Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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Only approved publications

35836 Publications

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.

[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

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

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


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

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

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.


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

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

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

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

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

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

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


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).


  • 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

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.


  • 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

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

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

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

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


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

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


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

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


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


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

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.

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.

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

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

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

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

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

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

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

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.

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.

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

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.

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.

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.

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.

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


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


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

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


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


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

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.

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

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

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.

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

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

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

Publ.-Id: 27080

Retention of Tc(VII) by pyrite nanoparticles

Rodríguez Hernández, D. M.; Mayordomo, 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.


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

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.

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.

[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

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

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

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

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
    Online First (2018) DOI: 10.1016/j.nima.2018.09.062


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

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.


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

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

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

Publ.-Id: 27068

Ion-Beam-Induced Self-Organisation of Nanostructures at Interfaces

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

Ion irradiation through an interface between the phases A and B causes atomic displacements which results at low temperatures in a diffusion-like concentration profile. Even if phases A and B are immiscible, a metastable layer of an A/B mixture forms at high ion fluence. A subsequent thermal treatment will activate phase separation in this A/B mixture via nucleation and coarsening. This phase separation process has the potential of self-organisation of nanostructures, where the resulting nanostructure can be tailored by understanding and controlling the reaction pathway.
(i) At first, in this presentation it will be shown how the ion beam mixing of a flat infinite interface can be simulated with the SRIM and TRIDYN programs.
(ii) Then, by means of 3D kinetic lattice Monte-Carlo simulations it will be demonstrated how a thermally activated phase separation of the A/B mixture starts either by formation of nuclei of the minority phase or by spinodal decomposition.
(iii) Simulations for long times show that the subsequent nanostructure evolution is driven by interface minimization, i.e. Ostwald ripening of nanocluster ensembles or coarsening of spinodal structures.
At this stage, a self-organisation process governed by Brailsford's diffusional screening length can evolve, which can be eventually controlled. The A/B interface which re-forms during phase separation plays a central role for self-organisation and self-alignment of nanostructures.
These general mechanisms are effective in ion beam mixing of a thin SiO2 layer buried in Si with the following observations: (i) Zones denuded of Si form during annealing at the upper and lower interface. (ii) Additionally, three, two or one layer of Si nanoclusters form and align with the interface. (iii) If only a tiny volume ~(10nm)^3 of metastable SiOx (such as in an ion beam mixed nanopillar of a Si/SiO2/Si stack) becomes phase separated, the reaction pathway leads always to the existence of a single Si dot for a rather long time period.
This single Si nanodot fabrication becomes even more stable if all boundaries of the tiny SiOx volume are sinks for Si diffusing in SiO2, which can be realized by sideways in-diffusion of oxygen into the nanopillar.
Finally it will be shown, how such a single Si nanodot fabrication process can be used for manufactoring of single electron transisrors working at room temperature.

Keywords: Nanostructure fabrication; ion-beam-mixing; phase separation; silicon nanodot; single electron transistor

  • Invited lecture (Conferences)
    FOR3NANO: Formation of 3D Nanostructures by Ion Beams, 28.-30.06.2017, Helsinki, Finland

Publ.-Id: 27067

Attempts to understand potential deficiencies in chemical procedures for AMS: Cleaning and dissolving quartz for ¹⁰Be and ²⁶Al analysis

Merchel, S.; Gärtner, A.; Beutner, S.; Bookhagen, B.; Chabilan, A.

The purity of the analysed samples (e.g. quartz) with respect to chemical composition and radionuclide contamination is essential for geomorphologic applications using so-called terrestrial cosmogenic nuclides (TCNs). To guarantee this, numerous cleaning and dissolution procedures have been developed. At the DREsden Accelerator Mass Spectrometry (DREAMS) facility, we also work on enhancing the chemical quartz-enrichment methodology from bulk rock and dissolution of quartz. Repeated exposure of the bulk material to acid mixtures (HCl/H2SiF6) at room temperature for cleaning and its monitoring by optical microscopy works for most quartz-rich samples. The quartz dissolution in HF under rather mild conditions (at room temperature on a shaker-table) has the advantage to leave difficult-to-dissolve minerals (e.g., tourmaline, zircon, rutile, sillimanite, kyanite, chromite, corundum), not separated by other physical methods before, as residue. Our comparison with a high-temperature dissolution method (in a microwave) indicates that an additional amount of interfering elements, such as in average about 3 mg of Ti, more than 7 mg of Al, and about 22 μg of Be to the sample (for 50 g SiO2), shows the superiority of our mild method. This way, we reduce problems for chemistry and AMS, but also ensure better comparability to production rates of cleaner stoichiometric quartz from calibration sites

Keywords: accelerator mass spectrometry; in-situ; terrestrial cosmogenic nuclide; residue; quartz

Publ.-Id: 27065

Current Status and Perspectives of the OECD/NEA sub-group on Uncertainty Analysis in Modelling (UAM) for Design, Operation and Safety Analysis of SFRs (SFR-UAM)

Rimpault, G.; Buiron, L.; Stauff, N. E.; Kim, T. K.; Taiwo, T. A.; Lee, Y.-K.; Zwermann, W.; Bostelmann, F.; Velkov, K.; Guilliard, N.; Fridman, E.; Kereszturi, A.; Batki, B.; Kodeli, I.-A.; Mikityuk, K.; Lopez, R.; Gomez, A.; Puente-Espel, F.; Del Valle, E.; Peregudov, A.; Semenov, M.; Manturov, G.; Abramova, M.; Trivedi, I.; Ivanov, K.; Pautz, A.; Yamaji, A.; Hill, I.; Ivanova, T.

An OECD/NEA sub-group on Uncertainty Analysis in Modelling (UAM) for Design, Operation and Safety Analysis of Sodium-cooled Fast Reactors (SFR-UAM) has been formed under the NSC/WPRS/EGUAM to check the use of best-estimate codes and data. This work comes from the desire to design reactors with improved safety performance while preserving a sustainable source of energy at a rather low cost.
Two SFR cores are being studied: a large 3600MWth oxide core and a medium 1000MWth metallic core. In order to assess tools being used for studying these cores, various sub-exercises have been set up for what concerns neutronics with cell, sub-assembly, super-cell and core benchmarks under steady state conditions either at BOL conditions or at EOEC. A sub-assembly depletion benchmark is being set up before going into full core calculations with depletion.
Since the objective is to define the grace period or the margin to melting available in the different accident scenarios and this within uncertainty margins, uncertainties of different origins (methods, neutronics, thermal-hydraulic, fuel behavior) once identified and evaluated will be propagated through.
In order to ensure validity to these exercises, the sub-group incorporates some experimental validations on neutronics, thermal hydraulics, fuels and systems. This will be done with experiments from IRPhE & ICSBEP, SEFOR, THORS and the SUPER-PHENIX start-up transient programme.

