Using programmable interfaces individual molds self-assemble into micrometer long mold superstructures. During the subsequent internal gold deposition, the mold walls constrain the metal growth, such that highly homogeneous nanowires with 20-30 nm diameter are obtained. Wire contacting using electron beam lithography and electrical conductance characterization at temperatures between 4.2 K and room temperature demonstrate, that metallically conducting wires can be produced, though in part of the wires the conductance is limited by boundaries between gold grains. Using different mold designs, our synthesis scheme will in the future allow the fabrication of complex metal structures with programmable shape.

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Permalink: https://www.hzdr.de/publications/Publ-27071
Publ.-Id: 27071


Control System Integration of a MicroTCA.4 Based Digital LLRF Using the ChimeraTK OPC UA Adapter

Steinbrück, R.; Kuntzsch, M.; Michel, P.; Hierholzer, M.; Killenberg, M.; Schlarb, H.; Iatrou, C. P.; Rahm, J.; Urbas, L.

The superconducting linear electron accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf is a versatile light source. It operates in continuous wave (CW) mode to provide a high average beam current. In order to meet the requirements for future high resolution experiments the analogue low level radio frequency control (LLRF) is currently replaced by a digital MicroTCA.4 LLRF system based on a development at DESY, Hamburg.
Operation and parametrization is realized by a server application implemented by DESY using the ChimeraTK software framework. To interface the WinCC 7.3 based ELBE control system an OPC UA adapter for ChimeraTK has been developed in cooperation of DESY, Technische Universität Dresden (TUD) and HZDR. The contribution gives an overview of the collaborating parties, the variable
mapping scheme used to represent LLRF data in the OPC UA server address space and integration experiences with different industrial OPC UA Clients like WinCC 7.3 and LabVIEW.

Keywords: MicroTCA.4 LLRF "OPC UA" ChimeraTK

  • Poster
    ICALEPCS2017 - 16th International Conference on Accelerator and Large Experimental Physics Control Systems, 03.-13.10.2017, Barcelona, Spain
    DOI: 10.18429/JACoW-ICALEPCS2017-THPHA166
  • Contribution to proceedings
    ICALEPCS2017 - 16th International Conference on Accelerator and Large Experimental Physics Control Systems, 08.-13.10.2017, Barcelona, Spain
    Proceedings of ICALEPCS2017
    DOI: 10.18429/JACoW-ICALEPCS2017-THPHA166

Permalink: https://www.hzdr.de/publications/Publ-27070
Publ.-Id: 27070


Stability investigations of actinide doped calcium silicate hydrate phases in highly saline electrolytes

Wolter, J.-M.; Schmeide, K.; Huittinen, N. M.; Stumpf, T.

To evaluate the retention potential of the concrete barrier in a nuclear waste repository towards actinides in the presence of high saline water, leaching experiments with actinide-doped calcium silicate hydrate (CSH) phases were performed in highly saline electrolytes. Therefore, U(VI)- and Cm(III)-doped CSH phases with different C/S ratios (1.0-2.0) were synthesized directly in presence of either U(VI) or Cm(III) and characterized by time-resolved laser-induced fluorescence spectroscopy (TRLFS), infrared (IR) spectroscopy, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The time-dependent release of Ca, Si, U, and Cm from CSH phases into brines containing either 2.5 M NaCl, 2.5 M NaCl/0.02 M Na2SO4, 2.5 M NaCl/0.02 M NaHCO3 or 0.02 M NaHCO3 for U(VI)-doped CSH phases or 2.5 M NaCl/0.02 M NaHCO3 or 0.02 M NaHCO3 for Cm(III)-doped CSH phases was monitored in batch leaching experiments for 30 or 60 days, respectively. Subsequently, leaching induced changes of the CSH structure and of the U(VI) or Cm(III) coordination environment were investigated with TRLFS, IR spectroscopy and XRD.

Site-selective TRLFS studies of the Cm(III)/CSH binding at 8 K revealed a luminescence line-narrowing effect, which could be ascribed to the presence of a continuum of similar curium species on two different sorption sites in the CSH interlayer. The leached CSH phases showed pronounced differences in terms of decomposition behavior and actinide release depending on their C/S ratio, leaching electrolyte, and incorporated actinide. U(VI)-doped CSH phases leached in 2.5 M NaCl showed an increased release of Ca and a U(VI) precipitation as uranophane while the leaching in 0.02 M NaHCO3 led to a mobilization of U(VI) as an aqueous Ca2UO2(CO3)3 species.