  • Contribution to proceedings
    ANS Best Estimate Plus Uncertainty International Conference (BEPU 2018), 13.-19.05.2018, Lucca, Italy

Publ.-Id: 27064

Von Mäusen und Menschen - Abschätzung der internen Strahlenexposition neuartiger Radiotracer unter Nutzung eines Kleintier-PET/MRT

Kranz, M.; Sattler, B.; Deuther-Conrad, W.; Patt, M.; Schildan, A.; Patt, J.; Tiepolt, S.; Wilke, S.; Smits, R.; Hoepping, A.; Fischer, S.; Wünsch, B.; Steinbach, J.; Brust, P.; Sabri, O.

Ziel: Bei der Translation neuartiger Radiotracer in die klinische Phase ist eine Abschätzung der Strahlenexposition vor Erstanwendung am Menschen notwendig. Hierbei werden die Organdosen (OD) sowie die effektive Dosis (ED) am Tiermodell abgeschätzt, welche nach i.v. Injektion eines Radiotracers entstehen. Erstmalig wurde Kleintier-PET/MRT zur rein bildgebungsbasierten Inkorporationsdosimetrie mit CD-1 Mäusen eingesetzt. Um den Einfluss von Speziesunterschieden zu untersuchen wurden PET/CT-Studien an Ferkeln durchgeführt und die Ergebnisse mit am Menschen erhobenen Ergebnissen (PET/CT) verglichen.
Methodik: Nach i.v. Injektion von (-)- oder (+)-[18F]Flubatine (a, b) bzw. (S)- oder (R)-[18F]Fluspidine (c,d) wurden (i) In-vivo-PET/MRT- (MEDISO nanoScan, Budapest) und PET/CT-Scans (SIEMENS Biograph 16) bis zu 7 h p.i. durchgeführt, die List-Mode Daten unter Nutzung der Standardkorrekturen rekonstruiert und die Organaktivitäten (OA) mit ROVER (ABX, Radeberg) bestimmt; (ii) (a, c, d) Ex-vivo-Organentnahme an Mäusen und Messung der OA in einem Gammacounter durchgeführt (Goldstandard). Nach Extrapolation der Tierdaten auf menschliche Verhältnisse, wurden die OD und die ED mit OLINDA für 3 Spezies berechnet.
Ergebnisse: Die Dosimetrie für a/b ergab eine ED (µSv/MBq) von 12,5/12,1 (30 Mäuse), 13,4/14,3 (8 Ferkel), 22,3/23,0 (n=6 Menschen) und für (c/d) 12,9/14,0 (6 Mäuse), 21,0/n.a. (4 Menschen). Während a und b eine vergleichbare Biokinetik sowie ED zeigen, ist die ED von c und d signifikant (p=0,025) verschieden basierend auf Enantiomeren Unterschieden. Weiterhin zeigt sich eine Unterschätzung der ED erhoben mit Tierdaten im Vergleich zum Menschen von 38% (Ferkel) bis 47% (Mäuse).
Schlussfolgerung: Die Strahlenexposition nach i.v. Applikation von a,b,c,d liegt im Bereich der durch andere F-18-markierter Radiotracer. Die Abschätzung der ED unter Nutzung von Tiermodellen mit Hilfe eines Kleintier-PET/MRT ist unter Berücksichtigung der genannten Limitationen möglich und liefert mit dem Ex-vivo-Goldstandard vergleichbare Ergebnisse.

  • Lecture (Conference)
    56. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 18.-21.04.2018, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 56(2018), V161

Publ.-Id: 27063

Underground Nuclear Astrophysics in 2017 at LUNA, LUNA-MV, and Felsenkeller

Bemmerer, D.

The state of the art of underground nuclear astrophysics is reviewed. Starting from recent progress on hydrogen burning and Big Bang nucleosynthesis at LUNA, the upcoming new underground accelerators LUNA-MV and Felsenkeller are discussed.

Keywords: Nuclear Astrophysics underground; LUNA; Felsenkeller

  • Invited lecture (Conferences)
    Strategietreffen "Astroteilchenphysik in Deutschland", 07.-08.12.2017, Bad Honnef, Deutschland

Publ.-Id: 27062

Strahlenschutzaspekte beim neuen Beschleunigerlabor im Dresdner Felsenkeller

Bemmerer, D.

Strahlenschutzaspekte beim neuen Beschleunigerlabor im Dresdner Felsenkeller. Zusätzlich zum klassischen Strahlenschutz am 5 MV Ionenbeschleuniger im Felsenkeller wird auch die Low-Background-Problematik unter Tage diskutiert.

  • Invited lecture (Conferences)
    TÜV Süd Akademie "Strahlenschutz in Medizin, Forschung und Industrie", 06.-07.12.2017, Marburg/Lahn, Deutschland
  • Invited lecture (Conferences)
    Webinar Deutsche Gesellschaft für Medizinische Physik, 24.05.2018, Gießen, Deutschland

Publ.-Id: 27061

Nuclear Astrophysics Basics II

Bemmerer, D.

Carbon-nitrogen-oxygen cycle, nuclear cosmology, Felsenkeller underground accelerator

  • Invited lecture (Conferences)
    Lecture Week on Nuclear Structure and Nuclear Astrophysics, 04.-05.12.2017, Zell / Mosel, Deutschland

Publ.-Id: 27060

Nuclear Astrophysics Basics I

Bemmerer, D.

Nuclear Astrophysics Basics I: Cross Section, Gamow Peak, Thermonuclear Reaction Rate, and the Sun.

  • Invited lecture (Conferences)
    Lecture Week on Nuclear Structure and Nuclear Astrophysics, 04.-05.12.2017, Zell / Mosel, Deutschland

Publ.-Id: 27059

Attempts to understand potential deficiencies in chemical procedures for AMS

Merchel, S.; Gurlit, S.; Opel, T.; Rugel, G.; Scharf, A.; Tiessen, C.; Weiß, S.; Wetterich, S.

A major research focus of the DREsden Accelerator Mass Spectrometry (DREAMS) facility is sample preparation: in-house and at cooperating laboratories. Besides routine applications, developments are mainly driven by the users' demands such as "new" radionuclides (e.g. short-lived 7Be), radionuclides from new matrices or in larger sample amounts and at lower concentrations. Within the chemical preparation of BeO for 7,10Be, Al2O3 for 26Al, AgCl for 36Cl, and Fe2O3 for 60Fe and actinide AMS targets, we investigated and improved mostly particular steps: For oxide preparation alteration for several hours and two-times rinsing of hydroxides is recommended, especially for Be(OH)2 and Al(OH)3, to prevent losses in the final preparation steps. Rinsing of freshly precipitated hydroxides can yield to losses as high as 31%. For Al(OH)3 rinsing with H2O (pH5) instead of pH8-9 is recommended for further reducing redissolving. For 60Fe and coprecipitated actinides (the latter tested by U6+ and Er3+), rinsing of overnight-altered Fe(OH)3, yield to 2.6-3.5% losses. The depletion of the isobar 7Li for (7)BeO is easily gained by hydroxide precipitation and rinsing. The quality of BeO and Al2O3 AMS targets can be monitored and improved (e.g. by using larger ion exchanger columns) by using the so-called "quality factor", which is the current of the stable nuclide (9Be or 27Al), normalised to the current of the standard of the same batch. Finally, there is a high potential for ion exchange as a pre-enrichment tool for Cl for large ice samples containing low natCl concentrations and low absolute amounts of natCl.

Keywords: accelerator mass spectrometry; 10Be; 26Al; 36Cl; 60Fe; cosmogenic nuclides

Publ.-Id: 27058

Invenio-Uploadbyurl - background uploads via SFTP and HTTP protocol for Invenio

Frust, T.

A lot of HZDR research data is already located on one of the storage systems in a data center. For those data there are better ways transfering them to Rodare than using an HTTP web upload. This module for Invenio allows you to browse all the files that reside on registered storage systems accessible via the SFTP protocol. They are transferred to the Invenio using SFTP in a background job.

Keywords: SFTP; Invenio; RODARE; Background upload

  • Software in external data repository
    Publication year 2018
    Programming language: Python 3
    System requirements: Python 3, SFTP, Paramiko, Celery, Invenio
    License: GPLv3 (Link to license text)
    Hosted on HZDR GitLab: Link to location

Publ.-Id: 27057

Gold transport in hydrothermal chloride-bearing fluids: Insights from in situ x-ray absorption spectroscopy and ab initio molecular dynamics

Tagirov, B. R.; Trigub, A. L.; Filimonova, O. N.; Kvashnina, K. O.; Nickolsky, M. S.; Lafuerza, S.; Chareev, D. A.

Chloride-bearing fluids are widespread in the Earth's interior from low-temperature subsurface conditions to deep lithosphere. The concentration of chloride salts varies from diluted aqueous solutions to concentrated brines and anhydrous (dry) chloride melts beneath volcanoes. Here we report an investigation of the state of Au in hydrothermal chloride fluids and anhydrous melts by means of in situ X-ray absorption spectroscopy combined with ab initio molecular dynamics simulations and thermodynamic modeling. The experiments included registration of Au L 3 -edge X-ray absorption near edge structure/extended X-ray absorption fine structure spectra of Au-bearing fluids in the temperature range from 350 to 575 °C at pressures of 150-4500 bar. Spectra of Au dissolved in dry CsCl/NaCl/KCl + K 2 S 2 O 8 melt were recorded at 650 °C. It was found that Au is coordinated by two Cl atoms (R Au-Cl = 2.25-2.28 Å). The alkali metal atoms (Me) were detected in the distant coordination sphere of Au at R Au-Me = 3.3-4.1 Å. The alkali metal cations in the vicinity of Au-Cl complex partly compensate the positive charge located on Au and, by this way, affect the Au-Cl distance. An increase of the fluid pressure causes expansion of the second coordination sphere composed of the alkali metal cations, which leads to the increase of the positive Au charge and results in slight contraction of the first coordination sphere of Au. Accordingly, the transport of Au in high-temperature chloride-bearing natural ore-forming fluids of moderate to high densities (>0.3 g·cm -3 ) can be explicitly described by the formation of the AuCl 2 - at any salt concentration from low-salinity fluids to hydrosaline liquids and anhydrous melts. In general, this means that the hydrothermal fluid chemistry simplifies with increasing temperature.


Publ.-Id: 27056

Using XFELs to Probe Kilotesla Magnetic Fields inside Solid Density Plasmas Driven by Optical High Power Lasers

Huang, L. G.; Schlenvoigt, H.-P.; Takebe, H.; Cowan, T. E.

The relativistic laser matter interaction is a complex interplay of ionization, extreme current densities, rapidly evolving strong fields and acceleration processes. Understanding the interaction physics is a challenging but highly rewarding endeavor. The unprecedented brightness of XFELs opens a new window for discovering the interior of solid-density plasmas created by relativistic laser interactions with matter, resolving the relevant femtosecond and sub-micrometer scales experimentally.
Here, we focus on discussing the feasibility of probing the magnetic fields by X-Ray polarimetry via Faraday rotation using XFEls.

Keywords: laser; plasmas; magnetic fields; faraday rotation; xfel

  • Poster
    European XFEL Users' Meeting 2018, 23.-26.01.2018, Hamburg, Germany

Publ.-Id: 27055

Quasifree (p,2p) Reactions on Oxygen Isotopes: Observation of Isospin Independence of the Reduced Single-Particle Strength

Atar, L.; Paschalis, S.; Barbieri, C.; Bertulani, C. A.; Díaz Fernández, P.; Holl, M.; Najafi, M. A.; Panin, V.; Alvarez-Pol, H.; Aumann, T.; Avdeichikov, V.; Beceiro-Novo, S.; Bemmerer, D.; Benlliure, J.; Boillos, J. M.; Boretzky, K.; Borge, M. J. G.; Caamaño, M.; Caesar, C.; Casarejos, E.; Catford, W.; Cederkall, J.; Chartier, M.; Chulkov, L.; Cortina-Gil, D.; Cravo, E.; Crespo, R.; Dillmann, I.; Elekes, Z.; Enders, J.; Ershova, O.; Estrade, A.; Farinon, F.; Fraile, L. M.; Freer, M.; Galaviz Redondo, D.; Geissel, H.; Gernhäuser, R.; Golubev, P.; Göbel, K.; Hagdahl, J.; Heftrich, T.; Heil, M.; Heine, M.; Heinz, A.; Henriques, A.; Hufnagel, A.; Ignatov, A.; Johansson, H. T.; Jonson, B.; Kahlbow, J.; Kalantar-Nayestanaki, N.; Kanungo, R.; Kelic-Heil, A.; Knyazev, A.; Kröll, T.; Kurz, N.; Labiche, M.; Langer, C.; Le Bleis, T.; Lemmon, R.; Lindberg, S.; Machado, J.; Marganiec-Gałązka, J.; Movsesyan, A.; Nacher, E.; Nikolskii, E. Y.; Nilsson, T.; Nociforo, C.; Perea, A.; Petri, M.; Pietri, S.; Plag, R.; Reifarth, R.; Ribeiro, G.; Rigollet, C.; Rossi, D. M.; Röder, M.; Savran, D.; Scheit, H.; Simon, H.; Sorlin, O.; Syndikus, I.; Taylor, J. T.; Tengblad, O.; Thies, R.; Togano, Y.; Vandebrouck, M.; Velho, P.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Wheldon, C.; Wilson, G. L.; Winfield, J. S.; Woods, P.; Yakorev, D.; Zhukov, M.; Zilges, A.; Zuber, K.