In contrast, Cm(III) was not mobilized by NaHCO3 but incorporated into newly formed secondary phases like calcite and vaterite as detected by site-selective TRLFS. The comparison between leaching experiments performed in 0.02 M NaHCO3 and 2.5 M NaCl/0.02 M NaHCO3 revealed that the presence of 2.5 M NaCl increases the carbonate-induced U(VI) mobilization from CSH phases with higher C/S ratios while no influence on the Cm(III) retention was detectable.

Keywords: CSH; Cm(III); U(VI); highly saline; electrolytes; leaching; TRLFS; IR; XRD

  • Contribution to proceedings
    RadChem 2018 – 18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázně, Česká republika
  • Poster
    18th Radiochemical Conference, 13.-18.05.2018, 13.-18.05.2018, Mariánské Lázně, Česká republika

Permalink: https://www.hzdr.de/publications/Publ-27069
Publ.-Id: 27069


Vertical Nanowire Based Single Electron Transistor Self-Assembled by Ion Beam Mixing and Phase Separation

Heinig, K.-H.; von Borany, J.; Hlawacek, G.; Hübner, R.; Wolf, D.; Engelmann, H.-J.; Bischoff, L.; Xu, X.; Prüfer, T.; Möller, W.; Facsko, S.

Electronics has been dominated by silicon since half a century. Si will dominate electronics another decade, however its functionality might change from classical field-controlled currents through channels (the Field Effect Transistor FET) to quantum mechanical effects like field-controlled hopping of single electrons to a quantum dot (Single Electron Transistor SET). The SET is the champion of low-power consumption. This is attractive for the Internet of Things: more and more devices need batteries and plugs. Together with improved batteries, advanced computation must be delivered at extremely low-power consumption. At low temperatures, the functionality of SETs has been proven. Large-scale use of SETs requires room temperature operation, which can be achieved with tiny Si dots (<4 nm) in SiO2, exactly located between source and drain with distances of ~1…2 nm. Manufacturability of such nanostructures is the roadblock for large-scale use of SETs. Lithography cannot deliver such feature sizes. Therefore, there are currently intense studies to fulfill these requirements by self-organization processes. The ion beam technique is a well-established technology in microelectronics used for doping and amorphization, and even for ion beam mixing [1]. The parameters of ion beam processing are very well controllable. We searched for a self-organization process in a vertical silicon nanowire with an embedded, very thin (~6nm) SiO2 layer. Ion beam mixing transforms this layer to metastable SiOx. If the nanowire is thin enough, a subsequent thermal treatment leads by phase separation to a single Si nanodot (~3nm) self-aligned to the lower and upper Si at distances of <2nm. Here, we present 3D computer simulations on ion beam mixing (TRI3DYN code [2]) and Si nanodot formation (3D kinetic Monte Carlo code [3]). Such simulations predicted successfully the fabrication of non-volatile memories using ion beam mixing [4]. Experimentally, single Si nanodot formation has been proven by local mixing in a c-Si/SiO2/a-Si layer stack. The nanoscale mixing has been performed with a Helium Ion Microscope using an Argon beam of ~2nm diameter. After Rapid Thermal Annealing, the self-organized single Si nanodot has been imaged by cross-section energy-filtered transmission electron microscopy EFTEM. In a vertical nanowire the very small volume of mixed SiO2 is not due to nanoscale ion beams but due to the small diameter of the wire. It will be shown, how a vertical nanowire gate-all-around SETs operating at room temperature can be CMOS-compatibly fabricated by this method.
This work has been funded by the European Union’s Horizon 2020 research and innovation program under grant
agreement No 688072.
[1] K.H. Heinig, T. Müller, B. Schmidt, M. Strobel, W. Möller, Appl. Phys. A77 (2003) 17.
[2] W. Möller, NIM B322 (2014) 23.
[3] M. Strobel, K.-H. Heinig, W. Möller, Phys. Rev. B64 (2001) 245422.
[4] T. Mueller et al., Appl .Phys. Lett. 81 (2002) 3049; ibid 85 (2004) 2373.

Keywords: ion beam mixing; phase separation; computer simulations; manufacturing; single electron transistor

  • Lecture (Conference)
    Symposium “Progress in Developing and Applications of Functional 1D Nanostructiures”, 2017 Fall Meeting of the Materials Research Society, 26.11.-01.12.2017, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-27068
Publ.-Id: 27068


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