Quasifree one-proton knockout reactions have been employed in inverse kinematics for a systematic study of the structure of stable and exotic oxygen isotopes at the
R3B/LAND setup with incident beam energies in the range of 300–450 MeV/u. The oxygen isotopic chain offers a large variation of separation energies that allows for a quantitative understanding of single-particle strength with changing isospin asymmetry. Quasifree knockout reactions provide a complementary approach to intermediate-energy one-nucleon removal reactions. Inclusive cross sections for quasifree knockout reactions of the type AO(p,2p)A−1N have been determined and compared to calculations based on the eikonal reaction theory. The reduction factors for the single-particle strength with respect to the independent-particle model were obtained and compared to state-of-the-art ab initio predictions. The results do not show any significant dependence on proton-neutron asymmetry

Publ.-Id: 27054

Femtosecond laser-generated high-energydensity states studied by x-ray FELs

Nakatsutsumi, M.; Appel, K.; Baehtz, C.; Chen, B.; Cowan, T. E.; Göde, S.; Konopkova, Z.; Pelka, A.; Priebe, G.; Schmidt, A.; Sukharnikov, K.; Thorpe, I.; Tschentscher, T.; Zastrau, U.

The combination of powerful optical lasers and an x-ray free-electron laser (XFEL) provides unique capabilities to study the transient behaviour of matter in extreme conditions. The high energy density science instrument (HED instrument) at the European XFEL will provide the experimental platform on which an unique x-ray source can be combined with various types of high-power optical lasers. In this paper, we highlight selected scientific examples together with the associated x-ray techniques, with particular emphasis on femtosecond (fs)-timescale pump–probe experiments. Subsequently, we present the current design status of the HED instrument, outlining how the experiments could be performed. First user experiments will start at the beginning of 2018, after which various optical lasers will be commissioned and made available to the international scientific community.

Keywords: x-ray free-electron laser; femtosecond dynamics; relativistic plasma; high-energydensity state

Publ.-Id: 27053

Isothermal differential dilatometry based on X-ray analysis applied to stress relaxation in thin ion-beam-sputtered Pt films

Gruber, W.; Baehtz, C.; Geue, T.; Stahn, J.; Schmidt, H.

Relaxation of stress and point defects in ion-beam-sputtered Pt films with a thickness of 20 and 40 nm during isothermal annealing was investigated. First, isothermal differential dilatometry measurements based on X-ray analysis were carried out between 130 and 400 °C. They show that the relaxation of compressive stress is associated with the formation of vacancies at the surface. From the measurements, an activation enthalpy of 0.14 eV was estimated for the stress relaxation process. In addition, self-diffusion experiments of Pt were carried out on the same type of films using stable 194Pt tracer. From secondary ion mass spectrometry on samples annealed for longer times, an activation enthalpy of 0.5 eV for Pt diffusion in grain boundaries was estimated. The influence of vacancy creation at the surface, vacancy transport, and the annihilation of nonequilibrium
bulk interstitials and thermally created vacancies on stress relaxation is discussed.

Keywords: Thin films; Synchrotron; X-ray diffraction; ion-beam-sputtering

Publ.-Id: 27052

Non-Reciprocal Spin-Wave Emission from Topological Spin Textures

Schneider, T.; Sluka, V.; Kakay, A.; Weigand, M.; Warnatz, T.; Mattheis, R.; Gallardo, R. A.; Roldan-Molina, A.; Landeros, P.; Tiberkevich, V.; Slavin, A.; Erbe, A.; Deac, A.; Lindner, J.; Fassbender, J.; Raabe, J.; Wintz, S.

Investigations of spin waves are of great interest for both fundamental science and applications. For the excitation of spin waves with short wavelengths, it was typically necessary to either use patterned transducers with sizes on the order of the desired wavelengths or to generate such spin waves parametrically.
Here, we will show a combined experimental and theoretical study of spin waves in a stacked vortex pair system formed in a NiFe/Ru/CoFeB trilayer. The magnetization dynamics was imaged by means of time-resolved scanning transmission x-ray microscopy (STXM). Thereby, two different spin wave regimes were identified. For excitation frequencies above 500 MHz, mainly 2D plane waves within the magnetic domains were observed. However, a transition from 2D to 1D wave transport occurs for excitation frequencies below 500 MHz. In this case almost no spin waves were detected within the domains but high amplitudes were found within the 180° domain walls. An analytic and numerical analysis was done for both regimes, resulting in both a qualitative and quantitative understanding of the finite frequency gap in the spin wave dispersion relation for the ferromagnetic domains. Moreover, the dispersion relation was found to exhibit a strong non-reciprocity.

Keywords: Spin-wave; non-reciprocity; spin textures

  • Lecture (Conference)
    APS March Meeting 2018, 05.-09.03.2018, Los Angeles, USA

Publ.-Id: 27051

Chiral-partner D mesons in a heat bath within QCD sum rules

Buchheim, T.; Hilger, T.; Kämpfer, B.; Leupold, S.

Utilizing QCD sum rules, we extract the temperature dependences of the spectral properties of the pseudo-scalar and scalar D mesons regarded as chiral partners. Besides the masses also decay constants are analyzed as the D meson yields in heavy-ion collisions may be sensitive to their altered decay properties in an ambient strongly interacting medium. Our findings are (i) a decreasing scalar D meson mass for growing temperatures while its pseudo-scalar partner meson seems hardly affected, which is in qualitative agreement with hadronic model calculations; (ii) inferring an equally weak temperature dependence of the pseudo-scalar D meson decay properties the decreasing residua and decay constants of the scalar particle point towards partial chiral restoration. As a bonus of our analysis in the pseudo-scalar sector we determine the pseudo-scalar decay constant at vanishing temperature. Due to the connection to particular leptonic branching fractions this decay constant is of great interest allowing for the determination of the off-diagonal CKM matrix element |Vcd| at zero temperature.


Publ.-Id: 27050

Assisted Vacuum Decay by Time Dependent Electric Fields

Otto, A.; Oppitz, H.; Kämpfer, B.

We consider the vacuum decay by electron-positron pair production in spatially homogeneous, time dependent electric fields by means of quantum kinetic equations. Our focus is on the impact of various pulse shapes as envelopes of oscillating fields and the assistance effects in multi-scale fields, which are also seen in photons accompanying the creation and motion of pairs.


Publ.-Id: 27049

Characteristics of large-scale structures in turbulent Rayleigh-Benard convection in a liquid metal layer

Yanagisawa, T.; Akashi, M.; Tasaka, Y.; Murai, Y.; Vogt, T.; Eckert, S.

We performed laboratory experiments on Rayleigh-Benard convection with a liquid metal in a square box geometry having an aspect ratio five. Horizontal velocity profiles of convective flow were measured at several lines by using ultrasonic velocity profiling. By combining the information from profiles, we can reconstruct organized large-scale flow structures with turbulent fluctuations. Systematic variation of the structure was detected with increasing the Rayleigh number (Ra) from 10^4 to 10^5; a quasi-two-dimensional roll changes to a cell having a relatively larger horizontal scale. In addition, we found that the large-scale structure, whether it is roll or cell, show quasi-periodic oscillation whose representative period is approximately same as the circulation time of the large-scale flow. We also performed numerical simulations of convection with the same geometry as our experiments by setting a small Prandtl number (Pr=0.025) like a liquid metal. Quantitative comparison on the velocity profiles between experiments and simulations provided quite satisfactory agreement, and we analyzed the whole structure of the flow and the style of oscillation in detail based on the result of simulation. By integrating results from experiments and simulations, we propose a scaling low on the Ra dependence of horizontal size of large-scale flow structure, and estimate an enlarged value of effective momentum diffusivity by turbulence in a low Pr convection.

  • Lecture (Conference)
    11th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering (ISUD 11), 05.-07.09.2018, Berlin, Germany

Publ.-Id: 27047

Large scale structures of a turbulent Rayleigh-Bénard convection in a liquid metal layer confined by a moderate aspect ratio box

Akashi, M.; Tasaka, Y.; Yanagisawa, T.; Murai, Y.; Vogt, T.; Eckert, S.

We report laboratory experiments of Rayleigh-Bénard convection with a liquid metal, Prandtl number Pr = 0.03, in a rectangular cell with a moderate aspect ratio. Rayleigh number, Ra, was set at a range from 7.9 × 10^3 to 3.5 × 10^5 at which the thermal turbulence regime is expected. Multiple horizontal velocity profiles in the fluid layer by ultrasonic velocity profiling elucidated formations of several large scale flow structures with periodic oscillations. The flow structure has transitions as increasing Ra from a quasi-two-dimensional roll-like structure to a three-dimensional cell-like structure via unstable intermediate regimes with stepwise increase of its horizontal scale. By using observed Ra dependences of the frequency of oscillation and the velocity of large scale flow, we made up a model to explain the increase of horizontal scale. We evaluated effective viscosities and diffusivities based on the turbulent fluctuations, and found that the morphology of roll-like structure can be understood by using these effective values.

  • Lecture (Conference)
    The 70th Annual Meeting of the American Physical Society Division of Fluid Dynamics, 20.11.2017, Denver, USA

Publ.-Id: 27046

High-resolution patterning of germanium for nanoelectronics applications

Gangnaik, A. S.; Khan, M. B.; Ghamsari, S. J.; Rebohle, L.; Erbe, A.; Holmes, J. D.; Georgiev, Y. M.

Ge is among the most attractive alternative channel materials for the next-generation nanoelectronics. However, Ge patterning with electron beam lithography (EBL) using the negative resist HSQ is challenging. The complex native oxide GeOx is soluble in the HSQ aqueous developers. As a result, lift-off of sub-20 nm features written by EBL occurs during development. In the presentation, it will be shown that this issue can be solved by: (i) removal of GeOx and passivation of Ge surface prior to HSQ deposition or (ii) application of a buffer layer between GeOx and HSQ. Arrays of sub-20 nm HSQ lines were successfully fabricated on Ge with both approaches. Moreover, a significantly simplified process for removal of GeOx and passivation of Ge surface will also be presented, which allows patterning of 6-7 nm Ge NWs, the smallest Ge nanostructures reported to date.

Finally, different applications of the above mentioned patterning processes will be discussed.

Keywords: Germanium; nanowires; nanoelectronics; electron beam lithography

  • Lecture (Conference)
    DPG Spring Meeting 2018 in Berlin, 11.-16.03.2018, Berlin, Germany

Publ.-Id: 27045

Technology for fabrication of suspended sub-5 nm silicon nanowires and applications thereafter

Petkov, N.; Georgiev, Y. M.

Si nanowires (Si NWs) are very promising as channels for field effect transistors (FETs) and also as sensing devices. When the NW diameter is in the sub-10 nm range, quantum confinement of carriers is observed at room temperature, which is very appealing from scientific and application point of view.

This paper will present a technology for fabrication of sub-5 nm suspended Si NWs on silicon-on-insulator wafers. News of 20 nm width are first defined in the top Si layer by electron beam lithography and reactive ion etching. Then the NWs are subjected to three consecutive cycles of rapid thermal oxidation in oxygen atmosphere and wet etching in hydrofluoric acid. The resulting suspended Si NWs have high-quality crystalline structure and sub-5 nm size.

The possible applications of such NWs will be discussed, including FET-based Si NW chemo-/biosensors as well as gate all around (GAA) FETs. Additionally, the development of self-aligned nickel silicide NW contacts will be presented. The formation mechanism was examined by in-situ electron microscopy as a function of NW diameter and surface oxide.

Keywords: Silicon nanowires; field effect transistors (FETs); nanowire sensors; silicon-on-insulator; nickel silicide; electron beam lithography

  • Lecture (Conference)
    DPG Spring Meeting 2018 in Berlin, 11.-16.03.2018, Berlin, Germany

Publ.-Id: 27044

New Heterodinuclear Zn/Ln (Ln = Gd, Tb, Er, Yb) Complexes of Hexadentate N,N'-Bis(3-alkoxy-2-hydroxybenzyl)cyclohexane-1,2-diamines: Synthesis and Structure

Kelly, N.; Schnaars, K.; Gloe, K.; Doert, T.; Weigand, J. J.; Gloe, K.

Two N,N′-bis(3-alkoxy-2-hydroxybenzyl)cyclohexane-1,2-diamine proligands, H₂L¹ (R = OCH₃) and H₂L² (R = OC₂H₅), and five heterodinuclear Znᴵᴵ/Lnᴵᴵᴵ complexes, [Zn(L)(µ-CH₃COO)Ln(NO₃)₂], containing [L¹]²⁻ and Gd³⁺, Tb³⁺, Er³⁺, or Yb³⁺ and [L²]²⁻ and Yb³⁺ have been synthesised and structurally characterised. The complexes are isostructural and crystallise in the P2₁/n monoclinic space group. Zinc(II) is coordinated by the inner N₂O₂ donor set of the ligand and an oxygen of the bridging acetate anion; the lanthanide(III) ions possess an O₉ coordination environment involving the interaction with the ligand’s outer O₄ donor set, two bidentate nitrate ions, and the bridging acetate.

Publ.-Id: 27043

Investigation of heavy metal release at a municipal solid waste incineration facility - an excellent example for the unique potential of intrinsic radiotracer application to the investigation of industrial processes in chemical engineering

Jentsch, T. B. O.

Radiotracers are widespread in use for investigation of material transport processes in industry and environment. Often they are used for the measurement of the residence time distribution in continuously operating chemical engineering facilities and reactors. Mostly intrinsic or physical tracers are used for these purposes.

In case of phase transformation processes are in the focus of interest physical or extrinsic tracers are not the labelling material of choice. Intrinsic or chemical tracers are required in that case.

At example of the heavy metal release investigation at a municipal solid waste incineration facility the unique potential of intrinsic radiotracers will be demonstrated in the given paper.

Goal of the investigation at the municipal solid waste incineration facility reported in this paper was the behaviour study of different heavy metal species at various incineration conditions. With the help of short lived radioisotopes of copper (Cu-64) and zinc (Zn-69m) could be shown at which position of the incinerator and in which amount the heavy metal under investigation was released.

The experimental results of this investigation were an essential contribution for better understanding the processes inside the incinerator and to optimize the processing conditions.

Keywords: heavy metal release; radiotracer; municipal solid waste incineration; copper-64; zinc-69m

  • Lecture (Conference)
    ICARST 2017 - International Conference on Applications of Radiation Science and Technology, 24.-28.04.2017, Wien, Österreich

Publ.-Id: 27039

PO-0619: Comparison of a nanoString and RNA microarray gene signature predicting LRC after PORT-C in HNSCC

Schmidt, S.; Linge, A.; Zwanenburg, A.; Leger, S.; Lohaus, F.; Gudziol, V.; Nowak, A.; Tinhofer, I.; Budach, V.; Sak, A.; Stuschke, M.; Balermpas, P.; Rödel, C.; Grosu, A. L.; Abdollahi, A.; Debus, J.; Belka, C.; Combs, S. E.; Mönnich, D.; Zips, D.; Baretton, G. B.; Buchholz, F.; Baumann, M.; Krause, M.; Löck, S.

A gene signature predicting loco-regional control (LRC) of locally advanced head and neck squamous cell carcinoma (HNSCC) after postoperative radiochemotherapy (PORTC) will be evaluated using nanoString and RNA microarray data. The prognostic power of the signature as well as the correlation between both methods is evaluated to underline the robustness of the proposed signature.


Publ.-Id: 27038

Pencil beam scanning treatments in free-breathing lung cancer patients–is 5 mm motion a limit?

Jakobi, A.; Perrin, R.; Knopf, A.; Richter, C.

To evaluate the dose degradation when treating lung cancer patie nts with proton pencil beam scanning during free-breathing. We assess if treatments without rescanning are feasible in order to avoid prolonged treatment time, especially for slow scanning facilities.


Publ.-Id: 27034

High-precision radiotherapy–Do we need better pre-treatment CT imaging?

Greilich, S.; Richter, C.

Computed tomography (CT) images from fan-beam medical grade scanners are the current gold standard for treatment planning in radiation oncology: they provide geometrically correct, reliable, and quantitative measures of photon attenuation in the patient. However, this information is not fully identical with the physical quantities needed for dose calculation and optimization and additional uncertainty is introduced by inferring them from the kV images. Also, the low soft tissue contrast in CT impacts delineation accuracy. While additional Imaging modalities are advocated as complementary – sometimes alternative – techniques to CT imaging, uncertainties in image registration can even deteriorate the quality of treatment planning. Dual-energy CT – i.e. using scans from two X-ray spectra or detection in two separate energy ranges – retains the virtues of computed tomography while it opens at the same time the possibility to overcome the restrictions mentioned. It can improve the accuracy of dose calculation and delineation and enables to abandon the use of a general translation rule (“Hounsfield look-up table”) for the photon attenuation (CT numbers) - replacing it by a patient-specific determination of radiological tissue quantities. DECT-derived quantities might additionally provide opportunities in advanced image analysis methods such as radiomics, i.e. the machine-learning-based approach for the prediction of patient outcome and treatment personalization. CT-based radiomics analyses might even be able to uncover information that can so far only be derived from additional multi-modal imaging. Currently, many applications based on innovations in pre-treatment CT imaging and image analysis are investigated that could have the potential to change clinical practice in future. This presentation is intended to set the stage for the focus session which tries to look into the question, which of These applications can find its way into routine clinical application.

  • Open Access Logo Abstract in refereed journal
    Biomedical Engineering / Biomedizinische Technik 62(2017), S292-S297
    DOI: 10.1515/bmt-2017-5057


Publ.-Id: 27032

PO-0819: 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.

To compare 4 different proton pencil beam scanning (PBS) treatment approaches for unilateral head and neck cancer (HNC) targets in terms of robustness, including anatomical changes during the treatment course.


Publ.-Id: 27030

Modeling patterns of anatomical deformations in prostate patients undergoing radiation therapy with an endorectal ballon

Brion, E.; Richter, C.; Macq, B.; Stützer, K.; Exner, F.; Troost, E.; Hölscher, T.; Bondar, L.

External beam radiation therapy (EBRT) treats cancer by delivering daily fractions of radiation to a target volume. For prostate cancer, the target undergoes day-to-day variations in position, volume, and shape. For stereotactic photon and for proton EBRT, endorectal balloons (ERBs) can be used to limit variations. To date, patterns of non-rigid variations for patients with ERB have not been modeled. We extracted and modeled the patient-specific patterns of variations, using regularly acquired CT-images, non-rigid point cloud registration, and principal component analysis (PCA). For each patient, a non-rigid point-set registration method, called Coherent Point Drift, (CPD) was used to automatically generate landmark correspondences between all target shapes. To ensure accurate registrations, we tested and validated CPD by identifying parameter values leading to the smallest registration errors (surface matching error 0.13±0.09 mm). PCA demonstrated that 88±3.2% of the target motion could be explained using only 4 principal modes. The most dominant component of target motion is a squeezing and stretching in the anterior-posterior and superior-inferior directions. A PCA model of daily landmark displacements, generated using 6 to 10 CT-scans, could explain well the target motion for the CT-scans not included in the model (modeling error decreased from 1.83±0.8 mm for 6 CT-scans to 1.6±0.7 mm for 10 CT-scans). PCA modeling error was smaller than the naive approximation by the mean shape (approximation error 2.66±0.59 mm). Future work will investigate the use of the PCA-model to improve the accuracy of EBRT techniques that are highly susceptible to anatomical variations such as, proton therapy.

  • Abstract in refereed journal
    Proceedings of SPIE 10135(2017), 1013506
    Online First (2017) DOI: 10.1117/12.2251933


Publ.-Id: 27028

Combined PET/MRI: Global Warming-Summary Report of the 6th International Workshop on PET/MRI, March 27-29, 2017, Tübingen,

Bailey, D. L.; Pichler, B. J.; Gückel, B.; Antoch, G.; Barthel, H.; Bhujwalla, Z. M.; Biskup, S.; Biswal, S.; Bitzer, M.; Boellaard, R.; Braren, R. F.; Brendle, C.; Brindle, K.; Chiti, A.; La Fougère, C.; Gillies, R.; Goh, V.; Goyen, M.; Hacker, M.; Heukamp, L.; Knudsen, G. M.; Krackhardt, A. M.; Law, I.; Morris, J. C.; Nikolaou, K.; Nuyts, J.; Ordonez, A. A.; Pantel, K.; Quick, H. H.; Riklund, K.; Sabri, O.; Sattler, B.; Troost, E.; Zaiss, M.; Zender, L.; Beyer, T.

The 6th annual meeting to address key issues in positron emission tomography (PET)/magnetic resonance imaging (MRI) was held again in Tübingen, Germany, from March 27 to 29, 2017. Over three days of invited plenary lectures, round table discussions and dialogue board deliberations, participants critically assessed the current state of PET/MRI, both clinically and as a research tool, and attempted to chart future directions. The meeting addressed the use of PET/MRI and workflows in oncology, neurosciences, infection, inflammation and chronic pain syndromes, as well as deeper discussions about how best to characterise the tumour microenvironment, optimise the complementary information available from PET and MRI, and how advanced data mining and bioinformatics, as well as information from liquid biomarkers (circulating tumour cells and nucleic acids) and pathology, can be integrated to give a more complete characterisation of disease phenotype. Some issues that have dominated previous meetings, such as the accuracy of MR-based attenuation correction (AC) of the PET scan, were finally put to rest as having been adequately addressed for the majority of clinical situations. Likewise, the ability to standardise PET systems for use in multicentre trials was confirmed, thus removing a perceived barrier to larger clinical imaging trials. The meeting openly questioned whether PET/MRI should, in all cases, be used as a whole-body imaging modality or whether in many circumstances it would best be employed to give an in-depth study of previously identified disease in a single organ or region. The meeting concluded that there is still much work to be done in the integration of data from different fields and in developing a common language for all stakeholders involved. In addition, the participants advocated joint training and education for individuals who engage in routine PET/MRI. It was agreed that PET/MRI can enhance our understanding of normal and disrupted biology, and we are in a position to describe the in vivo nature of disease processes, metabolism, evolution of cancer and the monitoring of response to pharmacological interventions and therapies. As such, PET/MRI is a key to advancing medicine and patient care.

Publ.-Id: 27024

Atomistic Simulation of Interface-Driven Self-Alignment of Si-SiO2 Nanostructures

Prüfer, T.; Heinig, K. H.; Möller, W.; von Borany, J.

Si nanostructures are very promising candidates for optical and electrical applications. Charged nanocluster can be used for data storage [2]; their discrete energy levels can be used for logic operations; sponge nanostructures can be used as the ion conductor in fuel cells. The size-dependency of their energy levels makes them interesting for application in colour displays.
Among a lot of other methods to synthesize nanoclusters or sponges we present an approach which allows a selfalignment of nanostructures at an interface. The basic idea is to bring together Si, SiO2 and SiOx and anneal it to cause phase separation of SiOx. The interfaces between Si/SiOx and SiOx/SiO2 act as driving forces for the selfalignment of the separated Si and SiO2. To create SiOx we consider 2 processes: (i) Deposition of SiOx films by PVD or CVD and (ii) Ion beam Mixing of Si/SiO2 interfaces.
By PVD it’s possible to create arbitrary shapes of Si/SiO2/SiOx layerstacks. The subsequent annealing causes different effects at the interface. Mainly depending on the structure of the layerstack, but also on the annealing time, different reaction pathways can be observed. The system can end up with different numbers of cluster layers or sponge structures, aligned parallel to the interface. Here we show how and why it is possible to control the sizes, densities and distances of these structures.
The ion irradiation through a Si/SiO2 interface causes mixing of both phases and transforms the interface into SiOx.
This method is not that flexible as PVD, but it’s easier to be implemented into common industrial technologies, like the production of CMOS compatible devices. The reformation of the Si/SiO2 interface during heat treatment is again acting as a driving force for the self-alignment and forms a zone between the interface and the resulting nanostructures which is denuded of excess Si. In this case, sizes and density can be controlled by irradiation and annealing parameters.
Earlier studies [1] have proven the reliability of dot formations using ion beam mixing technologies for application as memories [2]. Here, we show simulation results for the formation of Si nanostructures at interfaces in layerstacks of Si, SiOx, SiO2 and basic principles of the driving forces for this kind of self-alignment. Computer simulations using the binary collision approximation (TRIDYN [3]) and the kinetic monte carlo method [4] are employed to subsequently describe the ion irradiation and annealing processes, respectively.
This part of the work is being funded by the European Union’s Horizon 2020 research and innovation program under Grant Agreement No 688072 (Project IONS4SET).
[1] T. Müller et al., Appl. Phys. Lett. 81 (2002) 3049; ibid. 85 (2004) 2373.
[2] K.H. Heinig et al., Appl. Phys. A77 (2003)17.
[3] W. Möller, W. Eckstein, Nucl. Instr. and Meth. in Phys. Res. B2 (1984) 814
[4] M. Strobel et al., Phys. Rev. B64 (2001)245422.

  • Lecture (Conference)
    Material Research Society Fall Meeting 2017, 26.11.-01.12.2017, Boston, United States of America

Publ.-Id: 27018

WTZ Russland - Transientenanalysen für schnelle Reaktoren

Kliem, S.; Nikitin, E.; Rachamin, R.; Glivici-Cotruta, V.

Der Reaktordynamikcode DYN3D wird für Kernanalysen von Natrium-gekühlten schnellen Reaktoren (SFR) erweitert. In diesem Bericht werden neu implementierte thermomechanische Modelle für die adäquate Simulation von SFR-Transienten beschrieben, die die Simulation der axialen Wärmeausdehnung von Brennstäben und die radiale Ausdehnung des Reaktorkerns umfassen. Darüber hinaus wurde das Verfahren zur Erstellung von Querschnittsbibliotheken für DYN3D für SFR-Analysen erweitert. Die Verifizierung der neuen Modelle und der Querschnittserstellung erfolgte auf Vollkern-Ebene mit stationären Experimenten von der BFS-Testanlage des IPPE Obninsk und Daten des großen oxidischen Kerns des OECD/NEA-Benchmark und den Experimenten zum Zyklusende des Phenix-Kerns. Die DYN3D-Ergebnisse wurden mit der Monte-Carlo-Referenzlösung verglichen, die durch den SERPENT-Code berechnet wurde. Die Testergebnisse zeigen, dass die neu entwickelten Modelle die Wärmeausdeh-nungseffekte der Kernstruktur genau berücksichtigen können. Das neu entwickelte Verfahren zur Erstellung von Querschnittsbibliotheken wurde ebenfalls auf der Basis von SERPENT-Ergebnissen erfolgreich verifiziert. Zur Validierung wurden mehrere Tests, die sowohl stationäre als auch transiente Fälle aus den Phenix-Experimenten enthalten, mit DYN3D berechnet. Die DYN3D-Lösungen weisen eine gute Übereinstimmung mit den experimentellen Daten auf, was die Anwendbarkeit der Codes für Kernanalysen von Natrium-gekühlten schnellen Reaktoren bestätigt.

Keywords: DYN3D; SERPENT; Natrium gekühlter Reaktor; thermomechanische Modelle; Validierung

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-086 2018
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 27016

Process Simulation of Single Si Quantum Dot Formation for Single Electron Transistors

Prüfer, T.; Heinig, K. H.; Möller, W.; Hlawacek, G.; Xu, X.; Friedlund, C.; Djurabekova, F.; von Borany, J.

Conventional Lithography allows the fabrication of structures down to ~10 nm, being still too large for single electron transistors (SET) operating at room temperature (RT), which requires a tiny quantum dot (<5nm) embedded in SiO2, with tunnel distances to the source and drain <2nm. Here, we predict a fully CMOS-compatible method of self-assembly of a single Si quantum dot. We assume that 10…20nm thin nanopillars of a layer stack c-Si/6nm SiO2/30nm a-Si are made by conventional lithography. We predict that such a single dot is self-organized and self-assembled between the top and bottom silicon layer by phase separation of metastable SiOx. The SiOx is made by collisional mixing in the layer stack, which is simulated by TRI3DYN [1]. The phase separation of SiOx is described by 3D kinetic lattice Monte Carlo simulations [2]. Our results predict that a single Si nanodot forms if the volume of SiOx is smaller than (10nm)^3. This work has been funded by the European Union's Horizon 2020 research and innovation program under grant agreement No 688072.
[1] W. Möller; NIM B, 322, 23–33
[2] M. Strobel, K.H. Heinig, W. Möller, PRB 64, 245422

  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Deutschland

Publ.-Id: 27014

Influence of resistance and spin-torque bias dependence on the output power of MgO-based nano oscillators

Kowalska, E.; Fukushima, A.; Sluka, V.; Fowley, C.; Kákay, A.; Aleksandrov, Y.; Lindner, J.; Fassbender, J.; Yuasa, S.; Deac, A. M.

Spin-transfer torques (STTs) can be exploited in order to manipulate magnetic moments of nanomagnets, allowing for new consumer-oriented devices to be designed, such as tuneable radio-frequency spin-torque nano oscillators (STNOs) for wireless communication. Currently, the structure involving an MgO-based magnetic tunnel junction (MTJ) with hybrid geometry combining an IP reference layer and an out-of-plane free layer is the system of choice [1,2]. This configuration, Fig. 1a, maximizes the output power, reduces the critical current [3], and can allow for stable precession regardless of magnetic or applied current history [1,4,5].

Here, we experimentally observe an unusual curvature of the critical lines on the current-field phase diagram enclosing the region of steady-state dynamics (Fig. 2a) which has never been reported in similar metallic- or MTJ-based devices. Theoretically, we incorporate the angular dependence of the TMR (dRAP/dV) [6-8] and bias dependent spin-transfer torques [9-11] into the in-plane and the perpendicular STT and solve LLGS equation [12]. We find that the angular dependence of TMR introduces an asymmetry in the in-plane STT and gives rise to stable precession. Moreover, including the bias dependence of TMR (Fig. 1b) correctly reproduces the curvature of the dynamical region in the experimental phase diagram (Fig. 2b), gradually suppressing the induced asymmetry, and with it the output power. Therefore, the TMR ratio and its bias dependence are both equally crucial factors governing the performance of MTJ-based STNOs.

Keywords: STNO; MTJ; STT

  • Lecture (Conference)
    MMM 2017 - 62nd Annual Conference on Magnetism and Magnetic Materials, 06.-10.11.2017, Pittsburgh, USA

Publ.-Id: 27010

15 years of CW SRF operation at ELBE

Arnold, A.; Büchner, A.; Büttig, H.; Freitag, M.; Lehnert, U.; Michel, P.; Schneider, C.; Teichert, J.

ELBE is a compact, accelerator-driven photon and particle source. The variety of secondary radiation being offered extends from high-energy gamma rays to infrared and THz radiation as well as from neutrons to positrons and electrons. Since 2001 ELBE is operated as a user facility, providing more than 5500 hours of beamtime with an efficiency of more than 90% each year. The electron accelerator is based on four superconducting 9-cell TESLA cavities that are driven in CW operation to accelerate an average current of 1 mA up to beam energies of 40 MeV. Although these cavities performed well in the vertical test, they were limited by field emission from the very beginning to about 10 MV/m each. The reason is still unknown, but several candidates are being discussed. The prime suspect is particle contamination during cleanroom and beamline assembly but also a mechanism that allows particles to migrate from far away towards the cavity over an extended period of time might be possible. And also outgassing EPDM gaskets that are installed in the entire accelerator are a candidate for deterioration. Nevertheless, to ensure a reliable user operation, the performance of the cavities is determined in regular intervals by Q vs. E measurements and by means of high power RF processing and complete thermal cycling the performance could be partially returned to an earlier state. With the contribution we try to summarize our experiences in operating a superconducting CW LINAC over the last 15 years in an unclassified and probably dirty environment.

Keywords: CW; SRF; operation; ELBE; cryomodule

  • Invited lecture (Conferences)
    Operating SRF systems reliably in a "dirty" accelerator, 14.-15.09.2017, Berlin, Deutschland
  • Invited lecture (Conferences)
    TESLA Technology Collaboration Meeting, 06.-09.02.2018, Mailand, Italien

Publ.-Id: 27009

Cancer stem cells: Radioresistance, prediction of radiotherapy outcome and specific targets for combined treatments.

Krause, M.; Dubrovska, A.; Linge, A.; Baumann, M.

Inactivation of cancer stem cells (CSCs) is of utmost importance for tumor cure after radiotherapy. An increasing body of evidence complies with a higher radioresistance of CSCs compared to the mass of tumor cells, supporting the use of CSC related biomarkers for prediction of radiotherapy outcome. Treatment individualization strategies for patient groups with vastly different risk of recurrence will most likely require application of more than one biomarker. Specifically, inclusion of established biomarkers like tumor size for primary radio(chemo)therapy or human papilloma virus (HPV) infection status in head and neck squamous cell carcinoma seems to be of very high relevance. The high heterogeneity of CSC subclones along with changes of the functional behavior of individual tumors under treatment underlines the importance of the selection of the optimal timepoint(s) of biomarker evaluation, but also provides a potential therapeutic target for combined treatment approaches with irradiation.

Publ.-Id: 27005

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